bacteriological, physicochemical and sensory ...

Egypt . J. of Appl. Sci., 28 (12) 2013

295-313

BACTERIOLOGICAL, PHYSICOCHEMICAL AND SENSORY PROPERTIES OF PROBIOTIC FERMENTED CAMEL'S MILK AS AFFECTED BY ADDED INULIN Alaa H. Ibrahim*1and S. A. Khalifa2 1

Department of Animal and Poultry Breeding, Desert Research Center, Cairo, Egypt. 2 Food Science Department, Faculty of Agriculture, Zagazig University, Egypt *Correspondent Author: E-mail address ([email protected])

Key Words: Inulin; Dietary fiber; Probiotic cultures; Fermented camel's milk.

ABSTRACT In this work, the growth and activity of yoghurt culture and probiotic bacteria were evaluated in fermented camel's milk containing 2, 6, and8% (w/v) inulin. Viable cell counts of yoghurt culture and probiotic bacteria, physicochemical properties, syneresis index, viscosity, concentration of acetaldehyde and sensory evaluation of the fermented camel's milk were determined during refrigerated storage for 14 days at 4±1°C. In the presence of inulin, cultures showed better retention of viability comparing with control samples. Supplementation of camel's milk with inulin increased the viscosity and decreased the syneresis index of probiotic fermented camel's milk significantly (P< 0.05). Inulin behaved as prebiotic to improve quality of camel's milk fermented by yoghurt and probiotic cultures. Incorporation of inulin resulted in improved viability of Bifidobacterium bifidum, during cold storage but did not affect the viability of yoghurt bacteria compared with the control. The inulin addition enhanced the sensory properties of fermented camel's milk indicating that the addition of inulin up to 6% gave acceptable quality probiotic fermented camel's milk product.

INTRODUCTION Camel's milk products play an important role in the nutrition of rural communities in Africa, Asia and in the Middle East, especially, those living in the arid and semi-arid regions of the country which serve as a source of energy and nutrients consumed raw or as spontaneously fermented products (Dirar, 1993). Producing fermented camel's milk products may be difficult because of the coagulation problem of milk. Fermented products of camel’s milk vary according to the method of processing (Yagil, 1982). Shubat is camel’s sour milk from Kazakhstan (Thapa, 2000). Kefir is the Caucasian fermented camel’s milk (Yagil,

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1982). Lehban Rayeb is fermented product from camel’s milk in Syria and Egypt (Wernery, 2003). In Mongolia ''Tarag'' is cultured milk which is similar to yoghurt, while Unda is a product produced by lactic and alcoholic fermentation of camel’s and other animal’s milk (Yagil, 1982). Gariss is product made from camel’s milk in Sudan; it is a fermented camel’s milk, which is not always available for the family as camels are often driven far away in search of pastures (Dirar, 1993 and Abdel Gadir et al., 1998). Texture is one of the main characters that define the quality of yoghurt. The most frequent defects related to yoghurt texture, that may lead to consumer rejection, are apparent viscosity variations and the occurrence of syneresis. In an attempt to increase firmness and prevent syneresis, stabilizers , hydrocolloids and gelatin have been added to yoghurt (Keogh and O'Kennedy, 1998 & Supavititpatana et al., 2008). Inulin is a dietary fiber chemically composed of a mixture of oligo- and/or polysaccharides constituted of fructose unit chains (linked by β - (2/1) D –fructosyl fructose bonds) of various length, terminated generally by a single glucose unit (linked by an α- D - glucopyranosoyl bond) (French, 1993). It is extracted from chicory root (15-20%), onions (1-5% on a fresh weight basis), garlic (4-12%) and banana (0.2%). The benefits of inulin ingestion are not only limited to its condition as a dietetic fiber (reduction of cholesterol and lipid levels in blood plasma, intestinal traffic control, increase in calcium, magnesium and iron adsorption), which is notably important in osteoporosis prevention (Bosscher et al., 2006 & Flamm et al., 2001), but also include aspects related to its prebiotic nature, like growth stimulation of health-promoting bacteria e.g. bifidobacteria (Roberfroid and Slavin, 2000) and the regulation of intestinal flora in the colon, diminishing the growth of bacteria belonging to fusarium and clostridium (Kaur and Gupta, 2002). Dietary synbiotics, containing inulin and Bifidobacterium lactis reduced cancer risk factors, as recently reported by Rafter et al., (2007). Inulin also has interesting technological properties both as a low-caloric sweetener and bulking agent, as well as a fat substitute; it can also act as a texture modifier. The properties of inulin are linked to the degree of chain polymerisation (DP). The naturally occurring inulins have fructose polymerization degrees varying from 2 to >60 units. Long-chain inulin (DP between 23 and 25 units) is thermally more stable, less soluble and more viscous than the shorter-chain inulin (DP average of 11 units) (Wada, et al., 2005). The use of long-chain inulin as a fat substitute is


