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sensory characteristics in set yogurt reinforced by microencapsulated Bifidobacterium bifidum F-35. Ahmed Mousa,1 Xiao-ming Liu,1 Yong-quan Chen,1,2 Hao ...
International Journal of Food Science and Technology 2014

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Original article Evaluation of physiochemical, textural, microbiological and sensory characteristics in set yogurt reinforced by microencapsulated Bifidobacterium bifidum F-35 Ahmed Mousa,1 Xiao-ming Liu,1 Yong-quan Chen,1,2 Hao Zhang1 & Wei Chen1,2* 1 State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China 2 Synergistic Innovation Center for Food Safety and Nutrition, Wuxi 214122, China (Received 22 July 2013; Accepted in revised form 25 November 2013)

Summary

The objectives of this study were to encapsulate the Bifidobacterium bifidum F-35 into whey protein for the production of one-layer microcapsules, and then the microcapsules were covered by sodium alginate to produce double-layer microcapsules for examining the effectiveness of microcapsules in set yogurt. The reinforced treatment by double layer exhibited a significant increase (P < 0.05) in B. bifidum F-35 count more than the treatments of free cells and one-layer microcapsules. Microcapsules of double layer in yogurt led to record a value of titratable acidity that was 1.51 in comparison with the treatments of one layer and free cells that were 1.65 and 1.73, respectively. The hardness values were recorded as 206.88 at the treatment of double layer and 130.31 at the treatment of one layer after 7 days of storage. Microencapsulation of double layer caused a slight bitterness and creamy texture in yogurt, whereas the samples of free cells were described to have sour and bad texture.

Keywords

Bifidobacterium, microencapsulation, probiotics, yogurt.

Introduction

Food and Agriculture Organization (FAO) and the World Health Organization (WHO) defined probiotics as ‘Live microorganisms (bacteria or yeasts), which when ingested or locally applied in sufficient numbers confer one or more specified demonstrated health benefits for the host’ (FAO & WHO, 2001). Several studies have suggested the incorporation of probiotic organism mainly bifidobacteria and lactobacilli within fermented dairy products, such as yogurt. Therefore, yogurt has been considered as the most popular vehicles of probiotics transmission to the consumers (Capela et al., 2006; Ramchandran & Shah, 2010). Several surveys have showed a large fluctuation and poor viability of bifidobacterium in yogurt preparations which is the main probiotic carrier. Bifidobacterium strains vary greatly in their sensitivity to the harsh acidic environment of the stomach and many foods (McMaster & Kokott, 2005). Therefore, it was necessary to provide probiotic living cells with a physical *Correspondent: Fax: +86 510 85912155; e-mail: [email protected]

doi:10.1111/ijfs.12473 © 2014 Institute of Food Science and Technology

barrier to resist adverse environments (Kailasapathy, 2009). Several factors have reported the effects of probiotics in the environment of fermented dairy products, including titratable acidity, pH, hydrogen peroxide, dissolved oxygen content, storage temperature, species, strains of associative fermented dairy product organisms, concentration of lactic, acetic acids and even whey protein concentration (Dave & Shah, 1997). Therefore, many researchers had reported to use different techniques such as encapsulation technique for entrapping the probiotic cells into proper hydrocolloids and continuous fermentation process of cells that would give an idea of the cells’ behaviour in foods (Borgogna et al., 2010). The emulsion technique has been successfully used to encapsulate lactic acid bacteria and produce microspheres with acceptable mouthfeel in food products (Krasaekoopt et al., 2003). Microspheres production using whey proteins (native or denatured) associated with polysaccharides, including alginate, had been extensively investigated by Rosenberg & Lee (2004). Coating the capsules by another compound or applying structural modification of the alginate by using

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Characteristics in set yogurt A. Mousa et al.

different additives was also investigated (Krasaekoopt et al., 2003). The aims of present study were to evaluate the addition of encapsulated cells on the physicochemical, microbiological, textural and sensory properties of set yogurt. Materials and methods

Materials

Freeze-dried direct vat set (DVS) cultures containing yogurt bacteria Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus were obtained from Hansen Company, Shanghai, China. A probiotic culture composed of Bifidobacterium bifidum F-35 was used as an active material for the microcapsules, which was obtained from the Culture Collections of Food Microbiology, Jiangnan University (Wuxi, China). DeMan, Rogosa, Sharpe agar (MRS agar), MRSC (0.1% filter-sterilised L-cysteine•HCl) were used to activate B. bifidum F-35. Trypticase–phytone–yeast extract (TPY) medium (Biavati & Mattarelli, 2001) supplemented with 2 lg L 1 dicloxacillin (Sozzi et al., 1990) was used to cultivate B. bifidum F-35. Milk powder (full fat) was purchased from Guang Ming Company (Wenzhou, China). Chemicals

