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The Components, Functions and Fermentation Parameters of Kefir and Kefir Walnut

Author: WangYu
Tutor: HanJianRong
School: Shanxi University
Course: Microbiology
Keywords: Kefir Walnuts Antibacterial Component Fermentation Parameters
CLC: TS252.1
Type: Master's thesis
Year: 2010
Downloads: 80
Quote: 0
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Abstract

Fermented milks has thousands years in history, their new products and benefits reached to an extremity already. In the background of this situation, Kefir will replace others as a new product. Kefir is a kind of slightly sour taste and bubble feeling fermentation product which origins from the Caucasian region. Kefir uses Kefir grains as a starter and fermented in milk or goat milk. Kefir grains contain a complex microbial symbiotic mixture of lactic acid bacteria, acetic acid bacteria and yeasts. Because of its complex and different components, on the one hand, Kefir has some special functions, on the other hand, some problems exit during the fermentation. With the development of our life standard, most people pay attention to the functions of food, for example the walnut products. Walnut are wildly planted in our country, their nutritional values and functions are recorded at early time. So, produce a new drink, such as Kefir walnut milk, at the same time, deal with the difficulties during the fermentation. Kefir-walnut beverages will have good prospects in the future.With Kefir grains as starter, four factors (i.e., fermentation temperature, fermentation time, inoculums size and sugar consumption) which affected quality of Kefir products ultimately were selected to determine the optimal fermentation conditions by examining the physical and chemical indicators and evaluating its sensory indicators. The results showed that optimal parameters were fermentation temperature of 30℃, fermentation time of 12 h, inoculums size of 5% and sugar consumption of 8%. By this way, Kefir beverage was tasted fine and had no peculiar odor. Compare with other yogurt, Kefir’s components are different because of complex microbial of Kefir grains. This experiment studied the antimicrobial activity of Kefir and Kefir walnut components. The results showed that Kefir has more advantages than yogurt and antibiotics. This is also providing a theoretical basis for new antibiotics.This experiment was carried out to ferment milk and walnuts with Kefir grains as a starter. The changes of pH, acidity, microbial counts and utilization of lactose during Kefir fermentation were studied. The results showed that pH and acidity changed sharply. After fermentation of 24 hours, pH dropped to 4.102 from 6.798 and the acidity rose to 96.9°T from 16.1°T. Kefir walnut’s pH dropped to 3.71 from 6.68 and acidity rose to 72.3°T from 13.7°T after fermentation of 12 hours. In the initial fermentation stage, the colony counts of lactococcus increased fast in 4 hours, which resulted in the significant decrease of lactosed content and fast increased of acidity. At the end of fermentation, the colony counts of lactococcus, lactobacillus and yeast in Kefir reached to 1.6×107 cfu/mL,7.7×107 cfu/mL and 1.1×105 cfu/mL respectively, and lactose value declined to 1.90mg/mL from 4.05mg/mL; the microbial counts of Kefir’walnut reached to 1.47x108 cfu/mL,1.6×108cfu/mL and 2.5×106 cfu/mL respectively, and lactose value declined to 0.558mg/mL from 4.03mg/mL

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