FRIN-06218; No of Pages 12
Food Research International xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Food Research International
journal homepage: www.elsevier.com/locate/foodres
The influence of the roasting process conditions on the polyphenol
content in cocoa beans, nibs and chocolates
Dorota Żyżelewicz a,⁎, Wiesława Krysiak a, Joanna Oracz a, Dorota Sosnowska b,
Grażyna Budryn a, Ewa Nebesny a
a
b
Institute of Food Technology and Analysis, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, 90-924 Lodz, Poland
Institute of Technical Biochemistry, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, 90-924 Lodz, Poland
a r t i c l e
i n f o
Article history:
Received 28 October 2015
Received in revised form 25 February 2016
Accepted 19 March 2016
Available online xxxx
Keywords:
Cocoa bean
Cocoa nibs
Chocolate
Roasting
Phenolic compounds
LC–MS/MS
a b s t r a c t
The process of roasting is a significant step in cocoa bean processing. Heating results in the formation of many
advantageous features of beans, such as taste, color, texture. However, these positive changes can also be accompanied by reactions reducing the content of bioactive compounds such as polyphenols. It is therefore important
to select the appropriate roasting process conditions (time, temperature, humidity and flow rate of air), as well as
fineness of the beans. The article describes the research on the influence of roasting parameters (temperature,
roasting time, air flow rate and relative humidity) on the kinetics of changes in the content of phenolic compounds in whole beans and in cocoa nibs of different particle size. Additonally, chocolates were obtained from
cocoa liquor prepared from cocoa beans roasted as whole beans as well as from fraction of cocoa nibs of middle
particle size.
LC–MS/MS analysis of phenolic compounds in the roasted beans, nibs and chocolates showed that the degradation of these compounds in beans and nibs was lower when they were roasted in air with increased relative humidity. The greatest degradation of compounds both in whole beans and nibs was observed for epicatechin and
procyanidin B2, regardless of the roasting conditions applied. There were no differences as the course of degradation of polyphenolic compounds in beans and nibs, roasted under constant and non-constant process parameters. The loss of flavanols in the process of chocolate preparation was not high.
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
The cocoa beans constitute a basic raw material used in the production of chocolate and cocoa. Both beans and obtained from them products are still a subject of scientists' interest due to its unique properties.
To obtain chocolate from cocoa beans, the beans have to undergo a
complicated technological process. One very important step in this process is roasting with its primary aim to convert dry fermented beans
into microbiologically clean raw material with a characteristic aroma
and taste and with a proper brittleness. The convection roasting method
is most commonly applied. In this method, raw cocoa beans are subjected to a forced flow of hot air. The literature indicates the thermal processing of cocoa beans in the range of temperature between 130 and
150 °C and for time between 15 and 45 min (Belitz, Grosch, &
Schieberle, 2009; Krysiak, 2002, 2006; Minifie, 1999; Nebesny &
Rutkowski, 1998).
To roasting can also be subjected cocoa nibs or liquor (Beckett, 2000;
Fadini, Gilabert, Pezoa, & Marsaioli, 1997; Finken, 1996). The benefits of
such alternative allow to roast smaller particles at a lower temperature
⁎ Corresponding author.
E-mail address: [email protected] (D. Żyżelewicz).
and a more homogenous temperature profile. Such process also requires less time due to easier heat transfer through the product. This enables obtaining a product with more physico-chemical properties,
which is not without significance for further processing of this raw
material.
The cocoa bean is a material comprising a variety of nutritional compounds such as carbohydrates, proteins. It is also rich in biologically active compounds, such as phenolic compounds (Hammerstone, Lazarus,
Mitchell, Rucker, & Schmitz, 1999; Keen, Holt, Polagruto, Wang, &
Schmitz, 2002; Misnawi, Jinap, Jamilah, & Nazamid, 2004; Sanbogi,
Osakabe, Natsume, Takizawa, et al., 1998; Zhu et al., 2002).
The largest group of phenolic compounds found in raw cocoa beans
are flavanols, represented primarily by flavan-3-ol — catechin and
flavan-3,4-diols — leucoanthocyanins (Dreosti, 2000; Hannum,
Schmitz, & Keen, 2002; Zhu et al., 2002; Di Mattia et al., 2013; Oracz,
Nebesny, & Żyżelewicz, 2015). The cocoa beans contain also
procyanidins (condensed tannins) (Hammerstone et al., 1999;
Hannum et al., 2002; Kothe, Zimmermann, & Galensa, 2013). They constitute about 60% of the total polyphenol content (Dreosti, 2000). Other
phenolic compounds present in the beans include mainly flavonol —
quercetin and its glycosides, flavon-isovitexin, phenols — clovamide
and deoxyclovamide (Dreosti, 2000; Wollgast & Anklam, 2000).
http://dx.doi.org/10.1016/j.foodres.2016.03.026
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Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
2
Another phenolic compounds in fresh cocoa beans are anthocyanins
(4%), which occur most frequently as glycoside derivatives of cyanidin:
cyanidin 3-O-galactoside and cyanidin 3-O-arabinoside (Wollgast &
Anklam, 2000; Niemenak, Rohsius, Elwers, Omokolo Ndoumou, &
Lieberei, 2006; Andres-Lacueva et al., 2008). The type and amount of
phenolic compounds plays a significant role in the development of
such properties of the beans and products therefrom obtained as astringency or bitterness. They also play an important role of antioxidants.
The total content of phenolic compounds is about 6–8% based on the
dry matter of the bean (Dreosti, 2000; Ferrazzano, Amato, Ingenito, De
Natale, & Pollio, 2009; Othman, Ismail, Ghani, & Adenan, 2007;
Tomas-Barberan et al., 2007). The reason for such large differences in
the content of phenolic compounds is conditioned by: varieties of
cocoa beans, region of cultivation and running processes on plantations
(fermentation, drying). The literature (Clapperton et al., 1994; Wollgast
& Anklam, 2000; Jalil & Ismail, 2008; Nazaruddin, Seng, Hassan, & Said,
2006) reports that the richest in the phenolic compounds are cocoa
beans of bulk Forastero variety used for mass production.
It has been shown that processes such as fermentation, drying,
alkalization and roasting contribute to the degradation of phenolic compounds (Counet, Ouwerx, Rosoux, & Collin, 2004; Jorgensen, Marin, &
Kennedy, 2004; Ortega et al., 2008; Schinella et al., 2010; Di Mattia
et al., 2013; Albertini et al., 2015). A review of the literature indicates
that changes in polyphenol content in cocoa bean during convective
roasting were investigated in terms of temperature. It has been shown
that with increasing heat treatment, especially above 130 °C, the level
of polyphenols in cocoa beans is significantly reduced. However, only
a few works (Jolic, Redovnikovic, Markovic, Sipusic, & Delonga, 2011;
Kothe et al., 2013; Tamrin, Harijono, Yuwono, Estiasih, & Santoso,
2012; Zzaman, Bhat, & Yang, 2014; Ioannone et al., 2015) describe the
effect of temperature and roasting time on the changes in the content
of phenolic compounds in the cocoa beans.
In the literature, there is no study taking into account the effects of
other highly important process parameters, such as relative humidity
and air flow rate and application of modulating process parameters
over time on the level of degradation of phenolic compounds. Additionally, checking the possibility to reduce the energy expenditure for running the roasting process was in mind. The demonstration that the
application of modulating process parameters over time contribute to
maintaining a greater stability of phenolic compounds would enable
the cost reduction of the roasting process. The impact of cocoa beans
particle size on the kinetics of changes of polyphenol content was also
not analyzed. Among the numerous works on the impact of methods
for preparation of chocolate to change the content of polyphenolic compounds can be pointed studies conducted by Di Mattia et al. (2014).