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thought to be related to its ability to form microcrystals that interact with each other forming small aggregates. These aggregates encapsulate a great amount of water, thereby creating a smooth and creamy texture (Bot et al., 2004). Some investigators have studied the effects of inulin on the rheological and sensorial characteristics of ice-cream (El-Nagar, et al., 2002); yoghurt (Dello Staffolo et al., 2004), milk beverages (Villegas and Costell, 2007) and fresh cheese (Koca and Metin, 2004). In such context, the aim of this work was to evaluate bacteriological, physicochemical and sensory properties of probiotic fermented camel's milk as affected with inulin fortification.

MATERIALS AND METHODS Materials: Fresh whole camel's milk of Magrabi camel's (Camelus dromedarius) was obtained from northwestern coast of the Alexandria city, Egypt (fat 4.2%, protein 3.25%, total solids 12. 25% and pH 6.6). Starter cultures: Lactobacillus acidophilus DSMZ 20079 and Bifidobacterium bifidum DSMZ 20082 were used together with yoghurt culture, (Streptococcus salivarius spp. Thermophiles ATCC 19258 and Lactobacillus delbrueckii spp. Bulgaricus DSMZ20080). All cultures were obtained from Egyptian Microbial culture collection of Cairo MIRCEN (EMCC), Faculty of Agriculture, Ain-Shams University, Egypt. Commercial inulin products: The commercial chicory inulin powder, namely medium-chain inulin (Raftiline®GR with an average chain length DP of 10) was supplied by Mandurah Australia Pty. Ltd. (Dandenong, Vic., Australia). Manufacture of probiotic fermented Camel's milk: The method of Tamime and Robinson (1999) was followed for the manufacture of probiotic fermented Camel's milk. Camel's milk was homogenized at 20 Mpa, at65°C, heated to 90ºC for 5 min, rapidly cooled to 42ºCand then divided into two parts. The first part was inoculated with 3% (v/v) mixture of yoghurt culture (Streptococcus salivarius spp. thermophilus and Lactobacillus delbrueckii spp. bulgaricus) and Lactobacillus acidophilus (1:1) then divided into 4 equal portions. Inulin was added to three portions at 2, 6 and 8% (w/v), but the forth portion was left without inulin (control). The second part of camel's milk was inoculated with 3% (v/v) mixture of yoghurt culture and

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Lactobacillus acidophilus (1:1) and Bifidobacterium bifidum 3% then divided into 4 equal portions, three of them were fortified with inulin at rates of 2, 6 and 8% (w/v), but the forth portion was left without inulin (control). Milk for different treatments was dispensed into plastic cups (100 ml) capacity then incubated for 5-6 hours at 42°C or until complete coagulation. After fermentation, samples were stored at 4±1°C for 14 days and analyzed when fresh, 7 and 14 days. Bacteriological examination of fermented camel's milk. Fermented camel's milk samples were subjected to bacteriological examination when fresh, after 7, and 14 days. All microorganisms that were inoculated into fermented camel's milk samples were enumerated by using differential media and methods mentioned below. The number of colonies was counted on two serial plates. The results were expressed as log colony-forming units per gram (log cfu/g) of sample and the viability of each culture in different samples was calculated according to Paseephol and Sherkat ( 2009), as follows: % Viability = (CFU/g after 14 days of storage/initial CFU/g) × 100 Streptococcus salivarius spp. thermophilus count. M17 agar (Difco Laboratories) was used to enumerate streptococci in yoghurt samples (Torriani et al., 1996). Plates were incubated in aerobic incubator at 37° C for 72 h. Lactobacillus delbrueckii spp. bulgaricus count. Acidified MRS (pH 5.2) agar (Difco Laboratories) was used for enumeration (Dave and Shah, 1997). Plates were incubated under anaerobic conditions at 37° C for 72 h (Torriani et al., 1996). Lactobacillus acidophilus count. MRS agar (Difco Laboratories, Detroit, MI) with 0.20% oxgall (Difco Laboratories) was used (Marshall, 1992). Plates were incubated aerobically at 37° C for 72 h. Bifidobacterium bifidum count. MRS agar with added neomycin-paromomycin- nalidixic acidlithium chloride (NPNL) solution was used to enumerate B.bifidum (Martin and Chou, 1992). Bacteria were grown in a fresh medium under anaerobic conditions using anaerobic jars (AnaeroGen AN 25 sachets, Oxoid) at 37° C for 72 h (Laroia and Martin, 1991). The solution of NPNL broth with 1% L–cysteine was prepared according to Karagu`l-Yuceer et al., (2001).


