LWT - Food Science and Technology 68 (2016) 385e390
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LWT - Food Science and Technology
journal homepage: www.elsevier.com/locate/lwt
The comparison of quality and microbiological characteristic of
hamburger patties enriched with green tea extract using three
techniques: Direct addition, edible coating and encapsulation
a, *
€
Emin Burçin Ozvural
, Qingrong Huang b, Michael L. Chikindas c, d
a
Cankiri Karatekin University, Faculty of Engineering, Department of Food Engineering, Uluyazi Campus, 18200 Cankiri, Turkey
Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901, USA
Health Promoting Naturals Laboratory, School of Environmental and Biological Sciences, Rutgers State University, New Brunswick, New Jersey 08901, USA
d
Center for Digestive Health, New Jersey Institute for Food, Nutrition, and Health, New Brunswick, New Jersey 08901, USA
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 April 2015
Received in revised form
16 December 2015
Accepted 17 December 2015
Available online 22 December 2015
This study was aimed at the comparison of the effects of green tea extract (GTE) added with different
techniques (direct addition, edible coating and encapsulation) on quality (particularly oxidative) and
microbiological properties of hamburger patties. High molecular weight (1000 kDa) chitosan was utilized
as the coating material and chitosan-TPP solution was formed for encapsulation of the extract. At the
beginning (day 0) and in the middle of storage (day 4), control patty and the patties including GTE had
higher pH values than the coated patties (p < 0.05) probably due to the inhibition effect of coating
materials as a barrier on microbiological growth. TBARS value of control patty was higher than the other
treatments in each measuring time (on the days 0, 4 and 8). This showed that enrichment of treatments
by adding or coating with encapsulated green tea extract solution led to attenuation effect against lipid
oxidation. However, TBARS value of all the treatments increased throughout storage, except the treatment coated with 1% (w/w) chitosan solution (p > 0.05). According to microbiological results, there were
significant differences among the treatments.
© 2015 Elsevier Ltd. All rights reserved.
Keywords:
Green tea extract
Hamburger
Edible coating
Encapsulation
1. Introduction
Meat products are very popular among food items (Lee et al.,
2005). Although synthetic additives have been widely used in the
meat industry to inhibit both the process of lipid oxidation and
microbial growth, natural additives are preferred in place of them
in recent years because of the growing concern among consumers
about such chemical additives. Compounds obtained from natural
sources such as grains, oilseeds, spices, fruit and vegetables have
been investigated. Therefore, the development and application of
natural products with both antioxidants and antibacterial activities
in meat products may be necessary and useful to prolong their
storage shelf life and potential for preventing food diseases
ndez-Lo
pez, Zhi, Aleson-Carbonell, Pe
rez-Alvarez, & Kuri,
(Ferna
2005).
Although use of edible coatings and films to preserve food
quality is not a novel concept, research in this field at academic,
* Corresponding author.
http://dx.doi.org/10.1016/j.lwt.2015.12.036
0023-6438/© 2015 Elsevier Ltd. All rights reserved.
government, and private industry laboratories has intensified
recently. The action of these coatings as a barrier to the passage of
oxygen and water, thereby slowing oxidation reactions and
retaining moisture, is the main mechanism used by coatings to
enhance quality and extend storage life. Furthermore, adding plant
extracts gives the coatings antimicrobial and antioxidant properties
mez-Estaca, Montero, Gime
nez, & Gόmez-Guille
n, 2007). As
(Go
there is a demand for convenient ‘‘value added’’ meat products of
good acceptability and low price, much effort has been devoted to
improving the quality of precooked meat products using appropriate coatings and/or the addition of antioxidants (Biswas, Keshri,
& Bisht, 2004).
Encapsulation and controlled-release of active food ingredients
are important applications in food and nutrition that can be
attained with nanotechnological approaches (Huang, Yu, & Ru,
2010). Encapsulation involves the incorporation of food ingredients, enzymes, cells or other materials in small capsules. Applications for this technique have increased in the food industry
since the encapsulated materials can be protected from moisture,
heat or other extreme conditions, thus enhancing their stability and
386
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et al. / LWT - Food Science and Technology 68 (2016) 385e390
maintaining viability. Reducing the size of the encapsulates offers
opportunities related with prolonged gastrointestinal retention
time caused by bio-adhesive improvements in the mucus covering
the intestinal epithelium (Bouwmeester et al., 2009; Ferreira,
Rocha, & Coelho, 2007; Garcia, Forbe, & Gonzales, 2010; Gibbs,
Kermasha, Alli, & Mulligan, 1999; Neethirajan & Jayas, 2011).
