Abstract

This study aimed at producing soybean yoghurt containing bifidobacterium by temperature shifted fermentation process, and to increase the viable counts of bifidobacterium in the soybean yoghurt. First, parallel test was used to investigate the amount of carbon source of high fructose corn syrup. Secondly, using the Mathematic 7.01 software program, the relationships between the viable counts of bifidobacterium and fermentation conditions (temperature and duration) were simulated. Finally, the fermentation process was optimized through the uniform design. The optimized process conditions included 5% of soybean powder, 5.32% of high fructose corn syrup, 0.03% of lactic bacteria(Lactobacillus bulgaricus: Streptococcus thermophilus = 1:1), 0.15% of bifidobacteria, 3.5 h of the first phase fermentation process at 42°C, and 1.5 h of the second phase fermentation process at 37.2°C. The viable counts of bifidobacterium in the final product of soybean yoghurt were above 1.1×10⁶/ml. The fermentation process proposed by this study can increase the viable counts of bifidobacterium in the soybean yoghurt.

Key words: Uniform design, soybean yoghurt, lactic bacteria, bifidobacteria.