Impact of fortification with honey on some properties of bio-yoghurt

Abstract

The effect of supplementation with honey on yoghurt quality was studied. Five treatments of yoghurt were made from buffaloe's and cow's milk mixture (1:1). Control yoghurt was made using classic yoghurt culture, whereas the other four treatments were made by ABT culture and milk fortified with 0, 2, 4, and 6% honey. Changes in rheological, chemical, microbial and organoleptic properties of yoghurt were monitored during refrigerated storage (4°C) of yoghurt for 15 d. Results showed that addition of honey to milk had no significant effect on ABT starter activity. A curd tension increased, whereas curd syneresis decreased in bio-yoghurt fortified with honey. Acidity, TS, WSN and TVFA contents of yoghurt supplemented with honey were higher than those of control. The contents of fat, ash and TN were similar in both. Addition of honey to yoghurt improved the viability of bifidobacteria. Bifidobacteria counts were similar to accepted threshold (106 cfu g-1) for a probiotic effect. Also, addition of honey improved the body, texture and flavour of the yoghurt.

Full text

503
IMPACT OF FORTIFICATION WITH HONEY ON SOME PROPERTIES OF BIO-YOGHURT
El-Tahra M. A. Ammar1; Magdy M. Ismail *2; Abd El-Wahab E. Khalil1 and Mohamed Z. Eid2
Address(es):
1Dairy Department, Faculty of Agriculture, Mansoura University, El-Mansoura, Egypt.
2Dairy Technology Department, Animal Production Research Institute, Agricultural Research Center, Dokki, Giza, Egypt.
*Corresponding author: abo-omar98@hotmail.com
ABSTRACT
Keywords: Yoghurt, bifidobacteria, acidophilus, ABT, honey
INTRODUCTION
Yogurt is an important dairy product, particularly for consumers with lactose
intolerance. Yogurt is considered a healthy food because it contains viable
bacteria that are considered probiotics. LA and Bifidobacterium spp. also have
been reported to increase immunity of the host animals (Hughes and Hoover,
1991), lower the level of harmful enzymes such as α-glucosidase and α-
glucuronidase responsible for catalyzing the conversion of carcinogenic amines
(Reddy, 1983) and are beneficial for improvement in lactose utilization in lactose
malabsorbers (Shah, 1993). LA and bifidobacteria exert antagonistic effects on
the growth of pathogens such as Staphylococcus aureus, Salmonella
typhimurium, Yersinia enterocolitica and Clostridium perfringens (Ozbas and
Aytac, 1995). Inoculums size of probiotic bacteria is an important and a key
factor to ensure sufficient viable cells in the final yogurt. Therefore, it is
imperative for AB-yogurt manufacturers to ensure that at least one million viable
cells of Lactobacillus acidophilus and bifidobacteria g-1 are present at the end of
fermentation. If the required criterion is met, the number of probiotic bacteria
should remain stable throughout the anticipated shelf life (Samona and
Robinson, 1994).
On the other hand, the health benefits of honey have long been realized by
humans to treat a variety of ailments. Besides its sugar composition, honey
consists of a number of bioactive compounds such as phenolic compounds,
flavonoids, carotenoid-like derivatives, organic acids, Maillard reaction products,
catalase, ascorbic acid, and other compounds which function as antioxidants
(Bogdanov et al., 2008). Several therapeutic and medicinal effects such as
antibacterial, antimutagenic, antiproliferative, hepatoprotective, hypoglycemic,
and antioxidant effects have been ascribed to honey through last years (Erejuwa
et al., 2010 and Ghashm et al., 2010). Poorani et al. (2012) stated that honey,
which is naturally available good product with high nutritive and medicinal value
can be used preparing a bifidiogenic milk product by assessing the content of
bifidus growth factor and further incorporation will give a valuable product.
Therefore, the aim of this study was the possibility of increasing the nutritional
and health values of bio-yoghurt by adding honey and also possibility of using
honey as a prebiotics for yoghurt cultures.
