Study On Yogurt Cultures By Goat Milk-based Containing L.A. Strain

DVS cultures have been widely used in yoghurt production, and become the inevitabletrend for the dairy industry development of industrialization. At the same time, Lactobacillusacidophilus as important probiotics, they are able to pass the gastrointestinal environment andcolonize the large intestine, and give full play effect to their health-promoting. The healthfunctions of Lactobacillus acidophilus have been confirmed by many researchers. In thisstudy, combined with the results of previous studies on the key technology in the preparationprocess of fermentation, including the choice of excellent milk, quality matrix proliferationfactor and protactants, the regression model of the probiotics somatic, the survival rate ofprobiotics somatic during the storage period, which provide a foundation for producingfermented milk containing probiotics and functional dairy products. The main conclusionswere as follows:（1） Compared with cow’s milk, single strain of Lactobacillus acidophilus，Lactobacillusbulgaricus or Streptococcus thermophilus has better fermentation performance in the goatsubstrate. In the goat’s milk, the viable counts were5.37×10¹⁰mL^-1,2.10×10⁹mL^-1and1.31×10¹⁰mL^-1, greater than in cow’s milk which were9.33×10⁹mL^-1,1.25×10⁹mL^-1,6.31×10⁹mL^-1. The pH of fermented goat’s milk were4.15,4.16,4.29, and titratable acidity reached120.00oT,128.00oT,120.33oT. While the pH of Fermented cow’s milk were4.17,4.45,4.37,and titratable acidity reached110.90oT,114.80oT,110.20oT. The capacities of acetaldehydesin goat’s milk were superior to cow’s milk （P<0.05）. The acetaldehydes in fermented goat’smilk were11.23mg/L,6.09mg/L,8.21mg/L, which were higher than fermented cow’s milk9.85mg/L,5.12mg/L,7.35mg/L. But in term of diacetyls there was no significant differencebetween two substrates （P>0.05）. The acetaldehydes in fermented goat’s milk were17.77mg/L,11.72mg/L,13.44mg/L and18.25mg/L,11.56mg/L,13.07mg/L in cow’s milk.（2） There were slight differences between single strain and three strains mixed equallywith Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus acidophilus.The three strains mixed equally in the goat’s milk, keeping42℃after8h fermentation, theviable counts of Lactobacillus acidophilus, Streptococcus thermophilus and Lactobacillus acidophilus reached9.33×10⁹mL^-1,1.22×10¹⁰mL^-1,4.67×10⁹mL^-1.（3） The optimized ingredients, for the mixed strains equally proliferation, is1.2%whey,1.2%galactooligosaccharide（GOS）,0.6%casein phosphopeptides（CPP）,1.2%fructooligosaccharides（FOS）,1.0%inulin. The important order comes by FOS, inulin, CPP,GOS, whey. Under the best formula the number of viable cells can be obtained up to7.82×10¹¹mL^-1.（4） The important order of protectants of the three strains comes by trehalose, glycerol,sodium glutamate, ascorbic acid, and the optimum formula in goat’s substrate is: with theaddition of3%trehalose,4%glycerol,0.75%ascorbic acid,0.4%sodium glutamate. Theverifying test shows the survival of the three strains powder reaches to2.69×10¹²g^-1.（5） In the goat’s substrate, the regression model of mixed strains isY_CAP（t）=24.8632/（1+1.3778^*exp（-0.4910^*t））, DC==0.9853, R=0.9962. From these termsincluding fermentation performance and textural properties, freeze-dried powder compliedwith the standard of DVS yogurt culture. Besides, Freeze-dried powder containinglactobacillus acidophilus could be still able to maintain above10¹⁰in the atmosphericpressure at4℃during storage90d.