Evaluation of Peanut Roasting Using Oven and Microwave Technologies on the
Development of Color, Flavor, and Lipid Oxidation
THESIS
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University
By
Alicia LouAnn Smith, B.S.
Graduate Program in Food Science and Technology
The Ohio State University
2014
Master's Examination Committee:
Professor Dr. Sheryl Barringer, Advisor
Professor Dr. Luis Rodriguez-Saona
Professor Dr. Ahmed Yousef
Copyright by
Alicia LouAnn Smith
2014
Abstract
Roasted peanut color, flavor, and lipid oxidation values were evaluated for
different time and temperature combinations using oven, microwave, and combination
roasting technologies. Raw peanuts were oven roasted at 135 °C, 163 °C, 177 °C, and
204 °C, microwave roasted for 1-3 min, or combination roasted by microwave and oven
roasting for various times and temperatures. Roasted peanut color, volatiles, odor activity
values (OAVs), free fatty acid, peroxide values, and sensory attribute values based on
descriptive sensory panel analysis were determined. Two commercial peanut butter
samples were analyzed for color and volatile comparison. L* values were used to
categorize peanuts into under roasted, ideally roasted, and over roasted. Raw peanuts
were roasted by different methods to produce equivalent, commercially ideal L* roast
color. Volatiles were measured using selected ion flow tube mass spectrometry (SIFTMS). OAVs were calculated based on volatile levels quantified with SIFT-MS and
known odor thresholds. The total roasting time in order to achieve ideal color was not
shortened by most of the combination treatments compared to their oven roasted
equivalents. Oven before microwave roasting compared to the reverse was found to
significantly increase the L* value likely due to the increase in the dielectric loss factor.
Peanuts with ideal color had L* values that were not significantly different, but the
ii
volatile levels were different. Hexanal concentrations in all peanuts decreased then
increased with roasting, but were below the level previously found to be unacceptable to
consumers. Ethanol to methanol ratios in roasted peanuts were all below the level found
in raw peanuts. Pyrazine levels increased as roasting time increased, although oven at 177
°C treatments had the highest and microwave treatments had the lowest levels. Volatile
levels generally increased as roasting time or temperature increased with raw peanuts
having the lowest levels and over roasted peanuts having the highest volatile levels. Oven
177 °C for 15 min generally had the highest level of volatiles among the roasting
treatments tested. Based on the OAVs that were greater than one, roasted peanut samples
had similar volatiles important for flavor compared to the commercial samples. Lipid
oxidation values were not significantly different between the roasted peanut samples,
displaying no evidence to support that roasting time or temperature affected lipid
oxidation, when ideal color was produced. Sensory attribute values showed no significant
difference between oven, microwave, or combination roasting for most of the peanut
flavor descriptors. Microwave and microwave combination roasting produced similar
color, flavor, lipid oxidation, and sensory attribute values compared to oven roasting
treatments. Soft independent modeling of class analogies based on volatile levels showed
that raw peanuts were the most different, commercial samples were the most similar to
each other, and oven, microwave, and combination roasting were all similar in volatile
profile.
iii
Dedicated to my family and friends
iv
Acknowledgements
I would first like to thank my advisor Dr. Sheryl Barringer. She has been a
wonderful professional role model for me since I first had her as an instructor. She has
challenged me both scientifically and professionally to do my best and inspired me to be
passionate about my work and field. Her efforts throughout my academic career have
made me a better food scientist and for that, I am thankful. I would also like to thank my
committee members Dr. Ahmed Yousef and Dr. Luis Rodriguez-Saona for supporting me
throughout my research project. Dr. Jennifer Perry and Dr. Julie Marshall provided
additional laboratory support in completing this project and I am grateful for their
assistance and collaboration efforts.
Secondly, I would like to thank Dr. Valente Alvarez, who believed in me as an
undergraduate student. I would not be where I am today without his help and advice. It
has also been great working with his past and present staff at the Food Industries Center.
I am grateful for all the help and experience everyone gave me at the Food Industries
Center. I also appreciate the help and support from the faculty, staff, and students in the
Department Food Science & Technology at Ohio State.
I also appreciate the advice and friendship of my lab mates. It was truly a great
experience working with all of them. My family and friends have also been a huge
support group and I love them all very much. Last, but not least, I would like to thank
v
The J.M. Smucker Company and employees that provided me with the opportunity to
complete this research. It has been a wonderful experience working with them during my
Master’s degree and I appreciate the support and guidance.
vi
Vita
B.S. Food Science, The Ohio State University………………..………………………2012
Fields of Study
Major Field: Food Science and Technology
vii
Table of Contents
Abstract ............................................................................................................................... ii
Acknowledgements ..............................................................................................................v
Vita.................................................................................................................................... vii
List of Tables .......................................................................................................................x
List of Figures .................................................................................................................... xi
Chapter 1: Literature Review ...............................................................................................1
1.1 Peanut Color ...............................................................................................................1
1.2 Peanut Flavor..............................................................................................................2
1.2.1 SIFT-MS ..............................................................................................................5
1.2.2 Raw Peanut Volatiles...........................................................................................6
1.2.3 Maillard Browning Volatiles ...............................................................................7
1.2.4 Lipid Oxidation Volatiles ..................................................................................10
1.3 Lipid Oxidation ........................................................................................................10
1.4 Microwave Processing .............................................................................................11
Chapter 2: Comparison of Peanut Roasting Using Oven and Microwave Technologies on
the Development of Color, Flavor, and Lipid Oxidation ...................................................13
2.1 Abstract ....................................................................................................................13
2.2 Practical Application ................................................................................................14
2.3 Introduction ..............................................................................................................14
2.4 Methods ....................................................................................................................16
2.4.1 Peanut Roasting .................................................................................................16
2.4.2 SIFT-MS ............................................................................................................18
2.4.3 Color ..................................................................................................................22
2.4.4 Peanut Oil Analysis ...........................................................................................23
viii
2.4.5 Sensory ..............................................................................................................24
2.4.6 Statistical Analysis ............................................................................................25
2.5 Results and Discussion .............................................................................................25
2.5.1 Color ..................................................................................................................25
2.5.2 Volatiles .............................................................................................................26
2.5.3 Lipid Oxidation..................................................................................................32
2.5.4 Sensory ..............................................................................................................34
2.6 Conclusion................................................................................................................38
2.7 References ................................................................................................................38
Chapter 3: Color and Volatile Analysis of Peanuts Roasted Using Oven and Microwave
Technologies ......................................................................................................................43
3.1 Abstract ....................................................................................................................43
3.2 Practical Application ................................................................................................44
3.3 Introduction ..............................................................................................................44
3.4 Methods ....................................................................................................................46
3.4.1 Peanut Roasting .................................................................................................46
3.4.2 SIFT-MS ............................................................................................................47
3.4.3 Color ..................................................................................................................51
3.4.4 Statistical Analysis ............................................................................................52
3.5 Results and Discussion .............................................................................................52
3.5.1 Color ..................................................................................................................52
3.5.2 Volatile Levels in Raw Peanuts .........................................................................56
3.5.3 Volatile Levels in Ideally and Over Roasted Peanuts .......................................66
3.5.4 Soft Independent Modeling of Class Analogy ..................................................71
3.6 Conclusions ..............................................................................................................74
3.7 References ................................................................................................................74
References ..........................................................................................................................79
Appendix: Odor Thresholds ...............................................................................................87
ix
List of Tables
Table 1.1. Odors of selected volatiles in peanuts................................................................ 2
Table 2.1. Kinetics of volatile compounds in peanuts for SIFT-MS analysis .................. 19
Table 2.2. Average odor activity values (OAVs) from ideally roasted peanuts and
commercial peanut butter samples. OAVs less than one are indicated with white boxes. 29
Table 2.3. Sensory attribute values determined by a descriptive sensory panel for
different peanut roasting treatments*................................................................................ 37
Table 3.1. Kinetics of volatile compounds in peanuts for SIFT-MS analysis .................. 49
Table 3.2. Volatile levels (ppb) of raw and under roasted peanuts ................................... 58
Table 3.3. Volatile levels (ppb) of ideally roasted peanuts............................................... 60
Table 3.4. Volatile levels (ppb) of over roasted peanuts .................................................. 64
Table 3.5. Soft independent modeling of class analogy (SIMCA) interclass distances
comparing oven, microwave (MW), and combination roasting treatment volatile
concentrations (ppb).......................................................................................................... 73
Table A1. Odor thresholds of volatiles in air .................................................................... 87
x
List of Figures
Figure 1.1. Schematic of selected ion flow tube mass spectrometer (SIFT-MS) (Smith and
Spanel 2005) ....................................................................................................................... 6
Figure 1.2. Maillard browning reaction flow chart based on Hodge 1953 and Nursten
2005..................................................................................................................................... 9
Figure 2.1. Percent free fatty acid in treatments with no significant difference in L* value
with raw peanuts as the control ......................................................................................... 33
Figure 2.2. Peroxide values (MEQ/1000 g sample) of treatments with no significant
difference in L* value with raw peanuts as the control .................................................... 34
Figure 3.1. L* values of oven, microwave (MW), and combination roasting treatments,
ideal L* values range from 56-61 ..................................................................................... 54
Figure 3.2. Volatile levels of pyrazines as roasting time increases for Oven at 177 °C,
Oven at 204 °C, and Microwave roasting treatments ....................................................... 70
xi
Chapter 1: Literature Review
1.1 Peanut Color
Raw peanut seeds lack chromoplasts and other coloring agents, which results in a
white seed color (Abegaz and Kerr 2006). Roasting peanuts promotes the formation of
melanoidin pigments formed from amino acids reacting with reducing sugars, which
gives peanut butter its distinct color (Abegaz and Kerr 2006). Pigments formed during
roasting absorb in the blue-violet spectrum resulting in the perceived brown color of
peanut paste (Abegaz and Kerr 2006).
Roasted peanut color is used as a quality assurance parameter for peanut butter
producers (Pattee and others 1991). Hunter L or CIELAB L* values can be used to
determine the ideal roasted peanut color. Hunter L values of 51-52 or CIELAB L* values
of 58-59 are the optimum values when roasted peanut attribute is the main focus (Pattee
and others 1991). Pattee and others (1991) found that deviations less than 2 units away
from the ideal CIELAB L* values were difficult for an eight member trained roasted
peanut flavor profile panel to detect differences in roasted peanut intensity.
Moisture also plays an important role in peanut butter color. Felland and Koehler
(1997) found that peanut butter color became darker (lower Hunter L values) as 2.5% and
5.0% water was added. Abegaz and Kerr (2006) found that adding 2% or 5% moisture to
peanut paste produced darker samples over a storage period of 52 weeks with the 5%
1
added water having the darker color. Abegaz and Kerr (2006) also established that adding
180 ppm of tertiary butylhydroquinone (TBHQ) and 4% sucrose to peanut paste did not
have a significant effect on color.
1.2 Peanut Flavor
The Maillard reaction, Strecker degradation, caramelization of sugars, and lipid
oxidation are responsible for the volatiles in roasted peanuts (Neta and others 2010).
Pyrazines formed from Maillard browning reactions are responsible for the roasted nutty
flavor in peanuts (Buckholz and others 1980; Mason and others 1966). Carbonyls are
produced by oxidation and Strecker degradation (Buckholz and others 1980) and provide
a harsh green note found in roasted peanuts (Buckholz and Daun 1981). Peanut flavor is
complex and each volatile has a distinct odor that is perceived by humans (Table 1.1).
Table 1.1. Odors of selected volatiles in peanuts.
Volatile
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5methylpyrazine
Odor
Reference
fatty, green
fatty, green
fatty, deep fried
green, painty
fatty, deep fried
strong, cardboard
citrus, fatty, woody, waxy
mushroom
sweet, alcohol
solvent
buttery
Matsui and others 1998
Matsui and others 1998
Matsui and others 1998
Brown and others 1973
Matsui and others 1998
MacLeod and Coppock 1976
SAFC 2011
Ba and others 2012
Ruth 1986
Matsui and others 1998
Matsui and others 1998
roasty
Matsui and others 1998
continued
2
Table 1.1. Continued
2,5-dimethylpyrazine
2,6-dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methyl-3ethylpyrazine
2-methylbutanal
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methyl-2-butanone
3-methylbutanoic
acid
4-vinylguaiacol
5-methylfurfural
acetaldehyde
acetic acid
acetoin
acetone
alpha-pinene
ammonia
benzaldehyde
benzene
butanal
butanone
decanal
decane
dimethyl disulfide
dimethyl sulfide
malty, chocolate
nutty, earthy
cucumber-like
pungent, suffocating
fresh, nutty
oily, earthy
floral, apple
Braddock and others 1995
Schirack and others 2006a
Matsui and others 1998
Ruth 1986
Lei and Boatright 2001
SAFC 2011
Flores and others 1997
roasty
Matsui and others 1998
green
malty
chocolate, nutty, meaty, green
hot milk, soap, green, fruity,
floral
floral
orange peel
fruity
Matsui and others 1998
Matsui and others 1998
SAFC 2011
Ba and others 2012
camphor
Lei and Boatright 2001
Arora and others 1995
Ba and others 2012
Matsui and others 1998/ Flores and
others 1997
Singh and others 2003
sweaty
Matsui and others 1998
spicy, phenolic
sweet, spicy, caramel, bitter
almond
green, sweet, fruity
bread dough, yeasty
buttery, cream
minty chemical, sweet
weak pine
pungent, irritating
pleasant, bitter
sweet, solventy
smoky, fish, amylic, aldehydeenal or dienal
butterscotch
fresh, floral
fatty, waxy
onion like
decayed cabbage
Matsui and others 1998
malty/ cheesy-green
Vazquez-Araujo and others 2009
Ruth 1986
Braddock and others 1995
Ruiz and others 2010
Ruth 1986
Jiang and Kubota 2004
Ruth 1986
Ruth 1986
Ruth 1986
Ba and others 2012
Arora and others 1995
Olafsdottir and others 2005
Buckholz and Daun 1981
Olafsdottir and others 2005
Ruth 1986
continued
3
Table 1.1. Continued
dimethyl trisulfide
ethanol
ethyl 2methylbutanoate
ethyl acetate
furfural
sulfurous
sweet, alcoholic
Matsui and others 1998
Ruth 1986
fruity
Matsui and others 1998
fruity, pleasant
almonds
gasoline-like
solventy, green
gasoline-like
Ruth 1986
Ruth 1986
Niu and others 2011/ Matsui and
others 1998
Olafsdottir and others 2005
Ruth 1986
Matsui and others 1998/ Lei and
Boatright 2001
Flores and others 1997
Matsui and others 1998
Schirack and others 2006a
Ruth 1986
Ruiz and others 2010
Ruth 1986
Ruth 1986
Ruth 1986
Ruth 1986
Flores and others 1997
Matsui and others 1998/ Lei and
Boatright 2001
Ruth 1986
Neta and others 2010
Ruth 1986
cheese, sweaty
Niu and others 2011
sweet, honey-like/ floral, sweet,
caramel
honey, floral, green, sweet
caramel, sweet, alcoholic,
cooked, broth, spicy
sour
lemon-like
mild sweet
ether-like
sweet, chemical
earthy
vanilla-like
Matsui and others 1998/ Braddock
and others 1995
SAFC 2011
guaiacol
smokey/ burnt
heptanal
heptane
earthy, boiled potato
gasoline-like
hexanal
green/ oxidized, nutty
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
methyl mercaptan
methyl methanoate
nonanal
octanal
octane
pentanal
pentane
pentanoic acid
(valeric acid)
phenylacetaldehyde
phenylacetic acid
propanal
propanoic acid
R-limonene
terpinolene
tetrahydrofuran
toluene
trimethylpyrazine
vanillin
green-mold
sweaty
fruity
rotten eggs
rancid butter
sweet
fragrant, fruity
sulfidy
pleasant
green
fatty/ fresh leave
4
Ba and others 2012
Ruth 1986
Matsui and others 1998
Jiang and Kubota 2004
Ruth 1986
Schirack and others 2006a
Frauendorfer and Schieberle 2006
Matsui and others 1998
1.2.1 SIFT-MS
Selected ion flow tube mass spectrometry (SIFT-MS) is a quantitative mass
spectrometric method that utilizes chemical ionization to accurately quantify trace gases
in real time (Figure 1.1) (Smith and Spanel 2005). Volatile organic compounds (VOCs)
can be identified and quantified with SIFT-MS from whole-gas samples (Harper and
others 2011). Positive ions are created and filtered through a quadrupole mass filter to
obtain ions with the desired mass-to-charge ratio (Smith and Spanel 2005). H3O+, NO+,
and O2+ are the ions normally desired because they do not react with bulk components of
air (Harper and others 2011). The ions are injected into the carrier gas (helium) and
pushed along the flow tube to maintain the same temperature of the carrier gas (Smith
and Spanel 2005). At the downstream end of the flow tube, ions are sampled into a
differentially pumped quadrupole mass spectrometer and detected by a channeltron
multiplier/pulse counting system (Smith and Spanel 2005). The reactant gas and injected
ions are introduced into the carrier gas in measurable amounts through an entry port
(Smith and Spanel 2005). Primary ion current decay and growth of the product ion count
rates are observed with the downstream mass spectrometer/detection system taking into
account the reactant gas flow rate (Smith and Spanel 2005). This allows the rate
coefficient and ion products to be determined (Smith and Spanel 2005). The count of
product ions divided by the count of reagent ions determines the concentration of a
compound in real time (Harper and others 2011). Selected ion mode (SIM) provides
direct quantification of specific target compounds which increases the sensitivity and
precision of the analysis (Harper and others 2011).
5
SIFT-MS has a variety of applications for use in environmental science, medicine,
food science, cell biology, and agriculture (Smith and Spanel 2005). SIFT-MS has been
used to evaluate the volatile profile of roasted cashews (Agila and Barringer 2011) and
almonds (Agila and Barringer 2012).
Figure 1.1. Schematic of selected ion flow tube mass spectrometer (SIFT-MS)
(Smith and Spanel 2005)
1.2.2 Raw Peanut Volatiles
Acetone, acetaldehyde, ethanol, hexanal, methanol, octane, pentanal, pentane, and
2-butanone were identified in raw peanuts (Pattee and others 1969). Hexanal was
6
suggested to be a main contributor to raw peanut aroma based on this research; however,
other volatiles may also be important (Pattee and others 1969). Hexanal and possibly
pentanal, octanal, nonanal, and decanal are responsible for the “green or beany” flavor of
raw peanuts based on the flavor thresholds (Brown and others 1972). Methanol, ethanol,
pentane, acetone, dimethyl sulfide, methyl acetate, 2-methylpropanal, 2-methylbutanal, 3methylbutanal, pentanal, dimethyl disulfide, and hexanal were identified in raw peanuts
(Young and Hovis 1990). The enzymes alcohol dehydrogenase and lipoxygenase may
also be responsible for volatile production. Acetaldehyde, methanol, pentane, ethanol,
and hexanal were shown to be related to alcohol dehydrogenase and lipoxygenase activity
during peanut maturation (Patte and others 1970). Patte and others (1970) also detected
trace amounts of acetone and pentanal in peanuts.
1.2.3 Maillard Browning Volatiles
Maillard browning is a non-enzymatic reaction that takes place between reducing
sugars and amino acids in the presence of heat. Peanuts contain amino acids including
alanine, arginine, aspartic acid, cystine, glutamic acid, glycine, histidine, hydroxylysine,
isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine,
tryptophan, tyrosine, and valine (Hoffpauir 1953), which can participate in Maillard
browning. The main sugar source in peanuts is sucrose, which converts to glucose and
fructose during roasting and are the main contributors in the browning reactions (Mason
and others 1969). Maillard reactions produce pyrazines, pyrroles, furans, and low
molecular weight compounds (Schirack and others 2006a).
7
The parts of the Maillard reaction include the initial stage, intermediate stage and
final stage. During the initial stage, the products created are colorless and do not absorb
in the ultraviolet spectrum (Hodge 1953; Nursten 2005). This stage includes sugar-amine
condensation and Amadori rearrangement, which are reactions A and B, respectively
(Figure 1.2) (Nursten 2005). The intermediate stage produces products that are colorless
or yellow and absorb in the ultraviolet spectrum (Hodge 1953; Nursten 2005). Sugar
dehydration, sugar fragmentation, and amino acid degradation, also known as Strecker
degradation, make up the intermediate stage, which are reactions C, D, and E,
respectively (Firgure 1.2) (Hodge 1953; Nursten 2005). Highly colored products are
produced during the final stage and include aldol condensation (reaction F) and aldehydeamine condensation and formation of heterocyclic nitrogen compounds (reaction G)
(Figure 1.2) (Nursten 2005). Free-radical breakdown of Maillard intermediates is
represented by reaction H (Figure 1.2) (Nursten 2005).