Green tea is a popular beverage in Asia for many years and
believed to have more beneficial effects on health than other tea
beverages. Many studies showed that green tea extracts, which are
rich in polyphenols and catechins, have antibacterial, antiviral and
radical scavenging activities (Chiu & Lai, 2010; Manea, Vasile, &
Meghea, 2014).
Green tea catechins are the predominant group of polyphenolic
compunds present in unfermented dried leaves of the plant. Biological and pharmacological effects (anti-inflammatory, antimicrobial, antitumour, anti-oxidative and anti ageing) of green tea leaf
extract have been attributed to green tea catechins. Green tea
catechins are comprised of four compounds which are epicatechin,
epicatechin gallate, epigallocatechin and epigallocatechin gallate.
All the catechins have synergistic effect, therefore the crude green
tea leaf extract exhibits higher antimicrobial activity than do isolated green tea catechins (Sharma, Gupta, Sarethy, Dang, & Gabrani,
2012; Wanasundara & Shahidi, 1998).
The aim of the study is to incorporate various antioxidantive
substances into the hamburger patties by using different techniques in order to retard the deterioration of the patties during
storage and to find the healthiest products in terms of lipid
oxidation and microbial quality.
2. Materials and methods
2.1. Preparation of edible coating solution by using chitosan
A 1% (w/w) chitosan solution (95% deacetylated, MW: 1000 kDa,
obtained from Golden-Shell Pharmaceutical Co., Ltd., China) was
dispersed in acetic acid solution (10 ml glacial acetic acid (99.8%)/1L
distilled water) with addition of 25% glycerol. The film forming
chitosan solution was stirred until dissolution (Park, Daeschel, &
Zhao, 2004).
2.2. Preparation of solution including microparticles
Microparticles were achieved by the cross linking of chitosan
(95% deacetylated, MW: 1000 kDa) - sodium tripolyphosphate (CSTPP) solution (5:1 mass ratio). Chitosan (1%) was dissolved in 1%
acetic acid solution to form chitosan solution. TPP (85%, technical
grade, Acros Organics, Morris Plains, NJ) solution (0.2%, w/v) dissolved in Milli-Q water were dropped into 1% chitosan, in order to
form CS-TPP microparticles. After that, ultrasonication (3.75 W/mL
energy output) was applied to the solutions for 3 min.
The solution including 0.5% green tea extract (98%) was also
prepared. The green tea extract (98% pure) used in the study mainly
contained 63.73% (e)-epigallocatechin gallate (EGCG), 21.58%
(e)-epicatechin gallate (ECG), 3.76% caffeine, 3.44% epicatechin
(EC), 1.24% (e)-epigallocatechin (EGC). This extract was added into
the chitosan solution (1%) and then the dropwise addition of TPP
(0.2%) was performed to form microparticles loaded with green tea
extract.
2.3. Particle size of the solutions
Particle size of the solutions were measured by dynamic light
scattering instrument (Brookhaven BIC 90 plus) equipped with a
Brookhaven BI-9000AT digital correlator (Brookhaven Instrument
Corp, New York, NY). All measurements were performed in
triplicate with the detection angle of 90 at 25 ± 1 C.
2.4. Formulation of hamburger patties
Hambuger patties of the formulations with GTE were prepared
with minced meat from a local supermarket (80% lean beef þ 20%
fat), 0.80% salt and 0.20% black pepper. All the hamburger patties
were formed by using a steel mould made for hamburger preparation in order to maintain the size of the treatments totally same.
In this study, 8 different treatments of hamburger patties were
prepared (Table 1). First treatment was the control and prepared as
given above. In treatment 2, 5% GTE was added into the patty out of
total weight of the product. In treatments 3 and 4, the solution
including encapsulated GTE (CS þ 0.5% GTE þ TPP) was incorporated into the patties as 1% and 5% out of total weight, respectively.
The other treatments (5e8) were coated by dipping method. The
hamburger patty samples were immersed into the solutions given
in Table 1 at room temperature, held 5 s and then left to dry 30 s.
This process was repeated 3 times. After dipping process, patties
were dried in biological safety cabinet for 1 h.