Sodium alginate and Spanâ 80 (sorbitol ester) were purchased from Sigma–Aldrich (Shanghai, China), whey protein isolate (WPI, Hilmar TM 9400) was obtained from Milky Way Trade Co. (Beijing, China) with a protein content of 93%, 0.2% lactose, 2.0% ash and 4% moisture. Transglutaminase enzyme (TGase) preparation with a declared activity of 100 units (U) g 1 powder was obtained from Yiming Co. (Jiangsu, China), and pure soya oil was obtained from a local store. Methods Preparation of cells for microencapsulation

The technique was implemented according to the method of Arup et al. (2011) and Zou et al. (2012). Cells were subcultured in MRS broth containing (0.1% filter-sterilised L-cysteine•HCl) at least three times prior to being used for the preparation of cell suspensions; for each cell suspension, 4 mL of fresh culture was inoculated into 200 mL of MRS broth and incubated anaerobically for 18 h at 37 °C. The cells were centrifuged at 10375 g for 10 min at 4 °C. The supernatant was discarded, and the cell slurry was washed by sterilised sodium chloride solution (8.5 g L 1) and centrifuged again under the same conditions. The sample was mixed with sodium chloride

International Journal of Food Science and Technology 2014

solution (8.5 g L 1) to obtain a cell density of 109 colony forming units per mL (CFU mL 1) after harvesting and washing. Preparation of one-layer type of microcapsules

Preparation of one-layer type of microcapsules of B. bifidum F-35 using TGase-induced method was carried out according to the method of Zou et al. (2012). WPI powder was rehydrated with deionised water at a concentration of 10% (w/v) at 80 °C for 30 min to denature the proteins with pH of the solution adjusted to 6.4 after cooling to 40 °C with 1 N NaOH. Then, 2 mL of freshly concentrated cell slurry was added to 30 mL of WPI suspension, and TGase was added to the protein-cell mixture at an enzyme concentration of 10 U TGase g 1 substrate proteins at 40 °C. The mixture was emulsified into 150 g of tempered soy oil (40 °C) and stirred with a magnetic stirrer at 900 rpm for 180 min for the reaction of TGase-whey protein cross-linking. The gelatinised microcapsules were harvested from the oil by centrifugation (500 rpm, 1 min) and washed twice by 1/2 strength Ringer’s solution, at a ratio of 1:1 to the aqueous phase, and stored at 4 °C. Preparation of double-layer type of microcapsules

Preparation of double-layer type of microcapsules with sodium alginate as external layer was performed by the method of Mokarram et al. (2009) with modification. Fifteen grams of the filtered one-layer microcapsules (Whatman No. 4, filter paper; Fisher Scientific, Loughborough, UK) was added to 100 mL of 0.5% (w/v) alginate solution (pH 5.5) and stirred at an initial speed of 500 rpm to disperse the beads for 20 min before filtration, then the beads were collected and resuspended into 75 g of oil containing 5 g L 1, Tween 80 and 65.5 mM of CaCl2 for 20 min to initiate the external Ca2+ cross-linking of the peripheral alginate layer and formation the sodium alginate gel. The Ca2+ cross-linked microcapsules were filtered and washed twice with a 0.1% NaCl solution. Then, the double-layer microcapsules were stored at 4 °C. Production of yogurt

The design of yogurt production is shown in Fig. S1. The process was carried out according to the protocol of Adhikari et al. (2003) with some modifications. Physicochemical analyses

The pH was measured using a pH meter (MettlerToledo 320-S, Mettler Toledo Company, Zurich, Switzerland) and titratable acidity (TA) as % lactic acid was measured according to the method of Adhikari et al. (2003). Moisture and total solid (TS) were

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Characteristics in set yogurt A. Mousa et al.

measured according to the methods of Joseph & Olugbuyiro (2011). TS was determined by placing 10 g of each yogurt sample into a hot air oven at 105 °C for 3 h, and reading was taken after it reached a constant weight. The moisture content was determined by measuring the mass of a food before and after the water was removed by evaporation. Determination of lactose