8
+ amino
compound
N-SUBSTITUTED
GLYCOSYLAMINE
ALDOSE SUGAR
+ H2O
A
B
H
C
1-AMINO-1-DEOXY-2-KETOSE
- 3 H2O
D
C
- 2 H 2O
+ α-amino acid
SCHIFF BASE
OF HMF OR
FURFURAL
REDUCTONES
+2 H
-2 H
- amino compound
+ H2O
HMF OR
FURFURAL
FISSION PRODUCTS
+ α-amino acid
DEHYDROREDUCTONES
E
with or without
amino compound
+ α-amino
acid
G
E
E
F
+ amino
compound
ALDIMINES
G
F
F
G
ALDOLS AND
N-FREE
POLYMERS
+ amino
compound
G
CO2
+
ALDEHYDE
+ amino
compound
ALDIMINES
OR
KETIMINES
+ amino
compound
ALDIMINES
G
MELANOIDINS
(BROWN NITROGENOUS POLYMERS AND COPOLYMERS)
Figure 1.2. Maillard browning reaction flow chart based on Hodge 1953 and
Nursten 2005.
9
G
G
1.2.4 Lipid Oxidation Volatiles
Alcohols, alkanes, ketones, and aldehydes are the source of off-flavors in peanuts
formed from the breakdown of hydroperoxides during lipid oxidation (Schirack and
others 2006a). Oxidative rancid flavors or cardboard flavors are associated with low
molecular weight aldehydes such as pentanal, hexanal, octanal, and nonanal, which are
lipid oxidation products produced in peanuts (Warner and others 1996). Off-flavors such
as painty and cardboardy were determined to be associated with lipid oxidation in
peanuts (Braddock and others 1995).
1.3 Lipid Oxidation
Peanut kernels contain about 50% oil on a dry basis (Hoffpauir 1953). Peanut oil
contains several long-chain fatty acids including oleic, linoleic, palmitic, stearic,
arachidic, behenic, and lignoceric acids (Hoffpauir 1953). Oleic and linoleic acids make
up 48% and 31% of the fatty acids present in peanuts, respectively (Bett and Boylston
1992). Since peanuts contain a high amount of unsaturated fats, they are susceptible to
lipid oxidation. Free fatty acid (FFA) and peroxide value tests can be performed on
peanut oil to determine the extent of primary oxidation. A Runner peanut crop in 1942
was found to have 0.65% FFA on a moisture free basis (Hoffpauir 1953), although peanut
oil should have low levels of FFA ranging from 0.8% in immature seed to 0.05% in
mature seed (Sanders 2002). Peroxide values for peanut oil should have a maximum of
10 meq peroxides oxygen/kg oil in order to maintain acceptable flavor (Sanders 2002).
Flavor and oxidative stability were tested of peanuts that had high amounts of
oleic acid and lower amounts of linoleic acid (Braddock and others 1995). The
10
researchers found that the peanuts with higher amounts of oleic acid had a more desirable
flavor during storage and the shelf life was almost two times longer compared to normal
peanuts (Braddock and others 1995). Bolton and Sanders (2002) studied the stability of
oil roasting high-oleic peanuts in high-oleic peanut oil and found that shelf life decreased
when the high-oleic peanut oil was not used.
1.4 Microwave Processing
Peanuts are traditionally dry roasted commercially for peanut butter applications
and oil and/or dry roasted for other applications such as candy and snack peanuts (Young
and others 1974). In hot air (oven) heating, energy is conducted into the food matrix from
the surface of the product, which is a slower heating method (Datta and Rakesh 2013).
Factors that affect hot air heating are air temperature, air velocity, food thermal
conductivity, food density, and specific heat (Datta and Rakesh 2013). For microwave
heating, energy is absorbed in the volume of the food product resulting in fast internal
heating (Datta and Rakesh 2013). Power level, food size, food shape, and dielectric
properties of the food are all factors that affect microwave heating (Datta and Rakesh
2013).
Microwave energy has benefits including reduced product cost by increased
production, improved quality, and fewer heating problems (Decareau 1985). Microwaves
save energy by having instantaneous start-up and fast heating, which increases production
(Decareau 1985). Microwave heating allows internal evaporation to take place inside the
food, which enhances the moisture loss during heating (Datta and Rakesh 2013). The
heating is selective in that moist areas will heat more than dry areas and the heating is not
11
as uniform as conventional heating (Datta and Rakesh 2013). With shelled and in-shell
peanuts, dielectric properties were only measured up to 50 °C, but increasing temperature
decreased the dielectric loss factor (Boldor and others 2004).
Young and others (1974) compared dry, oil, and microwave roasting methods on
the flavor and composition of peanut butter. Although there were differences among
panelists, dry roasted peanuts scored lower in flavor compared to microwave roasted
peanuts with a trained taste panel (Young and others 1974). Microwave blanching
peanuts has also been explored as an alternative to traditional techniques (Schirack and
others 2006b). Schirack and others (2006b) found that microwave blanching could be
utilized without producing microwave-associated off-flavor. The objectives of this
research were to determine differences in color, volatile levels, sensory characteristics,
and lipid oxidation results between oven, microwave, and combination roasting
treatments.
12
Chapter 2: Comparison of Peanut Roasting Using Oven and Microwave
Technologies on the Development of Color, Flavor, and Lipid Oxidation
2.1 Abstract
Roasted peanut quality was evaluated using oven, microwave, and combination
roasting technologies. Raw peanuts were roasted by different methods to produce
equivalent, commercially ideal L* roast color. Raw peanuts were oven roasted at 163 °C,
177 °C, and 204 °C, microwave roasted, or combination roasted using oven and
microwave technologies at different times and temperatures. Roasted peanut color,
volatiles, free fatty acid, peroxide values, and sensory attribute values based on
descriptive sensory panel analysis were determined. Two commercial peanut butter
samples were analyzed for color and volatile comparison. Odor activity values (OAVs)
were calculated based on volatile levels quantified with selected ion flow tube mass
spectrometry and known odor thresholds. Based on the OAVs that were greater than one,
roasted peanut samples had similar volatiles important for flavor compared to the
commercial samples. Lipid oxidation values were not significantly different between the
roasted peanut samples, displaying no evidence to support that roasting time or
temperature affected lipid oxidation, when ideal color was produced. Sensory attribute
values showed no significant difference between oven, microwave, or combination
roasting for most of the peanut flavor descriptors. Microwave and microwave
13
combination roasting produced similar color, flavor, lipid oxidation, and sensory attribute
values compared to oven roasting treatments.
2.2 Practical Application
Roasted peanut color, flavor, lipid oxidation, and sensory attributes are important
quality parameters used to evaluate roasted peanuts. Oven and microwave roasting
technologies that were roasted to the same peanut color had similar volatiles responsible
for flavor as commercial peanut butter samples. Based on the evaluated quality
parameters, microwave or combination roasting technologies may be used as alternative
roasting methods to produce peanut butter.
2.3 Introduction
Peanuts are produced in Alabama, Florida, Georgia, Mississippi, New Mexico,
North Carolina, Oklahoma, South Carolina, Texas, and Virginia in the United States
(USDA 2013b). In 2012, there were 6.74 billion pounds of peanuts produced in the
United States, which was a record high (USDA 2013b). Drought and other weather
conditions can affect yields and production of crops (USDA 2013b). There are several
peanut products produced from peanuts including snack peanuts, peanut butter, and
peanut candy (USDA 2012). Out of those peanut products, peanut butter was the primary
product consumed between 1967 and 2010 (USDA 2012). Runner peanuts have increased
in price from $344.35 per ton on January 4, 2006 (USDA 2006), to $499.65 per ton on
January 2, 2013 (USDA 2013a).
Alternative roasting technology may help reduce production costs associated with
peanut butter manufacturing. Microwave energy has benefits including reduced product
14
cost by increased production, improved quality, and fewer heating problems (Decareau
1985). Microwaves save energy by having instantaneous start-up and fast heating, which
increases production (Decareau 1985). Microwave heating allows internal evaporation to
take place inside the food, which enhances the moisture loss during heating (Datta and
Rakesh 2013).
Melanoidin pigments form during peanut roasting giving peanut butter a distinct
color (Abegaz and Kerr 2006). Roast color is used as a control parameter for peanuts
commercially because of the relationship it has with flavor development (Smyth and
others 1998). The ideal CIELAB L* value for roasted peanuts ranges from 58-59 ± 2
(Pattee and others 1991). Different time and temperature combinations during peanut
roasting have been shown to produce equivalent surface color (McDaniel and others
2012). Similar quality can be achieved with different roasting conditions and roasting
technologies.
Equivalent external surface color for almonds was achieved with oven,
microwave, and oil roasting (Agila and Barringer 2012). Microwave roasted almonds
were found to have higher volatile levels with selected ion flow tube mass spectrometry
and better flavor in sensory testing compared to oven and oil roasting methods (Agila and
Barringer 2012). Dry, oil, and microwave roasted peanuts were evaluated for flavor and it
was found that dry roasted peanuts scored lower in flavor than microwave roasted
peanuts, while oil roasted peanuts had the highest flavor scores (Young and others 1974).
Microwave blanched peanuts and the associated off-flavors have been studied with
sensory panels and instrumentally (Schirack and others 2006a, Schirack and others
2006b).
15
Lipid oxidation in roasted peanuts also affects quality. High free fatty acid values
can indicate improper handling, moisture, or fungal growth, while peroxide values are
used as an indicator of lipid oxidation (Sanders 2002). The objectives of this study were
to determine which technology or combination treatment roasted to equivalent ideal color
provided ideal flavor, the lowest free fatty acid and peroxide values, and acceptable
sensory characteristics.
2.4 Methods
2.4.1 Peanut Roasting
Raw peanuts (Medium Runner, Birdsong Peanuts, Sylvester, GA, U.S.A.) with
the shells removed were stored for less than 10 mo in sealed containers under
refrigeration conditions (4 °C) to minimize lipid oxidation. Raw peanut samples (60 ± 0.1
g) were roasted with the skins intact. Oven roasting was performed using a bench top
roaster oven (Nesco Jet-Steam Oven, American Harvest, Two Rivers, WI, U.S.A.). The
bottom pan in the roaster oven was fitted with a 30.48 cm by 5.08 cm round baking pan
(Wilton Industries, Woodridge, IL, U.S.A.). Aluminum foil was fitted around the exterior
of the baking pan, which extended to the top of the roaster oven to prevent peanuts from
escaping. Oven roasting was performed with the fan speed on high to allow the peanuts to
freely circulate in the modified roaster. Microwave roasting was performed in an 1100 W
microwave oven (Panasonic, Matsushita Home Appliance Corporation of America,
Danville, KY, U.S.A.) on high power with the peanuts (60 ± 0.1 g) in a single layer in a
glass dish. Combination treatments were performed by first oven roasting or microwave
16
roasting and then peanuts were immediately transferred to the other respective roasting
treatment in less than 1 min. After roasting, the peanuts were cooled for 10 min at
ambient temperature in a single layer and the skins were removed with gloved hands
using a stainless steel mesh colander to rub off the skins. Samples were ground in an
electric blender (Magic Bullet Express, Homeland Housewares, New York, NY, U.S.A.)
with a stainless steel cross blade and short cup for 30 sec.
Roasting conditions were chosen to produce equivalent, ideal color. Oven roasting
was carried out at 177 °C for 10 min, at 204 °C for 7 min, and at 163 °C for 20 min.
Microwave roasting was carried out for 2 min 30 sec. Combination roasting treatments
included microwave roasting for 1 min then oven roasting at 204 °C for 6 min,
microwave roasting for 2 min then oven roasting at 177 °C for 8 min, and oven roasting
at 204 °C for 6 min then microwave roasting for 1 min.
Two commercial peanut butter samples manufactured by The J.M. Smucker
Company were purchased from a local market. These samples were selected due to
project sponsorship, and have not been associated with any previous microbiological
product or process issues. Commercial sample #1 was a stabilized peanut butter (Jif ®
Creamy Peanut Butter, The J.M. Smucker Company, Orrville, OH, U.S.A.). Commercial
sample #2 was a natural peanut butter sample that only contained peanuts (Smucker’s ®
Natural Peanut Butter Creamy No Salt Added, The J.M. Smucker Company, Orrville,
OH, U.S.A.). Commercial sample #2 was emptied into a glass beaker and thoroughly
mixed before flavor and color analysis.
17
2.4.2 SIFT-MS
Ground peanut samples and commercial peanut butter samples (50 ± 0.1 g) were
placed into a 500 mL Pyrex bottle and capped with open top caps fitted with
polytetrafluoroethylene (PTFE)-faced silicone septa. Bottled samples were stored under
refrigeration conditions and were allowed to equilibrate at ambient temperature for 2 h
before being placed in the water bath. The sample bottles were placed in a 50 ± 3 oC
water bath (Precision Scientific, Jouan Inc., Winchester, VA, U.S.A.) for 60 min before
the volatiles were measured. Five replicates of every roasting treatment and the
commercial peanut butter samples were analyzed.
Selected ion flow tube-mass spectrometry (SIFT-MS) (SYFT Voice 200, Syft
Technologies Ltd., Christchurch, New Zealand) was used to detect and quantify peanut
volatiles. A selected ion mode (SIM) method was developed using H3O+, NO+, or O2+ as
precursor ions; refer to Smith and Spanel (2005) for more information on SIFT-MS. The
method developed was based on known volatiles present in raw and roasted peanuts
(Matsui and others 1998; Young and Hovis 1990; Coleman and others 1994; Brown and
others 1973; Mexis and Kontominas 2009; Smyth and others 1998; Braddock and others
1995; Buckholz and Daun 1981; Singleton and Pattee 1991; Pattee and Singleton 1981;
Ku and others 1998; Shu and Waller 1971). Volatile kinetics are shown in Table 2.1.
Headspace of the Pyrex bottles was measured by piercing the septa with a
stainless steel passivated sampling needle (18 gauge x 1.9 cm length), which was
attached to the inlet of the SIFT-MS. A second stainless steel needle (14 gauge x 15 cm
length) also pierced the septa to maintain atmospheric pressure in the bottle. The
18
headspace of each bottle was scanned for 2 min. A blank water sample was the first
sample tested and was run after each peanut sample to ensure the needle was clear of
lingering volatiles. Roasting treatment replicates were analyzed in a random order to
account for variation in the roasting method. Validations were passed daily on the SIFTMS before volatiles were analyzed. The flow tube pressure during the SIFT-MS run was
0.086 ± 0.005 Torr.
Mixtures were reported for compounds that had mass conflicts. In this study, 2,3diethyl-5-methylpyrazine is a mixture of 4-vinylguaiacol and 2,3-diethyl-5methylpyrazine; 2-pentanone is a mixture of 3-methyl-2-butanone and 2-pentanone; 3methylbutanoic acid is a mixture of pentanoic acid and 3-methylbutanoic acid; butanal is
a mixture of acetaldehyde, butanal and pentanal; hexane is a mixture of 2-methylbutanal
and hexane; methyl methanoate is a mixture of acetic acid and methyl methanoate;
pentane is a mixture of tetrahydrofuran and pentane; 2,6 nonadienal is a mixture of (E,E)2,6-nonadienal and (E,Z)-2,6-nonadienal; hexenal is a mixture of (E)-2-hexenal and (Z)3-hexenal; dimethylpyrazine is a mixture of 2,3-dimethylpyrazine, 2,5-dimethylpyrazine,
and 2,6-dimethylpyrazine; terpenes are a mixture of R-limonene, alpha-pinene,
phenylacetic acid, and terpinolene.
Table 2.1. Kinetics of volatile compounds in peanuts for SIFT-MS analysis
Compound
(E)-2-heptenal
(E)-2-nonenal
Formula
Precursor
ion
Product ion
k (10-9
cm3/s)
m/z
Ref
C7H12O
C9H16O
NO+
NO+
C7H11O+
C9H15O+
3.9
3.8
111
139
5
5
19
continued
Table 2.1. Continued
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5methylpyrazine
dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methyl-3ethylpyrazine
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic
acid
5-methylfurfural
acetoin
acetone
ammonia
benzaldehyde
benzene
butanal
butanone
decanal
decane
C8H14O
C5H8O
NO+
NO+
C8H13O+
C5H7O+
4.1
4.0
125
83
5
5
C10H16O
NO+
C10H15O+
4.2
151
5
C10H2O
C8H18O
C8H16O
C5H12O
C5H8O
C4H6O2
NO+
NO+
H3O+
NO+
NO+
NO+
C10H20.NO+
C8H17O+
C8H15+
C5H11O+
C5H8O.NO+
C4H6O2+
2.1
2.3
3.1
2.5
2.5
1.3
170
129
111
87
114
86
2
C9H14N2
O2+
C9H14N2+
2.5
150
8
C6H8N2
C9H14O
C4H6O
C10H20O
C7H16O
C6H12O
NO+
NO+
NO+
NO+
NO+
NO+
C6N2H8+
C9H14O.NO+
C4H5O+
C10H20O.NO+
C7H15O+
NO+.C6H12O
2.8
2.5
4.1
2.5
2.4
3.6
108
168
69
186
115
130
8
8
5
8
10
4
C7H10N2
NO+
C7H10N2.NO+
2.5
152
8
C4H8O
C5H6N2
C9H18O
C8H16O
C5H10O
C11H22O
C5H10O
O2+
NO+
NO+
NO+
NO+
NO+
H3O+
C4H8O+
C5H6N2+
C9H18O.NO+
C8H16O.NO+
NO+.C5H10O
C11H22O.NO+
C5H6+
3.0
2.8
2.7
3.3
3.1
3.4
3.6
72
94
172
158
116
200
66
5
8
3
3
4
3
5
C5H10O2
NO+
C5H10O2.NO+
2.5
132
8
C6H6O2
C4H8O2
C3H6O
NH3
C7H6O
C6H6
C4H8O
C4H8O
C10H20O
C10H22
NO+
NO+
NO+
O2+
NO+
O2+
O2+
NO+
NO+
O2+
C6H6O2+
C4H8O2.NO+
NO+.C3H6O
NH3+
C7H5O+
C6H6+
C2H4O+
NO+.C4H8O
C10H19O+
C10H22+
3.1
2.5
1.2
2.6
2.8
1.6
3.5
2.8
3.3
2.0
110
118
88
17
105
78
44
102
155
142
10
8
4
7
4
7
4
4
5
7
6
8
4
8
4
continued
20
Table 2.1. Continued
dimethyl disulfide
dimethyl sulfide
dimethyl trisulfide
C2H6S2
C2H6S
C2H6S3
O2+
NO+
O2+
ethanol
C2H6O
NO+
C7H14O2
ethyl 2methylbutanoate
furfural
guaiacol
heptanal
heptane
hexanal
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
methyl mercaptan
methyl methanoate
nonanal
octanal
octane
pentane
phenylacetaldehyde
propanal
propanoic acid
pyrazine
terpenes
toluene
trimethylpyrazine
vanillin
(CH3)2S2+
(CH3)2S+
C2H6S3+
C2H5O+,
C2H5O+.H2O,
C2H5O+.2H2O
2.3
2.2
2.2
NO+
C7H14O2.NO+
C5H4O2
C7H8O2
C7H14O
C7H16
C6H12O
C6H14
C6H12O2
C6H10O
H2S
C4H8O2
NO+
NO+
NO+
H3O+
H3O+
O2+
NO+
NO+
O2+
O2+
CH4O
H3O+
C3H6O2
NO+
CH4S
H3O+
C2H4O2
C9H18O
C8H16O
C8H18
C5H12
C8H8O
C3H6O
C3H6O2
C4H4N2
C10H16
C7H8
C7H10N2
C8H8O3
NO+
NO+
NO+
O2+
O2+
NO+
NO+
O2+
NO+
NO+
NO+
O2+
O2+
C5H4O2+
C7H8O2+
C7H13O+
H3O+.C7H16
C6H11+
C6H14+
C6H12O2.NO+
C6H9O+
H2S+
(CH3)2CHCOOH+
CH5O+,
CH3OH2+.H2O,
CH3OH.H+.(H2O)2
NO+.CH3COOCH3
CH4S.H+,
CH4S.H+.H2O
NO+.HCOOCH3
C9H17O+
C8H15O+
C8H18+
C3H6+
C8H8O+
C3H5O+
C2H5COOH+
C4H4N2+
C10H16+
C7H8+
C7H10N2+
C8H8O3+
94
62
126
45,
63,
81
7
7
10
2.4
160
8
3.2
2.5
3.3
2.6
3.7
1.7
2.5
3.8
1.4
2.5
96
124
113
119
83
86
146
97
34
88
33,
51,
69
104
49,
67
90
141
127
114
42
120
57
74
80
136
92
122
152
10
8
5
1
4
7
8
4
11
7
1.2
2.7
1.6
1.8
5.0
2.7
3.0
1.9
1.6
2.5
2.5
2.2
2.8
2.2
1.7
2.5
2.8
6
6
7
11
7
8
5
7
7
8
4
7
8
8, 9
7
8
8
[1] Arnold and others 1998, [2] Diskin and others 2002, [3] Smith and others 2003, [4]
Spanel and others 1997, [5] Spanel and others 2002, [6] Spanel and Smith 1997, [7]
21
Spanel and Smith 1998, [8] Syft Technologies, Inc. 2011, [9] Wang and others 2003, [10]
Wang and others 2004, [11] Williams and others 1998
Odor activity values (OAVs) were calculated based on known odor thresholds of
volatiles in air (Table A1, Appendix). Odor thresholds were converted to ppm based on
25 °C and 1 atm of pressure. The smallest odor thresholds reported in literature were used
to make the OAVs conservative. Some odor thresholds were not found in literature.
