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International Journal of Farming and Allied Sciences
Available online at www.ijfas.com
©2013 IJFAS Journal-2013-2-17/599-606
ISSN 2322-4134 ©2013 IJFAS
The influence of Green Tea(Camellia sinensis L.)
Extract on characteristic of probiotic bacteria in
milk and yoghurt during fermentation and
refrigerated storage
Mohammad Hossein Marhamatizadeh1*, Elham Ehsandoost2, Paria Gholami3
1. Department of Food Hygiene, Veterinary Faculty, Kazerun Branch, Islamic Azad University, kazerun, Iran
2. Department of Food Science and Technology, Young Researchers Club, Kazerun branch, Islamic Azad
University, Kazerun, Iran
3. Department of Microbiology, Kazerun branch, Islamic Azad University, Kazerun, Iran
Corresponding author: Mohammad Hossein Marhamatizadeh
ABSTRACT: Green Tea is rich in polyphenols and other phenolic compounds that have been widely
reported to have beneficial health effects. The objective of present study was to determine the effect of
the supplementation of Green tea (Litsea coreana L.) Extract in probiotic milk and yoghurt on post-
acidification, total titratable acidity, bacteria counts by two probiotics strains: Lactobacillus acidophilus
and Bifidobacterium bifidum during 21 days of storage at 2°C. Green tea extract was added to low-fat
sterilized milk at 0.3%, 0.6 % and 0.9 % concentration and inoculated with yoghurt starter to obtain
Green tea yoghurts. Similar procedure was applied to prepare Green Tea milk. The results of this study
demonstrated the positive correlation between increased bacterial growth and increased Green Tea
concentration. Green Tea supplementation positively influenced the initial acidity and the count of
Lactobacillus acidophilus and Bifidobacterium bifidum compared with the plain milk and yoghurt (p <
0.05).In the samples containing Lactobacillus acidophilus and Bifidobacterium bifidum, it was observed
that increased concentrations of Green Tea extract create a favorable taste in milk and yoghurt.
Consumer sensory testing analysis found that green tea milk and yoghurt samples were liked as well
or better than the control milk and yoghurt samples. All the results suggest that Green Tea extract
promoted the metabolism of lactic acid bacteria in milk and yoghurt.
Keywords: Green Tea Extract, Lactobacillus acidophilus, Bifidobacterium bifidum, phenolic compounds
INTRODUCTION
Functional foods can be regarded as foods with a health benefit beyond satisfying traditional nutritional
requirements (Sanders, 1998). Moreover, there is an increasing demand by consumers of new functional food
products and the easiest way for developing these products, is the incorporation of functional ingredients to already
known food stuff.
Recently, there has been an increasing interest in the use of natural food additives and incorporation of health
promoting substances into the diet. Green tea was selected in this work because of their benefits to human health
and their popular consumption worldwide. Its low pH value, of approximately 4.2, makes tea compatible with many
food products in term of acidity.
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600
Green Tea (Camellia sinensis, family Theaceae) is a widely consumed beverage around the world for centuries,
and it has been reported to be beneficial to health. Many studies have evaluated tea and tea polyphenols as factors
for the potential lowering of risk of cardiovascular diseases and cancers. There have also been reports of many
other health benefits of tea consumption such as prevention of neurodegenerative diseases (Mandel et al. , 2008)
diabetes (Stote & Baer, 2008), liver diseases (Jin et al., 2008), antimutagenic properties (Bunkova et al., 2005),
hypocholesterolemic and hypolipidemic action (Hou et al., 2009) as well as anti-obesity activity (Wang et al., 2010),
protection against osteoporosis (Shen et al., 2009) and benefits for oral hygiene (Hara, 1999). All beneficial effects
of Green tea have been attributed to the strong antioxidative activity of the tea phenolic compounds, known as tea
catechins (Fig.1). Tea catechins possess strong antioxidant properties. They may protect the body from damage
caused by free radical-induced oxidative stress (Manzocco et al, 1998). In addition, many reports (Chou et al.,
1999; Yam et al., 1997) have presented data regarding the antimicrobial activity of different types of tea extracts on
various pathogenic microorganisms. Therefore, the consumption of tea has been associated with reduced risk of
major diseases, including coronary heart disease, stroke and cancer (Langley-Evans, 2000; Leenen et al, 2000).