HPLC method was carried out according to the protocol of Li et al. (2012). The equipment consisted of ICS-5000 ion chromatograph Dionex Corporation, USA, and a pulsed amperometric detector. The filtered supernatant fractions (20 lL) were injected into an HPLC column (CarboPac PA20). The size of column was 300 9 7.8 mm (9 lm), and the flow rate was 0.5 mL min 1. The mobile phase was 5 mM H2SO4 solution and the column temperature was 60 °C. Microbiological analyses

Resuspending of 1 g of each treatment was performed into 9 mL of physiological solution (0.2 M phosphate buffer NaH2PO4, pH 8.0), and the mixture was homogenised with high-speed homogenizer (Ultra-Turrax, Model T25- S1; Ika-Werke, Staufen, Germany) for 45 s at 20 000 rpm and disrupted mechanically in a blender for 20 min at 4 °C to allow release of probiotic cells from the microcapsules as suggested by Kailasapathy (2006) and Pavunc et al. (2011). The mixture was then diluted serially by peptone saline (1 g L 1 distilled water), and the dilutions were poured onto the TPY-dicloxacillin medium to enumerate B. bifidum F-35 for incubation for 48 h at 37 °C under aerobic conditions. Textural analysis

The Stable Micro Systems texture analyzer (Model: TA-XT22, TA Company, New Castle, DE, USA) was used to measure the hardness of yogurt according to the method of Yazici & Akgun (2004). The diameter of probe for measuring the hardness was 35 mm, and the ratio of yogurt cup diameter to probe diameter was 3.5:1.0. The probe was penetrated into the cylindrical containers holding the test sample, and two cycles were applied at a constant cross head velocity of (1.0 mm s 1) both downwards and upwards to a sample depth of 15 mm below the set-yogurt surface. Susceptibility to syneresis STS was implemented according to the method of El-Shenawy et al. (2012) by placing 50 g of each yogurt sample into the tube and centrifuging for 20 min at 270 g (Sigma Laborzentri Fugen, 2 K15, Germany). The weight fraction of the supernatant liquid was expressed as the percentage of the yogurt weight which gives the percentage of syneresis.

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Sensory evaluation

Yogurt samples were evaluated as suggested by the methods of Obi et al. (2010) and Joseph & Olugbuyiro (2011) through thirteen panellists from different countries including Asia, Africa and Europe. Panellists had previous knowledge of food science and sensory quality of yogurt and evaluated for their sensory properties (appearance and colour, body and texture, flavour and overall acceptability) on a 9-point hedonic scale (9 for like extremely, 1 for dislike extremely). Statistical analysis

Expression of study results were designed as means  SD of three duplicate analysis by using the SPSS 17.0 statistical software. One-way analysis of variance (ANOVA) and Duncan’s multiple range tests were carried out for any significant (P < 0.05) differences between the results as recommended by Salovuo et al.(2005). Results and discussion

Physicochemical analyses

Encapsulation processing influenced the pH and TA in set yogurt as shown in Table 1. A gradual decline in pH and increase in TA are obvious during the storage. The TA values of control treatments differed significantly (P < 0.05) in comparison with both treatments of free cells and one-layer microcapsules, while nonsignificant difference was observed (P > 0.05) at control treatment when compared with the treatment of double-layer microcapsules during storage. The pH values of nonencapsulated treatment (control and free cells) prior to storage differed significantly (P < 0.05) in comparison with the encapsulated treatment (one and double layer). After 7 days, the pH values of onelayer treatment decreased significantly in comparison with the free cells treatment. Meanwhile, the other treatments (control and double-layer treatment) did not differ significantly (P > 0.05). The pH values of all treatments differed nonsignificantly (P > 0.05) after the 14th day. When the lowest pH and the highest TA of free cells treatment were compared with the other treatments up to the end of storage, it might be attributed to the high metabolic activity of B. bifidum F-35 as free cells and the yogurt starter cultures (L. delbrueckii ssp. bulgaricus and S. thermophilus) during the storage (Adhikari et al., 2000). The encapsulated treatments especially double-layer treatments recorded high pH values and low TA values in comparison with the nonencapsulated treatments (control and free cells treatment) up to the end of storage, which might be attributed to the role of