299

pH and titratable acidity of fermented camel's milk samples. The pH of the various samples of fermented camel's milk was determined using a pH-meter (model Horiba, B-211, Shimadzu Analytical Instruments, Kyoto, Japan). The titratable acidity (as lactic acid %) of the different fermented milk samples were accomplished according to AOAC (1990). All measurements were carried out in triplicates. Concentration of acetaldehyde (µg/100 g). The acetaldehyde concentration determined by the methods described by Lees and Jago (1969). Syneresis determination. Whey syneresis carried out by the drainage method according to Lucey, et al., (1998). Viscosity. Viscosity of the samples were measured using a Brookfield viscometer (model DV-II+Pro, Brookfield Engineering Laboratories, Middleboro, MA)at 4°C with a spindle (No. 4) rotation of 60 rpm as described by Shihata and Shah (2002). Readings were made in triplicates and recorded as centipoises. Sensory evaluation of fermented camel's milk samples. Panel of seven judges, familiar with fermented milks were chosen from the staff members of the Faculty of Agriculture, Zagazig University, according to the scheme described by Farag et al., (2007). Statistical Analysis. Experimental data was statistically analyzed as Complete Random Design (CRD) according to SPSS package (SPSS v.20, 2012). Standard error of means was derived from the error mean square term of ANOVA, which was used for statistical analysis of the results and to multiple range tests using the least significant difference (LSD) test. Differences were considered significant at (P 0.05). The lowest counts were observed at days 14, while the highest numbers of streptococci were shown when fresh. Overall, this strain of all samples could utilize inulin. On the other hand, the growth of bacteria

300


in control samples was lower compared with other samples containing inulin. During storage, the population of L. delbrueckii spp. bulgaricus in samples was enhanced with addition of inulin up to 6%. When fresh and 7, whereas the samples with added inulin at 6% had the highest L. delbrueckii spp. bulgaricus count, but the samples with inulin at 8% had the lowest count. There was no significant difference (P> 0.05) between the populations of L. delbrueckii spp. bulgaricusin all samples compared with the control. The bacterial count decreased during storage. No significant differences were detected in the counts of L. acidophilus. The effect of inulin on the growth of B. bifidum during storage period was significant (P< 0.05). The count of B. bifidum was higher in samples contained 6% inulin (8.55 log cfu/g) than the control samples without inulin (6.91 log cfu/g) when fresh. The count of B. bifidum of all samples decreased with increasing the storage period. Bifidobacterium bifidum BB-12 showed efficiency in utilizing Jerusalem artichoke inulin (JAI) and chicory inulin powders, especially the oligofructose. However, it was reported that the majority of B. bifidum strains were not able to grow on inulins (Hidaka et al., 1986 and Bielecka et al., 2002) this inconsistency may be explained by the differences in the used strains. According to Voragen (1998), variations in chemical structure of saccharides (linear or branched), degree of polymerisation (DP), composition of monomer units and water solubility affect their utilisation by micro-organisms. Paseephol and sherkat (2009) reported that Raftilose® P95 was the best utilized material by all probiotic microorganisms because of its short chain length, unbranched nature and high water solubility, while the growth of probiotic strains in the presence of higher DP inulins was poor. These findings are in good agreement with Roberfroid et al. (1998) who concluded that short-chain inulin (DP < 10) was the most fermentable substrate, being fermented twice faster than longer-chain inulin. In addition to the DP of inulin chains, the utilization of inulin by probiotic microorganisms depends on the purity of the preparations where less purified inulins are fermented more favourably than the highly purified inulins (Biedrzycka & Bielecka, 2004). The results in Table (1) indicated that the retention of viability of Streptococcus thermophilus was better than those of Lactobacillus delbrueckii spp. bulgaricus and Lactobacillus acidophilus compared to the control. The addition of inulin did not influence the survival of Streptococcus thermophilus, Lactobacillus delbrueckii spp. bulgaricus, and Lactobacillus acidophilus, but significantly improved the viability of Bifidobacterium bifidum. These results are supported by Kaplan and Hutkins (2000) who reported that several strains of L. casei and L. acidophilus were able to ferment fructooligosaccharides well, but not most of the Lactobacillus delbrueckii spp.