Consequently, it was considered purposeful to undertake research
that would enable:
- defining the influence of roasting parameters such as temperature,
roasting time, air flow rate and relative humidity on the kinetics of
changes in the content of phenolic compounds in whole beans and
in cocoa nibs of different particle size; and
- choice of the conditions of roasting of whole beans and cocoa nibs,
which will provide chocolates products with the highest content of
phenolic compounds.
2. Material and methods
2.1. Chemicals and reagents
Standards of (±)-catechin (≥ 99%), (−)-epicatechin (≥ 98%), epigallocatechin (≥90%), procyanidin B2 (≥90%), procyanidin C1 (≥75%),
quercetin (≥ 95%), quercetin-3-O-glucoside (≥ 98%), quercetin-3-Ogalactoside (≥ 97%), quercetin-3-O-arabinoside (≥ 95%), gallic acid
(≥ 99%), caffeic acid (≥ 98%), chlorogenic acid (≥ 99%), acetonitrile of
HPLC grade (≥99.9%), formic acid for LC–MS (~98%) were all obtained
from Sigma-Aldrich (St. Louis, MO, USA). All other reagents used were
of analytical grade and purchased from POCH (Gliwice, Poland). Ultrapure water was obtained from a Millipore Milli-Q Plus purification system (Bedford, MA, USA).
2.2. Materials
The raw material was a bulk variety of cocoa beans (Forastero) originating from Togo (Togo) and purchased from polish company “Union
Chocolate” (Żychlin, Poland). Before roasting, cocoa beans were segregated in order to standardize the thermal conditions of the process.
The size of the beans was maintained in the range of 20.2 to 24.0 mm.
2.3. Roasting of cocoa bean and nibs
Roasting was carried out in a convective tunnel with a possibility to
regulate the process parameters (T — temperature, v — roasting air flow
rate, RH — roasting air relative humidity), also during the process of heat
treatment. Tunnel roaster made of stainless steel consists of pipes connected to each other in a closed circuit with adjustable degree of recirculation. Fan with a capacity of 0.13 m3/s provides in a measuring
section the air velocity in the range of 0.5–4.0 m/s and forces air circulation. The air is heated to a given temperature in the heater, and using the
heater switches located on the control panel it is possible to regulate
temperature in each section. The temperature is maintained at a constant level by the heater and controlled by a temperature controller.
The heated air flows through a pipe with a circular cross-section to a
pipe with rectangular cross-section consisting of several sections of different lengths and functions. The first section is responsible for the control of the air parameters. The next sections are used to even out the
velocity profile and to determine the parameters of roasting process.
The most important part of the tunnel roaster is the measuring section,
in which the proper implementation and control of the heat treatment
process is conducted.
The air leaving the measuring section flows to the air removing section and then through air off taking pipe into the outside. This is when
air is not re-circulated. The tunnel roaster may, however, be also
adapted to work when part of the air undergoes re-circulation. To reduce heat losses to the surrounding, the apparatus is covered with a
layer of the insulating mat with a thickness of 5 mm. In order to eliminate the impact of vibration on the measurement section and weight
readouts, a rubber connection between fan and tunnel and rubber
pads under the load-bearing construction is introduced. Tunnel roaster
allows also conducting the roasting process in air with increased humidity. Steam produced in steam generator is led through the main
heater and valve serves for adjusting its amount. Scheme of tunnel is included in the article of Żyżelewicz, Krysiak, Budryn, Oracz and Nebesny
(2014).
2.3.1. Cocoa bean
The whole cocoa beans were roasted by modulating the process parameters over the time and by keeping constant conditions for
comparison.
In order to determine the changes of the concentration of cocoa
beans phenolic compounds during roasting, independent roasting processes were carried out for each tested time-temperature-air flow
rate-relative humidity combination, so to reflect the actual sampling
of beans without changing the thermal conditions. All applied roasting
process conditions are included in Table 1. Each time of ignition, 200 g
of cocoa beans were unfolded in a single layer. The product mass to internal volume of roasting tunnel ratio was 0.168 kg/m3. The beans were
roasted until 2% water content (final sample).
After each roasting process, the beans were cooled to around 20 °C,
dehusked and crushed.
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
3
Table 1
Parameters of whole cocoa bean roasting.
Variant
T (°C)
v (m/s)
RH (%)
t (min)
Constant process parameters
I
II
III
IV
V
VI
VII
VIII
135
135
150
150
135
135
150
150
1
1
1
1
0.5
0.5
0.5
0.5
0.3
5
0.3
5
0.3
5
0.3
5
0, 15, 30 or 40
0, 15, 30 or 50
0, 15 or 25
0, 15, 30,35 or 40
0, 15, 35,50 or 55
0, 15, 35, 45, 60, 70 or 90
0, 15, 30 or 35
0, 15, 45, 50 or 55
135
135
150
150
135
135
150
150
1 m/s for 15 min, then 0.5 m/s
1 m/s for 15 min, then 0.5 m/s
1 m/s for 15 min, then 0.5 m/s
1 m/s for 15 min, then 0.5 m/s
0.5 m/s for 15 min, then 1 m/s
0.5 m/s for 15 min, then 1 m/s
0.5 m/s for 15 min, then 1 m/s
0.5 m/s for 15 min, then 1 m/s
0.3
5
0.3
5
0.3
5
0.3
5
0, 15, 35, 45 or 50
0, 15, 35, 60 or 65
0, 15 or 30
0, 15, 30 or 35
0, 15, 40 or 55
0, 15,35, 50 or 55
0, 15, 20 or 35
0, 15, 30 or 35
135 for 15 min, then 150
135 for 15 min, then 150
150 for 15 min, then 135
150 for 15 min, then 135
1
1
1
1
0.3
5
0.3
5
0, 15, 30 or 35
0, 15, 25, 35 or 40
0, 15, 25 or 35
0, 15, 0 or 35
135
150
1
1
5% for 15 min, then 0.3%
5% for 15 min, then 0.3%
0, 15, 30, 45 or 50
0, 15, 20, 30 or 35
Modulated process parameters
Modulated air flow rate
IX
X
XI
XII
XIII
XIV
XV
XVI
Modulated temperature
XVII
XVIII
XIX
XX
Modulated relative humidity
XXI
XXII
2.3.2. Cocoa nibs
In order to obtain cocoa nibs, whole beans were first dried
convectively to obtain around 3.5% water content. The following conditions of such drying were applied: initially, for 25 min “humid” air
(RH = 15%), then “dry” air (RH = 0.5%) for another 10 min. The temperature of 110 °C was applied for both variants of air humidity. Such prepared cocoa beans were dehusked, freezed and then mechanically
crushed using NMK-110 shredding device (“Spomasz Sp. z o. o.”,
Nakło n/Not., Poland). The obtained shredded beans were sieved in
order to obtain three fractions of nibs with different fineness: F1 — particle size ϕ ≥ 5 mm (sieve mesh below 3.5), F2 — particle size
5 mm N ϕ ≥ 3 mm (sieve mesh between 3.5 and 7 mesh), F3 — particle
size 3 mm N ϕ ≥ 0.8 mm (sieve mesh between 7 and 10 mesh).
Each of the obtained cocoa nibs fraction was subjected to roasting.
The roasting process was conducted using the same roasting tunnel as
for roasting whole cocoa beans. A single charge of cocoa nibs weighted
around 120 g. The product mass to internal volume of roasting tunnel
Table 2
Roasting parameters of cocoa nibs of different particle size.