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coating materials because it caused a slowdown of acids production by B. bifidum F-35. The total solid and moisture values are shown in Table 1. During the storage, the TS and moisture values did not vary significantly (P > 0.05) among all of the treatments. Lactose values exhibited a marginal decline at all of the treatments up to the end of storage. A lactose value of double-layer treatment was slightly higher prior to the storage in comparison with the other treatments and decreased progressively up to the end of storage. However, the double-layer treatment showed the similar values of the control treatment and recorded the highest values among all of the treatments, which might be attributed to the role of coating material in decreasing of the lactose utilisation by B. bifidum F-35. On the other hand, low lactose content at the free cells treatment was observed in comparison with the other treatments, which could be due to the behaviour of B. bifidum F-35 in metabolising lactose and producing lactic and acetic acids as was implied by Kaminarides et al.(2007) and Bano et al.(2011). Textural analyses

The effect of encapsulated B. bifidum F-35 on the hardness of set yogurt is shown in Table 2. The hardness values of all of the treatments increased gradually then decreased after the 14th day (Supavititpatana et al., 2010). The hardness of the double-layer treatment differed significantly (P < 0.05) prior to storage in comparison with the control treatment. After the 14th day, the one-layer treatment differed significantly in comparison with the control and double-layer treatment.

The obvious decrease at the hardness of one-layer treatment might be due to the effect of postacidification phenomenon on the gel structure. Furthermore, the enzymatic activity of LAB led to the proteolysis and ionic changes of proteins network through drop of pH. Prior to storage, the hardness of one-layer treatment is higher than free cells treatment, which might be due to the presence of TGase enzyme for induction of whey protein gelation which led to increase in the hardness values (Pavunc et al., 2011). On the other hand, the double-layer treatment had the highest values which differ significantly (P < 0.05) in comparison with the other treatments after the 7th day. A correlation between the high syneresis values and the less hardness strength is presented in Table 2. Prior to storage, the highest values of syneresis were observed at the free cells treatment as significant differences in comparison with the other treatments. However, no significant differences were observed (P > 0.05) at the free cells treatments after the 7th day up to the end of storage in comparison with the encapsulated treatments (one- and double-layer treatments). At the double-layer treatments, sodium alginate as polysaccharides reduced the production of acids by B. bifidum F-35 and enhanced the water holding capacity of yogurt, which led to decrease in the syneresis significantly. The one-layer treatment showed a syneresis value higher than the double-layer treatment prior to storage and after 7 days, which could be due to the difference of encapsulation types because the one layer of protection by whey protein did not reduce the acids production sufficiently which is caused by B. bifidum F-35 cells. On the other hand, the control treatment showed the lowest values of syneresis which

Table 1 Values of pH, titratable acidity, total solids, moisture and lactose of set yogurt during storage at 4  1 °C within 14 days

Treatments* Control

Free cells type

One-layer type

Double-layer type

Storage (days)

pH values

0 7 14 0 7 14 0 7 14 0 7 14

4.22 4.21 4.20 4.20 4.18 4.17 4.42 4.36 4.30 4.38 4.29 4.28

           

0.06Ab 0.04Aab 0.02Aa 0.08Ab 0.10Ab 0.08Aa 0.01Aa 0.01Ba 0.03Ca 0.04Aa 0.13Aab 0.12Aa

Titratable acidity TA (% lactic acid) 1.37 1.43 1.45 1.55 1.65 1.73 1.52 1.56 1.65 1.43 1.49 1.51

           

0.02Ab 0.06Ac 0.17Ac 0.06Ba 0.02ABa 0.06Aa 0.04Ba 0.04Bb 0.02Aab 0.02Ab 0.06Abc 0.08Abc

Total solids TS (% w/w) 13.78 13.89 14.21 13.39 13.50 13.67 13.53 14.00 14.11 13.56 13.60 14.27

           

0.51Aa 0.36Aa 0.40Aa 0.26Aa 0.50Aa 0.58Aa 0.19Ba 0.33ABa 0.19Aa 0.68Aa 0.44Aa 0.25Aa

Moisture (% w/w) 86.22 86.11 85.79 86.61 86.50 86.33 86.47 86.00 85.89 86.44 86.40 85.73

           

0.51Aa 0.36Aa 0.40Aa 0.26Aa 0.50Aa 0.58Aa 0.19Aa 0.33ABa 0.19Ba 0.68Aa 0.44Aa 0.25Aa

Lactose % 1.34 1.20 0.96 1.16 0.93 0.84 1.28 1.09 0.79 1.42 1.21 1.13

           

0.27Aa 0.26Aa 0.06Aa 0.22Aa 0.36Aa 0.35Aa 0.35Aa 0.37Aa 0.12Aa 0.48Aa 0.30Aa 0.32Aa