OAVs were calculated by dividing the volatile concentration by the odor thresholds
found in literature. Average OAVs were determined for all roasting treatments and
commercial samples.
2.4.3 Color
Peanut samples were blended for 20 sec in an electric blender (Magic Bullet
Express, Homeland Housewares, New York, NY, U.S.A.) with a stainless steel cross
blade and short cup. The paste was pressed into the bottom of an Optilux Petri Dish (BD
Biosciences, San Jose, CA, U.S.A.). Commercial peanut butter samples were spread on
the bottom of an Optilux Petri Dish (BD Biosciences, San Jose, CA, U.S.A.). Each petri
dish was completely filled before analysis. Color measurements were performed at
ambient temperature using a Color Quest XE colorimeter (Hunter Associate Laboratory,
Inc., Reston, VA, U.S.A.). A reflectance specular included method was used with
illuminant D65, 10° standard observer angle, and a 2.54 cm area view. The CIELAB
L*a*b* values were collected. Individual samples were measured in triplicate and
roasting treatments were analyzed in triplicate to obtain the averages.
22
2.4.4 Peanut Oil Analysis
Ground peanut samples were wrapped in two layers of cheesecloth. Oil was
extracted from the cheesecloth at ambient temperature using a Carver press Model C
3851-0 (Carver, Inc., Wabash, IN, U.S.A.). Samples were placed in a large stainless steel
cylinder pellet mold with a stainless steel pan on the bottom to collect the peanut oil. The
press was subjected to 9072 kg of clamping force then allowed to drop to 6804 kg. The
clamping force was increased again to 9072 kg and allowed to drop to 6804 kg. Finally,
the press was increased to 9072 kg of clamping force and allowed to drop for 3 min
before the sample was removed and oil was collected for analysis. Oil was extracted from
six replicates per roasting treatment to be able to perform triplicates on the free fatty acid
and peroxide value tests.
2.4.4.1 Free Fatty Acid
Free fatty acid values were determined with the AOCS Official Method Ab 5-49
(AOCS 1998a). Extracted oil (7.05 ± 0.05 g) was placed in a flask. Neutralized alcohol
(50 mL) and phenolphthalein indicator (1 mL) were added to the flask. The solution was
titrated with 0.25 N NaOH with constant stirring until a faint pink color was obtained for
at least 1 min. The percentage of free fatty acid (oleic acid) was calculated using the
following formula (AOCS 1998a), where mL was the amount of NaOH required:
% FFA =
23
2.4.4.2 Peroxide Value
Peroxide values were determined with the AOCS Official Method Cd 8-53
(AOCS 1998b). Extracted oil (5.00 ± 0.05 g) was placed into a 250-mL Erlenmeyer flask.
Acetic acid-chloroform 3:2 (v/v) solution (30 mL) was added to the flask to dissolve the
sample. Saturated KI solution (0.5 mL) was added to the flask. The solution was allowed
to stand for 1 min then distilled water (30 mL) was added to the flask. The solution was
titrated with 0.1 N sodium thiosulfate with constant stirring until the yellow iodine color
almost disappeared. Starch indicator solution (2.0 mL) was added to the flask and
titration continued until the blue color disappeared. A blank titration was conducted daily
using the reagents. The peroxide value was calculated using the following formula
(AOCS 1998b), where B was the volume of titrant (mL of blank), S was the volume of
titrant (mL of sample), and N was the normality of sodium thiosulfate solution:
Peroxide value (milliequivalents peroxide/1000g sample) =
(
)
( )
2.4.5 Sensory
Peanuts were roasted at The Ohio State University (Columbus, OH, U.S.A.),
vacuum sealed, and frozen. The sensory analysis was performed at Lubbock Christian
University (Lubbock, TX, U.S.A.). Peanuts were shipped and stored frozen until they
were processed. Peanut samples were ground into a paste before analysis. Seven trained
panelists completed the descriptive sensory analysis on the roasted peanuts. A peanut
lexicon based on Johnsen and others (1988) was used, which included roasted peanut,
sweet, salty, bitter, raw beany green, dark roast, woody hulls skins, sweet aromatic,
astringent, fruity fermented sour over ripe, cardboard oxidized, and painty oxidized oil as
24
flavor descriptors. An abbreviated 1-10 scale was used to rate the intensity of the sensory
attributes based on Johnsen and others (1988). The averages of the seven panelists’ scores
were reported for each sensory attribute.
2.4.6 Statistical Analysis
One-way analysis of variance (ANOVA) and Tukey’s post hoc test was
performed on the data using Minitab 16 (Minitab Inc., State College, PA, U.S.A.). For the
one-way ANOVA α = 0.05 and a Tukey’s family error rate of 5 was used.
2.5 Results and Discussion
2.5.1 Color
In commercial roasting, roast color is primarily used as a control parameter
because of the relationship it has with flavor development (Smyth and others 1998).
Hunter color-difference values are commonly used for quality assurance with commercial
peanut butter producers (Pattee and others 1991). CIELAB L* values of 58-59 are the
optimum values when the peanut sensory attribute ‘roasted peanut’ is the main focus
(Pattee and others 1991). In one study it was difficult for an eight member trained roasted
peanut flavor profile panel to detect differences in roasted peanut intensity with
deviations less than 2 units away from the ideal L* value (Pattee and others 1991).
All roasting treatments and one commercial sample fell within the desired L*
range of 58-59 ± 2. Commercial #1 fell within the ideal L* range, while commercial #2
(L* = 54.56 ± 0.28) was darker in color compared to most of the other samples. A darker
roast color was expected because “natural” peanut butter is roasted for a longer time
(Elder 2013).
25
2.5.2 Volatiles
Volatiles in roasted peanuts are mainly due to the Maillard reaction, which
produces pyrazines, Strecker degradation, caramelization of sugars, and lipid oxidation
(Neta and others 2010, Warner and others 1996). Maillard reactions produce pyrazines,
pyrroles, furans, and low molecular weight compounds (Schirack and others 2006a).
Pyrazines are responsible for the roasted flavor in peanuts (Buckholz and others 1980).
Carbonyls are produced by oxidation and Strecker degradation in peanuts, although some
can be lost during roasting because of the volatility of the compounds (Buckholz and
others 1980). Oxidative rancid flavors or cardboard flavors are associated with low
molecular weight aldehydes such as pentanal, hexanal, octanal, and nonanal, which are
lipid oxidation products produced in peanuts (Warner and others 1996).
Volatiles in all seven roasting treatments and two commercial samples had odor
activity values (OAVs) that were generally greater than one indicating the volatiles were
detectable to the consumer and were likely important to peanut flavor (Table 2.2). OAVs
greater than one are indicated by the gray boxes in Table 2.2. All roasting treatments and
commercial samples generally followed the same trend, in that for all treatments, the
volatile always had an OAV greater than one or always had an OAV less than one. This
indicated that the same volatiles are contributing to peanut flavor in samples that had
equivalent roast color.
Methyl mercaptan had the greatest OAVs among the volatiles, at 9.45 x 1010 to
8.86 x 1012, which indicated that this volatile should have a strong impact on aroma in
roasted peanuts (Table 2.2). Methyl mercaptan has a sulfidy aroma (Ruth 1986), and is
likely derived from methionine during Maillard browning (Nursten 2005). Vanillin, 2,326
butanedione, butanal, and hydrogen sulfide had OAVs greater than one thousand for all
roasting treatments and commercial samples indicating these volatiles were also very
important to peanut flavor. The aroma of vanillin, 2,3-butanedione, butanal, and
hydrogen sulfide are vanilla-like (Matsui and others 1998), buttery (Matsui and others
1998), smoky/fish/amylic/aldehyde-enal or dienal (Ba and others 2012), and rotten eggs
(Ruth 1986), respectively. These volatiles are formed during Maillard browning or are a
product of lipid oxidation, with the exception of vanillin. Vanillin was found to be a
product of peanut hull lignin hydrolysis in boiled peanuts (Sobolev 2001), although
peanut hulls were not used in the present study. The mechanism for vanillin formation in
roasted peanuts is not certain.
Not every volatile had an OAV greater than one (Table 2.2). The volatiles with
OAVs less than one are not detectable by the human nose and are indicated by the white
boxes in Table 2.2. Volatiles that had OAVs that were less than one for all samples
included (E)-2-pentenal, 1-decene, 2-octanone, 2-pentanone, 2-undecanone, benzene,
decane, octane, and toluene. Thus, these volatiles were probably not important to peanut
flavor based on this study. Except for toluene, these volatiles have not been shown to
have an aroma impact with roasted peanuts. Toluene was found to be a high impact
aroma-active compound in peanuts as determined by aroma extract dilution analysis
(AEDA) and based on dilution factors (Schirack and others 2006a), which does not
support the current study. However, the AEDA technique has flaws because it cannot
determine if compounds exist in concentrations above sensory thresholds and does not
take into account the volatile perception in the food matrix (Schirack and others 2006a).
27
Odor thresholds were not based on the food matrix or determined in this research;
therefore, OAV determinations also have flaws.
Almonds that were microwave roasted had higher levels of volatiles compared to
oven and oil roasted treatments (Agila and Barringer 2012), which did not occur in the
present research with peanuts. In this study, oven roasted treatments had higher OAVs or
were not significantly different from microwave or combination treatments (Table 2.2).
Microwave blanching of peanuts has been associated with stale/floral and ashy offflavors related to an increase in guaiacol, phenylacetaldehyde, and 2,6-dimethylpyrazine
concentrations (Schirack and others 2006a). Microwave roasted treatments had OAVs
that were lower or not significantly different from the oven roasted treatments and not
different from the microwave combination treatments for these three volatiles (Table
2.2). Therefore, microwave roasted treatments did not have higher concentrations of the
volatiles known to be associated with microwave blanched off-flavors.
Commercial #1 and #2 had lower volatile levels compared to the roasting
treatments tested in this study (Table 2.2). Commercial #1 contained ingredients other
than peanuts, which may contribute to the lower OAVs. Commercial #1 was produced
less than two months before the flavor analysis and commercial #2 was produced less
than three months before the flavor analysis, which may also contribute to the differences
in OAVs compared to the freshly roasted peanuts.
28
Table 2.2. Average odor activity values (OAVs) from ideally roasted peanuts and commercial peanut butter samples.
OAVs less than one are indicated with white boxes.
Oven 163
°C for 20
min
Oven 177
°C for 10
min
Oven 204
°C for 7
min
Microwave
2 min 30
sec
Microwave
2 min then
Oven 177
°C for 8
min
Microwave
1 min then
Oven 204
°C for 6
min
Oven 204
°C for 6
min then
Microwave
1 min
Commercial
#1
Commercial
#2
Volatile
(E)-2-heptenal
1.17cd
2.29a
1.61b
1.29bcd
1.52bc
1.09de
1.07def
0.66f
0.69ef
(E)-2-nonenal
22.24c
43.88a
32.31b
22.89c
24.34c
20.95cd
19.58cde
13.18e
14.40de
(E)-2-octenal
9.05c
17.21a
13.57b
10.16c
10.45c
8.19cd
7.87cde
5.37de
5.20e
(E)-2-pentenal
(E,E)-2,4decadienal
1-decene
0.02b
0.05a
0.03b
0.03b
0.03b
0.02b
0.02b
0.01c
0.01c
174.10c
340.21a
255.00b
205.37bcd
192.51c
162.88c
161.60c
103.82d
95.76d
<0.01ab
<0.01ab
<0.01a
<0.01ab
<0.01ab
<0.01ab
<0.01ab
<0.01ab
<0.01b
cd
a
ab
cd
bc
cd
cd
d
7.24d
29
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5methylpyrazine
dimethylpyrazine
2,6-nonadienal
2-butenal
12.99
30.28
22.29
12.82
17.64
13.50
13.23
8.48
25.34bcd
48.05a
34.32b
27.05bcd
32.82bc
22.73cd
24.75bcd
17.99d
18.23d
15.72bc
29.21a
19.38b
14.74c
14.52c
13.83c
12.53c
4.02d
3.16d
539.66bc
1038.71a
714.90b
619.11bc
694.11b
488.24cd
470.54cd
299.85d
310.90d
47706.23c
84187.95a
65917.72b
46825.81c
50695.69bc
48136.10c
45746.19c
15834.28d
12283.00d
2008.52cd
4704.82a
3259.53b
1757.31cde
2460.81bc
1985.31cd
1660.38cde
1207.72de
872.13e
2.09cde
5.25a
3.51b
2.18cde
2.79bc
2.29cd
2.02cde
1.31e
1.60de
312.00bc
541.56a
403.81b
309.47bc
393.17b
275.02cd
272.55cd
183.42d
212.38cd
c
a
b
c
c
c
c
d
0.09d
0.85
1.47
1.16
0.76
0.85
0.81
0.75
0.11
2-decanone
8.76abc
8.97abc
9.57abc
9.70ab
10.38a
8.47abc
8.99abc
5.82c
6.26bc
2-heptanol
1.56bc
3.71a
2.47b
1.59bc
1.79b
1.53bc
1.47bc
0.51c
0.51c
2-hexanone
1.09bc
1.52a
1.24b
1.03cd
1.00cd
0.89cd
0.82d
0.47e
0.40e
4059.75bc
6804.55a
5362.73ab
3380.47c
4687.77bc
3975.61bc
3671.40bc
834.72d
705.77d
2-methylpropanal
continued
29
Table 2.2. Continued
2-nonanone
0.91abc
1.07a
1.16a
1.07a
0.98ab
1.01ab
1.02ab
0.73bc
0.65c
2-octanone
0.50cd
0.72a
0.69ab
0.57abcd
0.66abc
0.54bcd
0.57abcd
0.46d
0.44d
2-pentanone
0.15bc
0.27a
0.19b
0.16bc
0.16bc
0.14c
0.13c
0.07d
0.05d
2-undecanone
0.41abc
0.50abc
0.57ab
0.59a
0.50abc
0.48abc
0.50abc
0.32c
0.35bc
b
a
c
de
d
de
de
de
119.46e
3-methylbutanal
3-methylbutanoic
acid
acetone
587.92
1300.28
419.64
188.00
262.24
193.81
216.81
189.75
1121.33c
2769.33a
1582.60b
952.97c
1134.50c
932.83c
890.78c
541.52d
401.87d
2.61bc
4.66a
3.16b
3.43b
3.13b
2.48bc
2.15c
0.86d
0.66d
ammonia
35.37bc
47.36a
38.60b
24.91d
38.71b
29.97cd
27.34d
13.65e
16.75e
benzaldehyde
304.68b
477.91a
312.87b
275.80bc
262.73bc
226.83c
221.31c
125.81d
99.64d
0.06b
0.11a
0.07b
0.07b
0.07b
0.05b
0.05b
0.02c
0.02c
6320.12bc
9451.42a
7816.66ab
5447.14c
5742.78c
5773.39c
5790.90c
1423.35d
1141.18d
1.36bc
2.56a
1.67b
1.42b
1.56b
1.18bcd
1.10bcd
0.59d
0.74cd
cde
a
b
cd
bc
cde
def
ef
31.89f
benzene
butanal
30
butanone
decanal
53.03
105.31
79.90
57.71
67.30
51.24
49.07
36.47
0.02cd
0.03a
0.02abc
0.02bcd
0.03ab
0.02bcd
0.02bcd
0.01d
0.01d
3903.36bc
9364.97a
5276.60b
4655.40b
5034.02b
3499.90bcd
3185.69bcd
1514.41d
1917.97cd
dimethyl sulfide
243.39a
243.98a
187.11b
142.52c
171.51bc
143.41c
140.15c
91.72d
56.26e
dimethyl trisulfide
16.42bc
27.12a
21.98ab
14.90c
17.67bc
14.39c
14.85c
7.15d
7.66d
10.69c
47.30a
16.54b
10.69c
11.27c
9.03cd
9.23cd
7.07de
5.93e
1991.99bc
3642.13a
2360.13b
1942.10bc
1845.34bc
1612.34c
1747.58c
966.09d
905.60d
5.70bc
10.42a
6.64b
5.82bc
5.73bc
4.56bcd
4.37cd
2.43de
2.07e
bcd
a
b
bc
bc
bcd
cd
d
481.59d
decane
dimethyl disulfide
ethanol
ethyl 2methylbutanoate
furfural
guaiacol
711.46
1879.70
1149.02
1037.23
1053.39
738.99
667.57
410.67
heptanal
64.98bc
86.46a
69.62b
62.01bcd
62.69bcd
51.16cde
49.24de
38.30ef
33.73f
heptane
5.38b
10.55a
5.00b
2.32cd
4.08bc
2.95c
3.05c
0.79d
0.66d
hexanal
77.63b
119.80a
69.63bc
70.74b
61.96bcd
54.15cd
52.31d
32.04e
22.54e
continued
30
Table 2.2. Continued
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
236.19bc
419.45a
317.17b
247.45bc
241.24bc
230.97c
221.07c
63.29d
49.12d
18.80cd
71.47a
31.08b
22.87bc
21.46cd
18.10cd
18.73cd
13.41cd
12.12d
64.08bcd
147.94a
89.12b
71.83bcd
87.85bc
60.53cd
54.21d
23.30e
22.84e
2498.07c
3622.24a
3750.18a
3195.16abc
3242.36abc
3308.68ab
2820.86bc
1503.23d
1480.73d
bc
a
b
c
bc
c
c
d
18.97d
117.54
273.73
157.54
87.89
113.26
98.68
90.24
23.22
methanol
5.46a
5.42a
4.10b
2.70d
4.10b
3.26cd
3.43c
1.92e
1.72e
methyl acetate
4.94b
7.39a
4.25bc
2.72d
4.88b
3.11cd
2.75d
0.89e
0.89e
7.15E+12ab
8.86E+12a
7.34E+12ab
4.30E+12c
6.70E+12b
5.69E+12bc
4.78E+12c
1.71E+11d
9.45E+10d
833.10b
1158.49a
808.07bc
578.67de
648.27cd
548.81de
609.32de
480.92ef
319.58f
155.13bc
230.84a
178.60b
137.24bcd
159.59bc
131.12cd
127.91cd
118.37cd
109.74d
octanal
900.65bc
1420.68a
1306.81a
801.94c
1196.47ab
793.24c
938.15bc
943.41bc
852.77c
octane
pentane
0.03b
0.04a
0.03ab
0.03b
0.03ab
0.02b
0.03b
0.01c
0.01c
a
ab
bc
a
d
cd
d
e
4.02e
methyl mercaptan
methyl
methanoate
nonanal
31
13.15
12.10
11.15
12.81
9.23
9.61
9.27
2.52
phenylacetaldehy
de
propanal
311.31b
429.51a
441.00a
336.80b
268.37b
318.66b
316.27b
143.04c
93.65c
608.89c
1267.47a
882.67b
523.64c
606.63c
600.56c
513.97c
133.99d
123.56d
propanoic acid
300.82bc
462.94a
268.20bcd
148.05ef
318.60b
201.08cde
170.13de
33.99g
42.30fg
toluene
0.66cd
0.99a
0.75b
0.72bc
0.59de
0.61de
0.54e
0.17f
0.20f
trimethylpyrazine
3.76cd
9.60a
6.59b
4.08cd
4.94bc
4.20cd
3.62cd
2.47d
3.16cd
80561.71bcd
3.07E+05a
1.49E+05b
83600.36bcd
1.33E+05bc
85073.32bcd
63193.59cd
30581.22d
25760.96d
vanillin
a-g
Samples with different letters for the same volatile are significantly different
31
2.5.3 Lipid Oxidation
No significant difference was found in percent free fatty acid (FFA) values when
comparing the roasting treatments with ideal L* values to the raw peanuts as the control
(Figure 2.1). FFA values ranged from 2.1 – 4.4% for the different roasting treatments.