Variant
T (°C)
Constant process parameters
Fraction F1
I
135
II
135
Fraction F2
III
135
IV
135
Fraction F3
V
135
VI
135
Modulated process temperature
Fraction F2
VII
135 for 2 min, then 150
VIII
135 for 2 min, then 150
IX
150 for 2 min, then 135
X
150 for 2 min, then 135
v (m/s)
RH (%)
t (min)
1
1
0.3
5
0, 2, 7 or 12
0, 2, 7 or 12
1
1
0.3
5
0, 2, 7 or 10
0, 2, 7 or 10
1
1
0.3
5
0, 2, 5 or 7
0, 2, 5, 7 or 10
1
1
1
1
0.3
5
0.3
5
0, 2, 3, 5 or 8
0, 2, 3, 5 or 8
0, 2, 3, 5 or 8
0, 2, 3, 5 or 8
ratio was 0.1 kg/m3. All applied roasting process conditions are included
in Table 2. The nibs were roasted until 2% water content (final sample).
2.4. Chocolate preparation
The formulation used for chocolate production contained 40% of
cocoa liquor obtained from cocoa beans roasted in the previously reported conditions (Table 1 – roasting variants I–IV; Table 2 – roasting
variants III and IV), 34% of cocoa butter (total fat content) manufactured
and purchased by Barry Callebaut (Łódź, Poland), 46.89% of powdered
sugar (sucrose manufactured by “Glinojeck S.A.”, Glinojeck, Poland),
0.3% of lecithin (“ZT Kruszwica” from Bunge Group, Kruszwica,
Poland) and 0.01% of ethylvanillin (“Plus Sp. z o. o.”, Łódź, Poland). Chocolates were prepared in a laboratory ball mill (type MK-5, “PROMET”,
Łodź, Poland) of rotational velocity of 75 rpm, operating on a similar
basis to the ball Wiener unit, as follows. Cocoa liquor and cocoa butter
was liquefied in a ball mill and then the powdered sugar was dosed.
Grinding, mixing and conching (“wet” conching) of the chocolate
mass was carried out at 70 °C during 4 h until an average size of solid
particles, which was measured using the micrometric screw NSK
Digitrix-MARK II ELECTRONIC MICROMETER with the electronic readout
of results (Japan Micrometer MFG. Co. Ltd., Osaka, Japan), reached approximately 25 μm. After this time the process' temperature was
lowered to 50 °C and lecithin and ethylvanillin were added. Total time
of grinding, mixing and conching was 5 h. Then, the tempering process
was carried out in a laboratory temperer (type Pomati T8, “POMATI
GROUP srl”, Codogno, Italy). Next, chocolate masses were poured to
forms, cooled, and removed from the forms. Chocolate bars were
wrapped in aluminum foil and subjected to analysis.
2.5. UHPLC-DAD-ESI–MS/MS analysis of phenolic compounds
Phenolic compounds were analyzed according to Oracz et al. (2015)
using UHPLC-DAD-ESI–MS/MS technique. UHPLC analyses were performed using an UHPLC+ Dionex UltiMate 3000 liquid chromatographic system which includes UHPLC pump, an autosampler, a column oven,
a diode array detector with multiple wavelength (Thermo Fisher Scientific Inc., Waltham, MA, USA), and an ultrahigh-resolution hybrid
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
4
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
Fig. 1. Changes in the content of flavanols during the roasting cocoa beans at different temperatures (T = 135 or 150 °C) and air flow rate (v = 0.5 or v = 1 m/s) and a constant humidity of
air (RH = 0.3%); the results are the arithmetic mean from three independent determinations, the relative standard deviation does not exceed 5%.
quadrupole/time-of-flight mass spectrometer (UHR-Q-TOF–MS/MS,
Bruker Daltonics GmbH, Bremen, Germany) using an electrospray ionization (ESI) source operating in negative mode. Instrument control,
data acquisition, and evaluation were done with the OTOFControl 3.2,
HyStar 3.2, and Chromeleon 6.8.1 Chromatography Data System softwares, respectively. The analytical column Accucore™ C18 2.6 μm,
150 mm × 3.0 mm i.d. column (Thermo Scientific, PA, USA) and twophase gradient system of formic acid/water (0.1/99.1, v/v) as mobile
phase A, and acetonitrile/water/formic acid (80/19.98/0.02,v/v/v) as
mobile phase B was used for separation of compounds. The mobilephase gradient used was: 0–5 min, 5% B; 5–6 min, 5–8% B; 6–25 min,
8–15% B; 25–30 min, 15–20% B; 30–35 min, 20–25% B; 35–38 min,
25–30% B; 38–45 min, 30–85% B; 45–52 min, 85–5% B; 52–62 min, 5%
B. The flow rate of the mobile phase was 0.300 mL/min, and the column
temperature was 30 °C. The injection volume was 10 μL. Detection and
quantification was performed with three wavelengths: 280 nm for
flavan-3-ols and gallic acid, 325 nm for chlorogenic acid caffeic acid,
and 365 nm for flavonols. The mass spectrometric conditions were as
follows: capillary voltage, 4500 V; drying gas temperature, 200 °C; drying gas flow, 8.0 L/min; and nebulizing gas pressure, 1 bar. The MS/MS
spectra were obtained in collision-induced dissociation (CID) mode
using nitrogen as the collision gas. The concentration of individual phenolic compounds was determined based on peak area and calibration
curves derived from corresponding reference compounds.
2.6. Statistical analysis
Analyses were carried out in triplicate, starting from cocoa bean and
nibs roasting. All obtained results were subjected to statistical analysis.
The determination comprised of both, average values and one-way
analysis of variance ANOVA using STATISTICA 10 software (StatSoft
Inc., Tulsa, USA) at the significance level of p ≤ 0.05.
3. Results and discussion
3.1. Roasted whole cocoa beans
In the raw cocoa beans the content of phenolic compounds was determined. The groups of flavanols, flavonols and phenolic acids were
identified. In the greatest amount the compounds from flavanones
group were present. These were: (−)epicatechin (196.22 mg/100 g),
(±)catechin (18.81 mg/100 g), procyanidin B1 (91.51 mg/100 g),
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
5
Fig. 2. Changes in the content of flavanols during the roasting cocoa beans at different temperatures (135 or 150 °C) and air flow rate (v = 0.5 or v = 1 m/s) and a constant humidity of air
(RH = 5%); the results are the arithmetic mean from three independent determinations, the relative standard deviation does not exceed 5%.
procyanidin B2 (50.54 mg/100 g), procyanidin C1 (127.46 mg/100 g)
(Figs. 1–3) and (−)gallocatechin (8 mg/100 g - data not included). Similar content of catechin and epicatechin were determined in analyzed
samples by Ioannone et al. (2015) and Kothe et al. (2013). Amounts of
procyanidins B1 were lower than those cited by Kothe et al. (2013) for
beans originating in Côte d'Ivoire. However, in the case of procyanidin
B2, obtained result is similar to that given by the same authors. The
other identified groups of compounds were present in far lower
amounts (from 1 to 40 mg/100 g — data not included). Thus, the research has been limited to the determination of the kinetics of changes
only for the flavanols.
Variants of roasted cocoa beans from I to XXII summarized in Table 1
indicate time intervals in which the kinetics of changes in the content of
polyphenolic compounds was determined. Figs. 1–3 show changes in
the content of each of flavanols relating to the roasting cocoa beans in
the variants I to VIII (Table 1).The influence of the conditions of the
cocoa bean roasting process had a substantial impact on the stability
of flavanols present in the analyzed raw material.
Fig. 1 shows the influence of temperature and air flow rate on the kinetics of changes in the content of the analyzed polyphenolic compounds. These effects were observed with regard to the roasting
carried out under “dry” air. Results obtained in Fig. 1a–f show a beneficial effect of lower flow velocity (v = 0.5 m/s) for all of the analyzed
contents of polyphenolic compounds, but only in relation to the
temperature of 135 °C. When applying such conditions of roasting degradation of most of polyphenol compounds was observed as the process
was prolangated. The exception was observed only for procyanidin B2
which was significantly degraded (approx. 50%) for up to 35 min
(Fig. 1d). Also in the case of catechin other changes of the content of
this compound were observed. Initially, after 15 min of roasting, a
rapid growth was observed, but through the process catechin content
decreased, reaching almost the level of output (Fig. 1a). This pattern
can be explained by changes in the distribution of procyanidins, which
was affirmed in the studies of Kothe et al. (2013).
