Preparation of instant probiotic yogurt powder

Seyfzadeh, S. (2016) Preparation of instant probiotic yogurt powder. Masters thesis, University of Zabol.

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Proper nutrition and consumption of probiotic dairy products in preventing diseases such as high blood pressure, high cholesterol, weight gain, cardiovascular disease and cancer are important. The aim of this study was to investigate the possibility of producing instance probiotic yogurt powder using freeze-drying technique.Yogurt samples were prepared from fermented milk (1.5% fat) by starter cultures of Streptococcus thermophillus and Lactobacillus bulgaricus PTCC 1737. After fermentation, yogurt sample was dried by freeze dryer.The design variables included wheat dietary fiber (the presence or absence), the composition of capsules wall (in three levels of whey protein concentrate, pectin, pectin+whey protein concentrate) in three time period of (0, 15 and 30 days). Probiotic bacterium, Bifidobacterium bifidum PTCC 1644 was used in the encapsulation process after activation. Encapsulated bateria samples were freeze dried and added to the dried yoghurt.The qualitative and quantitative properties of yogurt powder samples were evaluated for microbial analysis (cell counting of Bifidobacterium bifidum PTCC1644, investigation of survival rate of Bifidobacterium bifidum PTCC1644 in simulated stomach conditions), physicochemical properties (pH, acidity, morphology of encapsulated bacteria and yogurt powder, solubility index of yogurt powder, synersis value of immediate yogurt and rheological test) and sensory properties (color, odor and taste) at 0, 15 and 30 days intervals. Statistical analysis was performed based on a factorial experiment in a completely randomized design and comparison of means at 95 percent was conducted using SAS version 9.1. The results showed that the Whey Protein Concentrate + pectin gum coating, could be the best combination for microencapsulation and maintained the viability of Bifidobacterium bifidum PTCC1644 to the 3.55 log CFU/g after 30 days of storage at -4 °C. In all yogurt powders stored at 4 °C, reducing the number of bacteria Bifidobacterium bifidum PTCC1644 was observed in time period of 0, 15 and 30 days, but it was much lower than the control sample (yogurt powder containing free bacteria). Also, the application of whey protein concentrate + pectin gum, for Bifidobacterium bifidum PTCC1644 provided the highest survival in simulated gastric conditions compared to other coatings. The presence of wheat dietary fiber in coatings used in the microencapsulation hadn't a positive impact on the viability of Bifidobacterium bifidum PTCC1644 (P>0.05(.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Yogurt, Freeze dryer, Bifidobacterium bifidum 1644, Microencapsulation
Subjects: T Technology > TP Chemical technology
Depositing User: admin admin1 admin2
Date Deposited: 18 Apr 2017 08:38
Last Modified: 18 Apr 2017 08:38

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