The average free fatty acid percentage on a moisture-free basis from a Runner peanut
crop in 1942 was 0.65% (Hoffpauir 1953). Peanut oil has low levels of FFA ranging from
0.8% with immature seed to 0.05 % in mature seed (Sanders 2002). FFA values can
increase from improper handling, moisture, fungal growth, or other factors (Sanders
2002). The reported literature values were lower than the average free fatty acid values
determined in this study, indicating the peanuts may have been exposed to moisture,
fungal growth, or improper handling. The raw peanut FFA value was not significantly
different from the roasted peanut values, which indicated that when peanuts were roasted
to ideal color the FFA values were not affected.
No significant difference was found in peroxide values comparing the seven
roasting treatments with ideal L* values with raw peanuts as the control (Figure 2.2).
Peroxide value is used as an indicator of peanut quality with high values indicating that
lipid oxidation has taken place (Sanders 2002). The maximum peroxide value for peanut
oil is 10 meq peroxides oxygen/kg oil to maintain acceptable flavor (Sanders 2002). All
samples tested in this study were below 10 meq/kg oil indicating that the peanut oil had
low levels of lipid oxidation. The raw peanut peroxide value was not significantly
different from the roasted peanut values indicating that roasting treatment did not affect
the peroxide values.
32
4.0
a
Free fatty acid (%)
3.5
3.0
a
a
a
a
a
a
a
2.5
2.0
1.5
1.0
0.5
Oven 204 °C for 6 min then Microwave 1 min
Microwave 1 min then Oven 204 °C for 6 min
Microwave 2 min then Oven 177 °C for 8 min
Microwave 2 min 30 sec
Oven 204 °C for 7 min
Oven 177 °C for 10 min
Oven 163 °C for 20 min
Raw
0.0
Roasting Treatment
Figure 2.1. Percent free fatty acid in treatments with no significant difference in L*
value with raw peanuts as the control
a
Samples with different letters are significantly different
33
Peroxide value (MEQ/1000g sample)
2.0
1.8
a
1.6
a
1.4
1.2
1.0
a
a
a
a
a
a
0.8
0.6
0.4
0.2
Oven 204 °C for 6 min then Microwave 1 min
Microwave 1 min then Oven 204 °C for 6 min
Microwave 2 min then Oven 177 °C for 8 min
Microwave 2 min 30 sec
Oven 204 °C for 7 min
Oven 177 °C for 10 min
Oven 163 °C for 20 min
Raw
0.0
Roasting Treatment
Figure 2.2. Peroxide values (MEQ/1000 g sample) of treatments with no significant
difference in L* value with raw peanuts as the control
a
Samples with different letters are significantly different
2.5.4 Sensory
No differences were observed between any of the roasting treatments for woody
hulls skins, sweet aromatic, astringent, or salty sensory attributes (Table 2.3). None of the
34
roasting treatments contained fruity fermented sour over ripe, cardboard oxidized, or
painty oxidized oil sensory attributes. The panelists noted a musty/smoky aftertaste with
the oven 177 °C for 10 min treatment and microwave for 2 min then oven 177 °C for 8
min treatment.
Significant differences were observed with roasted peanut, sweet, dark roast,
bitter, and raw beany green sensory attributes (Table 2.3). In a previous study, roast
peanutty, sweet aromatic, and sweet taste attributes were positively correlated with each
other and negatively correlated with bitter, ashy, and total offnote attributes based on
descriptive sensory analysis performed with microwave blanched peanuts (Schirack and
others 2006b). In our study, the bitter attribute was found to be negatively correlated with
the roasted peanut attribute. Higher values were found with the lowest oven roasting
temperature and decreased as the oven temperature increased for the bitter attribute.
Higher oven roasting temperatures and combination treatments with higher oven
temperatures gave higher roasted peanut, sweet, and raw beany green sensory attribute
values. Dark roast has been positively correlated with bitter and negatively correlated
with the raw beany attribute for microwave blanched peanuts (Schirack and others
2006b). A similar trend was observed in this study with dark roast being negatively
correlated to the raw beany green attribute. The microwave and lowest temperature oven
roast had the highest level of dark roast attribute, which may be explained by the
unevenness of the microwave roasting and long roasting time in the oven, respectively.
Roasting treatments that had the highest sensory scores for the roasted peanut and sweet
attributes were oven 177 °C for 10 min, oven 204 °C for 7 min, and the combination
35
treatment microwave 1 min then oven 204 °C for 6 min. Most of the flavor descriptor
values were not significantly different between the oven, microwave, and combination
treatments.
36
Table 2.3. Sensory attribute values determined by a descriptive sensory panel for different peanut roasting treatments*.
Oven 163 Oven 177 Oven 204
°C for 20 °C for 10 °C for 7
min
min
min
37
Sensory Attribute
Roasted Peanut
5.00
6.00
6.00
Sweet
2.00
3.00
3.00
Dark Roast
3.67
2.67
3.33
Bitter
3.67
3.00
2.67
Raw Beany Green
0.67
2.00
1.67
Woody Hulls Skins
2.33
2.00
2.00
Sweet Aromatic
2.00
2.00
2.33
Astringent
3.33
3.00
3.33
Salty
0.67
0.67
0.67
Fruity Fermented Sour Over Ripe
0.00
0.00
0.00
Cardboard Oxidized
0.00
0.00
0.00
Painty Oxidized Oil
0.00
0.00
0.00
* Numbers are statistically significant if they are greater than ± 0.50
37
Microwave
2 min 30
sec
5.33
3.00
4.00
3.00
0.67
2.33
2.00
3.33
0.67
0.00
0.00
0.00
Microwave
2 min then
Oven 177
°C for 8
min
5.67
2.00
3.33
3.00
1.33
2.00
2.00
3.00
0.67
0.00
0.00
0.00
Microwave
1 min then
Oven 204
°C for 6
min
6.33
2.67
3.00
2.67
2.00
2.00
2.33
3.00
0.67
0.00
0.00
0.00
Oven 204
°C for 6
min then
Microwave
1 min
6.00
2.00
3.00
3.00
1.33
2.00
2.33
3.33
0.67
0.00
0.00
0.00
2.6 Conclusion
Oven, microwave, and combination technologies produced equivalent L* color
values and similar flavor quality based on the OAVs and sensory results. No significant
differences were found in free fatty acid or peroxide values between the raw and roasted
samples, which indicated that lipid oxidation was not affected by the roasting treatments
tested. Microwave technology can shorten the roasting time, which may decrease
processing costs, while still producing similar OAVs compared to the oven roasting and
commercial peanut butter samples. Microwave combination treatments can also produce
similar flavor quality based on OAVs and sensory results and could be considered as a
commercial processing option.
2.7 References
Abegaz EG, Kerr WL. 2006. Effect of Moisture, Sugar and Tertiary Butylhydroquinone
on Color, Texture and Microstructure of Peanut Paste. J Food Quality 29(6):643-657.
Agila A, Barringer S. 2012. Effect of Roasting Conditions on Color and Volatile Profile
Including HMF Level in Sweet Almonds (Prunus dulcis). J Food Sci 77(4):C461-C468.
AOCS. 1998a. AOCS Official Method Ab 5-49 Free Fatty Acids. In: Firestone D, editor.
Official Methods and Recommended Practices of the AOCS. 5th ed. Champaign, Illinois:
American Oil Chemists’ Society.
AOCS.1998b. AOCS Official Method Cd 8-53 Peroxide Value Acetic Acid-Chloroform
Method. In: Firestone D, editor. Official Methods and Recommended Practices of the
AOCS. 5thed. Champaign, Illinois: American Oil Chemists’ Society.
Arnold ST, Viggiano AA, Morris RA. 1998. Rate Constants and Product Branching
Fractions for the Reactions of H3O+ and NO+ with C2-C12 Alkanes. J Phys Chem
102(45):8881-8887.
Ba HV, Hwang I, Jeong D, Touseef A. 2012. Principle of Meat Aroma Flavors and
Future Prospect. In Akyar I, editor. Latest Research into Quality Control. Croatia:
InTech. p 145- 176.
38
Braddock JC, Sims CA, O’Keefe SF. 1995. Flavor and Oxidative Stability of Roasted
High Oleic Acid Peanuts. J Food Sci 60(3):489-493.
Brown DF, Senn VJ, Dollear FG, Goldblatt LA. 1973. Concentrations of Some Aliphatic
Aldehydes and Ketones Found in Raw and Roasted Spanish and Runner Peanuts. J Am
Oil Chem Soc 50(1):16-20.
Buckholz Jr. LL, Daun HK. 1981. Instrumental and Sensory Characteristics of Roasted
Peanut Flavor Volatiles. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected
Fruits and Vegetables of North America. Washington DC: American Chemical Society. p
163-181.
Buckholz Jr. LL, Daun H, Trout R. 1980. Influence of Roasting Time on Sensory
Attributes of Fresh Roasted Peanuts. J Food Sci 45(3): 547-554.
Coleman WM III, White JL Jr., Perfetti TA. 1994. Characteristics of Heat-Treated
Aqueous Extracts of Peanuts and Cashews. J Agric Food Chem 42(1):190-194.
Datta AK, Rakesh V. 2013. Principles of Microwave Combination Heating. Compr Rev
Food Sci F 12(1):24-39.
Decareau RV. 1985. Microwaves in the Food Processing Industry. Florida: Academic
Press, Inc, 9 p.
Diskin AM, Wang T, Smith D, Spanel P. 2002. A selected ion flow tube (SIFT), study of
the reactions of H3O+, NO+ and O2+ ions with a series of alkenes; in support of SIFT-MS.
Int J Mass Spectrom 218(1):87-101.
Elder J, The J.M. Smucker Company. 2013. Personal interview.
Hoffpauir CL. 1953. Peanut Composition Relation to Processing and Utilization. J Agri
Food Chem 1(10):668-671.
Johnsen PB, Civille GV, Vercellotti JR, Sanders TH, Dus CA. 1988. Development of a
Lexicon for the Description of Peanut Flavor. J Sens Stud 3(1):9-17.
Ku KL, Lee RS, Young CT, Chiou RYY. 1998. Roasted Peanut Flavor and Related
Compositional Characteristics of Peanut Kernels of Spring and Fall Crops Grown in
Taiwan. J Agric Food Chem. 46(8)3220-3224.
Matsui T, Guth H, Grosch W. 1998. A comparative study of potent odorants in peanut,
hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA)
and gas chromatography-olfactometry of headspace samples (GCOH). Eur J Lipid Sci.
Technol. 100(2):51-56.
39
McDaniel KA, White BL, Dean LL, Sanders TH, Davis JP. 2012. Compositional and
Mechanical Properties of Peanuts Roasted to Equivalent Colors using Different
Time/Temperature Combinations. J Food Sci 77(12):C1292-C1298.
Mexis SF, Kontominas MG. 2009. Effect of gamma irradiation on the physic-chemical
and sensory properties of raw shelled peanuts (Arachis hypogaea L.) and pistachio nuts
(Pistacia vera L.). J Sci Food Agri. 89(5):867-875.
Neta ER, Sanders T, Drake MA. 2010. Understanding Peanut Flavor: A Current Review.
In: Hui YH, editor. Handbook of Fruit and Vegetable Flavors. New Jersey: John Wiley &
Sons, Inc. p 985-1022.
Nursten H. 2005. The Maillard Reaction Chemistry, Biochemistry, and Implications.
Reading, UK: The Royal Society of Chemistry. 83 p.
Pattee HE, Giesbrecht FG, Young CT. 1991. Comparison of Peanut Butter Color
Determination by CIELAB L*a*b* and Hunter Color-Difference Methods and the
Relationships of Roasted Peanut Color to Roasted Peanut Flavor Response. J Agric Food
Chem 39(3):519-523.
Pattee HE, Singleton JA. 1981. Peanut Quality: Its Relationship to Volatile CompoundsA review. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected Fruits and
Vegetables of North America. Washington DC: American Chemical Society. p 147-161.
Ruth JH. 1986. Odor Thresholds and Irritation Levels of Several Chemical Substances: A
Review. Am Ind Hyg Assoc J 47(3):A142-A151.
Sanders TH. 2002. Groundnut (peanut) oil. In: Gunstone FD, editor. Vegetable Oils In
Food Technology: Composition, Properties and Uses. Florida: CRC Press LLC. p 231243.
Schirack AV, Drake M, Sanders TH, Sandeep KP. 2006a. Characterization of AromaActive Compounds in Microwave Blanched Peanuts. J Food Sci 71(9):C513-C520.
Schirack AV, Drake M, Sanders TH, Sandeep KP. 2006b. Impact of Microwave
Blanching on the Flavor of Roasted Peanuts. J Sens Stud 21(4):428-440.
Shu CK, Waller GR. 1971. Volatile Components of Roasted Peanuts: Comparative
Analysis of the Basic Fraction. J Food Sci 36(4):579-583.
Singleton JA, Pattee HE. 1991. Peanut Moisture/Size, Relation to Freeze Damage and
Effect of Drying Temperature on Volatiles. J Food Sci 56(2):579-581.
40
Smith D, Spanel P. 2005. Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) for online Trace Gas Analysis. Mass Spectrom Rev 24(5):661-700.
Smith D, Wang T, Spanel P. 2003. Analysis of ketones by selected ion flow tube mass
spectrometry. Rapid Commun Mass Sp 17(23):2655-2660.
Smyth DA, Macku C, Holloway OE, Deming DM, Slade L, Levine H. 1998. Evaluation
of Analytical Methods for Optimizing Peanut Roasting for Snack Foods. Pean Sci
25(2):70-76.
Sobolev VS. 2001. Vanillin Content in Boiled Peanuts. J Agric Food Chem 49(8):37253727.
Spanel P, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of alcohols. Int J Mass Spectrom 167/168:375-388.
Spanel P, Smith D. 1998. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of volatile carboxylic acids and esters. Int J Mass Spectrom 172(1):137-147.
Spanel P, Van Doren JM, Smith D. 2002. A selected ion flow tube study of the reactions
of H3O+, NO+, and O2+ with saturated and unsaturated aldehydes and subsequent
hydration of the products. Int J Mass Spectrom 213(2-3):163-176.
Spanel P, Yufeng J, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+
with a series of aldehydes and ketones. Int J Mass Spectrom 165/166:25-37.
Syft Technologies, Inc. 2011. Kinetics library database. Christchurch, New Zealand: Syft
Technologies Inc.
[USDA] United States Department of Agriculture, Economic Research Service. 2012.
USDA ERS – Food Availability (Per Capita) Data System. USDA. Available from:
http://www.ers.usda.gov/data-products/food-availability-(per-capita)-data-system.aspx.
Accessed Jan 30, 2013.
[USDA] United States Department of Agriculture, Farm Service Agency. 2006. Peanut
Reports. Washington, D.C.: USDA. Available from:
http://www.fsa.usda.gov/FSA/epasReports?area=home&subject=ecpa&topic=ftapn&summaryYear=2006&x=14&y=13. Accessed Jan 30, 2012.
[USDA] United States Department of Agriculture, Farm Service Agency. 2013a. Peanut
Reports. Washington, D.C.: USDA. Available from:
http://www.fsa.usda.gov/FSA/epasReports?area=home&subject=ecpa&topic=fta-pn .
Accessed Jan 30, 2012.
41
[USDA] United States Department of Agriculture, National Agricultural Statistics
Service. 2013b. Crop Production 2012 Summary. USDA. ISSN: 1057-7823. Available
from: USDA; 1, 95.
van Gemert LJ. 2011. Odour Thresholds. Compilations of odour threshold values in air,
water and other media. The Netherlands: Oliemans Punter & Partners BV. P 11-180.
Wang T, Spanel P, Smith D. 2003. Selected ion flow tub, SIFT, studies of the reactions of
H3O+, NO+ and O2+ with eleven C10H16 monoterpenes. Int J Mass Spectrom 228(1):117126.
Wang T, Spanel P, Smith D. 2004. A selected ion flow tube, SIFT, study of the reactions
of H3O+, NO+ and O2•+ ions with several N- and O-containing heterocyclic compounds in
support of SIFT-MS. Int J Mass Spectrom 237(2-3):167-174.
Warner KJH, Dimick PS, Ziegler GR, Mumma RO, Hollender R. 1996. ‘Flavor-fade’ and
Off-Flavors in Ground Roasted Peanuts As Related to Selected Pyrazines and Aldehydes.
J Food Sci 61(2):469-472.
Williams TL, Adams NG, Babcock LM. 1998. Selected ion flow tube studies of
H3O+(H2O)0,1 reactions with sulfides and thiols. Int J Mass Spectrom 172(1-2):149-159.
Young CT, Hovis AR. 1990. A Method for the Rapid Analysis of Headspace Volatiles of
Raw and Roasted Peanuts. J Food Sci 55(1):279-280.
Young CT, Young TG, Cherry JP. 1974. The Effect of Roasting Methods on the Flavor
and Composition of Peanut Butter. Proc Am Peanut Res Educ Assoc 6(1):8-16.
42
Chapter 3: Color and Volatile Analysis of Peanuts Roasted Using Oven
and Microwave Technologies
3.1 Abstract
Roasted peanut color and flavor was evaluated for different time and temperature
combinations of roasting. Raw peanuts were oven roasted at 135 °C, 163 °C, 177 °C, and
204 °C, microwave roasted for 1-3 min, or combination roasted by microwave and oven
roasting for various times and temperatures. Volatiles were measured using selected ion
flow tube mass spectrometry (SIFT-MS). L* values were used to categorize peanuts into
under roasted, ideally roasted, and over roasted. The total roasting time in order to
achieve ideal color was not shortened by most of the combination treatments compared to
their oven roasted equivalents. Oven before microwave roasting compared to the reverse
was found to significantly increase the L* value likely due to the increase in the dielectric
loss factor. Peanuts with ideal color had L* values that were not significantly different,
but the volatile levels were different. Hexanal concentrations in all peanuts decreased
then increased with roasting, but were below the level previously found to be
unacceptable to consumers. Ethanol to methanol ratios in roasted peanuts were all below
the level found in raw peanuts. Pyrazine levels increased as roasting time increased,
although oven at 177 °C treatments had the highest and microwave treatments had the
lowest levels. Volatile levels generally increased as roasting time or temperature
increased with raw peanuts having the lowest levels and over roasted peanuts having the
43
highest volatile levels. Oven 177 °C for 15 min generally had the highest level of
volatiles among the roasting treatments tested. Soft independent modeling of class
analogies based on volatile levels showed that raw peanuts were the most different,
commercial samples were the most similar to each other, and oven, microwave, and
combination roasting were all similar in volatile profile.
3.2 Practical Application
Peanuts can be roasted to equivalent colors and have similar volatile levels by
different roasting methods. Oven and microwave roasting technologies produced the
same roasted peanut color and had similar volatile trends as roasting time increased.
Combination roasting also produced ideal color and similar volatile levels indicating that
microwave technology may be used to roast peanuts on a commercial level.
3.3 Introduction
Peanuts are roasted to achieve desirable color and flavor characteristics in peanut
products, especially peanut butter. Similar quality can be achieved with different roasting
conditions and roasting technologies, so it is important to understand the quality
differences between roasting techniques. Roast color has a relationship with flavor
development and therefore color is used as a control parameter for commercially roasted
peanuts (Smyth and others 1998). The ideal CIELAB L* value for roasted peanuts ranges
from 58-59 ± 2 (Pattee and others 1991). In roasted peanuts, the Maillard reaction,
Strecker degradation, caramelization of sugars, and lipid oxidation are responsible for
volatile formation (Neta and others 2010).
44
Selected ion flow tube mass spectrometry (SIFT-MS) can identify and quantify
volatile organic compounds from whole-gas samples (Harper and others 2011). SIFT-MS
was used to measure Maillard reaction and lipid oxidation volatiles in almonds roasted
from oven, microwave, and oil roasting techniques and microwave roasting was found to
produce the highest volatile levels (Agila and Barringer 2012). Maillard reaction, sugar
degradation, and lipid oxidation volatiles were also measured during cashew roasting
using SIFT-MS and it was found that volatiles increased during roasting (Agila and
Barringer 2011). Raw almonds and cashews were found to have lower volatile levels than
roasted almonds or cashews (Agila and Barringer 2011, 2012). Cocoa volatiles including
alkylpyrazines and Strecker aldehydes were measured using SIFT-MS and found to
increase with increased roasting temperature from 120 to 170 °C (Huang and Barringer
2011).
As roasting time or temperature increases, the brown melanin color intensifies in
peanuts (Pattee and others 1991). Oven, microwave, and oil roasted almonds were able to
produce color equivalent to commercial almond samples (Agila and Barringer 2012).