All the treatments were stored in an aluminium plate covered
with cling film at 4 C for 8 days and analyzed on the 0, 4 and 8 days
of storage. The treatments were not stored more than 8 days,
because they began to spoil and stink.
2.5. Moisture analysis
Oven drying method was used to find the total moisture contents of the treatments. Moisture was calculated according to the
weight difference of the sample before and after drying for 2 h at
125 C and given as percent value (AOAC, 1990). Three repetitions
were implemented for each treatment.
2.6. pH values
The pH values of the treatments was conducted by immersing a
common pH-electrode into the sample and measuring the value.
The experiments were attained in quadruplicate for each
treatment.
2.7. TBARS (2-thiobarbituric acid) analysis
TBA method was performed as given by Pikul, Leszczynski, and
Kummerow (1989) and Ulu (2004). Aqueous extraction method
was preferred and perchloric acid (4% perchloric acid in distilled
water), butylated hydroxyanisole (7.2% BHA in 98% ethanol), and
TBA solution (0.02M in distilled water) were used as reagents. The
heating part of the experiment was done for 40 min at 80 C. TBA
values were determined as amount of malonaldehyde. Absorbance
values at 532 nm were used to calculate the TBA value as mg
malonaldehyde/kg sample. Four repetitions were applied at each
experimental group.
Table 1
Formulation of Treatments with green tea extract.
Green tea extract (GTE) added hamburger patties
Coated hamburger patties
1234-
5678-
Control
5% GTE
1% (CS þ 0.5% GTE þ TPP)
5% (CS þ 0.5% GTE þ TPP)
CS
CS þ 0.5% GTE
CS þ TPP
CS þ 0.5% GTE þ TPP
GTE: Green tea extract, CS: Chitosan, TPP: Sodium tripolyphosphate.
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2.8. Colour values
The colour analysis of the hamburgers was performed by ‘Konica
Minolta chroma meter CR-200 instrument based on Hunter colour
scale. The instrument was calibrated to standard black and white
tiles before analysis. CIE ‘L*’ lightness, ‘a*’ redness, ‘b*’ yellowness
were determined from four random different surface of the
samples.
2.9. Microbiological analysis
2.9.1. Total mesophilic aerobic count analysis
Plate Count Agar (PCA) was prepared and poured into Petri
dishes. After solidifying, the agar was stored in the fridge until used.
0.025 ml of each patty homogenate and of such dilutions were
pipetted into a petri dish in triplicate. Prepared dishes were incubated at 35e37 C for 48 h. Following incubation all colonies on
dishes were counted. The results were calculated and given as
logcfu/g sample.
2.9.2. Coliform bacteria analysis
0.1 ml of the patty homogenate and of each dilution were
pipetted into each of petri dishes (three repetitions). 10e12 ml
Violet Red Bile Agar (VRBA) which was tempered to 48 C was
poured into each petri dish and plates were swirled to mix and
allowed to solidify. After that, 3e5 ml VRBA was overlayed. Dishes
were inverted after solidification of the agar and incubated at
35e37 C for 18e24 h.
Following incubation, all colonies that were purple red in colour
and surrounded by a zone of precipitated bile acids are counted.
The total number of colonies per plate is multiplied with the
reciprocal of the dilution used and reported as logcfu/g sample.
2.9.3. Yeast and mould analysis
Potato Dextrose Agar (PDA) was prepared according to formulation. After sterilization, PDA was acidified with sterile 10% tartaric
acid to pH 3.5. Medium was not reheated once acid had been added.
10e12 ml of the agar medium (tempered to 45 C) was poured into
Petri dishes and allowed to solidify. The agar was stored in the
fridge until used.
0.025 ml of each patty homogenate and of such dilutions were
pipetted into a petri dish in triplicate. Prepared dishes were incubated at 30 C for 5 days. Following incubation all colonies on
dishes were counted. The results were calculated and given as
logcfu/g sample.
387
ranging from 200 to 300 nm. Hassani, Laouini, Fessi, and
Charcossett (2015) and Gan, Wang, Cochrane, and McCarron
(2005) stated that the particle size increased when increasing the
chitosan concentration and molecular weight. Chitosan with lower
molecular weight tends to form smaller nanoparticles because
shorter chitosan chains were easier to penetrate into the chitosaneTPP complexes. In that case, high concentration of chitosan
and TPP or high molecular weight of chitosan might lead to occur
larger particles in our study.