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bulgaricus and Streptococcus thermophilus strains. The experimental and control samples showed ability in sustaining high numbers of Streptococcus salivarius spp. thermophilus (P< 0.05) and only a marginal decline occurred in the following 7 days. After 14 days, all samples contained >7.21 log cfu/g of Streptococcus salivarius spp. thermophilus. This reflected the high stability of Streptococcus thermophilus in the products. These observations agree with the findings of Medina and Jordano (1994), Dave and Shah (1997), Akalin et al., (2004), and Ozer et al., (2005) they reported higher stability of Streptococcus thermophilus than Lactobacillus delbrueckii spp. bulgaricus and bifidobacteria in probiotic yoghurts during storage time. The initial counts of Lactobacillus delbrueckii spp. bulgaricus after overnight storage in all samples were comparable to those of Streptococcus thermophilus and Lactobacillus acidophilus. Supplementation with inulin did not help the viability of Lactobacillus delbrueckii spp. bulgaricus as their numbers in all supplemented samples dropped by 0.7-1 log after 14 day of storage, similar to those in the control. A steady decline in the numbers of Lactobacillus delbrueckii spp. bulgaricus was observed until the end of the storage period wherein the final counts. Ozer et al., (2005), also reported the decline of viable counts of Lactobacillus delbrueckii spp. bulgaricus by 2.5–4.2 times in inulinsupplemented yoghurts during 14 days of storage. Several workers have reported that low numbers of Lactobacillus delbrueckii spp. bulgaricus would help the survival of probiotic microorganisms due to reduced risks of post-acidification by Lactobacillus delbrueckii spp. bulgaricus (Holcomb and Frank, 1991& Shah, 1995). The utilization of inulin by various probiotic microorganisms has been reported earlier by Akalin et al. (2004), who found a significant improvement in the viability retention of bifidobacteria in yoghurts containing prebiotics (inulin/oligofructose) during storage. Similarly, Aryana et al. (2007) and Donkor et al. (2007) observed that chicory-based inulins were the favoured carbon source for Lactobacillus strains, hence increasing the growth performance and sustaining the viability during storage. However, some other publications by Ozer et al., (2005) reported that inulin did not support the growth and survival of L. acidophilus in fermented bovine milk and acidophilus– bifidus yoghurts. The inconsistencies reported here could be attributed mainly to strain-specific response of probiotics to prebiotic supplementation. The mechanism by which inulin improves the viability of the probiotic microorganisms during cold storage is still unclear. The two possible mechanisms proposed so far state that inulins provide additional nutrients for promoting culture growth (Makras et al., 2005) and/or that they protect probiotic cells from acid injury (Desai et al., 2004).

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Table (1): The viable counts (log CFU/g) of Streptococcus salivarius spp. thermophilus, Lactobacillus delbrueckii spp. bulgaricus, Lactobacillus acidophilus and Bifidobacterium bifidum in fermented camel's milk as affected with inulin addition during storage at 4±1°C. Treatments Microorganisms