MATERIALS AND METHODS
Starter Cultures and Honey
A commercial classic yoghurt starter containing Streptococcus thermophillus and
Lactobacillus delbrueckii subsp. bulgaricus (1:1) and ABT-5 culture which
consists of S. thermophiles, LA + B. bifidum (Chr. Hansen’s Lab A/S
Copenhagen, Denmark) were used. Starter cultures were in freeze-dried direct-to-
vat set form and stored at –18°C until used. Honey was obtained from local
market in Damiette Governorate, Egypt.
Yoghurt Preparation
Yoghurt treatments were prepared from fresh buffalo's and cow's milk mixture
1:1 (acidity 0.17%, pH 6.61, fat 5.1%, TS 14.56% and total protein 3.87%) in
Dairy Laboratory of El-Serw Animal Production Research Station, Animal
Production Research Institute, Agricultural Research Center. Five yoghurt
treatments were made using classic yoghurt or ABT cultures. The first treatment
was manufactured using classic yoghurt starter (control) whereas, treatments
from two to five were made by ABT culture and milk fortified with 0, 2, 4, and
6% honey, respectively. Fresh milk was tempered to 85°C for 15 min, cooled to
40°C, fortified with 0, 2, 4 and 6% (wt/wt) honey, inoculated with cultures (0.1 g
L-1 of yoghurt mix), transferred to 100-ml plastic cups, incubated at 40°C for
fully coagulation, and stored at 4°C for 15 days. Yoghurt samples were analyzed
when fresh and after 7 and 15 days of refrigerated storage. Three replicates of
each treatment were conducted.
Chemical Properties
Total solids, fat, TN and ash contents of samples were determined according to
(AOAC, 2000). Titratable acidity in terms of % lactic acid was measured by
titrating 10 g of sample mixed with 10 ml of boiling water against 0.1 N NaOH
using phenolphthalein indicator to an end point of faint pink color (Parmar,
2003). pH of the sample was measured using a pH meter (Corning pH/ion
analyzer 350, Corning, NY) after calibration with standard buffers (pH 4.0 and
7.0). Water soluble nitrogen (WSN) of yoghurt was estimated according to Ling
(1963). Total volatile fatty acids (TVFA) were determined according to
Kosikowiski (1978).
The effect of supplementation with honey on yoghurt quality was studied. Five treatments of yoghurt were made from buffaloe's and
cow's milk mixture (1:1). Control yoghurt was made using classic yoghurt culture, whereas the other four treatments were made by ABT
culture and milk fortified with 0, 2, 4, and 6% honey. Changes in rheological, chemical, microbial and organoleptic properties of
yoghurt were monitored during refrigerated storage (4°C) of yoghurt for 15 d. Results showed that addition of honey to milk had no
significant effect on ABT starter activity. A curd tension increased, whereas curd syneresis decreased in bio-yoghurt fortified with
honey. Acidity, TS, WSN and TVFA contents of yoghurt supplemented with honey were higher than those of control. The contents of
fat, ash and TN were similar in both. Addition of honey to yoghurt improved the viability of bifidobacteria. Bifidobacteria counts were
similar to accepted threshold (106 cfu g-1) for a probiotic effect. Also, addition of honey improved the body, texture and flavour of the
yoghurt.
ARTICLE INFO
Received 29. 9. 2014
Revised 31. 3. 2015
Accepted 31. 3. 2015
Published 1. 6. 2015
Regular article
doi: 10.15414/jmbfs.2015.4.6.503-508

J Microbiol Biotech Food Sci / Ammar et al. 2015 : 4 (6) 503-508
504
Rheological Properties
The curd tension was determined using the method of Chandrasekhara et al.
(1957) whereas the curd syneresis was measured as given by Mehanna and
Mehanna (1989). For test of coagulation time during yoghurt making, milk was
inculcated with starters and incubated at 40°C then coagulation was noticed at 30
min intervals.
Microbiological Analyses
The count of bifidobacteria was determined according to Dinakar and Mistry
(1994). A mixture of antibiotics, including 2 g of neomycin sulfate, 4 g of
paromomycin sulfate, 0.3 g of nalidixic acid, and 60 g of lithium chloride
(NPNL, Sigma Chemical Co.), was prepared in 1 L of distilled water, filter-
sterilized (0.22 um), and stored at 4°C until use. The mixture of antibiotics (5 ml)
was added to 100 ml of MRS agar medium. Cysteine-HC1 was added at the rate
of 0.05% to decrease the redox potential of the medium. Plates were incubated at
37°C for 48 to 72 h under anaerobic condition.