Moisture content of the patties are given in Table 2. Significant
differences were found among the moisture content of the treatments at the beginning (day 0) and the last day (day 8) of the
storage (p < 0.05), but there were no difference among the values in
the middle (day 4) of the storage. Moisture content of the control
decreased (p < 0.05) after production day. However, the moisture
content of both 5% pure and 1% encapsulated GTE solution added
treatments did not alter throughout storage time (p > 0.05). There
were also no significant difference in moisture contents of the
treatments coated with pure chitosan and chitosan with GTE solutions during time (p > 0.05). Treatments which were coated by
solutions including nanoparticles lost moisture after production
day (p < 0.05). Although significant differences were determined,
low differences were observed in numerical among the values. In
literature, coating of patties mostly decreased moisture loss. Kang
et al. (2007) indicated that moisture content of pork patties with
pectin-based coating materials was higher than the patties with
pectin-based coating material containing green tea power or control. Guerrero, Arana, O'Grady, Kerry, and de la Caba (2015) used soy
protein-based coating in beef patties and found that the coating
prevented moisture loss during storage at 4 C.
According to pH values shown in Table 2, significant differences
were detected among the treatments. The pH value of all the
treatments ascended during storage (p < 0.05). The increase in pH
is due to the accumulation of metabolites by bacterial action in
meat and deaminations of proteins (Biswas et al., 2004). It was
observed that both in the beginning (day 0) and in the middle days
of storage (day 4), control and the treatments including additives
(treatments 2e4) had higher pH values than the coated treatments
(treatments 5e8) (p < 0.05). This was likely because of the inhibition effect of coating materials as a barrier on microbiological
Table 2
Moisture (%) and pH values of hamburger patties processed with green tea extract
and stored for 8 days at 4 C.
Storage time (day)
2.9.4. Statistical analysis
The data from the frankfurter analysis were treated with the
procedure ANOVA from Minitab 16 for Windows program. Means
were compared with Tukey's test.
3. Results and discussion
According to the solutions of crosslinking chitosan (CS) with
sodium tripolyphosphate (TPP), the concentration of the solutions
affected the particle sizes. It was found that the solution including
1% CS þ 0.5% Green tea extract (GTE) þ 0.2% TPP contained larger
particles (7.585 mm) than the solution of 1% CS with 0.2% TPP
pez-Leo
n, Carvalho, Seijo, Ortega-Vinuesa, and Bas(6.658 mm). Lo
tos-Gonz
alez (2005) studied some physical properties of nanogel
particles formed by chitosan ionically cross-linked by tripolyphosphate (TPP) and detected the size of particles to be 0.2e0.3 mm.
Luo, Zhang, Cheng, and Wang (2010) mixing of low molecular
weight CS with TPP (5:1 mass ratio) led to the formation of
spherical particles with uniform particle size in the nanoscale,
Treatment 0
Moisture (%) 1
2
3
4
5
6
7
8
pH
1
2
3
4
5
6
7
8
66.96abcA
66.20cA
66.66bcA
68.24aA
66.95abcA
66.88bcA
66.88bcA
67.79abA
5.49bC
5.56aC
5.59aC
5.56aC
5.29dC
5.24dC
5.38cC
5.39cC
4
± 0.58
65.69aAB ± 0.94
± 0.44 65.49aA ± 0.67
± 0.37
65.64aA ± 1.41
± 0.20
67.14aAB ± 0.57
± 0.36
66.37aA ± 0.87
± 0.63
66.19aA ± 0.51
± 0.65
65.56aAB ± 1.38
± 0.35
65.32aB ± 0.34
± 0.03
6.85aB ± 0.09
± 0.03
6.34bcB ± 0.09
± 0.01
6.83aB ± 0.08
± 0.02
6.48bB ± 0.12
± 0.05
5.92eB ± 0.05
± 0.00
5.81eB ± 0.12
± 0.01
6.15cdB ± 0.12
± 0.02
6.02deB±0.03
8
64.57abB
64.98abA
65.96abA
66.57aB
66.56aA
65.75abA
63.75bB
64.85abB
8.02aA
7.78abA
7.84abA
7.49bcA
7.77abcA
7.38cA
7.77abcA
7.60bcA
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
0.68
0.56
0.24
0.70
0.80
1.27
1.18
0.67
0.07
0.10
0.17
0.14
0.17
0.24
0.22
0.15
aee, Means within each column followed by the same superscript letters are not
different (p > 0.05).
