Gur-Yoo Kim1, Jaehak Lee1, Seungtae Lim1, Hyojin Kang1, Sung-Il Ahn1, Jin-Woo Jhoo1, Chang-Six Ra2. 1. Department of Applied Animal Science, College of Animal Life Sciences, Kangwon National University, Chuncheon 24341, Korea. 2. Department of Animal Industry Convergence, College of Animal Life Sciences, Kangwon National University, Chuncheon 24341, Korea.
The shelf-life of food is defined as an acceptable time period based on sensory
aspects, nutrition, and food safety (Fu and Labuza,
1993). Prediction of shelf-life as soon as possible is important in the
food industry. The accelerated shelf-life test (ASLT) is a good option for rapid
prediction (Mizrahi, 2004). ASLT predicts the shelf-life of products based on the
results of testing at regular intervals. The testing is done until the selected
quality index reaches the quality limit after storing at the actual storage or
distribution temperature and at least two other temperatures, and, based on the
data, is predicted using the Arrhenius model (Park
et al., 2014). When only temperature is used as a single variable, the
Arrhenius model is useful to predict shelf-life (Kim, 2008).Coffee is one of the most widely consumed beverages worldwide (Dorea and da Costa, 2005; Higdon
and Frei, 2006; Sudano et al.,
2005). Coffee consumption has been increasing annually (Chen and Lee, 2015). The market share of
ready-to-drink type coffee beverages packed in glass bottles, metallic cans, and
polyethylene containers, has been consistently growing globally (Shinozaki and Harada, 2014). The quality of
coffee and beverages containing coffee begins to deteriorate immediately after
production. The major environmental factors that accelerate deterioration are oxygen
and storage temperature (Nicoli et al., 2009;
Yoon et al., 2017). Accordingly, various
methods need to be developed to prevent deterioration of the beverage quality.Cocoa-derived foods, such as cacao powder and cacao nibs, are rich in phenolic
compounds and have been widely studied globally (Wollgast and Anklam, 2000). The polyphenols identified from cacao nibs
comprise three groups: catechins or flavan-3-ols, anthocyanins, and
proanthocyanidins or leucoanthocyanins (Afoakwa et
al., 2015). Consequently, the addition of cacao nibs is expected to
extend the shelf-life of the milk beverage. Therefore, the objective of this study
was to determine antioxidant effect and physico-chemical properties of
coffee-containing milk beverage with cacao nibs extract and to predict its
shelf-life using Arrhenius model.
Materials and Methods
Materials
Theobroma cacao (cacao nibs) was purchased from Gilim
International Co., Ltd. (Kwangju, Korea). A commercial coffee-containing milk
beverage was provided by Seoul F&B Co. (Seoul, Korea). It was composed of
30% raw milk, 28% coffee extract, 29% purified water, 6% sucrose, and 0.03%
emulsifier.
Extraction of antioxidant compounds
Cacao nibs (400 g) were hydrothermally extracted with 1 L distilled water (DW)
for 24 h. After the primary hydrothermal extraction, 1 L DW was added again to
conduct the secondary hydrothermal extraction. The cacao nibs extract was
centrifuged at 2,391×g for 10 min to remove all residue. After removal of
the fat layer using n-hexane, the extract was lyophilized.
Preparation of coffee-containing milk beverage with cacao nibs
extract
To prepare the coffee-containing milk beverage with 0.8% cacao nibs, lyophilized
cacao nibs extract powder was dissolved in 10 mL sterilized Milli Q water at a
concentration of 0.1575 g/mL. After pasteurization of the mixture at
100°C for 30 min, 10 mL of the mixture was injected into 200 mL of the
milk beverage with a sterilized syringe, and the container was sealed using a
silicon glue gun in an ultraviolet-illuminated clean bench. The prepared samples
were used in the experiment after slight stirring. All samples were prepared for
triplication.
pH and titratable acidity (TA)
Ten milliliters of beverage samples were used to measure the pH at 4°C
using a pH meter (Mettler-Toledo, Shanghai, China). The measurement was
conducted in triplicate. To assay TA of the beverage sample, 10 g was mixed with
10 mL DW and titrated with 0.1 N NaOH (Factor (F)=1.022). The
volume of 0.1 N NaOH used for titration was substituted for lactic acid
calculation in the following equation:where F is the factor of 0.1 N NaOH.