Hexanal, ethanol, and methanol have been identified in raw peanuts (Pattee and others
1969, Brown and others 1972, Young and Hovis 1990) and negatively affect raw peanut
flavor (Brown and others 1977). Pyrazines, which are responsible for the roasted nutty
aroma of roasted peanuts (Mason and others 1966), increase as roasting time increases
(Buckholz and Daun 1981). Carbonyls provide a harsh green note found in roasted
peanuts (Buckholz and Daun 1981) and are produced by oxidation and Strecker
degradation (Buckholz and others 1980). Oven, microwave, or combination roasting
techniques could be used to produce similar color and volatile levels. The objectives of
45
this study were to determine the color and volatile differences of peanuts roasted with
oven, microwave, and combination roasting technologies. The effect that under, ideal,
and over roasted peanuts had on volatile levels was also determined.
3.4 Methods
3.4.1 Peanut Roasting
Raw peanuts (Medium Runner, Birdsong Peanuts, Sylvester, GA, U.S.A.) with
the shells removed were stored for less than 10 mo in sealed containers under
refrigeration conditions (4 °C) to minimize lipid oxidation. Raw peanut samples (60 ± 0.1
g) were roasted with the skins intact. Oven roasting was performed using a bench top
roaster oven (Nesco Jet-Steam Oven, American Harvest, Two Rivers, WI, U.S.A.). The
bottom pan in the roaster oven was fitted with a 30.48 cm by 5.08 cm round baking pan
(Wilton Industries, Woodridge IL, U.S.A.). Aluminum foil was fitted around the exterior
of the baking pan, which extended to the top of the roaster oven to prevent peanuts from
escaping. Oven roasting was performed with the fan speed on high to allow the peanuts to
freely circulate in the modified roaster. Microwave roasting was performed in an 1100 W
microwave oven (Panasonic, Matsushita Home Appliance Corporation of America,
Danville, KY, U.S.A.) on high power with the peanuts (60 ± 0.1 g) in a single layer in a
glass dish. Combination treatments were performed by first oven roasting or microwave
roasting and then peanuts were immediately transferred to the other respective roasting
treatment in less than 1 min. After roasting, the peanuts were cooled for 10 min at
ambient temperature in a single layer and skins were removed with gloved hands using a
stainless steel mesh colander to rub off the skins. Samples were ground in an electric
46
blender (Magic Bullet Express, Homeland Housewares, New York, NY, U.S.A.) with a
stainless steel cross blade and short cup for 30 sec.
Oven roasting was carried out at 135 °C, 163 °C, 177 °C, and 204 °C for 5-20
min. Microwave roasting was carried out from 1 to 3 min. Combination roasting
treatments included microwave roasting then oven roasting and oven roasting then
microwave roasting at 163-204 °C for 5-15 min and microwaving 1-2 min.
3.4.2 SIFT-MS
Ground peanut samples (50 ± 0.1 g) were placed into a 500 mL Pyrex bottle and
capped with open top caps fitted with polytetrafluoroethylene (PTFE)-faced silicone
septa. Bottled samples were stored under refrigeration conditions and were allowed to
equilibrate at ambient temperature for 2 h before being placed in the water bath. The
sample bottles were placed in a 50 ± 3 oC water bath (Precision Scientific, Jouan Inc.,
Winchester, VA, U.S.A.) for 60 min before the volatiles were measured. Five replicates
of every roasting treatment were analyzed.
Selected ion flow tube-mass spectrometry (SIFT-MS) (SYFT Voice 200, Syft
Technologies Ltd., Christchurch, New Zealand) was used to detect and quantify peanut
volatiles. A selected ion mode (SIM) method was developed using H3O+, NO+, or O2+ as
precursor ions; refer to Smith and Spanel (2005) for more information on SIFT-MS. The
method developed was based on known volatiles present in raw and roasted peanuts
(Matsui and others 1998; Young and Hovis 1990; Coleman and others 1994; Brown and
others 1973; Mexis and Kontominas 2009; Smyth and others 1998; Braddock and others
47
1995; Buckholz and Daun 1981; Singleton and Pattee 1991; Pattee and Singleton 1981;
Ku and others 1998; Shu and Waller 1971). Volatile kinetics are shown in Table 3.1.
Headspace of the Pyrex bottles was measured by piercing the septa with a
stainless steel passivated sampling needle (18 gauge x 1.9 cm length), which was
attached to the inlet of the SIFT-MS. A second stainless steel needle (14 gauge x 15 cm
length) also pierced the septa to maintain atmospheric pressure in the bottle. The
headspace of each bottle was scanned for 2 min. A blank water sample was the first
sample tested and was run after each peanut sample to ensure the needle was clear of
lingering volatiles. Roasting treatment replicates were analyzed in a random order to
account for variation in the roasting method. Validations were passed daily on the SIFTMS before volatiles were analyzed. The flow tube pressure during the SIFT-MS run was
0.088 ± 0.005 Torr.
Mixtures were reported for compounds that had mass conflicts. In this study, 2,3diethyl-5-methylpyrazine is a mixture of 4-vinylguaiacol and 2,3-diethyl-5methylpyrazine; 2-pentanone is a mixture of 3-methyl-2-butanone and 2-pentanone; 3methylbutanoic acid is a mixture of pentanoic acid and 3-methylbutanoic acid; butanal is
a mixture of acetaldehyde, butanal and pentanal; hexane is a mixture of 2-methylbutanal
and hexane; methyl methanoate is a mixture of acetic acid and methyl methanoate;
pentane is a mixture of tetrahydrofuran and pentane; 2,6 nonadienal is a mixture of (E,E)2,6-nonadienal and (E,Z)-2,6-nonadienal; hexenal is a mixture of (E)-2-hexenal and (Z)3-hexenal; dimethylpyrazine is a mixture of 2,3-dimethylpyrazine, 2,5-dimethylpyrazine,
48
and 2,6-dimethylpyrazine; terpenes are a mixture of R-limonene, alpha-pinene,
phenylacetic acid, and terpinolene.
Table 3.1. Kinetics of volatile compounds in peanuts for SIFT-MS analysis
Compound
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5methylpyrazine
dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methyl-3ethylpyrazine
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic
acid
Formula
Precursor
ion
Product ion
k (10-9
cm3/s)
m/z
Ref
C7H12O
C9H16O
C8H14O
C5H8O
C10H16O
C10H2O
C8H18O
C8H16O
C5H12O
C5H8O
C4H6O2
NO+
NO+
NO+
NO+
NO+
NO+
NO+
H3O+
NO+
NO+
NO+
C7H11O+
C9H15O+
C8H13O+
C5H7O+
C10H15O+
C10H20.NO+
C8H17O+
C8H15+
C5H11O+
C5H8O.NO+
C4H6O2+
3.9
3.8
4.1
4.0
4.2
2.1
2.3
3.1
2.5
2.5
1.3
111
139
125
83
151
170
129
111
87
114
86
5
5
5
5
5
2
C9H14N2
O2+
C9H14N2+
2.5
150
8
C6H8N2
C9H14O
C4H6O
C10H20O
C7H16O
C6H12O
NO+
NO+
NO+
NO+
NO+
NO+
C6N2H8+
C9H14O.NO+
C4H5O+
C10H20O.NO+
C7H15O+
NO+.C6H12O
2.8
2.5
4.1
2.5
2.4
3.6
108
168
69
186
115
130
8
8
5
8
10
4
C7H10N2
NO+
C7H10N2.NO+
2.5
152
8
C4H8O
C5H6N2
C9H18O
C8H16O
C5H10O
C11H22O
C5H10O
O2+
NO+
NO+
NO+
NO+
NO+
H3O+
C4H8O+
C5H6N2+
C9H18O.NO+
C8H16O.NO+
NO+.C5H10O
C11H22O.NO+
C5H6+
3.0
2.8
2.7
3.3
3.1
3.4
3.6
72
94
172
158
116
200
66
5
8
3
3
4
3
5
C5H10O2
NO+
C5H10O2.NO+
2.5
132
8
6
8
4
8
4
continued
49
Table 3.1. Continued
C6H6O2+
C4H8O2.NO+
NO+.C3H6O
NH3+
C7H5O+
C6H6+
C2H4O+
NO+.C4H8O
C10H19O+
C10H22+
(CH3)2S2+
(CH3)2S+
C2H6S3+
C2H5O+,
C2H5O+.H2O,
C2H5O+.2H2O
3.1
2.5
1.2
2.6
2.8
1.6
3.5
2.8
3.3
2.0
2.3
2.2
2.2
NO+
C7H14O2.NO+
C5H4O2
C7H8O2
C7H14O
C7H16
C6H12O
C6H14
C6H12O2
C6H10O
H2S
C4H8O2
NO+
NO+
NO+
H3O+
H3O+
O2+
NO+
NO+
O2+
O2+
CH4O
H3O+
C3H6O2
NO+
methyl mercaptan
CH4S
H3O+
methyl methanoate
nonanal
octanal
octane
pentane
C2H4O2
C9H18O
C8H16O
C8H18
C5H12
NO+
NO+
NO+
O2+
O2+
C5H4O2+
C7H8O2+
C7H13O+
H3O+.C7H16
C6H11+
C6H14+
C6H12O2.NO+
C6H9O+
H2S+
(CH3)2CHCOOH+
CH5O+,
CH3OH2+.H2O,
CH3OH.H+.(H2O)2
NO+.CH3COOCH3
CH4S.H+,
CH4S.H+.H2O
NO+.HCOOCH3
C9H17O+
C8H15O+
C8H18+
C3H6+
5-methylfurfural
acetoin
acetone
ammonia
benzaldehyde
benzene
butanal
butanone
decanal
decane
dimethyl disulfide
dimethyl sulfide
dimethyl trisulfide
ethanol
ethyl 2methylbutanoate
furfural
guaiacol
heptanal
heptane
hexanal
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
C6H6O2
C4H8O2
C3H6O
NH3
C7H6O
C6H6
C4H8O
C4H8O
C10H20O
C10H22
C2H6S2
C2H6S
C2H6S3
NO+
NO+
NO+
O2+
NO+
O2+
O2+
NO+
NO+
O2+
O2+
NO+
O2+
C2H6O
NO+
C7H14O2
110
118
88
17
105
78
44
102
155
142
94
62
126
45,
63,
81
10
8
4
7
4
7
4
4
5
7
7
7
10
2.4
160
8
3.2
2.5
3.3
2.6
3.7
1.7
2.5
3.8
1.4
2.5
96
124
113
119
83
86
146
97
34
88
33,
51,
69
104
49,
67
90
141
127
114
42
10
8
5
1
4
7
8
4
11
7
1.2
2.7
1.6
1.8
5.0
2.7
3.0
1.9
1.6
6
6
7
11
7
8
5
7
7
continued
50
Table 3.1. Continued
phenylacetaldehyde
propanal
propanoic acid
pyrazine
terpenes
toluene
trimethylpyrazine
vanillin
C8H8O
C3H6O
C3H6O2
C4H4N2
C10H16
C7H8
C7H10N2
C8H8O3
NO+
NO+
O2+
NO+
NO+
NO+
O2+
O2+
C8H8O+
C3H5O+
C2H5COOH+
C4H4N2+
C10H16+
C7H8+
C7H10N2+
C8H8O3+
2.5
2.5
2.2
2.8
2.2
1.7
2.5
2.8
120
57
74
80
136
92
122
152
8
4
7
8
8, 9
7
8
8
[1] Arnold and others 1998, [2] Diskin and others 2002, [3] Smith and others 2003, [4]
Spanel and others 1997, [5] Spanel and others 2002, [6] Spanel and Smith 1997, [7]
Spanel and Smith 1998, [8] Syft Technologies, Inc. 2011, [9] Wang and others 2003, [10]
Wang and others 2004, [11] Williams and others 1998
3.4.3 Color
Peanut samples were blended for 20 sec in an electric blender (Magic Bullet
Express, Homeland Housewares, New York, NY, U.S.A.) with a stainless steel cross
blade and short cup. The paste was pressed into the bottom of an Optilux Petri Dish (BD
Biosciences, San Jose, CA, U.S.A.). Each petri dish was completely filled before analysis
totaling 50 g or more of sample. Color measurements were performed at ambient
temperature using a Color Quest XE colorimeter (Hunter Associate Laboratory, Inc.,
Reston, VA, U.S.A.). A reflectance specular included method was used with illuminant
D65, 10° standard observer angle, and a 2.54 cm area view. The CIELAB L*a*b* values
were collected. Individual samples were measured in triplicate and roasting treatments
were analyzed in triplicate to obtain the averages.
51
3.4.4 Statistical Analysis
One-way analysis of variance (ANOVA) and Tukey’s post hoc test was
performed on the data using Minitab 16 (Minitab Inc., State College, PA, U.S.A.). For the
one-way ANOVA α = 0.05 and a Tukey’s family error rate of 5 was used.
Soft independent modeling of class analogies (SIMCA) was performed on the
volatile concentration data using Pirouette version 3.11 (Infometrix Inc., Bothell WA,
U.S.A.). Mean-center was selected for the processing, the probability threshold was 0.95,
the scope was local, and the maximum factor was three. A standard normal variate (SNV)
transformation was performed on the data in the statistical program before running the
SIMCA.
3.5 Results and Discussion
3.5.1 Color
Roasting peanuts promotes the formation of melanoidin pigments formed from
amino acids reacting with reducing sugars, which gives peanut butter its distinct color
(Abegaz and Kerr 2006). In commercial roasting, roast color is used as a primary control
parameter because of the relationship it has with flavor development (Smyth and others
1998). Hunter color-difference values are commonly used for quality assurance with
commercial peanut butter producers (Pattee and others 1991). CIELAB L* values of 5859 are the optimum values when the peanut sensory attribute ‘roasted peanut’ is the main
focus (Pattee and others 1991). When color was less than 2 units away from the ideal L*
value, it was difficult for an eight member trained roasted peanut flavor profile panel to
detect differences in roasted peanut intensity (Pattee and others 1991).
52
Ranges of time and temperature conditions were used to roast peanuts in oven and
microwave technologies. Nine roasting treatments fell within the desired L* range
(Figure 3.1). These treatments included three oven treatments, one microwave treatment,
and five combination treatments. Nine treatments were under roasted including raw, three
oven treatments, two microwave treatments, and three combination treatments. Five
treatments were over roasted including three oven treatments, one microwave treatment,
and one combination treatment. Raw peanuts and certain under, ideal, and over roasted
peanut treatments were selected to be evaluated for volatile levels.
53
80
70
ab abc
*
bcd
*
f
60
L* value
ab
a
*
hi hi
abc
*
gh
hi
de
*
ef
f
fg
50
abc
cd
*
f
f
* * *
ef ef ef
i
40
30
20
Oven 204 °C 6 min then MW 1 min
MW 1 min then Oven 204 °C 6 min
MW 2 min then Oven 204 °C 5 min
MW 1 min then Oven 204 °C 5 min
Oven 177 °C 8 min then MW 2 min
MW 2 min then Oven 177 °C 8 min
MW 2 min then Oven 177 °C 5 min
Roasting Treatments
MW 1 min then Oven 177 °C 5 min
MW 3 min
MW 2 min 30 sec
MW 2 min
MW 1 min
Oven 204 °C 10 min
Oven 204 °C 7 min
Oven 204 °C 5 min
Oven 177 °C 20 min
Oven 177 °C 15 min
Oven 177 °C 10 min
Oven 177 °C 5 min
Oven 163 °C 20 min
Oven 135 °C 20 min
Raw
0
MW 2 min then Oven 163 °C 15…
10
Figure 3.1. L* values of oven, microwave (MW), and combination roasting treatments,
ideal L* values range from 56-61
a-i
Samples with different letters are significantly different
* Samples with stars are within the ideal L* range
As roasting time or temperature increases, the brown melanin color also
intensifies (Pattee and others 1991). With increased roasting time, for a given treatment
type at the same temperature, L* values decreased (Figure 3.1). Lower L* values indicate
a darker roast color, while higher values indicate a lighter roast color. Similarly, the color
became darker with increased roasting temperature for the same roasting time.
54
Most combination treatments produced no statistically significant difference in
color compared to the oven roasting treatments with equivalent total roasting time (Figure
3.1). Microwave 2 min then oven at 177 °C for 8 min had a total roasting time of 10 min
and there was no significant difference in L* value compared to the oven at 177 °C for 10
min treatment. Similarly, microwave 1 min then oven at 204 °C for 6 min and its reverse
treatment had a total roasting time of 7 min with no significant difference in L* value
compared to the oven at 204 °C for 7 min treatment. In order to produce ideal color,
microwave roasting alone saved time compared to oven roasting; however, the
combination treatments tested did not shorten the total roasting time.
Reversing the order of combination treatments sometimes changed the L* value
(Figure 3.1). Microwave 2 min then oven at 177 °C for 8 min was significantly lighter in
color compared to its reverse treatment. In other words, oven before microwave had a
darker color than the reverse. This difference may be due to the effect of temperature on
the dielectric properties. Dielectric loss factor relates to the ability of a food to dissipate
electrical energy, so the higher the value the more energy a food absorbs (Fellows 2009).
With selected fruits and vegetables, as the temperature increases, the dielectric loss factor
first decreases, then above 34 °C increases as temperature increases up to 130 °C
(Sipahioglu and Barringer 2003). In ground almond shells, at a similar moisture content
to peanuts (6 %), the dielectric loss factor increased with increased temperature to at least
90 °C (Gao and others 2012). None of these studies perfectly matched the moisture
content of peanuts or the temperatures analyzed in this research (163 °C to 204 °C), but it
is hypothesized that dielectric loss factor values increase with increasing temperatures up
55
to 204 °C with low moisture content peanut samples. Oven roasting before microwave
roasting would increase the temperature of the peanuts before microwaving. The
increased temperature before microwaving would increase the dielectric loss factor of the
peanuts and provide more electrical energy dissipation in the same time period resulting
in a darker roast color. This theory may explain why the oven before microwave
treatment had a darker color than the reverse treatment. It is expected that oven roasting
before microwave roasting would be more efficient than the reverse.
3.5.2 Volatile Levels in Raw Peanuts
Raw and under roasted peanuts (L* value > 61) had L* values that were not
significantly different; however, the volatile levels were significantly different for many
volatiles (Figure 3.1 and Table 3.2). The volatile levels of the roasting treatments are
ordered based on L* value from highest to lowest in Tables 3.2, 3.3, and 3.4. Compared
to other methods, measuring the brown color is not sensitive in evaluating the degree of
the Maillard reaction (O’Brien and others 1989). Volatile levels created by the Maillard
browning reaction were more sensitive to roasting treatments than the L* values.
Hexanal is a main contributor to the aroma of raw peanuts (Pattee and others
1969; Brown and others 1972) and is connected with off-flavor in peanut butter (Brown
and others 1977). Hexanal is associated with alcohol dehydrogenase and lipoxygenase
activity during peanut maturation (Pattee and others 1970). Levels were the highest in the
raw and the most under roasted sample and concentrations decreased when the peanuts
were roasted to ideal color (Tables 3.2, 3.3, and 3.4). Aldehydes, such as hexanal, are
formed during storage from lipid oxidation (Bett and Boylston 1992; Reed and others
56
2002) and levels in roasted peanuts have been shown to increase during storage (Bett and
Boylston 1992; Grosso and Resurreccion 2002; Warner and others 1996). From ideally
roasted to over roasted peanuts, the hexanal levels increased, likely due to lipid oxidation,
since hexanal is a secondary oxidation product of linoleic acid (Frankel 1985). In roasted
peanuts, a hexanal content higher than 7.40 µg/g (7400 ppb) was found to be
unacceptable to consumers based on overall acceptance scores (Grosso and Resurreccion
2002). All peanut samples had hexanal levels well below the concentration found in
previous research to be unacceptable by consumers.
Ethanol and methanol are present in raw peanuts (Pattee and others 1969; Young
and Hovis 1990) and have been shown to negatively affect raw peanut flavor (Brown and
others 1977). Ethanol and methanol are related to alcohol dehydrogenase and
lipoxygenase activity during peanut maturation (Patte and others 1970). Ethanol is at the
highest levels in raw peanut samples and was determined to be the most important
volatile component for raw peanut flavor (Brown and others 1977). Cler scores, which
indicated better flavor, increased as ethanol levels decreased in raw peanut samples
(Brown and others 1977). As roasting time increased, there was no evident trend with
ethanol or methanol levels (Tables 3.2, 3.3, and 3.4).
A decrease in ethanol to methanol ratios was correlated with an increase in flavor
scores of raw peanut samples (Brown and others 1977). Raw peanuts had the highest
ethanol to methanol ratio (1.13) (Table 3.2). Ethanol to methanol ratios of roasted peanut
samples (0.06 – 0.26) were all lower than raw peanuts. There was no distinct trend with
the ratios as roasting time increased.