AeC, Means within each line followed by the same superscript letters are not
different (p > 0.05).
± Standard deviation.
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388
growth. The treatments coated with chitosan (5) and
chitosan þ 0.5% GTE (6) had the lowest pH values on the days 0 and
4, even if there was a statistical relation between treatment 8 and
these treatments on the day 4.
The effects of the applied processes on lipid oxidation of
hamburger patties are shown in Table 3. At the beginning of storage, the patties of the first sample group (1e4) which were not
coated with any material had generally lower values than the
second group (5e8) including coating materials. To the best of our
knowledge, there is no research regarding the addition of encapsulated green tea extract into beef patties, but there are studies
about the incorporation of this extract into the products. Kang et al.
(2007) coated pork patties with pectin-based material containing
green tea leaf extract powder and found that patties coated with
the extract powder showed lower TBARS value than the control and
the treatment coated with only pectin-based material. The green
tea leaf extract powder reduced lipid oxidation during storage.
Lorenzo, Sineiro, Amado, and Franco (2014) evaluated various extracts in pork patties and showed that green tea extract was one of
the most effective antioxidant against lipid oxidation. In our study
similar effects were observed. It was observed that, different
processings applied to the patties inhibited the lipid oxidation in
patties at different levels, so TBARS value of control was much
higher than the values of the other treatments at the end of storage
period (p < 0.05). Jo, Son, Son, and Byun (2003) added 1% irradiated
and nonirradiated freeze-dried green tea leaf extract powder into
the pork patties and both of the samples showed lower lipid
oxidation than the control during storage. In another study, the
TBARS values of the beef patties were reduced by using low level of
~o
n, Díaz, Rodríguez, Garrido, &
sulphite and green tea extract (Ban
Price, 2007). According to our study, similar effects were
observed. Although the treatment 2 which contained 0.5% green tea
extract had similar TBARS value with the control on the day
0 (p > 0.05), lipid oxidation of this treatment increased more slowly
as compared to control. The treatments 3 and 4 which had the
solutions of encapsulated green tea extract also showed similar
effects and reduced the lipid oxidation (p < 0.05). It was remarkable
that TBARS values of all the treatments increased due to lipid
oxidation throughout storage (p < 0.05), except the treatment 5,
which was coated with 1% chitosan solution (p > 0.05). Although
treatment 5 had the highest TBARS value in the beginning, that
value remained stable during storage.
Significant differences were found among the L* values in
Table 4 (p < 0.05). At the beginning of the storage the group
including control and the GTE added patties (1e4) exhibited higher
brightness than the group of coated patties (p < 0.05). On the day 4,
Table 3
TBARS values of hamburger patties processed with green tea extract and stored for 8
days at 4 C (mg malonaldehyde/kg treatment).
Treatment
Storage time (day)
0
1
2
3
4
5
6
7
8
0.39bC
0.35bB
0.37bB
0.36bC
0.53aA
0.47abB
0.48abB
0.41abB
±
±
±
±
±
±
±
±
0.02
0.01
0.01
0.01
0.06
0.06
0.06
0.01
4
8
0.88aB ± 0.04
0.32dB ± 0.02
0.64bcB ± 0.08
0.55cB ± 0.04
0.58bcA ± 0.05
0.55cB ± 0.02
0.73abB ±0.06
0.55cB ± 0.04
2.50aA
1.00cA
1.89abA
1.03cA
0.50cA
0.84cA
1.74bA
0.88cA
±
±
±
±
±
±
±
±
0.16
0.06
0.23
0.10
0.08
0.04
0.39
0.13
aed, Means within each column followed by the same superscript letters are not
different (p > 0.05).
AeC, Means within each line followed by the same superscript letters are not
different (p > 0.05).
± Standard deviation.
control, directly extract added treatment (2), treatment coated with
chitosan þ 0.5% extract (6) and the treatment coated with encapsulated extract (8) had a statistical relation and could be accepted
as similar. At the last day of storage, treatments which were added
low (1%) and high (5%) amounts of chitosan þ 0.5% extract þ TPP
solution (treatments 3 and 4) had the highest brightness (L*)
values, though treatment 3 had also relation with some other
treatments. According to storage period, whilst brightness value of
most of the patties showed irregular variations (p < 0.05), control
and the treatment containing directly added extract (2) were stable
during storage (p > 0.05).
