Effect of probiotic Lactobacillus plantarum P8 and Streptococcus thermophilus on the quality of fermented milk.

L.plantarum P8 was mixed respectively with S.thermophillus ND03,ND05 and ND07 with different proportion for bovine milk fermentation with single S.thermophillus fermented milk as the control.At the baseline(0 h),the end of fermentation(pH=4.5) and storage(4 ℃ for 24 h),fermentation time,pH,viscosity,syneresis,and sensory characteristics of yogurts as well as the bacterial viable counts were evaluated.The results indicated that fermention time of milk fermented by combined L.plantarum P8 and S.thermophilus ND03 was significantly longer than other groups(P0.05),while viscosity and syneresis had no significant differences(P0.05).Moreover,the fermented milk showed great quality with fine viscosity,moderate acidity,no whey separating,good spinnablility and nice flavor while combined L.plantarum P8 and S.thermophilus ND05 with 1∶1 ratio(5×106 mL-1 each) for fermentation,suggesting that this combination could be applied for yoghurt production.