These pharmacological properties have been mainly attributed to catechins (Zuo et al., 2002).
The goal of the present study was to prepare probiotic milk and yoghurt with different concentrations (0, 0.3,
0.6 & 0.9%) of Green Tea extract in order to produce a new functional food. To our knowledge this is the first study
on the feasibility of employing Green Tea extract for the supplementation of probiotic milk and yoghurt with
antioxidant and phenolic compounds.
Figure 1. Structure of major catechins present in Green tea extract.
MATERIALS AND METHODS
Materials
Dried green tea leaves were purchased from the local market (Kazerun, Iran). Low-fat sterilized milk and
yoghurt (1.5%) were locally purchased (Kazerun, Iran). Commercially available probiotic cultures of Lactobacillus
acidophilus LAFTI® L10 and Bifidobacterium bifidum LAFTI® B94 were obtained from DSM Food Specialities
Australia Pty Ltd. (Moorebank, NSW, Australia). MRS Agar culture medium was used for carrying out the microbial
test (MERCK, Germany).
Preparation of ethanol extract of Green Tea
Green Tea extract was prepared by mixing Green Tea extract with ethanol (96%) in the ratio of 20:400 by
soxhlet system. The extraction lasted for three hours and ethanol was evaporated on rotary evaporator. Then the
obtain extract was percolated through a bed of activated carbon (1 g of activated carbon for every 100 mL of
extract). The filtered sample transferred to vacuum oven for four days to concentrate the Green Tea extract and
after this time the extract kept for further use in a cold (4°C) and dry place. Rotary evaporator (Heidolph model no
Laboro TA4000) was used to separate Green Tea extract into its components based on their respective volatilities,
through the process of evaporation and condensation.
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601
Methods
Preparation of probiotic Bifidobacterium Bifidum milk containing Green Tea Extract (OLE) at first passage
In order to produce milk containing the probiotic bacterium Bifidobacterium bifidum, four containers each
containing 1 liter of low-fat sterilized milk (1.5% fat) were considered as our four groups. The starter
(Bifidobacterium bifidum) was added to all the containers, followed by adding Green Tea extract of 0 (Control
sample), 0.3, 0.6, and 0.9% to all the containers, respectively and finally they were placed in the incubator at 38°C.
The acidity test was performed approximately every 2 hours until reaching 42° Dornic.
The samples were then taken out of incubator and transferred to a refrigerator and stored at 2°C. The
produced probiotic milk was evaluated once every 7 days by counting the microbes using direct counting method.
Preparation of probiotic Bifidobacterium bifidum yoghurt containing Green Tea Extract (OLE) at the
second passage
To produce Bifidobacterium bifidum yoghurt in this stage, after providing 4 containers, 1 liter of the low - fat
sterilized probiotic milk (1.5 % fat) from the control group at first passage and the (1.5%) starter of low-fat yoghurt
(1.5%) were added to each container.
Different concentrations of Green Tea extract (0, 0.3, 0.6, and 0.9%) were added respectively to the containers
and mixed properly so that Green Tea extract was uniformly dissolved. Afterwards, all the containers were placed
in the incubator at 38°C. Approximately every 2 hours, the acidity and pH tests were done until acidity reached 90°
Dornic. Then, the samples were taken out of the incubator and transferred to a refrigerator and stored at 2°C. The
produced probiotic Green Tea yoghurt was evaluated every 7 days by counting the microbes using direct counting
method and after 7 days the yoghurt was evaluated for sensory properties, using questionnaires filled by 15
participants. The respondents were asked to rate the factors of scent, taste and permanence on a scale ranging
from very good, good, medium, to weak. The results were analyzed in a statistical descriptive test by SPSS
version 17 software.
Preparation of probiotic Lactobacillus acidophilus milk containing Green Tea Extract (OLE) at first passage
All the same procedures were followed as mentioned above with the difference of using Lactobacillus
acidophilus instead of Bifidobacterium bifidum.
Preparation of probiotic Lactobacillus acidophilus yoghurt containing Green Tea Extract (OLE) at second
passage
All the same procedures were followed as mentioned above with the difference of using Lactobacillus
acidophilus instead of Bifidobacterium bifidum.
Having produced the above-mentioned products, we stored 1000 gram of each product in a disposable container
placed in a refrigerator for 21 days. During this period, each sample was tested in days 1, 7, 14, and 21 for acidity,
pH, and sensory properties.