*Treatments of yogurt have different types with and without B. bifidum F-35: control is a treatment without B. bifidum F-35; free cells type is a treatment reinforced by free cells; one-layer type is a treatment reinforced by microcapsules of whey protein; and double-layer type is a treatment reinforced by microcapsules of whey protein coated by sodium alginate. Data are expressed as the mean  standard deviation (SD) of four treatments (triplicate samples) were analysed in each treatment. A–C means the same column superscript uppercase letters differ significantly (P < 0.05) among different storage period for each treatment. a–c means the same column superscript lowercase letters differ significantly (P < 0.05) among different treatments for the same storage period.

International Journal of Food Science and Technology 2014

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Characteristics in set yogurt A. Mousa et al.

differed significantly (P < 0.05) in comparison with the other treatments up to the end of storage (El-Shenawy et al., 2012).

Table 2 Changes of syneresis and hardness at set yogurt during storage at 4  1 °C within 14 days

Treatments*

Survival of B. bifidum F-35 in yogurt

Survivability of the B. bifidum F-35 in both free and encapsulated cells during storage in set yogurt up to the 14th day is presented in Table S1. In general, the viability of B. bifidum F-35 decreased during the storage, which could be attributed to the natural low pH of yogurt and further reduction of pH in yogurt during the postacidification (Kailasapathy, 2006). Both the one- and double-layer treatments were presented in higher viability than free cells treatment during storage € which is in accordance with results of OZer et al. (2008). As shown by ANOVA, there is nonsignificant difference in population (P > 0.05) between the onelayer treatment and double-layer treatment prior to storage, and significant difference in comparison of free cells treatments with the encapsulated treatments (one- and double-layer types). In general, there is an obvious decrease in the cell number at all of the treatments during the storage, which is due to the high acidity and low pH of yogurt that led to a sharp decline in the cell number in the free cells treatment to 109 CFU g 1 at the 4th day of storage. Meanwhile, the number of microencapsulated cells in the one-layer treatment decreased to the same level of 109 CFU g 1 at the 6th day and in the double-layer treatment decreased to 109 CFU g 1 at the 8th day, which reflected the role of whey protein as coating and protecting material for cells at one-layer treatment in addition to the sodium alginate as extra layer of protection for the cells in the double-layer treatment. As showed by our results, the adverse conditions of yogurt had an obvious impact on the viability of cells in both of the treatments (free cells and one-layer microcapsules) which was recorded on the 10th day that decreased significantly compared with the double-layer treatment. Despite this, the one-layer treatment stilled in minor variation higher than the free cells treatment as was observed by findings of Homayouni et al., 2008 and Stephanie et al. (2012). Hence, in spite of the microencapsulation, using whey protein did not introduce the sufficient protections for cells in comparison with using another extra layer of sodium alginate, but it was and still is the most promising technology to protect bacterial cells from the adverse environment as was recommended by Kailasapathy (2002). The results showed that the B. bifidum F-35 remained above the therapeutic requirement (109 CFU g 1) up to the 14th day in all of the treatments (free and encapsulated types), which might be related to the presence and high oxygen utilisation ability of S. thermophilus, one of yogurt starter, that led to the removal of dissolved

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Control

Free cells type

One-layer type

Double-layer type

Storage (days) 0 7 14 0 7 14 0 7 14 0 7 14

Syneresis ABc

46.13 50.00Ab 45.47Bb 60.00Aa 60.80Aa 58.00Aa 55.33Ab 58.80Aa 54.67Aa 54.67Ab 57.47Aa 56.13Aa

           

Hardness 2.20 2.00 2.20 0.40 2.12 3.46 3.06 2.43 2.31 1.97 2.20 0.23

144.3Ba 166.05Aa 167.42Aa 107.77Cb 147.88Aa 130.13Bb 110.08Bb 130.31Aa 118.26Bb 119.09Ab 206.88Bb 165.33Aa

           

6.17 7.67 4.66 2.76 1.36 4.16 6.49 3.32 6.45 6.50 9.50 3.50

*Treatments of yogurt have different types with and without B. bifidum F-35: control is a treatment without B. bifidum F-35; free cells type is a treatment reinforced by free cells; one-layer type is a treatment reinforced by microcapsules of whey protein; and double-layer type is a treatment reinforced by microcapsules of whey protein coated by sodium alginate. Data are expressed as the mean  standard deviation (SD) of four treatments (triplicate samples) which were analysed in each treatment. A–C means the same column superscript uppercase letters differ significantly (P < 0.05) among different storage period for each treatment. a–c means the same column superscript lowercase letters differ significantly (P < 0.05) among different treatments for the same storage period.