All the treatments were found to be similar (p > 0.05) in terms of
redness (a*) value on the day 0 and 8 while there were differences
on the day 4 (p < 0.05). On the fourth day, most of the treatments'
red colour turned into green and showed minus values. Even if the
redness values of the control and the treatments 2 and 3 were
stable by the day 4, the values of all the treatments tended to
decline (p < 0.05). On the other hand, a* values of all the treatments
other than the treatments 1, 2, 3 and 5 were stable between the
days 4 and 8 (p > 0.05), while the values of these mentioned
treatments altered during this period (p < 0.05). The treatments
with various coating materials exhibited lower b* values than the
treatments without coating on the first day of storage (p < 0.05).
The control and the treatment including 0.5% green tea extract (2)
did not vary throughout storage (p > 0.05). In general, the b* values
of most of the coated patties increased by the middle of storage, but
after that day they tended to decrease (p < 0.05).
Jo et al. (2003) indicated that pork patties with green tea leaf
extract powder, whether it was irradiated or not, had higher L*
values than that of the control. The Hunter colour a*-value of the
patties which were incorporated with irradiated and nonirradiated
freeze-dried green tea extract powder were higher than the value
of control during storage. Siripatrawan and Noipha (2012) used
chitosan-alone film and chitosan film incorporating green tea
extract as active packaging for shelf life extension of pork sausages.
Samples wrapped with only chitosan film showed lower changes in
colour values probably due to the antioxidant and antimicrobial
properties of the chitosan film. Their results also showed that
samples wrapped with chitosan film incorporating green tea
extract had significantly lower changes in L* and b* values than
those wrapped with chitosane-alone film, probably due to the
antioxidant and antimicrobial effects of polyphenolic compounds
from green tea. Bozkurt (2006) utilized green tea extract in sucuk
(Turkish dry-fermented sausage) and found that L*, a* and b* values
of control and the samples including green tea extract decreased
during 15 days of ripening time.
The total mesophilic aerobic count values of the hamburgers
including GTE are given in Table 5. On the day 0, values the hamburgers including pure and encapsulated green tea extract were not
significantly different from the control (p > 0.05). On the days 4 and
8, although some of the values are statistically similar with each
other, the treatment including 5% encapsulated GTE showed the
lowest amount among the uncoated treatments (1, 2, 3, 4). According to the results of coated treatments (5, 6, 7 and 8), the
treatment coated with chitosan solution (5) was not significantly
different with the treatment coated with the solution including
chitosan and GTE (6) on the days 0, 4 and 8 (p > 0.05). In the
beginning of storage, the treament coated with chitosan TPP matrix
(7) was similar with control, but higher than the treatment coated
with solution including encapsulated GTE (8). However, on the days
0 and 8, the treatments 7 and 8 were similar (p > 0.05), but lower
than the control (p < 0.05).
The amounts of total mesophilic aerobic microorganisms at the
end of storage (day 8) were higher than the amounts at the
beginning for all the treatments (p < 0.05). The value of the
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389
Table 4
Colour values of hamburger patties processed with green tea extract and stored for 8 days at 4 C.