57
Table 3.2. Volatile levels (ppb) of raw and under roasted peanuts
Oven 177
Microwave
°C for 5
2 min
min
6.84efg
6.81fg
f
1.47
1.43f
3.21fg
3.72efg
5.83d
6.67d
1.47bcde
0.92ef
8.09c
8.86bc
10.89de
12.06de
10.51e
9.44e
74.66cd
68.44d
ef
9.56
11.52def
205.82fg
362.40def
1.79ef
1.53ef
9.81g
33.43fg
2.20f
2.85ef
9.73hi
13.04gh
3.81a
4.50a
6.90e
8.36de
def
23.95
20.15ef
2.88f
3.61f
280.95g
525.03efg
6.84de
19.07de
4.73b
5.02b
5.41f
6.38def
28.71ef
30.28e
2.00ab
2.27ab
a
164.59
31.03fg
36.99def
21.29fg
2.42d
3.62d
40.87fg
38.77g
975.56d
938.15d
769.23hi
674.08i
61.13b
53.72bc
32.14cd
28.69d
ef
256.48
362.44de
Raw
Volatile
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5-methylpyrazine
2,5-dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methyl-3-ethylpyrazine
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic acid
5-methylfurfural
acetoin
acetone
ammonia
benzaldehyde
benzene
butanal
3.63g
1.21f
1.80g
4.09d
0.46f
10.66abc
10.54de
8.46e
20.22e
5.32f
15.45g
0.89f
1.24g
2.37ef
1.95i
5.19a
5.26e
8.34g
1.32f
43.94g
1.00e
6.02ab
7.12bcdef
6.94f
2.56ab
95.97c
13.22g
1.39d
12.36h
34.18e
82.95j
21.88d
13.20e
28.57f
58
Oven 204
°C for 5
min
6.17fg
1.44f
3.61fg
5.58d
1.19def
8.05c
10.23e
9.70e
66.85d
10.01def
335.13efg
1.80ef
28.10fg
2.75ef
12.43gh
4.00a
8.03de
23.13def
4.11f
467.84fg
14.16de
5.21b
6.55cdef
29.73e
2.02ab
79.21cd
28.65efg
2.84d
45.11efg
788.10d
829.56ghi
50.07bc
23.97de
350.11de
continued
Table 3.2. Continued
butanone
7.24h
30.96gh
52.00efgh
39.99fgh
decanal
1.30g
1.68fg
1.94efg
1.66fg
decane
10.82de
9.02e
10.74de
9.31e
d
d
d
dimethyl disulfide
2.90
16.77
37.32
28.41d
dimethyl sulfide
35.25g
302.48a
168.74cdef
196.18bcd
dimethyl trisulfide
11.88f
15.98def
14.67ef
17.43def
ethanol
2254.34c
3199.10b
954.33gh
1920.98cd
ethyl 2-methylbutanoate
16.44e
20.20de
17.60e
19.50de
furfural
2.46e
6.78e
6.78e
7.37e
guaiacol
4.49e
4.16e
9.09e
6.27e
heptanal
5.43f
10.52de
10.10de
10.17de
g
efg
fg
heptane
57.92
951.01
930.60
1137.78efg
hexanal
326.31ab
406.45a
149.83efg 187.67cdefg
hexane
73.14e
256.20e
364.21de
359.67de
hexanoic acid
9.24g
20.90bcd
9.54g
16.13cdefg
hexenal
1.29f
2.80ef
3.95def
2.99ef
hydrogen sulfide
803.71i
956.96hi
1091.00ghi
1052.74ghi
isobutanoic acid
25.28f
76.58ef
69.75ef
81.11ef
methanol
2003.26g 14523.52bc
7939.86f 10935.45de
g
fg
methyl acetate
15.95
241.46
243.31fg
296.94fg
methyl mercaptan
15.73j
978.14ij
1040.22ij
1462.23hi
methyl methanoate
124.39e
315.08d
239.94de
243.16de
nonanal
5.30g
6.14fg
6.47efg
6.55efg
octanal
9.97def
9.91def
10.95cdef
9.94def
octane
29.90f
38.72ef
41.66def
38.82ef
pentane
334.09f
984.02bcd
637.90e
898.20cd
phenylacetaldehyde
23.51e
56.25d
54.73d
67.54cd
h
h
gh
propanal
8.70
144.02
278.77
254.22gh
propanoic acid
10.40g
48.53fg
61.91fg
68.82fg
pyrazine
0.27e
2.74de
2.58de
2.60de
terpenes
3.67f
4.92f
5.17f
4.64f
toluene
22.78cdef
25.09bcde
20.69def
20.42def
trimethylpyrazine
1.93i
5.40hi
11.54fghi
9.66ghi
vanillin
1.09c
1.91c
1.64c
1.84c
a-j
Samples with different letters for the same volatile in Tables 3.2, 3.3, and 3.4 are
significantly different. Statistical analysis was performed comparing all roasting
treatments in Tables 3.2, 3.3 and 3.4.
59
Table 3.3. Volatile levels (ppb) of ideally roasted peanuts
60
Volatile
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5methylpyrazine
2,5-dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
Oven 204
°C for 6 min
Microwave
1 min
Microwave
2 min 30
sec
Microwave
1 min Oven
204 °C for
6 min
Microwave
2 min Oven
177 °C for
8 min
7.92fg
1.71ef
4.11efg
8.37d
1.04def
8.66bc
12.42de
11.13e
69.50d
13.67def
649.61cde
9.55ef
2.00def
5.31def
12.02d
1.32cde
8.74bc
12.03de
12.17de
81.73cd
17.99de
664.94cde
8.06fg
1.83def
4.28efg
9.43d
1.05def
7.50c
12.67de
10.23e
76.71cd
14.19def
683.54cd
11.28def
2.12cdef
5.47def
12.49cd
1.24cdef
9.55abc
16.55de
14.77cde
80.52cd
20.17cde
719.89c
8.64fg
1.94def
4.73defg
9.94d
1.12def
7.42c
12.19de
11.40e
87.20bcd
15.68def
677.44cd
11.94cdef
2.82bcde
7.10cde
12.51cd
1.64bcde
10.23abc
20.92bcd
15.44cde
107.47bc
20.78cd
936.05bc
16.98bcd
3.82b
9.00bc
20.98bc
2.19b
9.66abc
28.41bc
21.62bcd
161.99a
30.19bc
1195.49ab
2.43def
2.57def
2.91def
3.60cde
2.94def
4.77bcd
6.89b
77.48ef
2.89ef
17.41fgh
4.22a
12.66cde
19.67f
83.75def
3.28def
17.66fgh
4.55a
13.67cde
24.59cdef
88.13def
2.92ef
19.02efg
3.97a
13.20cde
21.21def
107.26de
4.17bcdef
19.78defg
4.87a
15.43cde
24.03def
80.18ef
3.31def
19.89defg
4.11a
13.45cde
26.03cdef
134.88cde
4.29bcde
27.03bcde
4.49a
21.28bcd
29.69bcd
201.90b
5.75bc
34.41ab
4.21a
31.97b
36.39b
continued
60
Oven 163
°C for 20
min
Oven 204
°C for 7
min
Oven 177
°C for 10
min
61
Table 3.3. Continued
2-methyl-3-ethylpyrazine
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic acid
5-methylfurfural
acetoin
acetone
ammonia
benzaldehyde
benzene
butanal
butanone
decanal
decane
dimethyl disulfide
dimethyl sulfide
dimethyl trisulfide
ethanol
ethyl 2-methylbutanoate
5.45ef
1244.67def
41.84de
5.40b
6.52cdef
35.37de
2.16ab
21.54fg
31.98def
4.85d
61.56cdef
848.87d
1044.14efgh
40.79c
24.67de
642.70c
78.29efgh
1.92efg
11.75de
82.68d
137.84f
17.83def
832.59h
19.69de
8.20def
1146.04def
60.10cde
5.65b
6.57cdef
44.42cde
2.55ab
18.67g
34.21def
9.65cd
52.73defg
1355.17cd
951.47fghi
50.83bc
32.29cd
604.55cd
100.89efg
2.26efg
12.23de
120.82cd
140.17f
17.89def
964.31gh
21.88cde
7.74ef
1347.80d
46.04de
5.32b
6.22def
38.04cde
2.09ab
19.25g
33.49def
5.27d
60.49cdef
981.61d
1144.61efg
41.81c
25.42de
640.76c
84.32efg
2.00efg
11.47de
90.83d
141.04ef
17.27def
814.34h
18.17de
61
12.30cdef
1589.24cd
64.88cd
5.19b
7.52bcdef
43.87cde
2.17ab
26.05fg
40.73cde
7.32d
65.65cde
1240.28cd
1478.37bcd
48.42bc
30.95cd
637.36c
110.72def
2.63def
16.57bcde
130.65cd
168.68cdef
21.21cdef
1016.48fgh
20.79de
8.00def
1376.33d
51.22de
4.80b
5.67ef
42.91cde
1.78b
58.40de
40.26cde
5.23d
68.95cd
1032.49d
1350.64cde
56.15bc
27.79de
701.44c
96.99efg
2.07efg
9.76e
101.30d
239.37b
19.71def
964.61gh
22.44bcde
12.41cdef
1818.06bcd
69.63cd
6.14ab
7.85bcde
53.59bcd
2.45ab
41.68ef
56.82bc
8.00d
93.75b
1250.20cd
1474.23bcd
57.66bc
33.19cd
867.53bc
119.14cde
3.12bcde
15.45cde
136.94cd
184.03cdef
26.38cd
1491.64def
26.59bcd
24.10bcd
2306.87bc
118.08bc
5.63b
8.23bcd
76.03b
2.16ab
129.16b
99.43a
12.19cd
122.58a
1843.65bc
1808.60a
88.08a
52.32ab
1048.97ab
182.24bcd
4.12bc
20.32bcd
243.05bc
239.96b
32.55bc
4266.36a
41.03a
continued
62
Table 3.3. Continued
furfural
guaiacol
heptanal
heptane
hexanal
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
methyl mercaptan
methyl methanoate
nonanal
octanal
octane
pentane
phenylacetaldehyde
propanal
propanoic acid
pyrazine
terpenes
toluene
8.89de
13.15e
8.96ef
2005.57def
104.69g
627.84cd
11.43efg
5.40def
1416.64efg
125.21def
10451.99def
453.27ef
2427.94fgh
248.09de
6.59efg
9.30ef
44.64cdef
848.81de
64.35cd
519.19fg
168.46defg
4.09cde
13.61de
17.27f
11.84cde
20.43de
11.28cde
1528.96efg
141.56fg
702.76cd
13.96cdefg
7.16cde
1604.61def
121.94def
8238.48ef
449.64ef
2183.31ghi
235.61de
7.08defg
7.95f
44.18cdef
1172.65ab
68.53bcd
528.95efg
146.60efg
5.18cde
9.31ef
23.01cdef
9.29de
14.55e
9.31ef
1943.27def
108.37g
655.97cd
11.04fg
6.03def
1661.62cdef
136.92def
9951.82def
513.09def
2892.27efg
223.45de
6.76efg
7.86f
41.25ef
879.70cde
64.84cd
606.66def
199.10def
4.77cde
8.38ef
19.42def
62
11.67cde
20.75cde
11.41cde
2687.31cde
124.01g
685.11cd
13.10defg
8.75cd
1628.32def
157.15de
12516.11cd
805.84de
3403.07defg
263.95de
8.23cdef
11.86bcdef
53.33cdef
844.41de
54.61d
612.79def
315.46cd
5.58cde
12.99de
18.92ef
11.61cde
14.01e
11.83bcde
3544.30bcd
155.37efg
670.79cd
11.47efg
6.38def
1254.53fgh
163.08de
16667.74b
815.13de
3635.91cdef
339.21cd
8.00defg
8.93ef
45.53cdef
1203.19ab
63.35cd
615.08def
297.86cde
5.73cd
8.30ef
21.04def
13.52cde
22.63cde
12.67bcde
3295.45bcd
139.35fg
900.76bc
18.97bcdef
8.88cd
1883.34cd
218.58cd
12526.33cd
701.99de
3732.09bcde
329.02cd
9.21bcde
12.96bcde
53.45cdef
1020.16bcd
89.73a
891.64cd
265.55de
6.71cd
14.19cde
24.02cdef
21.21bcd
37.02bcd
15.73ab
6945.89a
239.76bcde
1191.23ab
43.62a
14.74b
1819.09cde
379.80ab
16531.80b
1219.30bc
4500.73bcd
471.69bc
11.90b
14.08abcd
66.61abcd
1107.97bc
87.40ab
1280.35ab
458.38bc
8.67bc
22.68b
31.37ab
continued
Table 3.3. Continued
trimethylpyrazine
23.89efgh
26.93defg
27.76defg
32.63def
24.84defgh
43.53cde
63.39bc
vanillin
2.03c
2.69c
2.73c
4.27bc
2.59c
4.80bc
9.86b
a-i
Samples with different letters for the same volatile in Tables 3.2, 3.3, and 3.4 are significantly different. Statistical analysis was
performed comparing all roasting treatments in Tables 3.2, 3.3 and 3.4.
63
63
Table 3.4. Volatile levels (ppb) of over roasted peanuts
Volatile
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5-methylpyrazine
2,5-dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methyl-3-ethylpyrazine
2-methylpropanal
2-methylpyrazine
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic acid
5-methylfurfural
acetoin
acetone
Microwave
3 min
Oven 177
°C for 15
min
14.74bcde
2.93bcd
8.03bcd
22.61b
1.78bcd
9.53abc
17.93cde
23.27bc
87.12bcd
29.55bc
880.83bc
4.57bcd
147.10bcd
3.92cdef
23.14cdef
4.10a
22.89bc
25.08cdef
21.12bcde
1610.42cd
153.76ab
4.99b
6.29def
60.55bc
2.14ab
17.14g
47.06cd
30.83ab
60.00cdef
2413.23ab
24.95a
5.40a
13.31a
34.00a
3.33a
12.79a
40.96a
33.19a
169.19a
48.73a
1454.24a
10.03a
309.08a
7.96a
40.88a
5.54a
51.41a
47.50a
52.67a
3248.94a
215.55a
7.77a
10.97a
107.82a
3.03a
87.61c
107.14a
22.76bc
118.81a
2710.00a
64
Oven 204
°C for 10
min
17.40bc
3.42b
9.20bc
21.91b
2.01bc
9.64abc
28.72b
21.71bcd
116.79b
32.70b
1165.97ab
6.71b
207.76b
5.92b
31.24bc
5.11a
32.61b
33.54bc
26.55bc
2487.97bc
134.48b
6.29ab
8.91abc
74.19b
2.50ab
38.45efg
69.27b
14.11cd
93.18b
1858.37bc
Oven 177
°C for 8
min
Microwave
2 min
17.89b
3.17bc
10.66ab
25.15b
2.22b
11.44ab
28.36bc
31.16ab
97.13bcd
37.45b
1155.85ab
6.13bc
182.74bc
5.26bcd
28.26bcd
5.40a
34.81b
29.34bcde
29.08b
2222.80bc
213.49a
6.39ab
9.47ab
75.80b
2.63ab
30.24fg
66.47b
38.08a
79.29bc
2548.04a
continued
Table 3.4. Continued
ammonia
benzaldehyde
benzene
butanal
butanone
decanal
decane
dimethyl disulfide
dimethyl sulfide
dimethyl trisulfide
ethanol
ethyl 2-methylbutanoate
furfural
guaiacol
heptanal
heptane
hexanal
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
methyl mercaptan
methyl methanoate
nonanal
octanal
octane
pentane
phenylacetaldehyde
propanal
propanoic acid
pyrazine
terpenes
toluene
1273.36def
49.68bc
49.88ab
805.32bc
188.01bc
2.85cdef
16.39bcde
322.34ab
155.32def
24.33cde
1494.93def
22.73bcde
27.61ab
50.06ab
11.38cde
2188.25def
228.29cdef
906.30bc
19.36bcde
12.20bc
2360.51ab
209.07cd
9924.67def
896.35cd
3922.45bcde
339.88cd
7.89defg
11.00cdef
59.94bcde
946.44bcd
63.74cd
831.46cde
323.59cd
14.08a
14.21cde
29.57bc
65
1787.54ab
102.56a
56.83ab
1251.04a
277.93a
6.74a
33.27a
458.13a
299.71a
53.66a
2970.57b
48.46a
37.35a
70.65a
19.76a
8668.87a
282.85bc
1521.33a
39.10a
22.77a
1938.89bcd
489.98a
20922.75a
2176.47a
6073.56a
740.08a
14.71a
17.87a
89.29a
1368.71a
89.27a
1498.95a
878.06a
12.45ab
30.89a
37.59a
1623.45abc
66.54b
44.05bc
1015.53ab
189.39bc
4.18b
22.13bc
278.41b
210.12bc
31.74bc
1394.66efg
30.31bc
23.18bc
42.42bc
14.91bc
4689.33b
182.06defg
1156.82b
21.41bc
15.41b
2088.81abc
316.97bc
15175.35bc
1241.17bc
4790.00bc
474.72bc
10.93bc
14.70abc
67.71abc
1072.99bcd
76.93abc
1129.90bc
500.03b
8.69bc
19.17bcd
26.10bcd
1474.03bcd
61.27b
59.97a
1072.36ab
240.98ab
3.65bcd
25.53ab
455.19a
193.63bcde
38.15b
1574.81de
30.57b
38.42a
69.77a
13.70bcd
4410.31bc
263.14bcd
1240.83ab
25.32b
15.72b
2405.11a
323.83bc
14093.60bc
1377.66b
4973.78ab
560.36b
9.74bcd
16.17ab
84.82ab
1181.44ab
63.51cd
961.23c
523.95b
17.09a
20.70bc
29.19bc
continued
Table 3.4. Continued
trimethylpyrazine
46.27bcd
101.25a
65.82b
57.37bc
vanillin
6.72bc
20.14a
9.70b
10.02b
a-g
Samples with different letters for the same volatile in Tables 3.2, 3.3, and 3.4 are
significantly different. Statistical analysis was performed comparing all roasting
treatments in Tables 3.2, 3.3 and 3.4.
3.5.3 Volatile Levels in Ideally and Over Roasted Peanuts
Ideally roasted peanuts had L* values that were not significantly different and
within the desired range (58-59 ± 2); however, the volatile levels were significantly
different for almost all of the volatiles (Table 3.3). Only 1-decene, 2-decanone, 2nonanone, 2-undecanone, and 5-methylfurfural did not have significantly different levels
within the ideally roasted samples. Comparing raw peanuts and all roasting treatments, as
roasting time increased, the volatile levels generally increased. The general trend was that
raw peanuts had the lowest level of all volatiles followed by the under roasted peanuts,
ideally roasted peanuts, and over roasted peanuts had the highest level of volatiles.
Pyrazines are responsible for the roasted nutty aroma of roasted peanuts (Mason
and others 1966). Pyrazines including 2,3-diethyl-5-methylpyrazine, dimethylpyrazine, 2methyl-3-ethylpyrazine, pyrazine, and trimethylpyrazine increased as roasting time
increased for a given temperature (Figure 3.2). As roasting time increases, pyrazine levels
have been shown to increase (Buckholz and Daun 1981, Leunissen and others 1996).
Although pyrazines followed the same trend as roasting time increased for the treatments
oven at 177 °C, oven at 204 °C and microwave roasting, the pyrazine levels were not
equivalent for each roasting treatment. Generally, oven at 177 °C treatments had the
66
highest levels of pyrazines and microwave treatments had the lowest levels of pyrazines
(Figure 3.2). Although pyrazines are associated with roasted flavor, as pyrazine levels
increase the bitter flavors also increase (Leunissen and others 1996, Vercellotti and others
1992). Oven at 177 °C treatments generally had the highest levels of pyrazines, although
the higher levels may not be desirable for flavor.
Carbonyls are associated with the harsh green notes found in roasted peanuts
(Buckholz and Daun 1981). Strecker degradation is also a source of carbonyl formation
including acetaldehyde, 2-methylbutanal, 3-methylbutanal, and phenylacetaldehyde
(Mason and others 1967). The amino acids that form these compounds have been found
in raw peanuts and are destroyed during roasting (Mason and others 1969) due to the
conversion into carbonyls. Roasted peanuts were found to contain greater carbonyl
concentrations compared to raw peanuts, likely due to lipid oxidation at higher roasting
temperatures with the Maillard reaction and Strecker degradation being secondary causes
of the carbonyl increase (Brown and others 1972). More than 30 carbonyls were analyzed
with SIFT-MS in this research. Generally, the carbonyl levels increased with increased
roasting time (Tables 3.2, 3.3, and 3.4), which supported previous research.