oxygen in the product and enhanced the viability of bifidobacterium at yogurt. Therefore, our present study clearly showed that the encapsulation of B. bifidum F-35 cells led to the improvement of their viability in set yogurt. Sensory evaluations

All the parameters of the sensory analysis as shown in Table 3 differed nonsignificantly (P > 0.05) prior to storage, except the overall acceptability of the control treatment differed significantly (P < 0.05) in comparison with the treatments of free cells and double-layer microcapsules. Colour and appearance differed nonsignificantly (P > 0.05) during the storage among all of the treatments, which is reflecting the advantages of sodium alginate and whey protein as ineffective components on the colour of yogurt as it was confirmed by the results of Kailasapathy (2006). The high values of body and texture were observed in the double-layer treatment after the 7th day, followed by the one-layer treatment, which might be due to the ionic interaction between milk proteins, and alginate led to reinforce the yogurt gel, which is in agreement with the finding of Onsøyen (1992). The one-layer treatment was ranked as the highest values of smoothness and

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Table 3 Sensory scores of set yogurt during storage at 4  1 °C within 14 day Storage (days) 0

7

14

Treatments* Control Free cells One layer Double layer Control Free cells One layer Double layer Control Free cells One layer Double layer

Appearance and colour 6.92 7.00 6.92 6.62 6.36 7.03 6.95 6.69 6.23 6.08 5.79 5.87

           

Aa

0.53 0.75Aa 0.76Aa 0.97Aa 0.57Ba 0.46Aa 0.51Aa 0.57Aab 0.48Ba 0.47Ba 0.83Ba 0.90Ba

Body and texture 6.68 7.00 6.82 6.72 6.59 6.92 7.05 7.15 6.69 6.23 5.64 5.77

           

Aa

0.51 0.58Aa 0.48Aa 0.74Aa 0.56Ab 0.51Aab 0.68Aab 0.46Aa 0.48Aa 0.52Bab 0.55Bc 0.97Bbc

Flavour 7.03 6.87 7.13 6.95 6.51 6.26 7.00 6.67 6.49 5.58 5.18 6.33

           

Overall acceptability Aa

0.58 0.69Aa 0.65Aa 0.92Aa 0.38Bb 0.53Bb 0.73Aa 0.51Aab 0.62Ba 0.45Cb 0.69Bb 0.94Aa

7.33 6.74 7.10 6.72 6.62 6.62 7.10 6.74 7.15 5.87 5.72 6.33

           

0.59Aa 0.60Ab 0.75Aab 0.49Ab 0.33Bb 0.40Ab 0.37Aa 0.60Ab 0.35Aa 0.70Bc 0.45Bc 0.49Ab

*Treatments of yogurts with and without B. bifidum F-35: control is a treatment without B. bifidum F-35, free cells type refers to the sample with B. bifidum F-35; one-layer type is the sample added with microcapsules of whey protein; and double-layer type is the sample added with microcapsules of whey protein coated by sodium alginate. Data are expressed as the mean  standard deviation (SD) of four treatments (triplicate samples) which were analysed in each treatment. A–C means the same column superscript uppercase letters differ significantly (P < 0.05) among different storage period for each treatment. a–c means the same column superscript lowercase letters differ significantly (P < 0.05) among different treatments for the same storage period.

acceptable flavour by the panellists after the 7th day while the double-layer treatment received a high score of the acceptable flavour after the 14th day. The one-layer treatment had the highest value of overall acceptability after 7 days of storage and differed significantly (P < 0.05) in comparison with the other treatments. However, the overall acceptability of the one-layer treatment recorded the lowest value after the 14th day of storage and similar to the low value of free cells treatment. Meanwhile, the control and double-layer treatments remained to have a high value of overall acceptability after the 14th day and differed significantly (P < 0.05) in comparison with the other treatments. Generally, the panellists described the nonencapsulated treatment (free cells type) as a bad texture and sour taste, which might be due to the influence of the high acidity on the gel strength of yogurt. On the other hand, the texture of encapsulated treatment (double-layer type) was preferred and described as creamy, which might be attributed to the presence of alginate as polysaccharides added with concentration of 10% encapsulated cells led to improve the sensory profile (Tamime & Robinson, 2007). The disadvantage of double-layer treatment as observed by the panellists was the slight bitterness, which might be attributed to the bitter taste caused by the addition of Ca++ ions as calcium chloride was added during the encapsulation process to be crosslinking agent among the alginate polymers. Conclusion

Microencapsulating enhanced the survivability of B. bifidum F-35 during the storage till the 14th day.