Organoleptic Analysis
Samples of yoghurt were organoleptically scored by the staff of the El-Serw
Animal Production Research Station. The score points were 50 for flavour, 35 for
body and texture and 15 for colour and appearance, which give a total score of
100 points (El-Shazly et al., 2008).
Statistical Analysis
The obtained results were statistically analyzed using a software package (SAS,
1991) based on analysis of variance. When F-test was significant, least
significant difference (LSD) was calculated according to Duncan (1955) for the
comparison between means. The data presented, in the tables, are the mean (±
standard deviation) of 3 experiments.
RESULTS AND DISCUSSION
Changes in acidity during fermentation of yogurt
For measurement of starter activity as affected by adding 2, 4 and 6 % honey, the
development of acidity values (as lactic acid percentages) of buffaloe's and cow's
milk mixture inoculated with classic yoghurt and ABT cultures was determined
at 30 min intervals till 180 min. Results were tabulated in Table 1. As it is
expected, a gradual increase of titratable acidity values in control and all samples
was noticed during incubation for 180 min. Acidity percentages of treatment A at
the beginning and the end of incubation time were 0.15 and 0.52%, respectively.
Both acidity ratios and the development of acidity rats within fermentation were a
little bit higher in milk inoculated with classic starter (treatment A) than that of
milk inoculated with ABT culture (treatment B). These outcomes are similar to
that reported by Damin et al. (2008) who stated that milk fermented with
Streptococcus thermophilus and Bifidobacterium lactis had the lowest post
acidification. This behavior could be explained by the limited capacity of
Bifidobacterium to produce organic acids at low temperatures (Mattila-
Sandholm et al., 2002).
As shown from Table 1, the addition of various concentrations of honey to
yoghurt milk had no significant effect on the acidity values during the 180 min of
fermentation. After 180 min of incubation time, the acidity level was 0.48% for
yoghurt made by ABT (treatment B) and lowered to 0.46, 0.46 and 0.44% for
yoghurt fortified with 2, 4 and 6% honey, respectively. These results are
generally in harmony with those reported by Varga (2006) who found that the
honey had no significant effect on pH and lactic acid levels of the final products.
Changes in rheological properties of yoghurt
The effect of using ABT culture and adding different levels of honey to
buffaloe’s and cow’s milk mixture on coagulation time, curd tension and curd
syneresis were presented in Table 2. The contribution of bifidobacteria with
yoghurt culture has slightly changed the rheological attitude. Similar observation
was reported by Hassan et al. (2003). Coagulation time of control treatment (A)
was 3 h and slightly increased to 3.20 h as result of using ABT culture in yoghurt
manufacture (treatment B). These results may be attributed to the slow acid
production of ABT starter as compared with that of classic yoghurt. Saccaro et
al. (2009) found that growth of probiotic strains, when grown singly or blends
with yoghurt cultures affected the fermentation time and the rate of acidification.
No significant differences were obtained in curd tension values between
treatments A and B. The results of curd syneresis indicated that slight increasing
in yoghurt syneresis was found in sample B.
Blending of honey with milk caused very slight increase in coagulation time of
yoghurt (Table 2). Values of coagulation time of treatments B, C, D and E were
3.20, 3.25, 3.30 and 3.30 h, respectively. Because adding honey raised the total
solids content of milk, the produced honey yoghurt had the highest values of curd
tension comparing with control. De Jong (1978) stated that slight differences in
moisture may cause major differences in rheological parameters. Also, Murad et
al. (1998) and El-Nemer et al. (2003) showed that the hardness related to dry
matter of the product. In contrast to our results Ayad, et al. (2010) stated that
supplementation of yoghurt with honey and talbina (cooked barley bran flour) or
with molasses and talbina decreased the hardness which could be due to the
ability of polysaccharides in honey and molasses to bind with significant amount
of free water. However the same authors also cleared that a positive relationship
was found between hardness and TS% which increased in honey or molasses
yoghurt. Regarding of curd syneresis, bio-yoghurt fortified with honey possessed
lower syneresis values than those of control.
