Optimising fermentation of soymilk with probiotic bacteria

Abstract

Soymilk was fermented with probiotic culture ABT5 and yoghurt culture with the addition of bifidobacteria at different temperatures (37°C and 42°C) with the aim of shortening the fermentation time and producing a probiotic fermented soymilk. During the fermentation and storage of the fermented soymilk (28 days at +4°C), the changes in pH-value and viable cells count were observed. Incubation temperature did not affect significantly fermentation time (7 h at 42°C and 8 h at 37°C, respectively), with ABT5 culture (Lactobacillus acidophilus, Bifidobacterium spp., and Streptococcus thermophilus). However, Lactobacillus acidophilus survived poorly during cold storage and the viable cells count was under the probiotic minimum as soon as after the first week of storage. Therefore in the consequent phase of the experiment, soymilk was fermented at 42°C with yoghurt culture YCX11 enriched with Bifidobacterium animalis subsp. lactis Bb12. Consequently, the fermentation time was shortened to 4 hours whereby the viable cells count of bifidobacteria increased during fermentation for the half of the logarithm scale approximately. During 28 days of cold storage, bacterial count remained constant and above 107 CFU/ml.