The objective of this study is to identify the effect of two commercial Lactobacillus cultures, Lactobacillus plantarum (A) and a mixture of Lactobacillus rhamnosus, Lactobacillus plantarum and Lactobacillus paracasei, on the control of mold contamination, nutrients, texture and sensory qualities of stirred yogurt. The results demonstrated that these two cultures exerted different degrees of inhibition on mold growth. Culture B led to higher degree of mold inhibition than culture A when added at the manufacturer recommended amount (A: 2.0 × 106 CFU/mL, B: 1.38 × 107 CFU/mL). In contrast, culture B at 2.0 × 106 CFU/mL had less inhibition capability than culture A. The flavor of yogurt was adversely affected by culture B, while culture A showed no effect during the shelf-life period. Compared with the control group, the nutrients and texture of yogurt with culture A or B were not changed greatly. In conclusion, Lactobacillus cultures can inhibit the growth of mold in yogurt, where its bacteriostatic ability is related to the species and concentration of strains added.

The impact of mixed starters consisting of Streptococcus thermophilus PZST4 and Lactobacillus bulgaricus PZLB5 in different proportions on the fermentation period of fermented milk and its acidity, texture, syneresis and flavor during storage was investigated. The results showed that viable cell ratios between Streptococcus thermophilus PZST4 and Lactobacillus bulgaricus PZLB5 had a striking effect on the quality of fermented milk, and a ratio of 50000:1 was the optimal combination based on the quality parameters tested.