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Saccharomyces cerevisiae SCY1 by the research group is separated from the fermented vegetable juice, lychee wine is fermented for preliminary studies, the brewing wine and good flavor, good fermentation characteristics. Kefir is a mixture of lactic acid bacteria and yeast fermented dairy products, with lower serum cholesterol, enhance immunity, anti-aging and anti-cancer effect, so our group intends SCY1 for fermented kefir, and Kluyveromyces marxianus LAF-4 as controls. Studied SCY1 in milk, pineapple juice and juice composite milk fermentation characteristics. SCY1 growth in milk 36 h 32 ℃ reached the maximum number of 106 bacteria / mL, sucrose, glucose, or pineapple juice, its within 24 h can grow up to 107 / mL. SCY1 in milk at 28 ℃ and 35 ℃, after 36 h growth of only up to 10 5 / mL, shows, SCY1 not use lactose, but the addition of a suitable carbon source, may grow better in milk, the optimum growth temperature is 32 ℃. The LAF-4 can utilize lactose, the optimum growth temperature is between 32 ~ 35 ℃. Studied SCY1 kefir fermentation process conditions. By studying SCY1 inoculation, sterilization conditions, the fermentation temperature, the amount of sugar on kefir pH value, titratable acidity, adhesion, CO2 content of combined sensory evaluation to determine the optimum process conditions: SCY1 inoculum of 103 cells / mL ; 85 ~ 90 ℃ sterilized 10 min; fermentation temperature is 32 ℃; sugar content of 4%. LAF-4 process conditions and SCY1 the same, but the flavor and quality of different products. Studied kefir during storage at 4 ℃ quality changes. SCY1 resulting kefir fermentation the pH during storage 12 d minimize the flavor of which was 4.32, 4.31 fruity, titratable acidity did not change significantly. Plain kefir at 12 d of CO2 content reaches a maximum 58.93 mg/100g, fruity 16 d reaches a maximum 93.55 mg/100g, followed by a slight decline. When the number of viable cells 12 d lactate increased to 108 cfu / mL, and then decreased to 107 cfu / mL, while the yeast during storage by 103 cfu / mL increased to 106 cfu / mL. During storage has not detected coliform bacteria. SDS-PAGE showed that casein in fermentation, weak degradation during storage. Sensory records show that plain kefir 12 d after thinning curd, tastes too sour, fruity, there are obvious alcohol, it is recommended that storage should not exceed 12 d, at 8 d before eating better quality. Analyzed the nutritional content of kefir and yogurt compared with the ordinary. Kefir's pH, titratable acidity, protein and amino nitrogen levels were significantly higher than ordinary yogurt. Acid analysis showed that, kefir containing 10 g / L of L-lactic acid, and does not contain D-lactic acid, regular yogurt containing 1.1% of D-lactic acid, L-lactic acid content of only 5.64 g / L. the total amount of free amino acids in kefir 17 ~ 24 mg/100mL, regular yogurt only 8.65 mg/100mL, kefir after fermentation increases the total free amino acids increased more with glutamic acid, proline, styrene acid, but serine, glycine, histidine, arginine, alanine, methionine decreased slightly.
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