Treatment
1
L*
a*
b*
Day
0
4
8
0
4
8
0
4
8
43.02abcA
40.35deA
42.28bcA
2.12aA
1.78aA
4.35aB
72.75bcA
69.58deA
72.90bcA
±
±
±
±
±
±
±
±
±
1.33
0.98
3.16
0.41
0.36
1.01
1.87
1.69
5.44
2
3
4
5
43.62abA ± 0.51
40.82cdeA ± 2.02
42.64bcA ± 2.20
2.48aA ± 0.85
1.11aA ± 1.03
3.60aB ± 1.73
75.22abA ±0.88
70.92cdeA ± 3.08
73.53bcA ± 3.79
45.47aA ± 1.98
41.59cdB ± 0.33
44.05abA ±0.61
2.24aA ± 0.85
1.84aA ± 0.52
3.80aB ± 1.87
78.41aA ± 3.41
71.71cdB ± 0.56
75.96abA ± 1.05
45.98aA
43.55bcB
47.33aA
3.09aA
4.11bB
3.94aB
79.29aA
75.08bcB
81.62aA
±
±
±
±
±
±
±
±
±
1.37
0.71
0.78
0.26
0.08
1.41
2.36
1.22
1.34
6
41.74bcB
47.77aA
42.26bcB
1.94aA
7.39cC
4.94aB
71.97bcB
82.37aA
72.86bcB
±
±
±
±
±
±
±
±
±
1.61
0.79
1.21
0.51
0.81
1.06
2.78
1.36
2.10
7
38.39dAB
40.46deA
37.91dB
1.98aA
4.83bB
4.42aB
66.20dAB
69.78deA
65.37dB
±
±
±
±
±
±
±
±
±
1.44
0.92
0.68
0.59
0.23
1.01
2.48
1.59
1.17
8
40.16cdB
46.23abA
40.30cdB
2.84aA
6.99cB
5.69aB
69.38cdB
79.71abA
69.49cdB
±
±
±
±
±
±
±
±
±
1.89
1.97
0.74
1.61
0.12
0.88
3.20
3.39
1.28
40.48bcdA ±0.44
38.43eB ± 1.40
39.34cdAB ±0.25
2.14aA ± 1.05
4.53bB ± 0.91
5.05aB ± 1.34
69.95bcdA ± 0.87
66.27eB ± 2.42
67.83cdAB ± 0.44
aee, Means within each line followed by the same superscript letters are not different (p > 0.05).
AeB, Means within each column followed by the same superscript letters are not different (p > 0.05).
± Standard deviation.
Table 5
Microbiological mean values of the hamburgers including GTE in their formulations during storage for 8 days at 4 C (logcfu/g treatment).
Treatment
1
TMAC
KO
YM
Day
0
4
8
0
4
8
0
4
8
6.56abC
7.80aB
8.40aA
5.32aB
7.46aA
7.82aA
5.72abC
6.88bB
7.87abA
±
±
±
±
±
±
±
±
±
0.01
0.12
0.06
0.10
0.33
0.07
0.13
0.14
0.02
2
3
4
6.72aB ± 0.28
6.77bB ± 0.07
8.20abA ±0.12
5.08aC ± 0.17
6.53bcB ± 0.39
7.27abA ± 0.05
5.88aC ± 0.10
6.33dB ± 0.02
7.64cA ± 0.11
6.74aC ± 0.06
7.80aB ± 0.12
8.12bcA ± 0.12
5.18aC ± 0.16
6.89abB ±0.10
7.79aA ± 0.05
5.46abcdB ± 0.19
6.62cA ± 0.08
6.86dA ± 0.00
6.74aB
6.56bcB
7.98cdA
5.38aB
5.91cdB
7.80aA
5.12cdeC
6.04eB
6.88dA
5
±
±
±
±
±
±
±
±
±
0.04
0.14
0.06
0.21
0.42
0.00
0.41
0.13
0.02
6.20cdB
6.37cB
8.05bcdA
5.43aB
4.20fC
7.08bA
5.21bcdeB
7.71aA
7.85bA
6
±
±
±
±
±
±
±
±
±
0.05
0.16
0.02
0.02
0.05
0.18
0.27
0.04
0.06
5.99dC
6.53bcB
7.98cdA
5.14aB
4.76efB
7.08bA
4.75eB
7.58aA
7.62cA
7
±
±
±
±
±
±
±
±
±
0.01
0.06
0.02
0.45
0.18
0.13
0.13
0.02
0.06
6.86aC
6.61bcB
8.09bcdA
5.01aC
5.47deB
7.28abA
5.60abcC
7.68aB
8.01aA
8
±
±
±
±
±
±
±
±
±
0.03
0.04
0.05
0.14
0.07
0.04
0.00
0.05
0.05
6.35bcB
6.35cB
7.91dA
5.14aB
5.22deB
6.98bA
4.95deC
7.61aB
8.01aA
±
±
±
±
±
±
±
±
±
0.15
0.02
0.05
0.02
0.17
0.63
0.03
0.08
0.01
TMAC: Total Mesophilic Aerobic Counts, KO: Coliform bacteria, YM: Yeast and mould.
aed, Means within each line followed by the same superscript letters are not different (p > 0.05).
AeC, Means within each column followed by the same superscript letters are not different (p > 0.05).