Previous literature has reported ideal temperatures and roasting conditions needed
to achieve ideal roasted peanut flavor. Temperatures above 150 °C are used for roasting
peanuts in order to produce roasted peanut flavors and start chemical reactions (Davidson
and others 1999). In this study, roasting temperatures ranged from 135 °C to 204 °C. The
treatment roasted at 135 °C did not produce ideal color even after 20 min of roasting,
while the treatments above 150 °C were able to produce ideal color in 7-20 min. In one
67
study, certain peanut genotypes were roasted at 175 °C for 15 min and gave the highest
levels of pyrazines (except for 2-methoxy-3-methylpyrazine) and highest sensory scores
for roasted peanut flavor and aroma compared to other roasting temperatures (Baker and
others 2003). However, in this study peanuts roasted at 177 °C for 15 min were
considered over roasted in color, although the roasting treatment produced the highest
levels of pyrazines (Figure 3.2). Variables such as peanut size, temperature fluctuations
among roasters (Davidson and others 1999), peanut roasting sample size, and peanut
variety differences make it difficult to determine the ideal roasting conditions to achieve
the best roasted peanut volatile levels. While pyrazines are generally associated with
positive flavors produced from the Maillard reaction, lipid oxidation products are not
desirable. Therefore, higher volatile concentrations are not always an indication of better
roasted peanut flavor.
Over roasted peanuts had L* values < 56. Oven at 177 °C for 15 min generally
produced the highest levels of volatiles among all of the roasting treatments (Tables 3.2,
3.3, and 3.4). Lipid oxidation and Maillard reaction volatiles were generally higher in the
over roasted treatments compared to the under and ideally roasted samples.
3-Methylbutanal did not peak in the over roasted peanuts and generally decreased
as roasting time increased for the oven roasting treatments (Tables 3.2, 3.3, and 3.4). 3Methylbutanal is formed during Strecker degradation (Mason and others 1967) from the
amino acid leucine (Brown and others 1972). At low moisture contents, the amount of
free leucine in peanuts decreased as roasting time increased (Chiou and others 1991). In a
model system, 3-methylbutanal formation increased as temperature increased (Arnoldi
68
and others 1987). Strecker aldehydes, such as 3-methylbutanal, are not end products and
can react to form other compounds (Balagiannis and others 2009) therefore, it was
expected that 3-methylbutanal levels would decrease with increased roasting time. This
trend was observed with the oven roasted treatments although this volatile was not
significantly different between any of the microwave or combination treatments.
69
Raw
Oven 177 °C for 5 min
Oven 177 °C for 10 min
Oven 177 °C for 15 min
a
300
a
250
b
200
b
150
100
50
0
a
a
c c b a
c c
c c
b
b
a
d c b
c c
300
a
200
a
b
150
100
50
0
c c
Raw
Oven 204 °C for 5 min
Oven 204 °C for 7 min
Oven 204 °C for 10 min
250
a
b
b b a a
c
c
b
c bc
a
b
c c
b b a a
350
250
a
200
c c
Raw
Microwave 2 min
Microwave 2 min 30 sec
Microwave 3 min
300
a
150
b
c
a
b b b
c
bc
2-methylpyrazine
d
2-methyl-3-ethylpyrazine
0
c c b a
dimethylpyrazine
50
b
c
a
bc b
d c
b
a
trimethylpyrazine
100
2,3-diethyl-5-methylpyrazine
Volatile concentration (ppb)
Volatile concentration (ppb)
350
pyrazine
Volatile concentration (ppb)
350
Volatile
Figure 3.2. Volatile levels of pyrazines as roasting time increases for Oven at
177 °C, Oven at 204 °C, and Microwave roasting treatments
a-d
Different letters for a single volatile within a graph are significantly different.
70
3.5.4 Soft Independent Modeling of Class Analogy
Interclass distances are based on factor loadings and show the distance between
samples (Grasso and others 2009). Smaller interclass distances show more similarity
between volatile concentrations of roasting treatments, whereas larger interclass distances
indicate more differences between volatile concentrations. Soft independent modeling of
class analogies (SIMCA) using interclass distances and based on volatile concentrations
showed that some samples had a similar volatile profile (Table 3.5). Commercial sample
volatile results were obtained from Chapter 2 in the thesis. Raw peanuts were the most
different from all of the roasted samples having interclass distances 53 or greater
compared to roasted peanuts, so the data was removed in order to see differences between
the remaining samples. The commercial samples had a volatile profile more similar to
each other than to any of the roasted samples tested in this study. The greatest numbers of
high interclass distances were between the roasted and commercial samples. This was
likely due to the commercial samples having additional ingredients and longer storage
time compared to the freshly roasted peanuts in this study. Oven 177 °C for 15 min,
microwave 2 min 30 sec, and microwave 3 min treatments were the most similar to the
commercial samples. Two of those treatments were over roasted in color and the oven
177 °C for 15 min treatment generally had the highest volatile levels.
Oven 177 °C for 5 min had a large number of high interclass distances, which
indicated that this sample was also very different from the other roasted samples (Table
3.5). This treatment was the lightest color and thus was the most under roasted of the
treatments tested. The smallest interclass distance was between two microwave roasted
treatments, indicating those treatments produced the most similar volatile profile. Many
71
of the interclass distances were less than 11, indicating oven, microwave, and
combination treatments had similarities between the volatile profiles.
72
Table 3.5. Soft independent modeling of class analogy (SIMCA) interclass distances comparing oven, microwave (MW), and
combination roasting treatment volatile concentrations (ppb)
Oven
177 °C
for 5
min
MW 2
min
Oven
204 °C
for 5
min
Roasting Treatment
MW 2 min
Oven 204 °C for 5
min
Oven 204 °C for 6
min MW 1 min
Oven
204 °C
for 6
min
MW 1
min
MW 2
min 30
sec
MW 1
min
Oven
204 °C
for 6
min
MW 2
min
Oven
177 °C
for 8
min
Oven
163 °C
for 20
min
Oven
204 °C
for 7
min
Oven
177 °C
for 10
min
Commercial
#1
Commercial
#2
MW 3
min
Oven
177 °C
for 15
min
47
10
21
37
16
19
22
11
14
9
28
16
15
4
8
33
17
18
6
11
8
63
37
28
13
16
11
14
42
24
19
10
11
8
8
21
34
37
31
37
19
26
23
45
29
Commercial #1
41
33
31
38
24
37
39
56
52
60
Commercial #2
37
31
29
36
24
37
36
49
49
54
9
MW 3 min
22
15
15
10
3
8
11
15
8
13
25
26
16
11
15
12
11
10
6
10
7
7
25
25
10
24
13
16
8
10
5
4
9
5
14
32
32
9
4
37
22
25
11
9
10
7
17
8
16
40
40
6
5
MW 2 min 30 sec
73
MW 1 min Oven
204 °C for 6 min
MW 2 min Oven
177 °C for 8 min
Oven 163 °C for 20
min
Oven 204 °C for 7
min
Oven 177 °C for 10
min
Oven 177 °C for 15
min
Oven 204 °C for 10
min
Oven 177 °C for 8
min MW 2 min
Oven
204 °C
for 10
min
73
5
3.6 Conclusions
Peanuts were oven, microwave, or combination roasted to produce color that was
not significantly different between the roasting methods within each peanut color
classification of under, ideal, or over roasted. Most combination treatments did not
shorten the roasting time compared to the oven roasted time equivalents. The dielectric
loss factor likely played a role in producing darker color for oven before microwave
roasting compared to microwave before oven roasting. As roasting time increased,
pyrazine levels increased as well as most of the Maillard reaction and lipid oxidation
products. Soft independent modeling of class analogies showed that oven and microwave
roasting technologies could produce similar volatile profiles.
3.7 References
Abegaz EG, Kerr WL. 2006. Effect of Moisture, Sugar and Tertiary Butylhydroquinone
on Color, Texture and Microstructure of Peanut Paste. J Food Quality 29(6):643-657.
Agila A, Barringer SA. 2011. Volatile Profile of Cashews (Anacardium occidentale L.)
from Different Geographical Origins during Roasting. J Food Sci 76(5):C768-C744.
Agila A, Barringer S. 2012. Effect of Roasting Conditions on Color and Volatile Profile
Including HMF Level in Sweet Almonds (Prunus dulcis). J Food Sci 77(4):C461-C468.
Arnold ST, Viggiano AA, Morris RA. 1998. Rate Constants and Product Branching
Fractions for the Reactions of H3O+ and NO+ with C2-C12 Alkanes. J Phys Chem
102(45):8881-8887.
Arnoldi A, Arnoldi C, Baldi O, Griffin A. 1987. Strecker Degradation of Leucine and
Valine in a Lipidic Model System. J Agric Food Chem 35(6):1035-1038.
Baker GL, Cornell JA, Gorbet DW, O’Keefe SF, Sims CA, Talcott ST. 2003.
Determination of Pyrazine and Flavor Variations in Peanut Genotypes During Roasting. J
Food Sci 68(1):394-400.
Balagiannis DP, Parker JK, Pyle DL, Desforges N, Wedzicha BL, Mottram DS. 2009.
Kinetic Modeling of the Generation of 2- and 3-Methylbutanal in a Heated Extract of
Beef Liver. J Agric Food Chem 57(21):9916-9922.
74
Bett KL, Boylston TD. 1992. Effect of Storage on Roasted Peanut Quality. In St. Angelo
AJ, editor. Lipid Oxidation in Food. New York: American Chemical Society. p 322-343.
Braddock JC, Sims CA, O’Keefe SF. 1995. Flavor and Oxidative Stability of Roasted
High Oleic Acid Peanuts. J Food Sci 60(3):489-493.
Brown DF, Senn VJ, Dollear FG, Goldblatt LA. 1973. Concentrations of Some Aliphatic
Aldehydes and Ketones Found in Raw and Roasted Spanish and Runner Peanuts. J Am
Oil Chem Soc 50(1):16-20.
Brown DF, Senn VJ, Stanley JB, Dollear FG. 1972. Comparison of Carbonyl Compounds
in Raw and Roasted Runner Peanuts. I. Major Qualitative and Some Quantitative
Differences. J Agr Food Chem 20(3):700-706.
Brown ML, Wadsworth JI, Dupuy HP. 1977. Correlation of Volatile Components of Raw
Peanuts With Flavor Score. Pean Sci 4(2):54-56.
Buckholz Jr. LL, Daun HK. 1981. Instrumental and Sensory Characteristics of Roasted
Peanut Flavor Volatiles. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected
Fruits and Vegetables of North America. Washington DC: American Chemical Society. p
163-181.
Buckholz Jr. LL, Daun H, Trout R. 1980. Influence of Roasting Time on Sensory
Attributes of Fresh Roasted Peanuts. J Food Sci 45(3): 547-554.
Chiou RYY, Chang YS, Tsai TT, Ho S. 1991. Variation of Flavor-Related Characteristics
of Peanuts during Roasting As Affected by Initial Moisture Contents. J Agric Food Chem
39(6):1155-1158.
Coleman WM III, White JL Jr., Perfetti TA. 1994. Characteristics of Heat-Treated
Aqueous Extracts of Peanuts and Cashews. J Agric Food Chem 42(1):190-194.
Davidson VJ, Brown RB, Landman JJ. 1999. Fuzzy control system for peanut roasting. J
Food Eng 41(3-4):141-146.
Diskin AM, Wang T, Smith D, Spanel P. 2002. A selected ion flow tube (SIFT), study of
the reactions of H3O+, NO+ and O2+ ions with a series of alkenes; in support of SIFT-MS.
Int J Mass Spectrom 218(1):87-101.
Fellows PJ. 2009. Food processing technology principles and practice. 3rd ed. Florida:
CRC Press LLC. 583 p.
Frankel EN. 1985. Chemistry of Autoxidation: Mechanism, Products and Flavor
Significance. In: Min DB, Smouse TH, editors. Flavor Chemistry of Fats and Oils.
Illinois: American Oil Chemists’ Society. p 1-37.
Gao M, Tang J, Johnson JA, Wang S. 2012. Dielectric properties of ground almond shells
in the development of radio frequency and microwave pasteurization. J Food Eng
112(4):282-287.
75
Grasso EM, Yousef AE, Castellvi SDL, Rodriguez-Saona LE. 2009. Rapid Detection and
Differentiation of Alicyclobacillus Species in Fruit Juice Using Hydrophobic Grid
Membranes and Attenuated Total Reflectance Infrared Microspectroscopy. J Agric Food
Chem 57(22):10670-10674.
Grosso NR, Resurreccion AVA. 2002. Predicting Consumer Acceptance Ratings of
Cracker-coated and Roasted Peanuts from Descriptive Analysis and Hexanal
Measurements. J Food Sci 67(4):1530-1537.
Harper WJ, Kocaoglu-Vurma NA, Wick C, Elekes K, Langford V. 2011. Analysis of
volatile sulfur compounds in Swiss cheese using selected ion flow tube mass
spectrometry (SIFT-MS). In: Qian MC, Fan X, Mahattanatawee K, editors. Volatile
Sulfur Compounds in Food. Washington, DC: American Chemical Society. p 153-181.
Huang Y. Barringer SA. 2011. Monitoring of Cocoa Volatiles Produced during Roasting
by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS). J Food Sci 76(2):C279-C286.
Ku KL, Lee RS, Young CT, Chiou RYY. 1998. Roasted Peanut Flavor and Related
Compositional Characteristics of Peanut Kernels of Spring and Fall Crops Grown in
Taiwan. J Agric Food Chem. 46(8)3220-3224.
Leunissen M, Davidson VJ, Kakuda Y. 1996. Analysis of Volatile Flavor Components in
Roasted Peanuts Using Supercritical Fluid Extraction and Gas Chromatography-Mass
Spectrometry. J Agric Food Chem 44(9):2694-2699.
Mason ME, Johnson B, Hamming M. 1966. Flavor Components of Roasted Peanuts.
Some Low Molecular Weight Pyrazines and a Pyrrole. J Agric Food Chem 14(5):454460.
Mason ME, Johnson B, Hamming MC. 1967. Volatile Components of Roasted Peanuts.
The Major Monocarbonyls and Some Noncarbonyl Components. J Agric Food Chem
15(1):66-73.
Mason ME, Newell JA, Johnson BR, Koehler PE, Waller GR. 1969. Nonvolatile Flavor
Components of Peanuts. J Agric Food Chem 17(4):728-732.
Matsui T, Guth H, Grosch W. 1998. A comparative study of potent odorants in peanut,
hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA)
and gas chromatography-olfactometry of headspace samples (GCOH). Eur J Lipid Sci.
Technol. 100(2):51-56.
Mexis SF, Kontominas MG. 2009. Effect of gamma irradiation on the physic-chemical
and sensory properties of raw shelled peanuts (Arachis hypogaea L.) and pistachio nuts
(Pistacia vera L.). J Sci Food Agri. 89(5):867-875.
Neta ER, Sanders T, Drake MA. 2010. Understanding Peanut Flavor: A Current Review.
In: Hui YH, editor. Handbook of Fruit and Vegetable Flavors. New Jersey: John Wiley &
Sons, Inc. p 985-1022.
76
O’Brien J, Morrissey PA, Ames JM. 1989. Nutritional and toxicological aspects of the
Maillard browning reaction in foods. Crit Rev Food Sci 28(3):211-248.
Pattee HE, Giesbrecht FG, Young CT. 1991. Comparison of Peanut Butter Color
Determination by CIELAB L*a*b* and Hunter Color-Difference Methods and the
Relationships of Roasted Peanut Color to Roasted Peanut Flavor Response. J Agric Food
Chem 39(3):519-523.
Pattee HE, Singleton JA. 1981. Peanut Quality: Its Relationship to Volatile CompoundsA review. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected Fruits and
Vegetables of North America. Washington DC: American Chemical Society. p 147-161.
Pattee HE, Singleton JA, Cobb WY. 1969. Volatile Components of Raw Peanuts:
Analysis by Gas-Liquid Chromatography and Mass Spectrometry. J Food Sci 34(6):625627.
Pattee HE, Singleton JA, Johns EB, Mullin BC. 1970. Changes in the Volatile Profile of
Peanuts and Their Relationship to Enzyme Activity Levels During Maturation. J Agr
Food Chem 18(3):353-356.
Reed KA, Sims CA, Gorbet DW, O’Keefe SF. 2002. Storage water activity flavor fade in
high and normal oleic acid peanuts. Food Res Int 35(8):769-774.
Shu CK, Waller GR. 1971. Volatile Components of Roasted Peanuts: Comparative
Analysis of the Basic Fraction. J Food Sci 36(4):579-583.
Singleton JA, Pattee HE. 1991. Peanut Moisture/Size, Relation to Freeze Damage and
Effect of Drying Temperature on Volatiles. J Food Sci 56(2):579-581.
Sipahioglu O, Barringer SA. 2003. Dielectric Properties of Vegetables and Fruits as a
Function of Temperature, Ash, and Moisutre Content. J Food Sci 68(1):234-239.
Smith D, Spanel P. 2005. Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) for online Trace Gas Analysis. Mass Spectrom Rev 24(5):661-700.
Smith D, Wang T, Spanel P. 2003. Analysis of ketones by selected ion flow tube mass
spectrometry. Rapid Commun Mass Sp 17(23):2655-2660.
Smyth DA, Macku C, Holloway OE, Deming DM, Slade L, Levine H. 1998. Evaluation
of Analytical Methods for Optimizing Peanut Roasting for Snack Foods. Pean Sci
25(2):70-76.
Spanel P, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of alcohols. Int J Mass Spectrom 167/168:375-388.
Spanel P, Smith D. 1998. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of volatile carboxylic acids and esters. Int J Mass Spectrom 172(1):137-147.
77
Spanel P, Van Doren JM, Smith D. 2002. A selected ion flow tube study of the reactions
of H3O+, NO+, and O2+ with saturated and unsaturated aldehydes and subsequent
hydration of the products. Int J Mass Spectrom 213(2-3):163-176.
Spanel P, Yufeng J, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+
with a series of aldehydes and ketones. Int J Mass Spectrom 165/166:25-37.
Syft Technologies, Inc. 2011. Kinetics library database. Christchurch, New Zealand: Syft
Technologies Inc.
Vercellotti JR, Crippen KL, Lovengren NV, Sanders TH. 1992. Defining Roasted Peanut
Flavor Quality. Part 1. Correlation of GC Volatiles with Roast Color as an Estimate of
Quality. In: Charalambous G, editor. Food Science and Human Nutrition. The
Netherlands: Elsevier Science Publishers B.V. p 183-209.
Wang T, Spanel P, Smith D. 2003. Selected ion flow tub, SIFT, studies of the reactions of
H3O+, NO+ and O2+ with eleven C10H16 monoterpenes. Int J Mass Spectrom 228(1):117126.
Wang T, Spanel P, Smith D. 2004. A selected ion flow tube, SIFT, study of the reactions
of H3O+, NO+ and O2•+ ions with several N- and O-containing heterocyclic compounds in
support of SIFT-MS. Int J Mass Spectrom 237(2-3):167-174.
Warner KJH, Dimick PS, Ziegler GR, Mumma RO, Hollender R. 1996. ‘Flavor-fade’ and
Off-Flavors in Ground Roasted Peanuts As Related to Selected Pyrazines and Aldehydes.
J Food Sci 61(2):469-472.
Williams TL, Adams NG, Babcock LM. 1998. Selected ion flow tube studies of
H3O+(H2O)0,1 reactions with sulfides and thiols. Int J Mass Spectrom 172(1-2):149-159.
Young CT, Hovis AR. 1990. A Method for the Rapid Analysis of Headspace Volatiles of
Raw and Roasted Peanuts. J Food Sci 55(1):279-280.
78
References
Abegaz EG, Kerr WL. 2006. Effect of Moisture, Sugar and Tertiary Butylhydroquinone
on Color, Texture and Microstructure of Peanut Paste. J Food Quality 29(6):643-657.
Agila A, Barringer SA. 2011. Volatile Profile of Cashews (Anacardium occidentale L.)
from Different Geographical Origins during Roasting. J Food Sci 76(5):C768-C744.
Agila A, Barringer S. 2012. Effect of Roasting Conditions on Color and Volatile Profile
Including HMF Level in Sweet Almonds (Prunus dulcis). J Food Sci 77(4):C461-C468.
AOCS. 1998a. AOCS Official Method Ab 5-49 Free Fatty Acids. In: Firestone D, editor.
Official Methods and Recommended Practices of the AOCS. 5th ed. Champaign, Illinois:
American Oil Chemists’ Society.
AOCS.1998b. AOCS Official Method Cd 8-53 Peroxide Value Acetic Acid-Chloroform
Method. In: Firestone D, editor. Official Methods and Recommended Practices of the
AOCS. 5thed. Champaign, Illinois: American Oil Chemists’ Society.