Streptococcus salivarius spp. thermophilus

Lactobacillus acidophilus

Bifidobacterium bifidum

YA

YAB

Inulin

Inulin

LSD

Control 0%

2%

6%

8%

Control 0%

2%

6%

8%

Fresh

8.14±1.14a

8.22±0.57a

8.45±0.45a

8.11±0.66a

8.15±0.82a

8.26±1.01a

8.56±1.02a

8.13±1.01a

1.5

7

7.92±1.69a

8.13±0.58a

8.28±0.88a

8.02±0.47a

8.02±0.91a

8.14±0.62a

8.31±1.81a

8.05±0.99a

2.12

14

7.21±1.00a

7.71±0.27a

8.01±0.46a

7.36±0.36a

7.31±0.01a

7.76±1.44a

8.13±2.02a

7.51±1.31a

1.86

92.37±4.37AB

5.59

B

93.78±3.79

AB

94.79±2.79

A

90.75±2.75

AB

89.69±2.30

AB

93.95±0.95

AB

% Viability

88.57±3.57

Fresh

7.81±1.59a

7.94±0.73a

8.07±1.85a

7.81±0.56a

7.91±1.44a

8.11±2.00a

8.18±0.93a

7.79±1.54a

2.45

7

7.33±1.19a

7.43±0.88a

7.47±0.22a

7.19±0.65a

7.64±0.77a

7.65±1.40a

7.71±1.38a

7.46±1.24a

1.80

14

6.38±0.27a

6.66±0.77a

6.81±0.56a

6.31±0.17a

6.51±0.61a

6.86±0.36a

7.10±0.30a

6.32±0.38a

0.80

% Viability

81.69±1.69B

83.88±1.88AB

84.39±3.38AB

80.79±0.79B

82.30±1.30B

84.59±1.58AB

86.80±4.49A

81.13±2.13B

4.33

Fresh

7.96±1.51a

8.12±0.57a

8.27±1.29a

7.96±1.11a

7.91±1.37a

8.83±1.51a

8.87±1.36a

8.11±1.23a

2.20

7

7.54±1.31a

7.96±1.75a

8.12±0.89a

7.74±1.52a

7.76±0.65a

8.44±0.24a

8.59±0.94a

7.73±1.49a

2.07

14

7.01±0.79a

7.37±1.05a

7.65±0.43a

7.10±0.25a

7.19±0.91a

8.09±1.84a

8.28±1.17a

7.42±1.54a

1.92

% Viability

88.07±3.06A

90.76±4.76A

92.5±2.50A

89.2±3.19A

90.9±2.90A

91.62±1.62A

93.35±6.35A

91.49±8.49A

8.02

Fresh

-

-

-

-

6.91±1.04b

8.33±1.08a

8.55±0.44a

8.29±1.78a

2.17

7

-

-

-

-

6.24±0.37b

8.19±0.97a

8.33±0.22a

7.87±1.62a

2.44

14

-

-

-

-

6.08±0.52b

7.75±1.52a

8.16±1.71a

7.52±1.74b

3.69

% Viability

-

-

-

-

87.99±4.99B

93.04±5.03AB

95.44±1.44A

90.71±2.71AB

7.27

Data are means ± SD of three experiments, and each experiment was examined in duplicate. a–b Means in the same row with different letters differ significantly at (P< 0.05)by DMRT. A–B Means in the same column and row with different letters differ significantly at (P< 0.05) by DMRT. YA= yoghurt culture and Lactobacillus acidophilus YAB= yoghurt culture, Lactobacillus acidophilus and Bifidobacterium bifidum

94.98±3.97

A


Lactobacillus delbrueckii spp. bulgaricus

Storage period (days)


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Some physicochemical properties of fermented camel's milk as affected by added inulin. Titratable acidity, pH, whey syneresis, viscosity and acetaldehyde concentration were determined as indices for physicochemical properties (Table 2). Titratable acidity and pH: Titratable acidity (TA%) was significantly high (P< 0.05) for fermented camel's milk samples stored up to 14 days (Table, 2). Generally, within each inulin treatment TA% increased significantly with the advance of storage period. The rate of increase varies upon the concentration. The pH value decreased gradually until the end of storage period (P< 0.05) of all samples. These results agree with the findings of Jogdand et al. (1991). When the storage period was disregarded, the control fermented camel's milk samples had significantly lower TA values (P< 0.05). A similar trend was also reported by Guven et al., (2005) and Paseephol & Sherkat (2009). Khalifa et al., (2011) showed that the yoghurt stabilized with 0.27% mucilage had higher titratable acidity values than the control yoghurt and the effect of adding 4 or 6% inulin was compared with mucilage. The difference in titratable acidity decreased with the inulin treatment, titratable acidity % of yoghurt treated with inulin 6% was significantly higher than that produced with inulin 4%. Whey syneresis: The whey syneresis of the fermented camel's milk samples, expressed as mls of whey separated from samples during the storage period, is shown in Table (2).Whey syneresis was significantly high for the control and low for inulin treated samples (P< 0.05). In all fermented camel's milk samples, inulin had marked effects on whey syneresis. Apparently inulin was much effective in reducing whey syneresis. Regardless of the treatments, the highest whey separated was found to be at day 14 of storage (P< 0.05), while differences were observed for storage periods fresh, 7 and 14 days. However, on the consumer point of view whenever the less whey syneresis the better yoghurt. This contrasted to a previous report, which found that inulin was more effective in reduction of whey syneresis (Khalifa et al., 2011 and Debon et al., 2012).

304

Table (2): Changes in some physicochemical properties of fermented camel's milk with inulin addition during storage at 4±1°C. Treatments

Parameter

Storage period (days) Control 0% Fresh

Titratable acidity (%Lactic acid)