Color measurement
Color values of each sample were determined using a CT-340 colorimeter (Minolta,
Tokyo, Japan) calibrated using an original standard plate with the original
value (X=97.83, Y=81.58, Z=91.51). The beverage was poured into a beaker (50 mL
vol.). Then, the end of colorimeter detector was immersed into the beverage and
determined repeatedly (15 times). The analyzed L*, a*, and
b* values indicated lightness, redness, and yellowness,
respectively, in artificial light.
Brownness
The method reported by Morales and Jimnez-Prez
(2001) was used to measure brownness. The beverage sample was diluted
30-fold, and the absorbance was determined at 420 nm using an X-ma 1200
spectrophotometer (Human Corp., Seoul, Korea).
Five milliliters of 7 mM ABTS solution were mixed with 88 μL of 140 mM
potassium persulfate and sonicated for 10 min to generate cation radicals. The
mixture was incubated in a dark room for 12 to 16 h to prepare the ABTS stable
cation radical working solution. The working solution was diluted with DW to an
optical density at 734 nm of 0.7±0.02 just before use in the experiment.
Samples diluted to 0.5, 1, 1.5, 2, and 2.5 μg/mL were mixed with 1 mL
ABTS solution. Each mixture was kept in the dark for 10 min to allow the cation
radical scavenging reaction. The absorbance was assayed at 734 nm using an ELISA
plate reader, and the ABTS radical scavenging activity (%) was calculated as:where Asample is the absorbance measured after mixing with the sample
and ABTS, and Ablank is the absorbance measured with 1 mL ABTS
working solution and 1 mL DW instead of the sample. The slope was plotted using
the five converted values and expressed as the effective concentration
(IC50; concentration at which 50% of the cationic radical was
scavenged) determined by the regression equation derived from the slope.
Ferric reducing antioxidant power (FRAP) assay
To prepare the reagent for the ferric reducing antioxidant power (FRAP) assay,
acetate buffer (1) was using 0.25 M sodium acetate and 1 M sodium oxide, with
the pH adjusted to 3.6 with 1 M HCl. 2,4,6-tripyridyltriazine (TPTZ) solution
(2) was prepared by mixing 0.01 M TPTZ (Sigma-Aldrich Chemical Co., St. Louis,
MO, USA) with the acetate buffer. Ferric chloride solution (3) was made by
addition of 0.02 M ferric chloride in the acetate buffer. Finally, the working
FRAP buffer used to assay radical scavenging activity was prepared by mixing of
the above reagents in ratios of (1):(2):(3)=10:1:1, and stabilized at
37°C for 30 min. To assay scavenging activity, 25 μL of sample was
poured in wells of a 96 well-plate and mixed with 175 μL working FRAP
buffer. The mixture was incubated in a dark room for 30 min, and the absorbance
was measured at 593 nm. A standard curve was made with gallic acid at
concentrations of 0, 0.02, 0.05, 0.1, 0.2, 0.3, and 0.5 mg/L and converted to
gallic acid equivalent to express reducibility.
Peroxide value (POV) assay
To measure peroxide value (POV), extraction of fat in the samples was carried out
according to the ISO 14156 method. One hundred samples were mixed with 80 mL of
95% ethanol and 20 mL ammonia in a separatory funnel, and were slightly stirred.
For the primary fat extraction, 100 mL diethyl ether was added to the mixture
and shaken vigorously. After 25 min incubation, the aqueous layer was removed.
For the secondary fat extraction, 100 mL pentane was mixed with the residual
organic solvent layer and stirred slightly. After 15 min, the aqueous layer was
removed. To remove impurities, the solvent layer was processed with 100 mL of
10% (w/v) sodium sulfate and filtered through Whatman No. 2 filter paper
(Whatman Inc., Maidstone, UK). Solvent was evaporated from the filtrate at
40°C to recover the fat. To titrate the peroxide, 0.5 to 1.5 g of the
filtrate was mixed with 25 mL acetic acid and chloroform mixture in a ratio of
3:2, respectively, in saturated potassium iodide solution. Subsequently, 30 mL
DW and 1 mL starch solution as the indicator were mixed in the mixture, and
titrated with 0.01 N sodium thiosulfate. The POV was calculated as:where a is the titrated 0.01 N sodium thiosulfate, b is the titrated 0.01 N
sodium thiosulfate in the blank test, and f is the factor of 0.01 N sodium
thiosulfate.
