M.A. Thesis:

Evalution Of Some Probiotic Lactic Acid Bbacteria On Cholestrol Reduction In Creamy Yogurt

In the current century, probiotic products especially yogurt are popular among people, and this is due to their impact on consumer health. In this thesis, the impact of some probiotic species of bacterial lactic acid on the reduction of cholesterol in the weight of creamy yogurt of probiotic bacteria and some of the physicochemical and sensory properties of probiotic yogurt were investigated. This study was conducted as split plot design at time of analysis. In this study, the main factors of bacterial species and sub-factor of time and dependent variables were bacterial count, sample cholesterol, pH, acidity and sensory properties. The milk used to produce probiotic yoghurt samples was pasteurized and homogenized after formulation (adding cream, milk powder and cheese dip), then it placed under a 90 ° C heat treatment for 20 minutes. After cooling the fermented milk to a temperature of 43 ° C, the traditional bacteria of yogurt, along with the probiotic bacteria (BB12, LA5, C431), were packaged and subsequently packaged in polystyrene containers (PS). During fermentation, the pH decreased to 4.5-4.7. After fermentation, the samples of yogurt were stored in a refrigerator (4 ° C). Cholesterol levels, some physicochemical properties (pH, titratable acidity), sensory characteristics and survival probiotics were determined during the 21 days of storage at a temperature of 4 C. During the maintenance period, acidity increased but the probability of survival of the probiotics, Cholesterol and pH decreased, and the time elapsed with the sensory effects of the samples. The comparison results of the treatments mean over time showed that BB12 had the highest population and C431 population with the least population in probiotic yogurt during storage, and the highest reduction in cholesterol was related to C431 bacteria.Also, the interaction effect of bacteria type was significant on the determinant factors (pH, acidity and sensory evaluation) at 1% and 5% levels.

Keywords: probiotic yogurt.survival probiotics.Cholesterol levels.sensory characteristics