pH value

7

0.95±0.02c

0.98±0.03bc

a

a

1.02±0.05

b

1.19±0.08

1.03±0.11abc 1.03±0.92

a

ab

1.24±0.14

a

4.7±0.20a

1.08±0.09

1.11±0.09

4.76±0.14a

4.76±0.10a

ab

cd

7

4.67±0.12

4.43±0.08ab

4.41±0.04ab

4.38±0.03bc

ab

bc

de

20.4±2.40

16.8±3.80

4.49±0.06

de

14

7

4.56±0.04

12.0±3.00

24.0±2.00ab

20.0±2.04bc

17.0±2.00cd

ab

bc

d

30.0±4.00

Fresh

15.2±3.20f

7

17.4±2.40f

26.0±4.10

f

14

19.50±5.50

Fresh

90.30±2.30ab

7

110.50±17.50

14

90.14±8.14a

20.0±2.00

2%

LSD 6%

8%

0.94±0.30c

0.98±0.05bc

1.07±0.06ab

1.09±0.05a

1.02±0.04abc

0.09

a

a

a

1.16±0.08

a

1.13±1.03a

0.85

1.27±0.05

a

ab

0.12

4.67±0.13a

0.19

1.09±0.07 1.16±0.14

1.11±0.13

ab

1.18±0.03

1.14±0.09

ab

4.81±0.19a

4.76±0.05a

a

bc

4.75±0.10

4.65±0.06

4.47±0.04a

1.21±0.04

ab

4.660.15±a 4.49±0.02

de

1.17±0.12

4.63±0.08a 4.46±0.01

e

bcd

0.09

4.42±0.05ab

0.07

4.58±0.07

4.41±0.03ab

4.36±0.03bc

4.33±0.09c

a

ab

cd

e

21. 2±2.00

12.4±1.4e

25.6±3.60a

24.0±5.00ab

19.0±4.00c

13.2±3.20de

a

a

bc

cd

8.8±1.80

17.2±2.20

d

32.0±5.00

18.0±3.00

34.0±6.00

13.6±1.60

26.0±4.20

9.0±2.00

e

21.2±4.22

3.63 4.45 5.86

24.3±4.30def

30.7±15.70de

44.1±17.10bc

17.5±2.50ef

35.1±4.10cd

55.0±3.00b

70.4±9.40a

13.22

26.5±2.50e

35.4±5.40d

51.2±4.20c

18.5±4.50ef

41.2±5.20d

62.4±7.40b

76.6±8.60a

8.29

c

f

c

b

81.5±6.50a

8.73

80.68±5.68c

4.91

29.4±4.40

a

Control 0%

8%

e

38.70±5.70

90.01±0.99ab 100.28±4.28

ab

90.12±4.12a

d

86.30±1.30b 100.12±6.12

ab

90.04±3.04a

55.8±4.80

20.1±2.10

81.12±5.12c 100.02±14.02

47.6±7.60

90.41±4.41ab ab

79.57±3.43b

100.58±5.58

ab

92.63±7.63a

Data are means ± SD of three experiments, and each experiment was examined in triplicates. a–f Means in the same row with different letters differ significantly at (P< 0.05)by DMRT. YA= yoghurt culture and Lactobacillus acidophilus YAB= yoghurt culture, Lactobacillus acidophilus and Bifidobacterium bifidum

91.23±0.23a 90.85±1.15

b

90.23±2.23a

66.3±8.30

91.01±3.01ab 100.08±6.08

ab

91.85±6.85a

90.54±2.54

b

85.13±6.13ab

12.69 7.99


Acetaldehyde (µg/100g)

6%

14

14 Viscosity(cp)

YAB Inulin

2%

Fresh

Fresh Whey syneresis (ml/100g)

YA Inulin


305

Viscosity: Viscosity of fermented camel's milk samples with or without inulin are presented in Table (2). There were significant differences between control and treated samples. The samples treated with 2% inulin had a viscosity of 24.3-47.6cp which was comparable to the samples with 8% (44.1-81.5cp). A viscosity value was significantly higher for the samples treated with Bifidobacterium bifidum and inulin and also the samples without Bifidobacterium bifidum (P < 0.05), when compared to the control. Statistical analysis showed a significant effect of inulin and probiotic microorganisms (P < 0.05) on the viscosity of samples. The addition of inulin, especially in samples containing Bifidobacterium bifidum, resulted in a significantly (P< 0.05) higher viscosity compared with the control samples. In this case, the viscosity even increased during storage, possibly due to increasing hydration (Bouzar, et al., 1997). Different hydrocolloids, such as carrageenan and guar gum, are used in dairy formulations to physically stabilize dispersed materials and/or improve texture, resulting in high viscosity (Syrbeet al., 1998). Similar to the present study findings, high viscosity values were observed by Fernandez-Garcia et al., (1998) in yoghurts containing fructose. The increase in viscosity due to the addition of fiber has been attributed to interaction between oligo- or polysaccharides and dairy proteins (Fernandez-Garcia et al., 1998; Syrbe et al., 1998; Sodini, et al., 2002). Donkor et al., (2007) reported that the influence of prebiotics on viscosity showed a substantial effect of the probiotic microorganisms on viscosity. Based on the results obtained, it was observed that it is possible to make fermented camels milk of acceptable viscosity by incorporating inulin. Acetaldehyde concentration: The concentration of acetaldehyde in fermented camel's milk samples are presented in Table (2).The results showed a gradual increase in acetaldehyde concentration with the progress in the storage period. This increase with the advance of storage period was significantly different (P< 0.05). The highest concentration of acetaldehyde was found in the day 14. The obtanied results are in accordance with those reported by Lees and Jago (1976) who showed that Lactobacillus bulgaricus was able to produce acetaldehyde. In relation to the different treatments the results showed significant differences between the control and samples containing inulin (P< 0.05). A similar trend was also reported by Khalifa et al., (2011).