In the case of using the same air temperature (T = 135 °C) but
higher air flow rate (v = 1 m/s), a very large changes within first
15 min in the contents of most of polyphenol compounds were reported. At this time, the content of these compounds has remained almost
constant. The exception was for catechins, in which case we observed
continuing loss of this combination during the progress of the roasting
process. The observed rapid changes in the contents of individual polyphenol compounds can be explained by higher temperature in roasted
beans and smaller temperature differences between the core of roasted
beans and the temperature, as indicated by studies conducted by
Krysiak and Motyl-Patelska (2006). Applying higher temperature
(150 °C) turning the roasting process shows that to certain polyphenol
compounds the use of smaller air flow rate (v = 0.5 m/s) in the initial
stages of roasting may be advantageous in terms of the degree of
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
6
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
Fig. 3. Changes in the content of flavanols during the roasting cocoa beans at different temperatures (T = 135 or 150 °C) and humidity (RH = 0.3 or 5%) and a constant air flow rate (v =
1 m/s); the results are the arithmetic mean from three independent determinations, the relative standard deviation does not exceed 5%.
preservation of their contents. Such dependence was observed in the
case of catechin, epicatechin, procyanidins B1 and C1 (Fig. 1a, b, c and
e). Marked amounts of these compounds were on higher or similar
level to those identified in the samples of beans roasted in the same
time, but kept at a temperature of 135 °C. However, when the roasting
time is elongated in order to reach 2% water content in the bean, it
was found that in all analyzed samples content of polyphenolic compounds took the lowest value. This should be explained by the higher
temperature of the roasting process. Also Ioannone et al. (2015) observed a marked reduction in the content of flavanol and
proanthocyanidins beans roasted at a temperature of 145 °C and for a
time greater than 30 min. Other character has a curve of procyanidin
B2 loss (Fig. 1d). During the first 15 min the sharp reduction of the content of this compound in roasted bean was observed. After 30 min of the
process its content increased to an amount of 31 mg/100 g. Kothe et al.
(2013) in their study also affirmed that the content of procyanidin B2
increases in beans roasted for 30 min at a temperature of 150 °C.
When the roasting process was carried out at the same temperature,
but higher air flow rate (v = 1 m/s) similar values to that carried out at
v = 0.5 m/s were observed. Final content of the various polyphenolic
compounds achieved by roasted beans were for most of them slightly
lower than that achieved using the air flow rate v = 1 m/s. This is because the roasting process was carried out in a longer time.
In a further research we analyzed the influence of temperature, air
flow rates and use of the “humid” air (RH = 5%) on the degree of preservation of polyphenol compounds in the roasted beans. The results are
shown in Fig. 2a–f. Using the air humidity of 5% radically changed the
nature of the degradation of analyzed polyphenolic compounds. In the
case of application of roasting conditions T = 135 °C and v = 0.5 m/s,
we no longer observe degradation of polyphenolic compounds. For
most of polyphenol compounds change in their contents takes place in
a gradual manner during the roasting process, but is the lowest in comparison with other applied conditions of roasting. The exception is the
preservation of procyanidin B2, for which the greatest degradation occurs for up to 15 min (Fig. 2d). Other dependence resulting from the
course of the curves shows that increasing the flow rate of air to v =
1 m/s results in a better preserving of polyphenolic compounds. This
is because the process is carried out in a shorter time. The reverse dependence was observed for the roasting process carried out at the
higher temperature (T = 150 °C). In this case, application of a lower
air flow rate (v = 0.5 m/s) contributed to a slight degradation of the
compounds for time up to 45 min for polyphenol compounds such as
epicatechin, procyanidin C1. After this time, there was a significant reduction in their amount. Generally, the content of identified polyphenolic compounds was similar to the level obtained for the beans roasted at
a higher air flow rate (v = 1 m/s). Also in the case of air with RH = 5%, in
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
relation to the catechins, an increase in the initial content of these compounds in initial step (25 min) was observed. This may be due to the significant degradation of procyanidin B2.
We also compared the impact of different relative humidity (Fig. 3)
on the degree of preservation of polyphenolic compounds. Applying
the air flow rate of the roasting process at v = 1 m/s shows that, regardless of the air temperature applied preferable to preserve the studied
polyphenolic compounds is to operate in the “humid” air (RH = 5%).
Such changes should be attributed to the nature of the protective action
of the “humid” air. Krysiak, Adamski, and Żyżelewicz (2013) demonstrated that using air at RH = 5% causes less characteristic color of
cocoa beans which is formed as a result of the Maillard reaction. Also
Zzaman et al. (2014) found that roasting process using the superheated
steam allows to obtain beans having a higher content of polyphenolic
compounds. Generally, the slightest degradation of polyphenol compounds is observed when the air temperature of 135 °C and a relative
humidity RH = 5% were used in the roasting process. It should be
noted that the process of degradation of various compounds was different. The most significant degradation was observed for epicatechin,
wherein the reduction process is clear to that compound after 15 min.
Simultaneously for catechins in the initial stage of the process the
growth and then reduction of this value was observed. But after
55 min the amount of the compound was higher than in the raw
beans. Similar correlations were observed by Ioannone et al. (2015)
and Caligiani, Cirlini, Palla, Ravaglia, and Arlorio (2007) who attributed
7
this to phenomenon of epimerization of (−)epicatechin to (+)catechin.
In the case of procyanidin B2 smallest reduction is observed in the case
of using air at 150 °C and also “humid” air. This can be attributed to the
greater presence of cocoa butter in such a roasted nucleus of cocoa
beans as demonstrated in studies conducted by Krysiak and MotylPatelska (2005). This fat forms a protective layer protecting beans
against excessive oxidation or creating other connections, e.g. proteins,
carbohydrates, and Maillard reaction products.
Due to the demonstrated significant effect of the air temperature,
flow rate and relative humidity on the level of preservation of flavanol
compounds, the influence of modulating the process parameters over
time on the kinetics of changes of these substances has been studied.
Since in many cases the significant changes in the polyphenol content
were observed as soon as after 15 min of the process, and it has been
established that after this time the conditions of the process will be varied. The results are shown in Tables 3–5.
Table 3 shows changes in the content of polyphenol compounds
when the roasting process was carried out in a modulated air flow
rates. The results indicate that when the roasting process was conducted at an air temperature of 135 °C, RH = 0.3% and air flow rate of v =
0.5 m/s in first 15 min and then v = 1 m/s until the beans have 2% of
water content, the degradation of the polyphenol compounds occurred
gradually to the end of the process to achieve minimum values. This
change in the quantity of polyphenolic compounds should be explained
by slower heating of the kernels of cocoa beans in the initial stage of
Table 3
The content of flavanol compounds in cocoa beans roasted under modulated air flow rate.