Caffeine content determination using high-performance liquid chromatography
(HPLC)
Caffeine contents of the samples were analyzed by HPLC using a model LC-20A
(Shimadzu Co., Tokyo, Japan). The retention time was compared between the
caffeine contents of the samples and standard caffeine (Sigma-Aldrich Co.). A
Luna C18 column (10 μm, 250×4.6 mm; Phenomenex,
Torrance, CA, USA) was used for the caffeine analysis. The mobile phase was
prepared with methanol, water, and acetic acid at a ratio of 20:79:1. The flow
rate of the mobile phase was 1.0 mL/min and the temperature of the column oven
was kept at 40°C. The samples, which were filtered with a 0.45 μm
syringe filter (Advantec Toyo Roshi Kaisha, Ltd., Tokyo, Japan) and diluted with
0.01 mg/min, were injected. The injected volume was 10 μL. The compounds
isolated from the column were analyzed at 280 nm for 25 min.
ASLT and shelf-life prediction
ASLT was conducted to determine shelf-life of the beverage. Beverages with and
without cacao nibs extract were stored at 10°C, 20°C, and
30°C for 4 wk. pH, TA, antioxidant activity, caffeine contents, and POV
were analyzed, and sensory evaluation was done to predict shelf-life. The
prediction involved linear regression calculated using the Arrhenius equation n
from the ASLT data as described by Yoon et al.
(2017).Deterioration of a food quality was calculated as:where A denotes food quality at time t,
n is the order of the reaction,
dA/dt denotes changes in the deterioration
of food quality A with time, and k is a reaction constant. If
the food quality deterioration followed zero-order reaction, it could be
expressed as Eq. (2).
Subsequently, Eq. (3) was
obtained by integration of Eq.
(2).When the deterioration followed the first-order reaction, it could be expressed
as Eq. (4). After integration of
the first-order reaction Eq.
(4), Eq. (5) was
obtained.Eq. (5) could be expressed as
Eq. (6) by taking the
natural logarithm.The widely-used Arrhenius equation was applied to explain the temperature
dependence of food quality deterioration, expressed as Eq. (7).where T is absolute temperature, k is the reaction constant at
temperature T, R is the gas constant (1.987
kcal/mol), and Ea is the activation energy.By taking natural logarithm of Eq.
(7), Eq. (8) was
obtained.where S is the slope and lnA,
I represent the intercept.Finally, in the case of zero-order reaction, the self-life was predicted as Eq. (9) and, if it followed the
first-order reaction, it was expressed as Eq. (10).where t is predicted storage period,
A0 is the food quality at the initial time, and
A is the food quality at a specific storage
time.
Statistical analysis
Statistical analysis of the data obtained from each experiment involved the
analysis of variance (ANOVA) determined using SAS software version 9.3 (SAS
Institute Inc., Cary, NC, USA). Significance was defined at the 5% level, unless
indicated.
Results and Discussion
Changes in color and brownness of milk beverages
Changes in color and brownness of coffee-containing milk beverage with and
without cacao nibs extract at 10°C, 20°C, and 30°C during
storage are listed in Table 1. Color
measurements revealed no significant difference in lightness (L*) values, except
for samples stored at 30°C (p>0.05). However, most of the L*
values somewhat increased during storage. This result was not corresponded with
Sopelana et al. (2013) who reported
that the L* value of coffee brews slightly decreased and is distributed between
approximately 19.77 to 25.60 during storage at 4°C. The L* value of the
milk beverages was higher than the results from Sopelana et al. (2013). It is thought that the L* values of this
study were higher than that of the researchers due to the addition of milk in
the sample for this study. Redness (a*) values tended to decrease with longer
storage time. The a* value of samples containing cacao nibs extract was 1.4-fold
higher than that of the control group. The dark red color of the
extract-containing samples may have been influenced by the redness of the
beverage. Yellowness (b*) values were not significantly different in all samples
(p>0.05).
Table 1.
