Effects of inoculum ratios of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus on the quality of probiotic fermented milk by Bifidobacterium lactis

Different ratios(1∶1,1∶10,1∶100,1∶1000) of Lactobacillus delbrueckii subsp.bulgaricus ND02(LB-ND02) and Streptococcus thermophilus ND03(ST-ND03) plus with Bifidobacterium lactis V9(B.lactis V9,2.0×107 g-1) were used as starter cultures for milk fermentation.Some indexs of prepared probiotic fermented milk were determined for evaluation for effect of different ratios of inoculum on the quality of probiotic fermented milk during the fermentation and storage.The results showed the fermentation time was significantly prolonged,viable numbers of B.lactis V9 was significantly increased.After the fermentation followed by a 28 d storage,the survival of B.lactis V9 were significantly different and the postacidifition was weakened as the ratio of LB-ND02 decreased..It is suggested that different ratios of LB-ND02 and ST-ND03 significantly influence the fermentation time,viable numbers of B.lactis V9,postacidifition and visicosity during the fermentation and storage.