Statistical analysis:
All the above experiments were repeated three times with each test carried out in triplicate. SPSS17 was used
for one-way analysis of variance for all data, and significant differences
(p < 0.05) among means were determined by the least significant difference test.
RESULTS AND DISCUSSION
Results
Table 1 and Table 4 show the acidity degrees of Green Tea extract milk and yoghurt in Lactobacillus
acidophilus and Bifidobacterium bifidum samples during storage time in the refrigerator. The acidity of the obtained
yoghurts was affected by both the storage time and the amount of Green Tea concentration. As expected, the initial
pH value steadily decreased during the experiment. There were significant differences between the Green Tea
milks and yoghurts and the control, but there were no differences within the Green tea milks and yoghurts group.
The results of these tables show the positive correlation between increased acidity values and increased Green
Tea extract concentration which the samples containing 0.9% Green Tea extract in milk and yoghurt had high
acidity value than the other sample investigated.
Table 2 and Table 5 show the growth rates of microbes in Green Tea extract milk and yoghurt in Lactobacillus
acidophilus and Bifidobacterium bifidum samples at storage time. The results show that the growth rate of bacteria
Intl J Farm & Alli Sci. Vol., 2 (17): 599-606, 2013
602
was increased by increasing the concentration of Green Tea extract and reached the desired acidity at shorter
period.
Table 3 shows the microbial growth on MRS-A cultivation environment of Lactobacillus acidophilus Green Tea
extract milk and yoghurt at refrigerator during 21 day of storage. The samples containing 0.9% Green Tea extract
possessed the highest count of bacteria.
The microbial growth on MRS-A cultivation environment of Bifidobacterium bifidum Green Tea milk and
yoghurt at refrigerator during 21 days was poor because Bifidobacterium bifidum has good growth on MRS Broth.
The microbial growth of Bifidobacterium bifidum on MRS Broth was high. It was observed that Bifidobacterium
bifidum has high inhibitory activity in MRS Agar during 21 days of storage. These results showed that Green Tea
extract was suitable for this intestinal bacterium that was kept viable up to the end of fermentation (21days). All
tested Bifidobacterium bifidum was capable of growing well on Green Tea extract milk and yoghurt without nutrient
supplementation.
Table 1. The acidity level based on Dornic degree in milk and yoghurt containing Lactobacillus acidophilus with Green Tea
Extract(GTE) within 21days storage in the refrigerator.
Acidity level in Dornic degree
21th
day
14th
day
7th
Day
first
day
GTE
yoghurt
21th
Day
14th
day
7th
day
first
day
GTE
milk
94
94
96
94
0%
46
43
43
41
0%
99
98
95
95
0.3%
56
50
47
43
0.3%
107
105
99
97
0.6%
54
50
48
43
0.6%
116
110
104
97
0.9%
63
59
51
45
0.9%
Table 2. Growth of microbes in milk and yoghurt containing Lactobacillus acidophilus with Green Tea Extract(GTE) within
21days storage in the refrigerator
21th
day
14th
day
7th
Day
first
day
(GTE)
yoghurt
21th
Day
14th
day
7th
day
first
day
(GTE)
milk
11.25×1010
3.5×1010
12.25×1010
10. 5×1010
0%
7.5×1010
10.25×1010
5.5×1010
6.5×1010
0%
7×1010
13. 5×1010
11.5×1010
7.25×1010
0.3%
14.5×1010
29.5×1010
26. 5×1010
21.25×1010
0.3%
19.5×1010
29.75×1010
24×1010
20.25×1010
0.6%
21. 5×1010
35.25×1010
31.25×1010
29. 5×1010
0.6%
37.5×1010
41. 5×1010
39. 5×1010
23. 5×1010
0.9%
34.25×1010
32.5×1010
29. 5×1010
18.25×1010
0.9%
Table 3. The microbial growth on MRS-A cultivation environment of Lactobacillus acidophilus Green Tea Extract (GTE) milk and
yoghurt at refrigerator during 21 days insolubility
21th
day
14th
day
7th
Day
first
day
(GTE)
yoghurt
21th
Day
14th
day
7th
day
first
day
(GTE)
milk
45×109
95×109
70×109
45×1010
0%
30×109
75× 109
135× 109
109 ×85
0%
70×109
118×109
61×109
15×1010
0.3%
45×109
219×109
365× 109
269× 109
0.3%
150×109
115×109
265×109