306

Table (3): Sensory evaluation of fermented camel's milk with inulin addition during storage at 4±1°C. Treatments

Parameter

Storage period (days) Control

Flavour(45)

Consistency(35)

39.50±0.50a

37.25±1.25a

38.25±3.25a

37.50±4.50a

41.25±7.25a

40.50±4.50a

39.50±4.50a

38.50±4.50a

6.08

ab

a

a

b

a

a

a

a

4.26

35.15±2.15a

35.44±1.44a

30.25±2.25b

33.25±2.25ab

35.25±3.25a

35.58±1.58a

30.25±0.25b

3.03

a

a

a

34.50±2.50

a

31.14±2.14

a

a

a

a

3.88

32.14±1.14

a

c

ab

3.80

29.25±3.25

abc

20.25±2.25c

25.5±3.50ab

abc

abc

7.56±0.06

8.11±1.11

34.22±3.22 30.42±2.42

ab

29.25±5.25a 8.57±0.43

a

30.12±2.12a 7.25±0.25

32.50±1.50 27.50±2.50

bc

5.04

abc

ab

bc

1.17

7.65±1.35

7.85±0.15

9.12±2.12

Fresh

8.25±0.75

9.14±1.14

a

7

8.11±0.11a

9.25±1.25a

9.51±2.51a

8.22±1.22a

8.58±0.58a

9.25±2.25a

a

a

a

a

a

a

7.34±1.34

8.22±0.22ab

8.51±0.49ab

9.11±1.11a

8.14±1.14ab

1.22

8.15±2.15

a

8.41±0.41

a

8.57±1.57

a

9.23±2.23

a

8.22±2.22

a

2.64

8.11±2.11

a

a

9.14±1.14

a

9.24±2.24

a

8.15±2.15

a

2.31

9.51±1.51a

8.31±2.31a

2.38

a

a

7.12±0.12

86.81±2.31a

87.00±6.00a

90.29±7.29a

87.36±9.36a

88.54±9.54a

89.99±6.99a

91.70±8.70a

88.33±11.33a

11.55

7

79.97±4.97a

83.27±7.27a

86.51±8.51a

79.18±5.18a

80.55±4.55a

81.67±7.67a

86.62±8.62a

82.67±11.67a

10.88

b

ab

ab

b

ab

a

ab

11.72

77.29±8.29

82.26±10.26

7.25±1.25

8.5±1.50

14

70.08±5.08

8.17±1.17

8.46±0.54

7.55±0.55b

Fresh

14

7.52±0.52

30.51±3.51

abc

a

9.25±1.25

34.34±3.34

29.25±4.25a

8.21±0.21

a

29.50±2.50

ab

30.15±3.15a

a

9.4±2.40

34.50±2.50

35.71±4.71

26.25±3.25ab

a

a

38.50±3.50

21.50±3.50bc

8.52±0.52ab

14

9.33±1.33a

c

25.5±1.50

36.41±3.41

8.11±0.89ab

7

Total scores(100)

32.50±2.50

38.25±2.25

a

75.77±7.77

7.28±1.28

70.44±7.44

Data are means ± SD of three experiments, and each experiment was examined in triplicates. a–c Means in the same row with different letters differ significantly at (P< 0.05) by DMRT. YA= yoghurt culture and Lactobacillus acidophilus. YAB= yoghurt culture, Lactobacillus acidophilus and Bifidobacterium bifidum.