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Microencapsulation of B. bifidum F-35 gave the yogurt product acceptable characteristics that were observed in decreasing the pH to ≥4.28 and titratable acidity to ≥1.65 at the encapsulated treatment. The encapsulation of B. bifidum F-35 conferred the samples’ smoothness with acceptable favour, besides a creamy texture in case of double-layer type. Therefore, the encapsulation of probiotic using double layer of whey protein and sodium alginate probably is a favourable process to enhance the physiochemical, textural, microbiological and sensory characteristics of set yogurt in comparison with the reinforced yogurt by free cells probiotic. Acknowledgments

This work was supported by the key projects in the national science & technology pillar program during the twelfth five-year plan period (No. 2013BAD18B01, 2013BAD18B02, 2012BAD28B07, 2012BAD28B07) and the Priority Academic Program Development of Jiangsu Higher Education Institutions. References Adhikari, K., Mustapha, A. & Gr€ un, I.U. (2000). Viability of microencapsulated bifidobacteria in set yogurt during refrigerated storage. Journal of Dairy Science, 83, 1946–1951. Adhikari, K., Mustapha, A. & Gr€ un, I.U. (2003). Survival and metabolic activity of microencapsulated Bifidobacterium in stirred yogurt. Journal of Food Science, 68, 275–280. Arup, N., Kyoung-Sik, H. & Harjinder, S. (2011). Microencapsulation of probiotic bacteria using pH-induced gelation of sodium caseinate and gellan gum. International Dairy Journal, 21, 247–253.

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Characteristics in set yogurt A. Mousa et al.

Bano, P., Abdullah, M., Nadeem, M., Babar, M.E. & Khan, G.A. (2011). Preparation of functional yoghurt from sheep and goat milk blends. Pakistan Journal of Agricultural Sciences, 8, 211–215. Biavati, B. & Mattarelli, P. (2001). The family Bifidobacteriaceae. In: The Prokaryotes. An Evolving Electronic Resource For Microbiological Community, 3 edn (edited by E. Stackebrandt). Pp. 322– 382. New York: Springer-Verlag. Borgogna, M., Bellich, B., Zorzin, L., Lapasin, R. & Cesaro, A. (2010). Food microencapsulation of bioactive compounds: rheological and thermal characterisation of non-conventional gelling system. Food Chemistry, 122, 416–423. Capela, P., Hay, T.K.C. & Shah, N.P. (2006). Effect of cryoprotectants, prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt. Food Research International, 39, 203–211. Dave, R.I. & Shah, N.P. (1997). Viability of yogurt and probiotic bacteria in yogurts made from commercial starter cultures. International Dairy Journal, 7, 31–41. El-Shenawy, M., El-Aziz, M.A., El-kholy, W.I. & Fouad, M.T. (2012). Probiotic yogurt manufactured with tiger-nut extract (Cyperus Escuilentus) as a functional dairy food. Journal of Agricultural Research and Natural Resources, 1, 20–31. FAO & WHO Experts’ Report. (2001). Evaluation of Health and Nutritional Properties Of Probiotics In Food Including Powder Milk With Live Lactic Acid Bacteria. Cordoba: FAO & WHO. Homayouni, A., Azizi, A., Ehsani, M.R., Yarmand, M.S. & Razavi, S.H. (2008). Effect of microencapsulation and resistant starch on the probiotic survival and sensory properties of synbiotic ice cream. Food Chemistry, 111, 50–55. Joseph, A.O. & Olugbuyiro, E. (2011). Physico-chemical and sensory evaluation of market yogurt in Nigeria Pakistan. Journal of Nutrition, 10, 914–918. Kailasapathy, K. (2002). Microencapsulation of probiotic bacteria: technology and potential applications. Current issues in intestinal microbiology, 3, 39–48. Kailasapathy, K. (2006). Survival of free and encapsulated probiotic bacteria and their effect on the sensory properties of yoghurt. LWT-Food Science and Technology, 39, 1221–1227. Kailasapathy, K. (2009). Encapsulation technologies for functional foods and nutraceutical product development. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 4, 1–19. Kaminarides, S., Stamou, P. & Massouras, T. (2007). Comparison of the characteristics of set type yogurt made from ovine milk of different fat content. International Journal of Food Science and Technology, 42, 1019–1028. Krasaekoopt, W., Bhandari, B. & Deeth, H. (2003). Evaluation of encapsulation techniques of probiotics for yoghurt. International Dairy Journal, 13, 3–13. Li, Q., Zhang, L.W. & Zhang, Y.C. (2012). Determination of lactose, glucose and galactose contents in fermented milk by HPLC. Food science journal, 33, 162–166. McMaster, L.D. & Kokott, S.A. (2005). Micro-encapsulation of Bifidobacterium lactis for incorporation into soft foods. World Journal of Microbiology and Biotechnology, 21, 723–728. Mokarram, R.R., Mortazavi, S.A., Najafi, M.B. & Shahidi, F. (2009). The influence of multi stage alginate coating on survivability of potential probiotic bacteria in simulated gastric and intestinal juice. Food Research International, 42, 1040–1045.