25×1010
0.6%
95×109
215×109
194×1010
110×1010
0.6%
215×109
319×109
175×109
65×1010
0.9%
95×109
340×109
223×1010
187×1010
0.9%
Table 4. The acidity level based on Dornic degree in milk and yoghurt containing Bifidobacterium bifidum with Green Tea
Extract (GTE)within 21days storage in the refrigerator
Acidity level in Dornic degree
21th
day
14th
day
7th
Day
first
day
(GTE)
yoghurt
21th
Day
14th
day
7th
day
first
day
(GTE)
milk
98
95
94
91
0%
47
46
45
42
0%
100
94
99
96
0.3%
65
49
46
43
0.3%
108
103
100
99
0.6%
72
58
49
49
0.6%
121
113
109
105
0.9%
79
62
53
51
0.9%
Table 5. Growth of microbes in milk and yoghurt Bifidobacterium bifidum with Olive Leaf Extract(OLE) within 21days storage in
the refrigerator
21th
day
14th
day
7th
Day
first
day
(GTE)
yoghurt
21th
Day
14th
day
7th
day
first
day
(GTE)
milk
11.25×1010
13. 5×1010
17.5×1010
12. 5×1010
0%
15×1010
8.25×1010
6. 5×1010
1010×3.25
0%
28.75×1010
34.25×1010
24.5×1010
16. 5×1010
0.3%
9.5×1010
27.5×1010
22.75×1010
11. 5× 1010
0.3%
21×1010
40×1010
29.5×1010
12.75×1010
0.6%
21.5×1010
41.5×1010
31.75×1010
15.25×1010
0.6%
45.75×1010
37.75×1010
16.5×1010
19.25×1010
0.9%
45×1010
39.5×1010
42.25×1010
22. 5×1010
0.9%
Intl J Farm & Alli Sci. Vol., 2 (17): 599-606, 2013
603
Discussion
In the present study, the effects of Green Tea extract on the growth and viability of the bacteria Bifidobacterium
bifidum and Lactobacillus acidophilus in probiotic milk and yoghurt were investigated. The acidity, pH and survival
of the bacteria in Green Tea extract probiotic milk and yoghurt were evaluated at 2 hours intervals till reaching
42°Dornic acidity degrees for milk and 90°Dornic degree for yoghurt in the incubator at 38°C. At the first hours of
production, the Lactobacillus acidophilus milk containing 0.6 and 0.9% Green Tea extract reached the acidity of
42°Dornic earliest, followed by 0.3, and 0% milk. Once they reached this acidity level, they were transferred to a
refrigerator at 2°C. The storage time in the refrigerator was determined to be 21 days.
In direct microbial counting in first day, the highest counts were sequentially in the samples with 0.3, 0.6, &
0.9% and the controls, indicating the positive correlation between increased bacterial growth and increased Green
Tea extract concentration. Upon evaluation of the cultured samples on MRS agar media, the same correlation was
revealed. The Lactobacillus acidophilus yoghurt with 0.9% Green Tea extract reached the acidity of 90°Dornic
earliest, followed by the samples with 0.6, & 0.3% and the control, Once they reached this acidity level, they were
transferred to a refrigerator at 2°C .The storage time in the refrigerator was found to be 21days.
The basic feature of the probiotic products consumption is their medicinal effects (bio value), their associated
sensory properties are also important. In other words, sensory properties rather than medicinal effects play the
most important role in their daily consumptions. Among the probiotic products, fermented ones especially the
probiotic yoghurt is popular worldwide for its unique sensory properties. (Mortazavian and Sohrabvandi, 2006)
The sensory evaluation was performed by 15 participants for the probiotic Lactobacillus acidophilus yoghurt
with varying concentrations of Green Tea extract, after seven days. There were significant differences between the
samples (p >0.05) and it was shown that the increase of Green Tea extract gives rise to favorable taste, color,
scent and thickness.
The minimum required level of probiotic bacteria to be useful for the consumer’s body is 107CFU.ml-1 of living
bacteria and the level in the present study was found to be 1010, thus, it could be beneficial for the consumers.
(Marhamatizadeh et al., 2009)
Upon evaluation of the samples on MRS Agar, the Lactobacillus acidophilus with Green Tea extract had the
counts equal to logarithmic 109 in day 14, and the sample product with 0.9% Green Tea extract possessed the
highest count of bacteria.