Changes in chemical composition of yoghurt
The effect of using ABT culture and supplementation of yoghurt with 2, 4 and
6% honey on the titratable acidity (% lactic acid), pH, total solids (TS%), Fat%
and Ash% during the refrigerated storage was illustrated in Table 3. Using of
ABT starter (treatment B) decreased titratable acidity ratios and increased pH
values of fresh yoghurt and during storage period (15 days) as compared with
that made by classic culture (treatment A). Acidity percentages of samples A and
B at zero time were 0.79 and 0.62%, respectively. These results agreed with
Shihata and Shah (2002) and disagreed with Kehagias et al. (2006). Shihata
and Shah (2002) reported that the ABT cultures are known to produce yoghurt
with a fine, mild taste and low post acidification whereas Kehagias et al. (2006)
stated that the addition of bifidobacteria to yoghurt starter increased acidity of
yoghurt which attributed to the formation of both acetic and lactic acids by B.
bifidum. In bio-yoghurt special attention should be given to avoid over
acidification since this could affect the stability of bifidobacteria during storage
period. No significant differences in TS, fat and ash contents between yoghurt
made using classic or ABT cultures at zero time or within storage period. These
results were confirmed by resulted of Ayad, et al. (2010) who stated that TS,
SNF, fat, F/DM and protein values in bifidus yoghurt-like products were not
affected by bifidobacteria incorporation with yoghurt-like products.
Table 1 Effect of adding honey to buffaloe's and cow's milk mixture on activity
of ABT culture (expressed as acidity percentage)
Incubation time (min)
Treatments
180
150
120
90
60
30
0
0.52
0.42
0.33
0.23
0.18
0.16
0.15
A
0.48
0.39
0.31
0.22
0.16
0.14
0.14
B
0.46
0.38
0.29
0.21
0.17
0.15
0.15
C
0.46
0.37
0.29
0.21
0.17
0.15
0.14
D
0.44
0.35
0.28
0.21
0.17
0.15
0.15
E
A- Yoghurt made using classic yoghurt starter (control)
B- Yoghurt made using ABT
C- Yoghurt made using ABT + 2% honey
D- Yoghurt made using ABT + 4% honey
E- Yoghurt made using ABT + 6% honey
Table 2 Effect of using of ABT culture and adding of honey to buffaloe's and
cow's milk mixture on rheological properties of yoghurt
Curd syneresis (g 15 g-1 of curd)*
Curd
tension
(g)
Coagulation
time (h)
Treatments
Time (min)
120
60
30
10
5.16
3.97
2.99
1.52
32.55
3.00
A
5.37
4.14
3.11
1.76
32.73
3.20
B
5.19
4.03
2.90
1.50
33.22
3.25
C
5.23
4.01
3.03
1.55
34.68
3.30
D
5.26
4.08
3.06
1.57
35.83
3.30
E
*Whey excluded (g) from 15 g of curd kept at room temperature after 10, 30, 60 and 120
min.
On the other hand, addition of honey to yoghurt (treatments C, D and E) slightly
increased titratable acidity and decreased pH values which could be attributed to
fructooligosacchrides in honey (Akalin et al., 2007). Abd El-Salam et al. (2011)
cleared that the pH and titratable acidity of yoghurt supplemented with honey
affected slightly compared with that supplemented with Bifidobacterium lactis
Bb.12. On the contrary, Varga (2006) reported that honey has the ability to
decrease solutions sourness. This property might serve to increase consumer
acceptability to acidic products such as yogurt. Yoghurt acidity and pH value
were affected (P<0.001) by treatments and the interaction of treatment × age
(Tables 3 and 7). Titratable acidity values of all yoghurt treatments were
acceptable according to Mehanna et al. (2003a) and Mortazavian et al. (2007)
while were less than recommended by Egyptian Standards (2005). Fortification
of yoghurt with honey increased TS content and the increasing rate was
proportional to the honey ratios added. Total solids contents of treatments B, C,
D and E after 7 days of storage were 15.60, 17.11, 18.51 and 20.09%,
respectively. Fat and ash contents were not affected by honey incorporation with
bio-yoghurt. Generally, during storage titratable acidity values of all treatments

J Microbiol Biotech Food Sci / Ammar et al. 2015 : 4 (6) 503-508
505
and control increased due to the activity of the starter culture. These results
agreed with Vijayalakshmi et al. (2010) who found that a significant increase in
acidity and decrease in pH were noticed in low fat yoghurt during the storage
period but within the permissible levels. Also, TS, fat and ash contents of all
treatments increased due to the loss of moisture during storage period. Similar
observation was reported by Farag et al. (2007). The statistical analysis of
variance (Table 7) showed that the differences in acidity and TS values between
treatments and the effect of storage time were significant (P<0.001).