Roasting time
(min)
(+)C
(−)EC
B1
B2
C1
Total
Raw beans
18.81 ± 0.40a
196.22 ± 4.02b
91.51 ± 6.08a
50.54 ± 2.45a
127.46 ± 5.82a
484.54 ± 14.77b
T = 135 °C, RH = 0.3%, v1 = 1 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 0.5 m/s
15
16.91 ± 7.70a
36.15 ± 9.34a
55.10 ± 5.78a
35
13.63 ± 0.28a
58.81 ± 1.38b
46.52 ± 0.82ab
45
6.88 ± 0.20a
38.68 ± 0.92a
41.14 ± 1.62b
50
7.25 ± 1.48a
51.43 ± 1.53ab
54.56 ± 0.79a
21.98 ± 1.98a
20.54 ± 0.37a
23.18 ± 0.40a
28.51 ± 0.72b
67.03 ± 5.09a
85.28 ± 0.34b
60.40 ± 1.23a
78.67 ± 0.49b
197.16 ± 14.49ab
224.77 ± 1.76a
170.27 ± 1.13b
220.42 ± 0.60a
T = 135 °C, RH = 5%, v1 = 1 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 0.5 m/s
15
51.46 ± 0.09b
184.53 ± 0.50c
75.09 ± 0.59b
35
22.91 ± 0.82a
74,.4 ± 14.59b
47.70 ± 2.06a
60
20.78 ± 0.22a
27.20 ± 1.01a
42.85 ± 0.01a
65
20.12 ± 4.17a
48.35 ± 9.12ab
31.75 ± 8.03a
27.22 ± 0.49a
20.69 ± 0.11a
17.77 ± 0.01a
26.83 ± 5.73a
129.63 ± 0.39c
52.21 ± 4.27a
68.09 ± 1.29ab
77.77 ± 6.56b
467.92 ± 2.07b
218.24 ± 20.21a
176.68 ± 2.54a
204.82 ± 33.62a
T = 150 °C, RH = 0.3%, v1 = 1 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 0.5 m/s
15
19.80 ± 0.44b
57.26 ± 1.72a
46.39 ± 2.23b
30
13.52 ± 0.38a
55.09 ± 2.58a
33.93 ± 1.80a
24.90 ± 0.17a
23.22 ± 0.93a
75.21 ± 0.82a
81.69 ± 0.68b
223.56 ± 5.38a
207.45 ± 6.37a
T = 150 °C, RH = 5%, v1 = 1 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 0.5 m/s
15
29.50 ± 3.44b
52.54 ± 3.93a
82.87 ± 10.94b
30
17.72 ± 1.10a
35.27 ± 4.24a
31.64 ± 0.71a
35
15.07 ± 0.43a
42.69 ± 7.33a
19.85 ± 0.94a
36.27 ± 2.62b
20.32 ± 5.70a
22.53 ± 0.28ab
86.60 ± 8.47a
69.86 ± 2.64a
76.11 ± 2.76a.
287.77 ± 29.40b
174.80 ± 5.50a
176.24 ± 11.18a
T = 135 °C, RH = 0.3%, v1 = 0.5 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 1 m/s
15
52.13 ± 0.21c
149.17 ± 4.65a
90.29 ± 4.38c
40
47.56 ± 1.00b
152.12 ± 4.64a
72.17 ± 0.77b
55
9.66 ± 0.33a
30.7 ± 5.52b
36.43 ± 1.18a
45.98 ± 0.81a
45.55 ± 0.30a
24.61 ± 1.08b
102.74 ± 5.07a
109.64 ± 1.02a
63.36 ± 2.02b
440.30 ± 15.11a
427.04 ± 7.73a
164.61 ± 0.92b
T = 135 °C, RH = 5%, v1 = 0.5 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 1 m/s
15
28.61 ± 1.32b
120.27 ± 0.04b
80.63 ± 3.01c
35
13.10 ± 0.02a
61,.65 ± 0.09a
36.09 ± 0.26ab
50
10.16 ± 0.16a
51.27 ± 0.20a
41.93 ± 1.56b
55
15.36 ± 2.90a
55.66 ± 5.14a
28.68 ± 2.32a
25.60 ± 0.30b
19.96 ± 0.23a
23.34 ± 0.28b
18.55 ± 1.38a
108.14 ± 0.57b
61.19 ± 9.09a
59.54 ± 0.19a
74.78 ± 5.85a.
363.24 ± 5.23b
191.97 ± 8.71a
186.23 ± 1.61a
193.02 ± 5.88a
T = 150 °C, RH = 0.3%, v1 = 0.5 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 1 m/s
15
20.81 ± 3.03a
104.16 ± 14.52a
84.45 ± 11.41a
20
17.97 ± 2.37a
59.9 ± 7.01a
71.83 ± 9.87a
35
19.63 ± 3.83a
37.96 ± 23.67b
19.06 ± 1.16b
28.96 ± 4.22b
19.37 ± 0.91ab
12.85 ± 2.77a
104.26 ± 3.25b
74.06 ± 0.70a
83.89 ± 716a
342.63 ± 36.42b
243.01 ± 20.85ab
173.38 ± 28.62a
T = 150 °C, RH = 5%, v1 = 0.5 m/s (for the first 15 min of the process — t1 = 15 min) v2 = 1 m/s
15
76.48 ± 7.37a
157.80 ± 11.55c
64.14 ± 6.03b
30
54.69 ± 0.14a
86.21 ± 0.51b
38.98 ± 0.21a
35
14.99 ± 1.24b
20.31 ± 4.43a
32.91 ± 6.75a
36.08 ± 6.31a
22.67 ± 0.04a
19.57 ± 4.57a
113.66 ± 19.29a
77.23 ± 0,56a
74.23 ± 1.05a
448.15 ± 0.65c
279.7 ± 0.96b
162.00 ± 15.94a
(mg/100 g)
Where: (+)C — (+)catechin, (−)EC — (−)epicatechin; B1, B2, C1 — procyanidins; a–c — values marked with the same letter in a column (for a given roasting process conditions) do not
differ significantly at α = 0.05 in a Tukey test.
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
8
Table 4
The content of flavanol compounds in cocoa beans roasted under modulated air temperature.
Roasting time
(min)
(+)C
(−)EC
B1
B2
C1
Total
(mg/100 g)
T1 = 135 °C (for the first 15 min of the process — t1 = 15 min), T2 = 150 °C, RH = 0.3%, v1 = 1 m/s
36.15 ± 9.34a
55.10 ± 5.78b
15
16.91 ± 7.70a
30
13.37 ± 0.66a
34.26 ± 0.90a
40.69 ± 0.17a
35
17.39 ± 0.57a
29.38 ± 0.25a
51.75 ± 0.25ab
21.98 ± 1.98a
23.79 ± 3.55a
33.91 ± 0.66b
67.03 ± 5.09a
76.19 ± 0.61a
70.47 ± 0.69a
197.16 ± 14.49a
188.29 ± 5.88a
202.90 ± 1.42a
T1 = 135 °C (for the first 15 min of the process — t1 = 15 min), T2 = 150 °C, RH = 5%, v1 = 1 m/s
184.53 ± 0.50b
75.09 ± 0.59ab
15
51.46 ± 0.09a
25
23.50 ± 3.28b
70.60 ± 5.69a
107.37 ± 15.43b
35
43.08 ± 0.01ab
76.87 ± 0.71a
62.14 ± 0.47a
40
47.19 ± 9.08a
78.56 ± 1.03a
58.6 ± 11.38a
27.22 ± 0.49a
32.60 ± 4.82a
31.97 ± 0.08a
25.95 ± 4.89a
129.63 ± 0.39c
97.39 ± 8.61b
6273 ± 0.24a
61,56 ± 9.28a
467.92 ± 2.07b
331.46 ± 37.84a
276.78 ± 0.40c
271.88 ± 35.67c
T1 = 150 °C (for the first 15 min of the process — t1 = 15 min), T2 = 135 °C, RH = 0.3%, v1 = 1 m/s
15
19.80 ± 0.44c
57.26 ± 1.72a
46.39 ± 2.23a
25
18.09 ± 0.46b
59.25 ± 3.48a
46.95 ± 4.00a
35
16.05 ± 0.09a
54.99 ± 0.33a
35.10 ± 0.45b
24.90 ± 0.17b
19.97 ± 0.66a
20.17 ± 0.07a
75.21 ± 0.82a
74.42 ± 4.46a
73.00 ± 0.57a
223.56 ± 5.38a
218.67 ± 12.14a
199.30 ± 0.72a
T1 = 150 °C (for the first 15 min of the process — t1 = 15 min), T2 = 135 °C, RH = 5%, v1 = 1 m/s
15
29.50 ± 3.44a
52.54 ± 3.93a
82.87 ± 10.94b
30
27.97 ± 2.90a
54.11 ± 0.11a
30.80 ± 0.91a
35
28.72 ± 1.20a
66.70 ± 1.03b
20.23 ± 0.21a
36.27 ± 2.62b
22.90 ± 0.17a
23.62 ± 0.96a
86.60 ± 8.47a
76.45 ± 1.05a
81.41 ± 2.11a
287.77 ± 29.40b
212.23 ± 3.37a
220.67 ± 5.50a
Where: (+)C — (+)catechin, (−)EC — (−)epicatechin; B1, B2, C1 — procyanidins; a–c — values marked with the same letter in a column (for a given roasting process conditions) do not
differ significantly at α = 0.05 in a Tukey test.