± Standard deviation.
treatment coated with 5% encapsulated GTE (8) was more stable
than the value of the treatment coated with chitosan-TPP crosslinked solution (7) during 4 days. Lorenzo et al. (2014) found that
green tea extract led to a decrease of total viable counts in pork
patties compared to the control. Kang et al. (2007) indicated that
the numbers of total aerobic bacteria were significantly reduced in
the treatments containing pectin-based coating material and
~o
n
coating material with 0.5% green tea powder. In the study of Ban
et al. (2007), beef patties including low sulphite and green tea
extract had lower total viable count than control througout the
storage of 9 days.
Coliform bacteria amounts of the hamburger patties which had
GTE in their formulations are given in Table 5. The coliform bacteria
amounts of all the treatments were similar at the beginning of
storage. These values are the indicator of hygienic conditions of the
raw meat which was bought from a local supermarket. The amount
of coliform bacteria could likely be different if the meat was purchased from a different supermarket due to the different processing
conditions of meat. On the day 8, the uncoated treatments (1e4)
had generally higher values than the coated treatments (5e8)
probably due to the protective and/or inhibitory effect of coating
materials against bacteria. Although some treatments, such as 4, 6
and 8 did not show any difference until the fourth day of storage
(p > 0.05), the values of all the treatments increased at the end of
storage (p < 0.05).
Yeast and mould amounts of the hamburger patties during
storage are also presented in Table 5. There were significant differences among most of the treatments in the beginning of storage,
whilst the values of coated hamburger patties (5e8) were higher
than the uncoated treatments (1e4) on the day 4 (p < 0.05). The
treatment with 5% GTE in the cross-linked solution (4) led to lower
yeast and mould values compared to control on the day 0, but this
treatment and the treatment with 1% encapsulated GTE (3) were
both lower than control on the day 4 and 8. The treatments
including encapsulated GTE (3 and 4) had also the lowest values of
all samples at the end of storage. It was noticable that the treatments coated with CS-TPP (7) and CS-TPP with GTE (8) were higher
than the control on the days 4 and 8. Encapsulation of GTE may
prevent the antifungal activity of the material, so further study is
needed for that topic. The samples which were included 1%
encapsulated GTE (3) and coated with chitosan (5) and chitosan
with GTE (6) solutions did not vary after the day 4 (p > 0.05), but all
the other patties exhibited continuous increase during storage
(p < 0.05).
4. Conclusion
This study showed the effects of green tea extract which was
added into hamburger patties using different techniques. pH values
of all the treatments increased during time due to microbiological
metabolites and deamination of proteins. On the day 0 and 4, pH
values of the control and the products containing additives were
higher than the values of coated treatments. This may be the result
of the protective effect of coating material against bacterial growth.
The results of TBARS values showed that the products which were
not coated with any material had lower values than the coated
390
€
E.B. Ozvural
et al. / LWT - Food Science and Technology 68 (2016) 385e390
group in general on the day 0. According to results, coating of
patties with 1% chitosan had the highest antioxidant activity in the
first group, because this treatment was stable during storage. The L*
values of the control and the patties including additives were
higher than the values of coated patties at the beginning of storage.
a* values of most of the treatments turned into minus values.
According to microbiological analysis of the hamburger patties,
there were significant differences among the total mesophilic
count, coliform and yeast and mould values of the treatments.
Encapsulation significantly affected the number of bacteria, so the
amount of bacteria usually increased during storage (p < 0.05). The
kind and the origin of the meat sample are important factors for the
overall and particularly microbiology quality of the products. The
amount of salt and pepper used in the patties may also have
considerable effects.
As a consequence, treatments coated with CS, CS þ GTE and
CS þ GTE þ TPP were more resistant to lipid oxidation at the end of
the storage. Moreover, treatments containing high amount of
CS þ GTE þ TPP (5%) and the treatments coated with CS þ GTE and
CS þ GTE þ TPP had the lowest values in terms of microbiological
deteriorations, particularly for total mesophilic aerobic counts.
Therefore, the treatments coated with CS þ GTE and
CS þ GTE þ TPP could be the best choices, but further studies are
needed.
Acknowledgement
The Scientific and Technological Research Council of Turkey
€
_
(TÜBITAK)
financially supported the researcher Emin Burçin Ozvural,
under the International Postdoctoral Research Scholarship Programme (Grant number: 2219), to perform the study in USA. The
authors also acknowledge the help and support of the graduate students and the staff of Rutgers University Food Science Department.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.lwt.2015.12.036.
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