© 2014 Institute of Food Science and Technology

Obi, T.E., Henshaw, F.O. & Atanda, O.O. (2010). Quality evaluation of plain-stirred probiotic yoghurt produced from skim and whole milk powder during refrigerated storage. Electronic Journal of Environmental, Agricultural and Food Chemistry, 9, 1203–1213. Onsøyen, E. (1992). Alginates. In: Thickening and Gelling Agents for Food (edited by A. Imeson). Pp. 1–24. New York: Blackie Academic & Professional, Springer. € OZer, B., Uzun, Y.S. & Kirmaci, H.A. (2008). Effect of Microencapsulation on Viability of Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum BB-12 During Kasar Cheese Ripening. International Journal of Dairy Technology, 61, 237–244. Pavunc, A.L., Beganovic, J., Kos, B., Buneta, A., Beluhan, S. &  skovic, J. (2011). Influence of microencapsulation and transgluSu taminase on viability of probiotic strain Lactobacillus helveticus M92 and consistency of set yoghurt. International Journal of Dairy Technology, 64, 254–261. Ramchandran, L. & Shah, N.P. (2010). Characterization of functional, biochemical and textural properties of symbiotic low-fat yogurts during refrigerates storage. LWT–Food Science and Technology, 43, 819–827. Rosenberg, M. & Lee, S.J. (2004). Calcium-alginate coated whey protein-based microspheres: preparation, some properties and opportunities. Journal of Microencapsulation, 21, 263–281. Salovuo, H., Ronkainen, P., Heino, A., Suokannas, A. & Ryh€anen, E.L. (2005). Introduction of automatic milking system in Finland: effect on milk quality. Agricultural and Food Science, 14, 346–353. Sozzi, T., Brigidi, P., Mignot, O. & Matteuzzi, D. (1990). Use of dicloxacillin for the isolation and counting of Bifidobacteria from dairy products. Le Lait, 70, 357–361. Stephanie, S.P., Carlise, B.F., Isabella, B.M., Pedro, L.M., Elane, S.P. & Renata, D.M.C. (2012). Effects of the addition of microencapsulated Bifidobacterium BB-12 on the properties of frozen yogurt. Journal of Food Engineering, 111, 563–569. Supavititpatana, P., Wirjantoro, T.I. & Raviyan, P. (2010). Characteristics and shelf-life of corn milk yogurt. Chiang Mai University Journal of Natural Sciences, 9, 133–149. Tamime, A.Y. & Robinson, R.K. (2007). Tamime and Robinson’s yoghurt: Science and Technology Pp. 651–652. Boca Raton: Woodhead Publishing Ltd. Yazici, F. & Akgun, A. (2004). Effect of some protein based fat replacers on physical, chemical, textural, and sensory properties of strained yogurt. Journal of Food Engineering, 62, 245–254. Zou, Q., Liu, X., Zhao, J. et al. (2012). Microencapsulation of Bifidobacterium bifidum F-35 in Whey Protein-Based Microcapsules by Transglutaminase-Induced Gelation. Journal of Food Science, 77, M270–M277.

Supporting Information

Additional Supporting Information may be found in the online version of this article: Figure S1. Production of set yogurt supplemented with free and encapsulated Bifidobacterium bifidum F-35. Table S1. Changes in Bifidobacteriun bifidum F-35 counts (log CFU g 1) as free and encapsulated in set yogurt during storage at 4  1 °C within 14 day.

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