The milk containing Bifidobacterium bifidum with 0.9 and 0.6 % Green Tea extract reached 42°Dornic acidity
earliest than others, followed by the milk with 0.3% and finally the control. Once reached 42°Dornic, the samples
were transferred to a refrigerator at 2°C. The permanence of the product in the refrigerator was determined to be 21
days during which the acidity of control sample was lower than other samples.
The release of lactic acid is an indication of the activity of the probiotic bacteria (Ustunol, 2000) and the pH of
all the cultures was monitored to provide an indication of The milk and yoghurt fermented with Lactobacillus
acidophilus and Bifidobacterium bifidum in the presence of Green Tea extract had a significant lower pH than the
control, suggesting an appreciable amount of lactic acid had been produced. These results of lower pH values in
the milk containing Lactobacillus acidophilus with Green Tea extract could be attributed to the phenolic compounds
of the extract, which are known to serve as an oxygen scavenger and to reduce the redox potential of the growth
media, as probiotic bacteria grow better in the absence of oxygen.
As phenolic compounds present in tea are able to interact with milk proteins, these may affect the sensory and
functional properties (heat stability, rennet ability, foaming), microbiological quality and oxidative stability of milk
and dairy products (O’Connell & Fox, 2001). On the other hand, such interactions are considered to be responsible
for an inhibition of the antioxidant properties and well-documented protective vascular functions of Green Tea
when consumed with addition of milk (Lorenz et al., 2007; Ryan & Petit, 2010). However, there are also many
studies that do not confirm this phenomenon (Kyle, Morrice, McNeill, & Duthie, 2007; Reddy, Vidya Sagar,
Sreeramulu, Venu, & Raghunath, 2005). Moreover, to the best of our knowledge there is a lack of information on
the protein-polyphenol interactions in fermented milk.
As revealed in direct microbial counting, the count in day 14th was higher, compared to day 1, for all Green Tea
extract concentrations, but possessed logarithmic coefficient 1010. The bactericidal and inhibitory effect of low pH
was stronger for Bifidobacterium bifidum than Lactobacillus acidophilus and it seems that during the storage time
and enhanced fermentations process, decreased pH caused decreased growth of Bifidobacterium bifidum.
At the first hours of production, the Bifidobacterium bifidum yoghurt with 0.9 and 0.6% Green Tea extract reached
90°Dornic acidity earliest, followed by the yoghurt sample with 0.3% and the control. They were transferred to a
refrigerator at 2°C, once reached the 90°Dornic acidity.
The product permanence in the refrigerator was found to be 21 days. No significant difference was observed in
the Bifidobacterium bifidum yoghurt with Green Tea extract in terms of color, thickness, taste and scent. The
Intl J Farm & Alli Sci. Vol., 2 (17): 599-606, 2013
604
sample with 0.9% was with the highest bacterial counts, as revealed in the evaluation of the samples in direct
counting method.
These findings indicate that probiotic bacteria were not inhibited during their growth or during their survival by
different concentrations of Green tea extract. These results are in concordance with studies (Lee, Jenner, Lowa, &
Lee, 2006) showing that some lactic acid bacteria we're not severely affected by tea phenolic compounds in
opposition to other pathogenic bacteria.
The positive effect of the tea additive on probiotic bacteria in milk and yoghurt found in our study can be in
some part confirmed by the data found in literature. Among many health benefits, tea is known to possess
antimicrobial effect against many microorganisms including pathogens but does not inhibit lactic acid bacteria
(LAB).
Michalczyk and Zawislak (2008) reported that the addition of Green tea extracts significantly inhibited the
growth of Staphylococcus aureus, Escherichia coli, Salmonella enteritidis, whereas it had no significant effect on
the growth of selected LAB such as: Lactobacillus plantarum, Leuconostoc mesenteroides, Lactobacillus
rhamnosus.
Hara (1998) also reported that when administered orally, tea catechins did not affect lactic acid bacteria, but
when incorporated in the diet for several weeks reduced the level of putrefactive products and increased the
concentration of organic acids. Jaziri et al. (2009) studied the effect of green and black tea addition on the survival
of the starter bacteria in yoghurts but no significant effect of tea supplementation on the level of yoghurt bacteria or
acidity was stated. However, the production procedure described by these authors differed from our method in
many points such as type of tea and its level, UHT milk used, tea infused directly in milk etc. that might have a
significant impact on the results.