The contents of TN, TN/DM, WSN, WSN/TN and TVFA of yoghurt as affected
by using various cultures and supplementation with honey were represented in
Table 4. The effect of storage time on TN content was more significant (P<0.001)
than those of starter type or incorporation of honey. As storage period advanced,
TN values of all treatments raised while they nearly remained constant between
different treatments. These results are in agreement with those obtained by
Akalin (1996), who reported that the type culture used in the fermentation didn't
affect on the TS, TP, fat and lactose ratios of yoghurt, Bioghurt, Bifighurt and
Biogarde.
Using of classic starter increased WSN content of the resulted yoghurt as
compared with using ABT culture (Table 4). This may be due to proteolytic
activity (endopeptidase) of L. delbrueckii subsp. bulgaricus which hydrolyzed
casein to polypeptides then; the later was hydrolyzed to amino acids with
exopeptidases produced by S. thermophilus (Tamime and Robinson, 1999). In
all yoghurt treatments, WSN contents significantly increased during storage
period. WSN content of treatment B at zero time was 0.134% and increased to
0.178% at the end of storage period. These results suggest some degradation in
yoghurt protein during storage as also found by El-Shibiny et al. (1979) and
Mehanna and Hefnawy (1988). Fortification of yoghurt with 2, 4 and 6% honey
(samples C, D and E) slightly increased WSN contents which may refer to the
stimulation effect of fructooligosaccharides in honey on bifidobacteria (Akalin et
al., 2004).
Table 3 Effect of using ABT culture and adding of honey on the chemical composition of yoghurt
Ash
%
Fat/DM
%
Fat
%
TS
%
pH
values
Acidity
%
Storage
period (days)
Treatments
0.88
0.91
0.95
38.14
37.91
38.22
5.9
5.9
6.0
15.47
15.56
15.70
4.70
4.42
4.21
0.79
1.09
1.25
Fresh
7
15
A
0.86
0.89
0.93
37.39
37.79
38.17
5.8
5.8
6.0
15.51
15.60
15.72
4.98
4.76
4.53
0.62
0.84
1.01
Fresh
7
15
B
0.89
0.92
0.92
34.75
35.07
35.36
5.9
6.0
6.1
16.98
17.11
17.25
4.87
4.64
4.46
0.69
0.90
1.08
Fresh
7
15
C
0.89
0.91
0.96
31.62
31.33
31.62
5.8
5.8
5.9
18.34
18.51
18.66
4.82
4.59
4.42
0.72
0.95
1.11
Fresh
7
15
D
0.90
0.92
0.95
28.63
28.87
29.09
5.7
5.8
5.9
19.91
20.09
20.28
4.80
4.56
4.41
0.73
0.97
1.11
Fresh
7
15
E
Total volatile fatty acids (TVFA) are taken as a measure of the degree of fat
hydrolysis during storage (Table 4). As storage time increased, TVFA contents
significantly (P< 0.001) increased in all yoghurt treatments. These increases may
be due to small degree of lipolysis exhibited by L. delbrueckii subsp. bulgaricus,