Changes in color of coffee-containing milk beverage with and without
cacao nibs extract stored at 4°C for 4 wk
Storage (wk)
Sample
Color
Brownness
L*
a*
b*
0
N10
44.22°0.02[abcd]
4.80°0.09[de]
13.78°0.80[a]
0.9036°0.001[b]
N20
42.04°3.22[bcde]
4.98°0.23[d]
14.49°0.68[a]
0.9413°0.109[a]
N30
39.58°3.59[e]
5.04°0.10[d]
14.02°0.34[a]
0.9246°0.064[a]
C10
43.79°0.00[abcd]
6.64°0.23[ab]
13.13°0.68[a]
0.9364°0.010[a]
C20
40.81°1.84[cde]
6.89°0.44[a]
14.39°0.67[a]
0.9373°0.046[a]
C30
40.61°4.52[de]
6.29°0.24[b]
14.48°0.71[a]
0.9315°0.097[a]
4
N10
46.25°1.04[a]
4.35°0.37[e]
13.62°3.51[a]
0.7685°0.089[e]
N20
44.72°2.37[abc]
3.55°0.49[f]
13.45°1.56[a]
0.7678°0.058[e]
N30
45.88°1.94[ab]
3.68°0.36[f]
13.21°2.48[a]
0.8458°0.008[c]
C10
43.72°1.61[abcd]
5.66°0.12[c]
15.06°0.12[a]
0.7541°0.043[e]
C20
44.69°1.63[abc]
5.23°0.49[cd]
14.77°0.97[a]
0.8193°0.062[d]
C30
44.54°1.57[abcd]
5.34°0.54[cd]
14.76°1.00[a]
0.8627°0.026[c]
Data are expressed as mean°SD of triplicate experiments.
Means in the same column with different superscripts are
significantly different (p<0.05).
N, extract-free beverage stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.
Data are expressed as mean°SD of triplicate experiments.Means in the same column with different superscripts are
significantly different (p<0.05).N, extract-free beverage stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.Also, brownness of control and extract-added groups displayed a similar tendency
of a* value decrease with storage time. Furthermore, the brownness decreased
during storage. According to Delgado-Andrade and
Morales (2005), brown-colored compounds of coffee as a result of
caramelization and Maillard reactions during the roasting process is related to
antioxidant activity. It is considered that a decrease of a* value and brownness
involved with an antioxidant activity during storage is related to the report of
Lopane (2018), who reported that the
caffeine content of cold brew coffee decreased during storage.
Changes in pH and TA
Changes in pH and TA of control beverage and beverage containing cacao nibs
extract are depicted in Fig. 1. The pH of
all samples significantly decreased as storage temperature increased and storage
period passed (Fig. 1A; p<0.05). In
addition, as storage period passed, cacao nibs added sample showed approximately
0.15-0.22 lower pH value than that of control. The pH decrease was accentuated
at higher storage temperatures. The findings were consistent with So et al. (2014), who reported that the pH
of Dutch coffee decreased during storage, with a more pronounced decrease at
higher storage temperature. Rosa et al.
(1990) reported that the increase in various organic acids and
caffeic or quinic acid due to the degradation of chlorogenic acid leads to the
decrease of pH during storage. In addition, high storage temperature of coffee
accelerates chlorogenic acid decomposition and increases sourness (Manzocco and Lagazio, 2009; So et al., 2014).
Fig. 1.
Changes in pH (A) and titratable acidity (B) of coffee-containing
milk beverage with or without cacao nibs extract during storage at
various temperatures for 4 wk.
A–FDifferent letters in the same color bars are
significantly different (p<0.05).a–gDifferent
letters in the same temperature groups are significantly different
(p<0.05). N, extract-free beverage sample stored at
10°C,20°C, and 30°C; C, beverage containing cacao
nibs extract stored at 10°C,20°C, and 30°C.
Changes in pH (A) and titratable acidity (B) of coffee-containing
milk beverage with or without cacao nibs extract during storage at
various temperatures for 4 wk.
A–FDifferent letters in the same color bars are
significantly different (p<0.05).a–gDifferent
letters in the same temperature groups are significantly different
(p<0.05). N, extract-free beverage sample stored at
10°C,20°C, and 30°C; C, beverage containing cacao
nibs extract stored at 10°C,20°C, and 30°C.The TA of all samples significantly increased during storage (p<0.05); the
increase was more pronounced at higher storage temperatures (Fig. 1B). In addition, samples containing
cacao nibs extract displayed an approximately 1.5-fold higher TA than the
control. Jinap and Dimick (1990) reported
that the pH and TA values of Malaysian cacao were 4.89% and 0.198%,
respectively. So et al. (2014) reported
that the TA of Dutch coffee increased during the storage period and the higher
storage temperature leads to the greater TA increase. Consequently, it is
considered that an organic acid component contained in cacao nibs extract lowers
the pH and increases TA of the coffee-containing milk beverage.