The results of the studies addressing the probiotic bacteria have demonstrated the following: The increased
concentration of malt and soya caused increase in the microorganism growth and rising acidity level which in turn
resulted in shorter incubation time for the desired acidity. In a study on the effects of soya powder on the growth of
the bacteria, Lactobacillus acidophilus and Bifidobacterium bifidum, in probiotic products, it was demonstrated that
the shelf life for the acidity reaching the desired level during incubation decreased for the milk with both bacteria
and combined soya and malt, compared to the milk with only soya. As for the yoghurt with both bacteria, the same
results were yielded and incubation time for the yoghurt with malt and soya was decreased. (Marhamatizadeh et
al., 2009; 2011)
The effect of honey on the growth of the above-mentioned bacteria introduced simultaneously into dairy
products and drinks was investigated, and the results indicated that yoghurt with only Lactobacillus acidophilus
tasted sourer than the yoghurt with both bacteria. The products containing Bifidobacterium bifidum, compared to
those with Lactobacillus acidophilus, were with slower growth rate and also tasted less sour and were of longer
permanence. They were not of favorable taste when honey concentration increased and the control was of the best
taste among all the samples. (Marhamatizadeh et al., 2010)
In another study addressing the effect of cinnamon on the bacterial growth, it was demonstrated that the
increased cinnamon concentration promoted the growth of the bacteria in probiotic milk and yoghurt. (Yaghtin,
2010)
In another study addressing that investigated the effect of spearmint on the bacterial growth, it was
demonstrated that increased spearmint concentration promoted the growth of Lactobacillus acidophilus and
Bifidobacterium bifidum in probiotic milk and yoghurt. (Marhamatizadeh et al., 2011)
In another study addressing the effect of juice on the bacterial growth, it was demonstrated that the increased
juice product promoted the growth of the bacteria in probiotic orange and apple. (Marhamatizadeh et al., 2012)
In a study that investigated the effect of garlic on bacterial growth and survival, it was observed that increased
garlic concentration promoted the growth and viability of probiotic bacteria in milk and yoghurt during refrigerated
storage. (Marhamatizadeh et al., 2012)
In another investigation addressing the effect of dill extract on growth and survival of Lactobacillus acidophilus
and Bifidobacterium bifidum, it was represented that dill extract has positive effect on growth and viability of
probiotic bacteria in milk and yoghurt during permanence period and finally leaded to produce new fermented dairy
product. (Marhamatizadeh et al., 2012)
In experiment that researchers investigated the effect of permeate on the growth and survival of the above
mentioned bacteria (Lactobacillus acidophilus and Bifidobacterium bifidum) was indicated that the permeate was
suitable support for intestinal bacteria that had kept viable up during 21 days of refrigerated storage and final
evaluation of products showed that permeate can be successfully used in the preparation of nutritive probiotic
beverages. (Marhamatizadeh et al., 2012)
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CONCLUSION
The effect of Green Tea Extract on characteristic of selected probiotic bacteria in milk and yoghurt during
fermentation and refrigerated storage was studied. To our knowledge this is the first study on the feasibility of
employing Green Tea extract for fortified probiotic milk and yoghurt with antioxidant and phenolic compounds. The
result of this experiment demonstrating that Green Tea extract was successfully employed for production of
polyphenol fortified probiotic milk and yoghurt. Addition of Green Tea Extract significantly affected the acidity of
yoghurts. Lower pH values were found for supplemented milk and yoghurt but the level of fortification had little
effect on that parameter. All probiotic milk and yoghurt maintained a high level of probiotic bacteria during three-
week cold storage, but Green tea-fortified milk and yoghurt were characterized by a higher number of viable
Lactobacillus acidophilus and Bifidobacterium bifidum cells compared with plain milk and yoghurt. Consumer
sensory testing analysis found that green tea milk and yoghurt samples were liked as well or better than the
control milk and yoghurt samples. If the right polyphenol concentration is chosen, the desired health-
promoting effects of the functional ingredient can be achieved without negatively affecting the functional
properties of probiotic milk and yoghurt. Addition of green tea in the process of milk and yoghurt is recommended
because Green tea is a natural herbal product with a wide range of beneficial and nutritional properties; this
makes this milk and yoghurt a new functional food.
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