L. acidophilus and S. thermophilus. Lactobacillus produces more TVFA than S.
thermophilus. The increases of TVFA contents also may be due to oxidative
deamination and decarboxylation of amino acids, which convert the amino acids
into its corresponding volatile fatty acids (Tamime and Robinson, 1999). Total
volatile fatty acids of yoghurt manufactured using classic starter were very
slightly higher than those of yoghurt made using ABT culture. On the other side,
it could be seen that the yoghurt contained various levels of honey showed the
highest increase of TVFA. In supplementary, Chick et al. (2001) mentioned that
the organic acids production was enhanced when bifidobacteria were grown in
the presence of honey, where various oligosaccharides found in honey may be
responsible for enhancing organic acids production by bifidobacteria. Honey also
contains a variety of organic acids (0.17 to 1.17%) such as acetic, butyric, citric,
formic, gluconic, lactic, malic, pyroglutamic and succinic acids (NHB, 1996).
Table 4 Effect of using ABT culture and adding of honey on TN, WSN and TVFA contents of yoghurt
TVFA*
WSN/TN
%
WSN
%
TN/ DM
%
TN
%
Storage
period (days)
Treatments
6.0
6.7
7.7
21.76
24.68
25.62
0.151
0.173
0.185
4.49
4.50
4.60
0.694
0.701
0.722
Fresh
7
15
A
5.8
6.4
7.3
20.52
23.58
24.58
0.143
0.166
0.178
4.49
4.51
4.60
0.697
0.704
0.724
Fresh
7
15
B
6.0
6.6
7.6
21.01
23.90
25.03
0.146
0.168
0.180
4.09
4.11
4.17
0.695
0.703
0.719
Fresh
7
15
C
6.4
7.2
7.9
21.45
24.36
25.28
0.148
0.171
0.182
3.76
3.79
3.86
0.690
0.702
0.720
Fresh
7
15
D
6.5
7.5
8.6
21.84
24.71
25.94
0.152
0.174
0.187
3.49
3.50
3.55
0.696
0.704
0.721
Fresh
7
15
E
* expressed as ml 0.1 NaOH 100 g-1 cheese
Changes in bifidobacteria counts of yoghurt
Data of counts of bifidobacteria of yogurts made using classic and ABT cultures
are shown in Table 5. Counts of bifidobacteria gradually declined through
refrigerated preservation of yoghurt. Loss of viability of probiotic bacteria in
fermented milk was reported to be due to acid injury to the organisms (Shah,
2000). However, slight increasing of acidity ratios of honey samples (Table 3)
which have negative effect on probiotic cultures as low acid tolerance,
bifidobacteria count of samples contained honey were higher than those of
control which may be caused by oligosaccharides presence in honey.
Oligosaccharides were found to enhance the viability of starter culture as
prebiotics (El-Baz and Zommara, 2007). Ustunol (2000) cleared that dairy
products are the favored food for introducing lactic acid bacteria and
bifidobacteria into the human digestive tract. The purpose for doing this is to
improve the microbial balance of the intestine. Bifidobacteria, however, are
fastidious microorganisms. Keeping their numbers large enough to be meaningful
can be a challenge to food manufacturers. Honey contains a small percentage of
oligosaccharides that could serve as a food source for these beneficial bacteria,
thereby, making honey a “prebiotic” for the “probiotic” dairy food. Mehanna et
al. (2003b) and Sanz et al. (2005) found that as a prebiotic, honey contains
carbohydrates called oligosaccharides, which may improve gastrointestinal health
by stimulating the growth of good bacteria in the colon. Honey has been shown
to enhance growth, activity of bifidobacteria in fermented dairy food. Abd- El-
Salam et al. (2011) stated that supplementation of yoghurt with honey and B.
lactis improved growth of bacterial starter.
However, a little decrease of bifidobacteria numbers was observed during storage
period. The recommended level of bifidobacteria is of 106 or 107 cfu g-1 as a
probiotic, while, this number was exceeded for all treatments of bio-yoghurt

J Microbiol Biotech Food Sci / Ammar et al. 2015 : 4 (6) 503-508
506
around 106 cfu g-1 until the end of storage period. After 15 days of storage period,
bifidobacteria counts of treatments B, C, D and E were 1.7, 2.3, 2.7 and 3.5 x106
cfu g-1, respectively. Ouwehand and Salminen (1998) stated that in order to
exhibit positive health effects of probiotics, they have to deliver in certain
numbers. As a guide, the International Dairy Federation (IDF) suggested a
minimum of 107 cfu of probiotics g-1 product should be alive at the time of
consumption. Similar results and recommendations were obtained by Moreno et
al. (2006) and Jayamanne and Adams (2006).