roasting, but by the end of the process, it has attained a temperature
close to the temperature of the air scorching. For other conditions, a
rapid degradation of the analyzed compounds was observed since the
beginning of the process. In this case, the determining factor of polyphenols degradation was air temperature (150 °C) and the high humidity
(RH = 5%). If the roasting process was carried out for first 15 min
with air flow rate v = 1 m/s and then 0.5 m/s, at temperature of
135 °C, but at RH = 5%, the degradation of polyphenols was a bit milder.
Exception is the behavior of procyanidin B2, for which significant degradation occurred already within the first 15 min irrespective of the conditions used in the roasting process. However, comparing the final
content of polyphenolic compounds in roasted beans should be stated
that they were at a similar level, regardless of the version of the air
flow rate.
The way in which a modulated air temperature will affect the
degree of degradation of polyphenolic compounds was also
analyzed. Results given in Table 4 show that the use of the “wet”
air in the roasting process (RH = 5%) and the modulated temperatures in the system, 135 °C first for 15 min and then 150 °C, until
the beans have approx. 2% of water content resulted in the smallest
marked degradation of the polyphenolic compounds. In other
cases, the greatest degradation of polyphenols occurs within
15 min. The most significant degradation was observed for epicatechin and procyanidin B2 and was independent of the used roasting
conditions used.
The data in Table 5 shows the changes in the content of different
polyphenolic compounds, occurring when modulated relative humidity
was used during the roasting process. Not for all of polyphenol compounds, the use of lower (135 °C) temperature of the roasting air was
better because of the lower degree of degradation. In case of
procyanidin B1 and B2, the roasted beans were characterized by lower
levels of their content.
3.2. Roasted cocoa nibs
The next stage of the study concerned the determination of the content of flavanol compounds in fractions of cocoa nibs of different particle
size (3 fractions). The roasting air temperature was 135 °C, and the humidity was set at 0.3 or 5%. The flow rate was v = 1 m/s. The choice of
these roasting parameters was dictated by the previously conducted researches of Krysiak (2006); Krysiak et al. (2013) and Żyżelewicz,
Krysiak Nebesny and Budryn (2014), wherein it is shown that the
cocoa beans earn a number of beneficial characteristics (e.g. brown
color) in the proposed thermal processing conditions. The content of analyzed flavanol compounds in cocoa nibs subjected to roasting is summarized in Fig. 4.
In the course of the study, no significantly adverse effect of the process of obtaining dried nibs on the content of phenolic compounds in
different nib fractions was reported. The same flavanol compounds
were determined in obtained cocoa nibs as in raw cocoa beans. It was
Table 5
The content of flavanol compounds in cocoa beans roasted under modulated air relative humidity.
Roasting time
(min)
(+)C
(−)EC
B1
B2
C1
Total
T1 = 135 °C, RH1 = 5% (for the first 15 min of the process — t1 = 15 min), RH2 = 0.3%, v1 = 1 m/s
15
51.46 ± 0.09d
184.53 ± 0.50d
75.09 ± 0.59c
30
21.09 ± 0.38a
142.04 ± 1.15c
43.50 ± 1.27a
45
24.50 ± 0.98b
98.08 ± 5.19a
30.92 ± 0.64b
50
30.46 ± 1.04c
128.68 ± 1.32b
46.37 ± 1.06a
27.22 ± 0.49b
26.62 ± 0.06b
18.44 ± 0.28a
19.05 ± 0.52a
129.63 ± 0.39c
111.15 ± 1.07b
141.15 ± 1.85d
77.07 ± 0.97a
467.92 ± 2.07c
344.39 ± 1.66b
313.08 ± 8.94b
301.62 ± 4.91b
T1 = 150 °C, RH1 = 5% (for the first 15 min of the process — t1 = 15 min), RH2 = 0.3%, v1 = 1 m/s
15
29.50 ± 3.44a
52.54 ± 3.93a
82.87 ± 10.94a
20
28.39 ± 1.32a
53.01 ± 17.20a
69.81 ± 0.07a
30
29.10 ± 1.10a
60.88 ± 6.40a
57.28 ± 0.86a
35
21.37 ± 5.88a
59.01 ± 5.08a
54.59 ± 11.22a
36.27 ± 2.62a
28.50 ± 0.71a
22.12 ± 0.81a
26.31 ± 7.51a
(mg/100 g)
86.60 ± 8.47b
62.54 ± 0.37a
64.98 ± 0.95ab
77.47 ± 7.09ab
287.77 ± 29.40b
242.25 ± 19.66a
234.35 ± 10.61a
238.74 ± 25.02a
where: (+)C — (+)catechin, (−)EC — (−)epicatechin; B1, B2, C1 — procyanidins; a–c – values marked with the same letter in a column (for a given roasting process conditions) do not
differ significantly at α =0.05 in a Tukey test.
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
Fig. 4. Changes in the content of flavanols during the roasting cocoa nibs at different humidity of air (RH = 0.3 or 5%) and a constant temperature of air (T = 135 °C) and constant (flow rate (v = 1 m/s); CNF1 — cocoa nibs-fraction F1; CNF2 — cocoa
nibs-fraction F2; and CNF3 — cocoa nibs-fraction F3; the results are the arithmetic mean from three independent determinations, the relative standard deviation does not exceed 5%.
9
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
10
Table 6
The composition of phenolic compounds extracted from cocoa nib fraction roasted under modulated process conditions.
