Development And Application Of The Lactobacilus Helveticus Mb2-1Freeze-Drying Starter

Yoghurt is a traditional dairy beverage, which is rich of lactic bacteria. The lactic bacteria not only transform the lactose in milk, but also bring delicious taste and nutritional value. The bacteria used in this study is named Lactobacilus helviticus mb2-1of high viscosity, which was separated from the sayram yogurt produced in Xinjiang.In order to better inherit and develop this local yogurt, the study prepared a freeze-drying starter by using Lactobacilus helviticus mb2-1which can recover this yoghurt, and successfully developed a probiotic yogurt effervescent tablet with functions of chewing, effervescent and reproducing yoghurt. The production of effervescent tablet is based on the Lactobacilus helviticus mb2-1yoghurt powder. The main results were as follows:1. Study on the enrichment cultivation of Lactobacilus helviticus mb2-1Based on whey culture medium, and selected right growth factors and pH-buffer, determined the optimum culture medium (L-1):whey powder60g, carrot juice150mL, citric acid-sodium citrate buffer (0.1mol/L, pH6.6)25mL and water1000mL. By using orthogonal experimental design of enrichment cultivation conditions and drawing cell growth curve, determined the optimal cultivation conditions:maintaining the natural pH7.4of enrichment medium, temperature40℃, inoculums4%, cultivation time12h. In the optimized condition, cell concentration was increased to1.35×109cfu/mL, which was2.7times of cell density (0.50×109cfu/mL) before the enrichment cultivation.2. Study on the concentrate conditions of Lactobacilus helviticus mb2-1By using centrifugation at room temperature (20℃) method, and studying the impact of centrifugation speed and time on the rate of cell concentration, viability and viable cell number, determined the optimal concentration conditions:centrifugation speed of9000rpm/min, centrifugation time of30min. In this situation, the rate of cell concentration reached89%, viable cell density of the concentrates was8.38×109cfu/g which was6.2 times of original enrichment culture (1.35×109cfu/mL).3. Study on the croprotectants of Lactobacilus helviticus mb2-1By the single factor experiments of different kinds of ten cyroprotectants, found out four protectants which had significantly protective effects on the Lactobacilus helviticus mb2-1. By orthogonal experiment, determined the formula of cryoprotectants (L-1):skim milk100g, sugar150g, L-glutamate25g, L-cysteine5g and water1000mL. The cell viability of the freeze-drying starter reached94%and the viable cell number was2.31×1010cfu/g.4. Comparison between the Lactobacilus helviticus mb2-1freeze-drying starter and the traditional liquid starterBy comparing the fermentation performance between freeze-drying starter and the traditional liquid starter and between the different inoculums of the freeze-drying starter, results showed that the fermentation activity of the Lactobacilus helviticus mb2-1freeze-drying starter was no less or even better than traditional liquid starter, and the inoculums of the freeze-drying starter was5‰. The best storage conditions of the starter were:Vacuum,-20℃.5. Study on the multi-functional probiotic yoghurt effervescent tabletsBy addition of yoghurt powder rich in Lactobacilus helviticus mb2-1and the acid-alkali effervescent agents and other excipients, developed a new probiotic yoghurt effervescent tablets with functions of chewing, effervescent and reproducing yoghurt. The recipe was as follows:yoghurt powder30%, citric acid24%, NaHCO318%, maltodextrin4.5%, aspartame2%, polyethylene glycol60003%and mannitol18.5%. One effervescent tablet, in about7h, could reproduce100ml yougurt which had a similar flavor and texture with the XinJiang yogurt of high viscosity. This study could meet the reauirement of home-make youfurt.