Changes in sensory evaluation of yoghurt during refrigerated storage
Organoleptic properties evaluation is an important indicator of potential
consumer preferences. The popularity of yoghurt as a food component depends
mainly on its sensory characteristics and addition of different flavours to yoghurt
has been found to increase options for consumers and helps in marketing yoghurt
and retaining consumer interests (Routray and Mishra, 2011). Impact of culture
type and incorporation of honey on sensory quality of yoghurt is given in Table
6. Organoleptic profiles of yoghurt made using of classic starter were found to be
comparable to those of yoghurt samples manufactured by ABT culture at zero
time and during storage period. Total scores of sensory evaluation for samples A
and B at the end of storage period were 89 and 88 respectively. Ayad et al.
(2010) stated that using bifidus culture with yoghurt culture in yoghurt like
products manufacturing enhanced body and texture of all treatments.
Because of the sweet taste of honey, which is preferable for many consumers, it
was not surprising that the flavour evaluation test of yoghurt supplemented with
different honey concentrations gained the highest scores. Addition of honey not
only improved yoghurt flavour, but also body and texture. All honey yoghurt
samples were considered acceptable. Treatment E (6% honey) received the
highest total score, which may be attributed to the suitable firmness body and
sweet taste. Confirmation for these results, it could be seen from Table 2 that
treatment E had the longest fermentation time (3.30 h) which may resulted in
greater firmness (Damin et al., 2006). Our results are in agreement with those of
Riazi and Ziar (2012) who stated that as for sensory properties, the product
formulation with the highest concentration of honey (that is, 10% w/v) was too
sweet and was evaluated as strong in honey flavour. However, the yogurt samples
containing 5% (w/v) of honey were found to have optimum sweetness. The
points allocated for colour, body-texture and taste showed that an increase in
honey content brought about an improvement in the texture, flavour and aroma of
the products (P<0.05). Also, they cleared that the addition of honey had a good
effect on sensory properties of fermented milk with bifidobacteria (P<0.05), and
a particular noticeable yogurt or probiotic flavour was found. All the samples
gave a good total impression, were medium sour and did not have any marked
off-flavour during the storage period. None of the sweetened fermented milks
were judged to be weak.
Table 5 Effect of using ABT culture and adding of honey on bifidobacteria count
(cfu g-1) of yoghurt
Bifidobacteria (x 106)
Storage period (days)
Treatments
-
-
-
Fresh
7
15
A
2.8
2.3
1.7
Fresh
7
15
B
3.3
2.8
2.3
Fresh
7
15
C
3.9
3.4
2.7
Fresh
7
15
D
4.7
4.0
3.5
Fresh
7
15
E
Table 6 Effect of using ABT culture and adding of honey on organoleptic properties of yoghurt
Total
(100)
Flavour
(50)
Body &
texture
(35)
Color &
appearance
(15)
Storage
period (days)
Treatments
89
89
83
45
45
42
31
31
29
13
13
12
Fresh
7
15
A
88
88
87
44
44
42
31
31
28
13
13
12
Fresh
7
15
B
93
92
89
47
47
46
33
33
31
13
12
12
Fresh
7
15
C
95
95
90
48
48
46
34
34
32
13
13
12
Fresh
7
15
D
95
94
92
48
48
47
34
34
33
13
12
12
Fresh
7
15
E
CONCLUSIONS
Addition of honey increased the total solids content of the product thereby
increasing its total food value. Bifidobacteria were greatly activated by mixing of
honey with yoghurt milk which main that honey could be utilized as sweeter and
prebiotic in bio-yoghurt production. The result of the organoleptic properties of
yoghurt cleared that there was no difference in color and appearance while there
were differences in the body, texture and flavour. Incorporation of honey highly
improved the sensory evaluation scores of the resulted yoghurt.
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