Conditions of roasting
(+)C
(−)EC
B1
B2
C1
Total
159.82 ± 3.22b
88.25 ± 2.56b
36.30 ± 1.04b
120.15 ± 3.01b
412.32 ± 11.67b
159.98 ± 4.00b
127.37 ± 1.25a
153.4 ± 2.00b
151.34 ± 1.37b
82.16 ± 0.16b
52.01 ± 0.20a
55.17 ± 0.55a
52.01 ± 1.08a
30.10 ± 0.08b
12.02 ± 0.10a
13.02 ± 0.50a
12.10 ± 0.35a
111.42 ± 1.56b
87.02 ± 1.02a
88.28 ± 3.47a
86.98 ± 2.05a
409.24 ± 6.20b
298.84 ± 2.88a
332.37 ± 6.97a
322.79 ± 5.29a
140.19 ± 1.25a
148.97 ± 4.00a
163.81 ± 1.53b
146.86 ± 1.34a
70.10 ± 0.01b
78.22 ± 2.78b
68.13 ± 1.98b
67.07 ± 0.12b
25.08 ± 0.02a
24.18 ± 1.02a
23.05 ± 1.05a
24.10 ± 0.02a
78.95 ± 0.04a
92.22 ± 3.52a
80.25 ± 2.47a
79.20 ± 0.31a
333.97 ± 1.77a
361.44 ± 11.86a
353.81 ± 7.38a
335.38 ± 2.09a
177.57 ± 1.78c
145.01 ± 1.03a
148.11 ± 1.12a
145.45 ± 1.00a
51.13 ± 1.05a
45.44 ± 0.70a
44.50 ± 0.82c
44.09 ± 1.50c
12.12 ± 0.79a
10.08 ± 0.67a
9.58 ± 0.52a
10.01 ± 0.82
87.39 ± 2.66a
80.40 ± 0.63a
79.51 ± 0.16a
78.96 ± 0.18a
348.47 ± 6.60a
295.53 ± 3.28c
295.14 ± 2.82c
292.59 ± 3.75c
145.00 ± 1.20a
153.20 ± 1.30a
135.33 ± 1.07c
53.39 ± 1.35a
65.12 ± 2.02a
52.05 ± 0.95a
14.21 ± 0.54a
18.02 ± 0.79a
13.12 ± 0.45a
89.39 ± 2.66a
90.18 ± 2.69a
85.28 ± 0.65a
324.79 ± 6.07a
345.85 ± 7.25a
294.76 ± 4.24c
(mg/100 g)
Dried nibs
18.80 ± 0.80a
Changing the temperature from 135 to 150 °C
RH = 0.3%
135 °C/2 min
16.58 ± 0.40c
135 °C/2 min + 150 °C/3 min
20.42 ± 0.31b
135 °C/2 min + 150 °C/5 min
22.50 ± 0.45b
135 °C/2 min + 150 °C/8 min
21.36 ± 0.46b
RH = 5%
135 °C/2 min
19.65 ± 0.45a
135 °C/2 min + 150 °C/3 min
17.85 ± 0.54a
135 °C/2 min + 150 °C/5 min
18.57 ± 0.35a
135 °C/2 min + 150 °C/8 min
18.15 ± 0.30a
Changing the temperature from 150 to 135 °C
RH = 0.3%
150 °C/2 min
20.26 ± 0.32a
150 °C/2 min + 135 °C/3 min
14.37 ± 0.25b
150 °C/2 min + 135 °C/5 min
13.44 ± 0.20b
150 °C/2 min + 135 °C/8 min
14.08 ± 0.25b
RH = 5%
150 °C/2 min
22.80 ± 0.32b
150 °C/2 min + 135 °C/3 min
19.33 ± 0.45a
150 °C/2 min + 135 °C/8 min
8.98 ± 0.12c
Where: (+)C — (+)catechin, (−)EC — (−)epicatechin; B1, B2, C1 — procyanidins; a–c — values marked with the same letter in a column (for a given roasting process conditions) do not
differ significantly at α = 0.05 in a Tukey test.
found that the extract obtained from the raw cocoa nibs contained the
largest amount of the following compounds: epicatechin (159.82 mg/
100 g), procyanidin B1 (88.25 mg/100 g), procyanidin B2 (36.30 mg/
100 g), procyanidin C1 (120.15 mg/100 g) and catechin (18.80 mg/
100 g) (Fig. 4).
In the literature, there is no study on the kinetics of changes in the
content of phenolic compounds during the course of the roasting process of cocoa nibs, including nibs of different particle size. Lee, Yoo,
Lee, Kwon, and Yu-Ryang (2001) determined changes in polyphenol
content using Burns and vaninilin-HCl method. The degradation of phenolic compounds was indicated in cocoa nibs but without specifying the
particle size.
It was found that the stability of flavanol compounds is influenced
both by a degree of cocoa nibs fineness and relative humidity of roasting
air. Generally, the greatest changes in the content of polyphenol compounds were observed for the cocoa nibs having the highest degree of
milling (fraction F3) and was applied independently of relative
humidity. The exception is the behavior of procyanidin B2, which has
the highest degree of degradation in the roasted nibs of the largest particles (fraction F1). Moreover, roasting cocoa nibs under “dry” air
(RH = 0.3%) resulted in constant degradation of the individual polyphenol compounds during the roasting process. In contrast, when the
roasting was performed in the “humid” air a sudden loss of polyphenolic
compounds was observed usually at the time of 2 or 7 min followed by a
stabilization in their content. This behavior can be attributed to the protective action of moisture in the air surrounding the roasted cocoa nibs.
A protective effect of “humidity” of air also indicates a higher content of
flavanols marked as roasted nibs, regardless of the degree of
fragmentation.
Comparing the character of changes of polyphenolic compounds
taking place in the roasted nibs and whole cocoa beans it should be
noted that in the case of roasting the cocoa nibs an increase in the content of catechins in the analyzed samples (Fig. 1a, Fig. 4a, b) is not observed. Furthermore, although a high degree of fragmentation of a
Table 7
The composition of phenolic compounds extracted from received chocolates.
Conditions roasting cocoa beans and receiving chocolate
(+)C
(−)EC
Procyanidin B2
Total
Chocolates obtained from cocoa liquor prepared from beans roasted as whole cocoa beans
T = 135 °C, RH = 0.3%, v = 1 m/s, t = 35 min — sample 0⁎
7.08 ± 0.35a
T = 135 °C, RH = 0.3%, v = 1 m/s, t = 35 min — sample 5⁎⁎
6.90 ± 0.33a
T = 135 °C, RH = 5%, v = 1 m/s, t = 50 min — sample 0⁎
7.14 ± 0.25a
T = 135 °C, RH = 5%, v = 1 m/s, t = 50 min — sample 5⁎⁎
7.66 ± 0.26a
T = 150 °C, RH = 0.3%, v = 1 m/s, t = 25 min — sample 0⁎
8.50 ± 0.31b
T = 150 °C, RH = 0.3%, v = 1 m/s, t = 25 min — sample 5⁎⁎
10.16 ± 0.67b
T = 150 °C, RH = 5%, v = 1 m/s, t = 30 min — sample 0⁎
10.22 ± 0.53b
T = 150 °C, RH = 5%, v = 1 m/s, t = 30 min —sample 5⁎⁎
10.35 ± 0.45
498.84 ± 5.40a
495.48 ± 6.06a
455.77 ± 5.09c
434.02 ± 5.11c
578.81 ± 4.96b
583.91 ± 3.98b
629.24 ± 4.56b
607.00 ± 2.90
13.77 ± 0.45a
14.77 ± 0.96a
14.37 ± 0.89a
11.27 ± 0.78b
14.63 ± 0.91a
13.10 ± 0.65aa
13.18 ± 0.94a
13.47 ± 0.87
519.69 ± 6.20a
517.15 ± 7.35a
477.28 ± 6.23b
452.95 ± 6.16b
601.94 ± 6.18a
607.17 ± 5.30a
652.64 ± 6.03c
630.82 ± 4.22
Chocolates obtained cocoa liquor prepared from beans roasted as cocoa nibs
T = 135 °C, RH = 0.3%, v = 1 m/s, t = 7 min — sample 0⁎
7.36 ± 0.21a
T = 135 °C, RH = 0.3%, v = 1 m/s, t = 7 min — sample 5⁎⁎
8.26 ± 0.56a
T = 135 °C, RH = 5%, v = 1 m/s, t = 10 min — sample 0⁎
7.94 ± 0.78a
T = 135 °C, RH = 5%, v = 1 m/s, t = 10 min — sample 5⁎⁎
8.76 ± 0.36a
508.51 ± 4.68a
502.05 ± 3.59a
512.80 ± 2.79a
507.53 ± 5.11b
14.83 ± 0.93a
10.48 ± 0.76b
9.82 ± 0.78b
11.49 ± 0.85b
530.70 ± 5.82a
520.79 ± 4.91a
530.56 ± 4.35a
527.78 ± 6.32a
(mg/kg d.m.)
