Studies On The Technology And Stability Of Milk Beverage Fermented By Lactobacillus Casei

Lactobacillus casei is a probiotics which can withstand the organism's defense mechanisms and colonize in the intestine. In recent years, Lactobacillus casei becomes the focus of research, development and production because of its nutrition, immunization, disease prevention and other significant prebiotic effect. Therefore, the development of Lactobacillus casei fermented milk beverage is very important.Lactobacillus casei fermented milk on a single fermentation was investigated. The results showed that Lactobacillus casei has a long growth cycle, slow growth and a low rate of acid production in milk. But as Lactobacillus casei has good acid resistance and stability, the product has a high number of viable cells in 72h, and the maximum viable count 4.7×1010cfu/mL. Through the exploration of different sterilization process for raw milk, the optimal sterilization conditions were final determined at 116℃,15min due to the account of the color and state of the curd also with the taste of fermented milk beverage. The best end of fermentation was identified at 150-160℃T combined with other aspects of the viscosity and the living Lactobacillus casei number.Fermented milk beverage has the problem of instability caused by suspended fat and proteins sedimentation and so on. The effects of the stabilizer, emulsifier, chelator, saccharinic acid ratio and homogenization pressure on the stability and the process of pasteurization were studied. According to orthogonal designs, quadratic regression orthogonal design and response surface analysis methods, the obtained optimized fermented milk beverage formula was as followed: composite emulsifier (trimeric esters:tween 80:ten poly esters=2:2:1) 0.01%, CMC 0.25%, pectin 0.31%, compound chelator (sodium hexametaphosphate:sodium pyrophosphate:sodium tripolyphosphate =2:5:3) 0.10%, sucrose 10%, pH 4.0 and homogenization pressure 30MPa.Metabolites of Lactobacillus casei also have lower cholesterol, improve immunity and other effects. And sterilized beverage is easy for people to eat because it can be stored for long periods at room temperature. Therefore, the development of sterilization type of Lactobacillus casei fermented milk beverage is particularly important. The obtained optimized sterilized fermented milk beverage formula was as followed:composite emulsifier (ten poly esters:Tween 80=1:9) 0.01%, CMC 0.30%, pectin 0.36%, compound chelator (sodium hexametaphosphate:sodium tripolyphosphate:sodium citrate=2:5:3) 0.15%. The obtained optimized process parameters was pasteurizing at 75℃for 15min.To save costs, skim milk was used instead of part curd to deploy sterilzed fermented milk beverages. The deployment proportion between skim milk and fermented curd has significant impact on the taste and stability of the product. Consider as two factors, the best allocation ratio is determined:65% fermented curd and 35% skim milk.During the storage at 4℃or 37℃for 30 days, the fermented milk beverage under different treatment presented a good physical stability and had a slight degree of delamination in post-storage. Particle size distribution, viscosity, centrifugal sedimentation didn't change significantly. The living Lactobacillus casei number counted for 1.2×10 cfu/mL in the initial period after living fermented milk beverage preparation. After stored at 4℃for a period, the living Lactobacillus casei number decreased slightly, but it maitained 4.3×108 cfu/mL after 30 days cold storage. This indicated the product maintained a high viable count in refrigerated time.