8.33±1.33

78.4±9.40

8.50±1.50

83.46±8.46

7.41±1.41

75.13±8.13

1.66


Fresh

28.50±3.50

abc

31.27±2.27

8%

34.50±2.50a 31.50±3.50

37.25±2.25

0%

6%

35.25±2.25

Fresh

36.25±2.25

2%

LSD

8%

7

7

Appearance(10)

Control

6%

14

14 Acidity(10)

YAB Inulin

2%

0% Fresh

YA Inulin


307

Sensory evaluation of fermented camel's milk. In order to elucidate whether the presence of different inulin levels (2, 6 and 8%) could modify the sensory properties of fermented camel's milk, sensory evaluation of all samples was carried out at fresh, 7 and 14 days of cold storage (Table 3). When fresh of refrigeration panelists did not detect differences between all fermented camel's milk samples. However, after 14 days of refrigerated storage mean scores were higher in fermented camel's milk with inulin up to 6% (significant differences for flavour, consistency, acidity and appearance; (P< 0.05)than in the corresponding control samples, indicating that fermented camel's milk with inulin up to 6% was acceptable for consumption. It could be concluded from the obtained results of fermented camel's milk made from different levels of inulin up to 8% with yoghurt culture and probiotic bacteria, the inulin contains nutrients and flavour compounds suitable for fermented camel's milk manufacture. The ability of inulin to improve the growth of probiotic bacteria was comparable to control. There was improvement in the growth and survival of bacteria in the presence of inulin up to 6%. Inulin could be good substitute or partial replacer to some of the well-known stabilizers in fermented camel's milk industry. Acknowledgments The present document was achieved in the frame of PROCAMED project, supported by the European Union (ENPI - Joint operational Programme of the Mediterranean Basin -IEVP-CT). The contents of this document are the sole responsibility of the ‘Division of Animal Production, Animal Breeding Department, Desert Research Center (Egypt) and can (under no circumstances) be regarded as reflecting the position of the European Union.

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‫ الطبيعية الكيميائية والحسية أللبان النوق المتخمرة‬،‫الخواص البكتريولوجية‬ 2

‫الحيوية وتأثرها بإضافة األنولين‬

‫– صالح أحمد خليفة‬1‫عالء حامد إبراهيم‬

‫مركز بحوث الصحراء – مصر‬- ‫ قسم تربية الحيوان – شعبة اإلنتاج الحيواني‬-1 ‫ قسم علوم األغذية – كلية الزراعة – جامعة الزقازيق – مصر‬-2

‫يهدف هذا العمل الى دراسة نمو ونشاط مزارع اليوجهورت وبكتريا البروبيوتك في ألبان‬ ‫ قدرت حيوية خاليا مزارع اليوجهورت‬.‫ أنولين‬% 8، 6 ،2 ‫النوق المتخمرة المحتوية على‬ ‫ تركيز‬،‫ اللزوجة‬،‫ انفصال الشرش‬،‫ وكال من الخواص الطبيعية الكيميائية‬،‫والبروبيوتك‬ ‫ يوم على‬41 ‫األسيتالدهيد والتقييم الحسي أللبان النوق المتخمرة الحيوية أثناء التخزين لمدة‬

‫‪313‬‬

‫‪Egypt . J. of Appl. Sci., 28 (12) 2013‬‬

‫‪° 4±1‬م‪ .‬أدى وجود االنولين أدى إلى بقاء وحيوية الخاليا البكتيرية بدرجة أفضل مما في‬ ‫عينات المقارنة‪ .‬أدى إضافة األنولين إلى لبن النوق إلى زيادة اللزوجة وانخفاض انفصال‬ ‫الشرش معنوياً في ألبان النوق المتخمرة والمحتوية على بكتريا البروبيوتيك‪ .‬أخذ االنولين سلوك‬ ‫البريبيوتك فى تحسين جودة ألبان النوق المتخمرة بمزارع اليوجهورت وبكتريا البروبيوتك‬ ‫‪(Streptococcus salivarius spp. thermophilus, Lactobacillus delbrueckii‬‬ ‫‪spp. bulgaricus, Lactobacillus acidophilus and Bifidobacterium‬‬ ‫‪bifidum).‬‬ ‫أدى إضافة االنولين إلى ألبان النوق إلى تحسين القوام والخواص الحسية للمنتج أثناء‬ ‫التخزين على ‪°4±1‬م‪ .‬كما أدت إضافة االنولين الى تحسين حيوية ‪Bifidobacterium‬‬ ‫‪ bifidum‬لتصل اعدادها إلى أكثر من ‪ 7‬لوغاريتم ‪ /‬وحدة مكونة للمستعمرة‪ /‬جرام أثناء‬ ‫التخزين على ‪° 4±1‬م ولكنه لم يؤثر على حيوية بكتريا مزارع اليوجهورت مقارنة بالعينات‬ ‫المقارنة‪ .‬أدى إضافة االنولين الى تحسين الخواص الحسية أللبان النوق المتخمرة وكانت أكثر‬ ‫وضوحا وقبوال عند اضافته بنسبة ‪.%6‬‬