Where: (+)C — (+)catechin, (−)EC — (−)epicatechin; a–c — values marked with the same letter in a column (for a given roasting process conditions) do not differ significantly at α =
0.05 in a Tukey test.
⁎ 0 — sample after mixing the raw materials.
⁎⁎ 5 — ready chocolate (the chocolate mass of grinding 5 h).
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
larger meal, there was no degradation of the analyzed polyphenol compounds, compared to their content in the whole roasted beans. The exception is the content of procyanidin B2, the smallest amounts (approx.
12 mg/100 g) was determined in samples of nibs (Fig. 1d, Fig. 4h).
Analyzing the changes in the content of flavanol compounds in the
whole cocoa beans roasted under variable temperature conditions, it
has been shown that for certain applied variants changing the temperature had a positive impact. By analogy, such study was undertaken
for nibs. So far, no such study is described in the literature. Only nibs
from fraction F2 were subjected to roasting. The choice of fraction
with this particle size was dictated by its high degree of preservation
of the total sum of flavanol compounds. Additionally, Brito et al.
(2000), conducting a research on the impact of the roasting process
on the changes in structure roasted cocoa nibs and the chemical compounds (carbohydrates, free amino acids) recommended roasting nibs
to 3 mm.
Moreover, other obtained results (low acidity – unpublished data,
high degree of fatty acids conservation, low levels of acrylamide and
acrolein content – unpublished data) point to the advantages resulting
from roasting cocoa nibs with this particle size.
The results summarized in Table 6 illustrate how applied modulated
conditions of air temperature affect the rate of phenolic compounds
degradation. The roasting process was carried out in two variants of
modulated temperature. One of them was roasting nibs for 2 min at
135 °C and then at 150 °C at time required for nibs to reach a 2%
water content. The second variant was applying 150 °C for first 2 min
and then changing the temperature to 135 °C again for time required
for nibs to reach a 2% water content. For both versions of variable temperature, the roasting process was conducted under conditions of “dry”
(RH = 0.3%) and “humid” air (RH = 5%).
The roasting of cocoa nibs at 135 °C for 2 min followed by roasting at
150 °C for another 8 min, irrespective of the relative humidity applied,
resulted in the loss of most of the phenolic compounds. The amount of
epicatechin was decreased for about 12–20% and of procyanidins for
about 27–36%. In the case of catechin, an increase in its content was observed after the process of roasting. According to Dorta, Lobo, and
González (2012) and Suazo, Davidov-Pardo, and Arozarena (2014),
this may be due to the release of the simpler forms of phenolic compounds from their complex structures under the influence of elevated
temperature. Loss of total phenolic compounds was observed as soon
as after 2 min of the process. The use of “humid” air (RH = 5%) allowed
for better preservation of flavanol compounds.
The second variant of roasting process, i.e. starting at 150 °C for
2 min followed by roasting at the temperature reduced to 135 °C in
time required for nibs to reach 2% water content, regardless of relative
humidity of air, resulted in a greater reduction in the content of all
flavanol compounds as compared to the method described above. A decisive factor was then the initial temperature, which heated the nibs
with such intensity that further heating with air at lower temperature
(135 °C) had still the impact of the higher one.
3.3. Chocolate
The last stage of the study included the receipt of the chocolates
from a selected versions of whole roasted beans or cocoa nibs. The conditions of roasting the beans and nibs as well as the results of the content of polyphenolic compounds in chocolates obtained from prepared
cocoa liquor from this forms cocoa are shown in Table 7. Amount of
polyphenolic compounds was determined in the chocolates directly
after mixing of all components in a ball mil (without the lecithin — sample labeled “0”) and the chocolates after 5 h of conching (sample labeled
“5”).
In the analyzed chocolate samples, independently of the time of
conching, polyphenolic compounds from flavanol group were determined. Epicatechin appeared in the largest amounts. Depending on
the conditions of roasting of whole cocoa beans or nibs determined
11
epicatechin content was at the level of 434.02 mg/kg d.m. (T =
135 °C; RH = 5%; v = 1 m/s; t = 50 min) (Table 7 line 4, row 3) to
629.24 mg/kg d.m. (T = 150 °C; RH = 5%; v = 1 m/s; t = 30 min)
(Table 7 line 7, row 3). Catechin was also present in obtained chocolates,
in amounts of 6.90 mg/kg d.m. (T = 135 °C; RH = 0.3%; v = 1 m/s; t =
35 min) (Table 7 line 2, row 2) to 10.35 mg/kg d.m. (T = 150 °C; RH =
5%; v = 1 m/s; t = 30 min) (Table 7 line 8, row 2). In addition, the
Table 7 shows the contents of procyanidin B2. This kind of a polyphenolic compound is selected from yet other designated procyanidins mainly
due to the previously disclosed significant deterioration in both roasted
beans, and nibs. The obtained results do not indicate clearly that the
conduction of the process of conching unambiguously contribute to reduce level of procyanidin B2. In some cases, it has been shown a marked
reduction (up to 20%) of this compound compared to its content in mass
immediately after mixing. This resulted at the same time in increase in
the content of catechin and epicatechin. Also, Di Mattia et al. (2014)
studying the impact on the process of “wet” conching on the content
of procyanidins observed increase or decrease of some of their types.
Moreover, the chocolates obtained from the nibs were characterized
by a higher content of the individual flavanol compounds compared to
the chocolates obtained from the whole cocoa beans roasted under
the same conditions.
Taking into account total content of polyphenolic compounds in the
chocolate masses it has to be noted that the conching process does not
contribute to the significant degradation of this compounds. This should
be attributed to the conduction of the process of conching in the mild
temperatures (50–70 °C), but also the use of “wet” conching. A large
amount of cocoa butter present from the beginning of the process in
the chocolate mass hampers oxidation of polyphenol compounds. It
can be confirmed by Di Mattia et al. (2014), who observed a greater degradation of procyanidins in the masses, for whom the process of “wet”
conching lasted only 1 h.
4. Conclusions
The roasting process conditions affected the stability of polyphenols
contained in the cocoa beans. These compounds were more stable in
samples of beans roasted in air with increased relative humidity, regardless of other applied constant conditions of temperature and air flow
rate. It has been shown that the use of air flow rate v = 0.5 m/s and
RH = 0.3% resulted in lower degradation of polyphenolic compounds
compared to use of the flow rate v = 1 m/s during roasting. It has
been found that regardless of the roasting conditions the greatest degradations were observed for epicatechin and procyanidin B2, while at the
same time the catechin content increased. Modulated air temperature,
flow rate and relative humidity applied in the course of the process resulted in a reduction of flavanol compounds stability as compared to
constant conditions of the process, but the character of degradation is
similar. In the case of roasting cocoa nibs under constant conditions of
a significant importance were both the particle size of roasted nibs
and relative humidity of roasting air applied during the process. The
largest degradation of polyphenolic compounds was observed in the
roasted nibs' fraction of sieve mesh between 7 and 10 and nibs roasted
in “humid” air. It has been shown that roasting cocoa nibs by modulating temperature over time causes the greatest polyphenols degradation
when the following variant of temperatures was applied: 150 °C/
2 min + 135 °C/8 min.
The process of chocolate preparation adversely influenced the concentration of various phenolic compounds in the finished products,
however, the loss of these substances was not high.
Acknowledgments
Authors are grateful for the financial support provided by National
Science Centre (project No. N N312 1020 38).
Please cite this article as: Żyżelewicz, D., et al., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs and
chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026
12
D. Żyżelewicz et al. / Food Research International xxx (2016) xxx–xxx
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chocolates, Food Research International (2016), http://dx.doi.org/10.1016/j.foodres.2016.03.026