Antioxidant effect of cacao nibs extract-added coffee-containing milk
beverage
Fig. 2 shows the changes in the antioxidant
effects of milk beverage supplemented with and without cacao nibs extract. The
ABTS scavenging and FRAP assays we used are commonly used methods to determine
antioxidant activity (Muller et al.,
2011). Concerning the ABTS radical scavenging effect, the extract group
displayed a lower IC50 value than the control group (Fig. 2A). A lower IC50 value
indicates a higher antioxidant effect (Li et
al., 2009). The IC50 values of control stored at
10°C, 20°C, and 30°C were slightly increased during
storage, implying a time-dependent influence on the antioxidant effect in the
control. There was no significant difference in the IC50 value of
samples containing cacao nibs extract at the different storage temperatures in
the 4 wk storage (p>0.05). Klimczak et
al. (2007) reported that storage temperature did not affect phenolic
compounds. Based on their results, data suggested that compounds in the extract
have ABTS radical scavenging activity that is not relatively sensitive to
temperature.
Fig. 2.
Changes in ABTS radical scavenging activity (A) and ferric reducing
antioxidant power (B) of coffee-containing milk beverage with or without
of cacao nibs extract during storage at various temperatures for 4
wk.
N, extract-free beverage sample stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.
Changes in ABTS radical scavenging activity (A) and ferric reducing
antioxidant power (B) of coffee-containing milk beverage with or without
of cacao nibs extract during storage at various temperatures for 4
wk.
N, extract-free beverage sample stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.The changes in FRAP of the beverage samples during storage are depicted in Fig. 2B. Taken as a whole, samples containing
cacao nibs extract displayed a higher FRAP than the control. The FRAP values of
the samples containing cacao nibs extract, such as C10, C20, and C30, were
17.529, 17.126, and 16.890 TE/mM, respectively, initially and 19.260, 18.495,
and 19.603 TE/mM, respectively, after the 4 wk storage. The average and standard
deviation FRAP value of the extract-containing samples between the initial time
and after 4 wk of storage was 17.182°0.323 and 19.269°0.328 TE/mM,
respectively; the deviation was decreased by approximately 2%. For the control
group, there was no significant difference among samples initially (p>0.05).
FRAP values of N10, N20, and N30 were 11.232, 12.621, and 12.158 TE/mM,
respectively, at 2 wk of storage and 12.519, 13.668, and 14.223 TE/mM,
respectively, at 3 wk of storage. The average and standard deviation of the FRAP
value of the control between the initial time and after 4 wk of storage was
12.893°0.377 and 12.411°0.142 TE/mM, respectively; the deviation
was somewhat decreased. A similar trend was reported by Zafrilla et al. (2001). The authors described that the
phenolic compound, ellagic acid, increased at the beginning of storage and then
decreased slightly over the remaining storage period. It is known that the
antioxidant effect of cacao nibs is caused by catechin, epicatechin, tannin and
theobromine (Azam et al., 2003; Conti et al., 2012; Miller et al., 2006; Payne
et al., 2010). Due to this, it is considered that the antioxidant
effect of the cacao nibs added sample was higher than that of control.
Consequently, the addition of cacao nibs extract could maintain antioxidant
activity of the beverage over a certain level, and that the inhibition of lipid
oxidation of the beverage could be expected.
Analysis of lipid oxidation by POV
Fig. 3 shows lipid oxidation of the samples
stored at 10°C, 20°C, and 30°C for 4 wk. As the storage
temperature increased, the POV of all samples tended to increase. In addition,
samples containing cacao nibs extract generally displayed a lower POV than that
of the control. Especially, the POV of samples containing the extract and
extract-free samples stored at 30< (C30 and N30, respectively) initially
showed no significant difference (1.91 and 1.98 meq/kg, respectively;
p<0.05). However, the POV of C30 and N30 was 7.42 and 9.64 meq/kg,
respectively, after the 4 wk storage. According to the IOC standard (IOC, 2006), in the case of animal fats or
oils, 20-40 meq/kg is regarded as a rancid lipid, while 10 meq/kg or less is
defined as fresh lipid. Based on these criteria, rancidity was absent in both
groups. However, lipid rancidity was lower in the samples containing cacao nibs
extract than in the extract-free group. This is thought to be due to the
polyphenol compounds of cacao nibs extract. Hermann (1995) identified the polyphenol compounds of cacao nibs as
epicatechin, catechin, gallocatechin, and epigallocatechin. According to Othman et al. (2007), these compounds
remove hydroxyl and superoxide radicals, and have bioactivity comprising the
inhibition of lipid peroxidation. Consequently, it is considered that the
compounds from the cacao nibs extract used in this study affected the decrease
in lipid oxidation.