Arnold ST, Viggiano AA, Morris RA. 1998. Rate Constants and Product Branching
Fractions for the Reactions of H3O+ and NO+ with C2-C12 Alkanes. J Phys Chem
102(45):8881-8887.
Arnoldi A, Arnoldi C, Baldi O, Griffin A. 1987. Strecker Degradation of Leucine and
Valine in a Lipidic Model System. J Agric Food Chem 35(6):1035-1038.
Arora G. Cormier F, Lee B. 1995. Analysis of Odor-Active Volatiles in Cheddar Cheese
Headspace by Multidimensional GC/MS/Sniffing. J Agric Food Chem 43(3):748-752.
Ba HV, Hwang I, Jeong D, Touseef A. 2012. Principle of Meat Aroma Flavors and
Future Prospect. In Akyar I, editor. Latest Research into Quality Control. Croatia:
InTech. p 145- 176.
Baker GL, Cornell JA, Gorbet DW, O’Keefe SF, Sims CA, Talcott ST. 2003.
Determination of Pyrazine and Flavor Variations in Peanut Genotypes During Roasting. J
Food Sci 68(1):394-400.
Balagiannis DP, Parker JK, Pyle DL, Desforges N, Wedzicha BL, Mottram DS. 2009.
Kinetic Modeling of the Generation of 2- and 3-Methylbutanal in a Heated Extract of
Beef Liver. J Agric Food Chem 57(21):9916-9922.
79
Bett KL, Boylston TD. 1992. Effect of Storage on Roasted Peanut Quality. In St. Angelo
AJ, editor. Lipid Oxidation in Food. New York: American Chemical Society. p 322-343.
Boldor D, Sanders TH, Simunovic J. 2004. Dielectric Properties of In-Shell and Shell
Peanuts at Microwave Frequencies. T ASAE 47(4):1159-1169.
Bolton GE, Sanders TH. 2002. Effect of Roasting Oil Composition on the Stability of
Roasted High-Oleic Peanuts. J Am Oil Chem Soc 79(2):129-132.
Braddock JC, Sims CA, O’Keefe SF. 1995. Flavor and Oxidative Stability of Roasted
High Oleic Acid Peanuts. J Food Sci 60(3):489-493.
Brown DF, Senn VJ, Dollear FG, Goldblatt LA. 1973. Concentrations of Some Aliphatic
Aldehydes and Ketones Found in Raw and Roasted Spanish and Runner Peanuts. J Am
Oil Chem Soc 50(1):16-20.
Brown DF, Senn VJ, Stanley JB, Dollear FG. 1972. Comparison of Carbonyl Compounds
in Raw and Roasted Runner Peanuts. I. Major Qualitative and Some Quantitative
Differences. J Agr Food Chem 20(3):700-706.
Brown ML, Wadsworth JI, Dupuy HP. 1977. Correlation of Volatile Components of Raw
Peanuts With Flavor Score. Pean Sci 4(2):54-56.
Buckholz Jr. LL, Daun HK. 1981. Instrumental and Sensory Characteristics of Roasted
Peanut Flavor Volatiles. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected
Fruits and Vegetables of North America. Washington DC: American Chemical Society. p
163-181.
Buckholz Jr. LL, Daun H, Trout R. 1980. Influence of Roasting Time on Sensory
Attributes of Fresh Roasted Peanuts. J Food Sci 45(3): 547-554.
Chiou RYY, Chang YS, Tsai TT, Ho S. 1991. Variation of Flavor-Related Characteristics
of Peanuts during Roasting As Affected by Initial Moisture Contents. J Agric Food Chem
39(6):1155-1158.
Coleman WM III, White JL Jr., Perfetti TA. 1994. Characteristics of Heat-Treated
Aqueous Extracts of Peanuts and Cashews. J Agric Food Chem 42(1):190-194.
Datta AK, Rakesh V. 2013. Principles of Microwave Combination Heating. Compr Rev
Food Sci F 12(1):24-39.
Davidson VJ, Brown RB, Landman JJ. 1999. Fuzzy control system for peanut roasting. J
Food Eng 41(3-4):141-146.
80
Decareau RV. 1985. Microwaves in the Food Processing Industry. Florida: Academic
Press, Inc, 9 p.
Diskin AM, Wang T, Smith D, Spanel P. 2002. A selected ion flow tube (SIFT), study of
the reactions of H3O+, NO+ and O2+ ions with a series of alkenes; in support of SIFT-MS.
Int J Mass Spectrom 218(1):87-101.
Elder J, The J.M. Smucker Company. 2013. Personal interview.
Felland SL, Koehler PE. 1997. Sensory, Chemical, and Physical Changes in Increased
Water Activity Peanut Butter Products. J Food Quality 20(2):145-156.
Fellows PJ. 2009. Food processing technology principles and practice. 3rd ed. Florida:
CRC Press LLC. 583 p.
Flores M, Grimm CC, Toldra F. Spanier AM. 1997. Correlations of Sensory and Volatile
Compounds of Spanish “Serrano” Dry-Cured Ham as a Function of Two Processing
Times. J Agric Food Chem 45(6):2178-2186
Frankel EN. 1985. Chemistry of Autoxidation: Mechanism, Products and Flavor
Significance. In: Min DB, Smouse TH, editors. Flavor Chemistry of Fats and Oils.
Illinois: American Oil Chemists’ Society. p 1-37.
Frauendorfer F, Schieberle P. 2006. Identification of the Key Aroma Compounds in
Cocoa Powder Based on Molecular Sensory Correlations. J Agric Food Chem
54(15):5521-5529.
Gao M, Tang J, Johnson JA, Wang S. 2012. Dielectric properties of ground almond shells
in the development of radio frequency and microwave pasteurization. J Food Eng
112(4):282-287.
Grasso EM, Yousef AE, Castellvi SDL, Rodriguez-Saona LE. 2009. Rapid Detection and
Differentiation of Alicyclobacillus Species in Fruit Juice Using Hydrophobic Grid
Membranes and Attenuated Total Reflectance Infrared Microspectroscopy. J Agric Food
Chem 57(22):10670-10674.
Grosso NR, Resurreccion AVA. 2002. Predicting Consumer Acceptance Ratings of
Cracker-coated and Roasted Peanuts from Descriptive Analysis and Hexanal
Measurements. J Food Sci 67(4):1530-1537.
Harper WJ, Kocaoglu-Vurma NA, Wick C, Elekes K, Langford V. 2011. Analysis of
volatile sulfur compounds in Swiss cheese using selected ion flow tube mass
spectrometry (SIFT-MS). In: Qian MC, Fan X, Mahattanatawee K, editors. Volatile
Sulfur Compounds in Food. Washington, DC: American Chemical Society. p 153-181.
81
Hodge JE. 1953. Dehydrated Foods Chemistry of Browning Reactions in Model Systems.
J Agri Food Chem 1(15):928-943.
Hoffpauir CL. 1953. Peanut Composition Relation to Processing and Utilization. J Agri
Food Chem 1(10):668-671.
Huang Y. Barringer SA. 2011. Monitoring of Cocoa Volatiles Produced during Roasting
by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS). J Food Sci 76(2):C279-C286.
Jiang L, Kubota K. 2004. Differences in the Volatile Components and Their Odor
Characteristics of Green and Ripe Fruits and Dried Pericarp Japanese Pepper
(Xanthoxylum piperitum DC.). J Agric Food Chem 52(13):4197-4203.
Johnsen PB, Civille GV, Vercellotti JR, Sanders TH, Dus CA. 1988. Development of a
Lexicon for the Description of Peanut Flavor. J Sens Stud 3(1):9-17.
Ku KL, Lee RS, Young CT, Chiou RYY. 1998. Roasted Peanut Flavor and Related
Compositional Characteristics of Peanut Kernels of Spring and Fall Crops Grown in
Taiwan. J Agric Food Chem. 46(8)3220-3224.
Lei Q, Boatright WL. 2001. Compounds Contributing to the Odor of Aqueous Slurries of
Soy Protein Concentrate. J Food Sci 66(9):1306-1310.
Leunissen M, Davidson VJ, Kakuda Y. 1996. Analysis of Volatile Flavor Components in
Roasted Peanuts Using Supercritical Fluid Extraction and Gas Chromatography-Mass
Spectrometry. J Agric Food Chem 44(9):2694-2699.
MacLeod G, Coppock BM. 1976. Volatile Flavor Components of Beef Boiled
Conventionally and by Microwave Radiation. J Agric Food Chem 24(4):835-843.
Matsui T, Guth H, Grosch W. 1998. A comparative study of potent odorants in peanut,
hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA)
and gas chromatography-olfactometry of headspace samples (GCOH). Eur J Lipid Sci.
Technol. 100(2):51-56.
Mason ME, Johnson B, Hamming M. 1966. Flavor Components of Roasted Peanuts.
Some Low Molecular Weight Pyrazines and a Pyrrole. J Agric Food Chem 14(5):454460.
Mason ME, Johnson B, Hamming MC. 1967. Volatile Components of Roasted Peanuts.
The Major Monocarbonyls and Some Noncarbonyl Components. J Agric Food Chem
15(1):66-73.
Mason ME, Newell JA, Johnson BR, Koehler PE, Waller GR. 1969. Nonvolatile Flavor
Components of Peanuts. J Agric Food Chem 17(4):728-732.
82
McDaniel KA, White BL, Dean LL, Sanders TH, Davis JP. 2012. Compositional and
Mechanical Properties of Peanuts Roasted to Equivalent Colors using Different
Time/Temperature Combinations. J Food Sci 77(12):C1292-C1298.
Mexis SF, Kontominas MG. 2009. Effect of gamma irradiation on the physic-chemical
and sensory properties of raw shelled peanuts (Arachis hypogaea L.) and pistachio nuts
(Pistacia vera L.). J Sci Food Agri. 89(5):867-875.
Neta ER, Sanders T, Drake MA. 2010. Understanding Peanut Flavor: A Current Review.
In: Hui YH, editor. Handbook of Fruit and Vegetable Flavors. New Jersey: John Wiley &
Sons, Inc. p 985-1022.
Niu Y, Zhang X, Xiao Z, Song S. Eric K, Jia C, Yu H, Zhu J. 2011. Characterization of
odor-active compounds of various cherry wines by gas chromatography-mass
spectrometry, gas chromatography-olfactometry and their correlation with sensory
attributes. J Chromatogr B 879(23):2287-2293.
Nursten H. 2005. The Maillard Reaction Chemistry, Biochemistry, and Implications.
Reading, UK: The Royal Society of Chemistry. 2-3, 83 p.
O’Brien J, Morrissey PA, Ames JM. 1989. Nutritional and toxicological aspects of the
Maillard browning reaction in foods. Crit Rev Food Sci 28(3):211-248.
Olafsdottir G, Jonsdottir R, Lauzon HL, Luten J, Kristbergsson K. 2005. Characterization
of Volatile Compounds in Chilled Cod (Gadus morhua) Fillets by Gas Chromatography
and Detection of Quality Indicators by an Electronic Nose. J Agric Food Chem
53(26):10140-10417.
Pattee HE, Giesbrecht FG, Young CT. 1991. Comparison of Peanut Butter Color
Determination by CIELAB L*a*b* and Hunter Color-Difference Methods and the
Relationships of Roasted Peanut Color to Roasted Peanut Flavor Response. J Agric Food
Chem 39(3):519-523.
Pattee HE, Singleton JA. 1981. Peanut Quality: Its Relationship to Volatile CompoundsA review. In: Teranishi R, Barrera-Benitez B, editors. Quality of Selected Fruits and
Vegetables of North America. Washington DC: American Chemical Society. p 147-161.
Pattee HE, Singleton JA, Cobb WY. 1969. Volatile Components of Raw Peanuts:
Analysis by Gas-Liquid Chromatography and Mass Spectrometry. J Food Sci 34(6):625627.
Pattee HE, Singleton JA, Johns EB, Mullin BC. 1970. Changes in the Volatile Profile of
Peanuts and Their Relationship to Enzyme Activity Levels During Maturation. J Agr
Food Chem 18(3):353-356.
83
Reed KA, Sims CA, Gorbet DW, O’Keefe SF. 2002. Storage water activity flavor fade in
high and normal oleic acid peanuts. Food Res Int 35(8):769-774.
Ruiz MJ, Zea L, Moyano L. 2010. Aroma active compound during the drying of grapes
cv. Pedro Ximenez destined to the production of sweet Sherry wine. Eur Food Res
Technol 230(3):429-435.
Ruth JH. 1986. Odor Thresholds and Irritation Levels of Several Chemical Substances: A
Review. Am Ind Hyg Assoc J 47(3):A142-A151.
SAFC. 2011. Flavors & Fragrances Catalog. Sigma-Aldrich Co. LLC. Available from:
http://www.sigmaaldrich.com/chemistry/chemistry-products.html?TablePage=12916829.
Accessed May 24, 2013.
Sanders TH. 2002. Groundnut (peanut) oil. In: Gunstone FD, editor. Vegetable Oils In
Food Technology: Composition, Properties and Uses. Florida: CRC Press LLC. p 231243.
Schirack AV, Drake M, Sanders TH, Sandeep KP. 2006a. Characterization of AromaActive Compounds in Microwave Blanched Peanuts. J Food Sci 71(9):C513-C520.
Schirack AV, Drake M, Sanders TH, Sandeep KP. 2006b. Impact of Microwave
Blanching on the Flavor of Roasted Peanuts. J Sens Stud 21(4):428-440.
Shu CK, Waller GR. 1971. Volatile Components of Roasted Peanuts: Comparative
Analysis of the Basic Fraction. J Food Sci 36(4):579-583.
Singh TK, Drake MA, Cadwallader KR. 2003. Flavor of Cheddar Cheese: A Chemical
and Sensory Perspective. Compr Rev Food Sci F 2(4):166-189
Singleton JA, Pattee HE. 1991. Peanut Moisture/Size, Relation to Freeze Damage and
Effect of Drying Temperature on Volatiles. J Food Sci 56(2):579-581.
Sipahioglu O, Barringer SA. 2003. Dielectric Properties of Vegetables and Fruits as a
Function of Temperature, Ash, and Moisutre Content. J Food Sci 68(1):234-239.
Smith D, Spanel P. 2005. Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) for online Trace Gas Analysis. Mass Spectrom Rev 24(5):661-700.
Smith D, Wang T, Spanel P. 2003. Analysis of ketones by selected ion flow tube mass
spectrometry. Rapid Commun Mass Sp 17(23):2655-2660.
84
Smyth DA, Macku C, Holloway OE, Deming DM, Slade L, Levine H. 1998. Evaluation
of Analytical Methods for Optimizing Peanut Roasting for Snack Foods. Pean Sci
25(2):70-76.
Sobolev VS. 2001. Vanillin Content in Boiled Peanuts. J Agric Food Chem 49(8):37253727.
Spanel P, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of alcohols. Int J Mass Spectrom 167/168:375-388.
Spanel P, Smith D. 1998. SIFT studies of the reactions of H3O+, NO+ and O2+ with a
series of volatile carboxylic acids and esters. Int J Mass Spectrom 172(1):137-147.
Spanel P, Van Doren JM, Smith D. 2002. A selected ion flow tube study of the reactions
of H3O+, NO+, and O2+ with saturated and unsaturated aldehydes and subsequent
hydration of the products. Int J Mass Spectrom 213(2-3):163-176.
Spanel P, Yufeng J, Smith D. 1997. SIFT studies of the reactions of H3O+, NO+ and O2+
with a series of aldehydes and ketones. Int J Mass Spectrom 165/166:25-37.
Syft Technologies, Inc. 2011. Kinetics library database. Christchurch, New Zealand: Syft
Technologies Inc.
[USDA] United States Department of Agriculture, Economic Research Service. 2012.
USDA ERS – Food Availability (Per Capita) Data System. USDA. Available from:
http://www.ers.usda.gov/data-products/food-availability-(per-capita)-data-system.aspx.
Accessed Jan 30, 2013.
[USDA] United States Department of Agriculture, Farm Service Agency. 2006. Peanut
Reports. Washington, D.C.: USDA. Available from:
http://www.fsa.usda.gov/FSA/epasReports?area=home&subject=ecpa&topic=ftapn&summaryYear=2006&x=14&y=13. Accessed Jan 30, 2012.
[USDA] United States Department of Agriculture, Farm Service Agency. 2013a. Peanut
Reports. Washington, D.C.: USDA. Available from:
http://www.fsa.usda.gov/FSA/epasReports?area=home&subject=ecpa&topic=fta-pn .
Accessed Jan 30, 2012.
[USDA] United States Department of Agriculture, National Agricultural Statistics
Service. 2013b. Crop Production 2012 Summary. USDA. ISSN: 1057-7823. Available
from: USDA; 1, 95.
van Gemert LJ. 2011. Odour Thresholds. Compilations of odour threshold values in air,
water and other media. The Netherlands: Oliemans Punter & Partners BV. P 11-180.
85
Vazquez-Araujo L. Verdu A, Navarro P, Martinez-Sanchez F, Carbonell-Barrachina AA.
2009. Changes in volatile compounds and sensory quality during toasting of Spanish
almonds. Int J Food Sci Tech 44(11):2225-2233.
Vercellotti JR, Crippen KL, Lovengren NV, Sanders TH. 1992. Defining Roasted Peanut
Flavor Quality. Part 1. Correlation of GC Volatiles with Roast Color as an Estimate of
Quality. In: Charalambous G, editor. Food Science and Human Nutrition. The
Netherlands: Elsevier Science Publishers B.V. p 183-209.
Wang T, Spanel P, Smith D. 2003. Selected ion flow tub, SIFT, studies of the reactions of
H3O+, NO+ and O2+ with eleven C10H16 monoterpenes. Int J Mass Spectrom 228(1):117126.
Wang T, Spanel P, Smith D. 2004. A selected ion flow tube, SIFT, study of the reactions
of H3O+, NO+ and O2•+ ions with several N- and O-containing heterocyclic compounds in
support of SIFT-MS. Int J Mass Spectrom 237(2-3):167-174.
Warner KJH, Dimick PS, Ziegler GR, Mumma RO, Hollender R. 1996. ‘Flavor-fade’ and
Off-Flavors in Ground Roasted Peanuts As Related to Selected Pyrazines and Aldehydes.
J Food Sci 61(2):469-472.
Williams TL, Adams NG, Babcock LM. 1998. Selected ion flow tube studies of
H3O+(H2O)0,1 reactions with sulfides and thiols. Int J Mass Spectrom 172(1-2):149-159.
Young CT, Hovis AR. 1990. A Method for the Rapid Analysis of Headspace Volatiles of
Raw and Roasted Peanuts. J Food Sci 55(1):279-280.
Young CT, Young TG, Cherry JP. 1974. The Effect of Roasting Methods on the Flavor
and Composition of Peanut Butter. Proc Am Peanut Res Educ Assoc 6(1):8-16.
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Appendix: Odor Thresholds
Table A1. Odor thresholds of volatiles in air
Volatile
(E)-2-heptenal
(E)-2-nonenal
(E)-2-octenal
(E)-2-pentenal
(E,E)-2,4-decadienal
1-decene
1-octanol
1-octen-3-ol
1-pentanol
1-penten-3-one
2,3-butanedione
2,3-diethyl-5-methylpyrazine
2,5-dimethylpyrazine
2,6-nonadienal
2-butenal
2-decanone
2-heptanol
2-hexanone
2-methylpropanal
2-nonanone
2-octanone
2-pentanone
2-undecanone
3-methylbutanal
3-methylbutanoic acid
acetone
ammonia
benzaldehyde
benzene
butanal
butanone
Odor Threshold
(mg/m3) in air
0.034
0.0005
0.0027
1.4
0.00004
37
0.005
0.00236
0.02
0.0001
0.00005
0.000009
0.17
0.00006
0.067
0.003
0.041
0.098
0.001
0.032
0.06
0.098
0.03
0.00035
0.00015
0.94
0.0266
0.0008
1.5
0.0002
0.21
87
Reference
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van Gemert 2011
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continued
Table A1. Continued
decanal
decane
dimethyl disulfide
dimethyl sulfide
dimethyl trisulfide
ethanol
ethyl 2-methylbutanoate
furfural
guaiacol
heptanal
heptane
hexanal
hexane
hexanoic acid
hexenal
hydrogen sulfide
isobutanoic acid
methanol
methyl acetate
methyl mercaptan
methyl methanoate
nonanal
octanal
octane
pentane
phenylacetaldehyde
propanal
propanoic acid
toluene
trimethylpyrazine
vanillin
0.00025
3.6
0.0001
0.0025
0.0062
0.17
0.00006
0.008
0.0001
0.00085
2.7
0.0082
0.01
0.0029
0.0004
0.0007
0.005
4
0.5
1E-12
0.001
0.0003
0.000052
8
0.27
0.001
0.0024
0.003
0.12
0.033
0.0000002
88
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