Fig. 3.
Changes in peroxide values of coffee-containing milk beverage with or
without cacao nibs extract during storage at various temperatures for 4
wk.
A–DDifferent letters in the same color bars are
significantly different (p<0.05). a.f Different letters in the
same degree groups are significantly different (p<0.05). N,
extract-free beverage sample stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.
Changes in peroxide values of coffee-containing milk beverage with or
without cacao nibs extract during storage at various temperatures for 4
wk.
A–DDifferent letters in the same color bars are
significantly different (p<0.05). a.f Different letters in the
same degree groups are significantly different (p<0.05). N,
extract-free beverage sample stored at 10°C, 20°C, and
30°C; C, beverage containing cacao nibs extract stored at
10°C, 20°C, and 30°C.
Caffeine content analysis using HPLC
Fig. 4 depicts the changes in the caffeine
content of beverage samples containing cacao nibs extract during storage. The
caffeine content was higher than that of control samples. The caffeine content
of samples containing cacao nibs extract may have been increased because of the
extract. In addition, the caffeine contents of all samples tended to decrease
during storage, and as the storage temperature increased, the decrease in
caffeine content tended to increase slightly. This result is consistent with the
findings of So et al. (2014), who
described the decreased caffeine content of Dutch coffee during storage.
Similarly, as mentioned above, Lopane
(2018) reported that the caffeine content of cold brew coffee
decreased during storage. However, the present results are inconsistent with the
findings of Perez-Martinez et al. (2008),
who reported that the caffeine content was not influenced by storage time and
temperature. Caffeine exists as a monomer, dimer, tetramer or pentamer in
aqueous solution (Balbuena et al., 2008).
This leads to a shift of the absorbance in the detector. In the detector which
was set to a single wavelength, it could not detect all of caffeine content
(Lopane, 2018). It is considered that
the use of a photodiode array detector which can detect various wavelength at
the same time could analyze more accurately.
Fig. 4.
Caffeine contents of coffee- containing milk beverage with or without
cacao nibs extract during storage at various temperatures for 4
wk.
A–DDifferent letters in the same color bars are
significantly different (p<0.05). a–hDifferent
letters in the same degree groups are significantly different
(p<0.05). N, extract-free beverage sample stored at 10°C;,
20°C;, and 30°C; C, beverage containing cacao nibs extract
stored at 10°C;, 20°C;, and 30°C;.
Caffeine contents of coffee- containing milk beverage with or without
cacao nibs extract during storage at various temperatures for 4
wk.
A–DDifferent letters in the same color bars are
significantly different (p<0.05). a–hDifferent
letters in the same degree groups are significantly different
(p<0.05). N, extract-free beverage sample stored at 10°C;,
20°C;, and 30°C; C, beverage containing cacao nibs extract
stored at 10°C;, 20°C;, and 30°C;.
Determination of shelf-life
POV was chosen as the indicator to assess shelf-life of the beverage samples.
Regressions and coefficient (r2) were calculated from the samples
stored at 10°C, 20°C, and 30°C based on the POVs (Table 2). The coefficient values of the
zero-order regression were higher than those of first-order regression,
indicating that POVs increased following zero-order kinetics. The findings were
different from the report of Labuza and
Bergquist (1983) describing the first-order reaction kinetics of POV.
The discrepancy could reflect the relatively short experimental period, even
though it was ASLT. Yoon et al. (2017)
also reported that the POV kinetics of coffee-containing milk beverage followed
first-order reaction in an 8 wk ASLT.
Table 2.
Regressions from accelerated shelf-life test of cacao nibs
extract-added coffee-containing milk beverage at various storage
temperatures
Sample
Regression order
Temperature
Regression
Coefficient (r2)
Control
0
10
Y=1.4535X+1.6437
0.9901
20
Y=1.7523X+1.7147
0.9823
30
Y=1.9056X+1.6680
0.9855
1
10
Y=0.3583X+0.6771
0.9696
20
Y=0.3711X+0.7804
0.9821
30
Y=0.3878X+0.7846
0.9837
Cacao
0
10
Y=0.8789X+1.7552
0.9611
20
Y=1.0798X+1.8054
0.9981
30
Y=1.3832X+1.9675
0.9991
1
10
Y=0.2868X+0.6021
0.9084
20
Y=0.3027X+0.6848
0.9564
30
Y=0.3318X+0.7873
0.9523
The activation energies and regression values of control and cacao nibs
extract-added samples calculated with the Arrhenius equation are provided in
Table 3. The regressions of the
extract-added and control group was
lnK=−2,287.2468X+ 7.8665
(r2=0.9960) and
lnK=−1,333.7587X+5.0599
(r2=0.9437), respectively. The respective activation energy was
−4,526.8764 and −2,650.1785. The absolute value of the activation
energy of samples containing cacao nibs extract was higher than that of control.
Ahn et al. (2018) reported that a high
absolute value for the activation energy corresponds to a longer storage
period.
Table 3.
Activation energies and regressions from zero-order kinetic analysis
of cacao nibs extract-added coffee-containing milk beverage
K, kinetic constant, lnK,
logarithmically transformed kinetic constant; R,
gas constant (1.987 kcal/mol); X, 1/T.Assuming that the product is distributed at refrigeration temperature, the
storage period at 4°C was calculated and is depicted in Fig. 5. The kinetic regression of the
predicted shelf-life of samples containing cacao nibs extract and control was
YPOV=1.2212X-2.097
(r2=0.9717) and
YPOV=1.9440X-2.211
(r2=0.9883), respectively. The respective predicted shelf-life to
reach quality limit (20 meq/kg POV) was approximately 18.09 and 11.43 wk. These
findings indicate the effectiveness of the cacao nibs extract in prolonging the
shelf-life of coffee-containing milk beverage. Lee and Kim (2003) reported that the shelf-life of the Korean
traditional food, Gangjung, was extended by the addition of 1.5% ginseng.
Similarly, according to Lee (1999), the
addition of Ganoderma lucidum, Camellia
sinensis, and Lycii fructus extracts effectively
inhibited the increase of POV in walnut.
Fig. 5.
Shelf-life prediction of coffee-containing milk beverage with cacao
nibs extract (A) and coffee-containing milk beverage without cacao nibs
extract (B) at 4°C.
Peroxide value of the coffee-containing milk beverages during storage
using zero-order deterioration kinetics.
Shelf-life prediction of coffee-containing milk beverage with cacao
nibs extract (A) and coffee-containing milk beverage without cacao nibs
extract (B) at 4°C.
Peroxide value of the coffee-containing milk beverages during storage
using zero-order deterioration kinetics.The Arrhenius model is simple, but fairly accurate equation, which can explain
temperature dependent chemical kinetics (Mckeen,
2016). As mentioned above, the quality deterioration factors of
coffee or coffee-containing beverages are known to temperature and oxygen. Thus,
it is thought that this model is suitable to predict shelf-life of the
coffee-containing milk beverage and to determine the effect of cacao nibs
addition on shelf-life in the beverage.
Conclusion
This study aimed to extend the shelf-life of coffee-containing milk beverage. The
addition of cacao nibs extract to the milk beverage caused physico-chemical changes
The extract also improved the antioxidant effect compared to the extract-free
control. Investigating the shelf-life using ASLT with POV as an indicator confirmed
that the shelf-life of the milk beverage was extended by approximately 1.58 times by
the addition of cacao nibs extract. The regression of the predicted shelf-life of
the extract-added milk beverage was
YPOV=1.2212X−2.097
(r2=0.9717) during storage at 4°C. The collective findings
demonstrate that the addition of cacao nibs extract in coffee-containing milk
beverage effectively prolonged the shelf-life of the beverage.
Authors: Mark J Payne; William Jeffrey Hurst; David A Stuart; Boxin Ou; Ellen Fan; Hongping Ji; Yan Kou Journal: J AOAC Int Date: 2010 Jan-Feb Impact factor: 1.913
Authors: Isabella Sudano; Christian Binggeli; Lukas Spieker; Thomas Felix Lüscher; Frank Ruschitzka; Georg Noll; Roberto Corti Journal: Prog Cardiovasc Nurs Date: 2005
Authors: Kenneth B Miller; David A Stuart; Nancy L Smith; Chang Y Lee; Nancy L McHale; Judith A Flanagan; Boxin Ou; W Jeffrey Hurst Journal: J Agric Food Chem Date: 2006-05-31 Impact factor: 5.279
Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.