Sugar and acid contents in soymilk fermented with lactic acid bacteria alone or simultaneously with bifidobacteria

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In this study, two strains of lactic acid bacteria, Lactobacillus acidophilus CCRC 14079 and Streptococcus thermophilus CCRC 14085 were used in single culture and in combination with either Bifidobacteria infantis CCRC 14633 or Bifidobacteria longum B6 for the production of fermented soymilk. Changes in the content of some components including sugars, organic acids and acidity in soymilk during fermentation were examined. Results revealed that L. acidophilus and S. thermophilus were capable of metabolizing stachyose and raffinose in soymilk. In addition, S. thermophilus exploited these substrates more efficiently than L. acidophilus. During the 24–32 h of fermentation with single culture of either L. acidophilus or S. thermophilus, content of raffinose, stachyose, sucrose, and pH in soymilk decreased, while content of fructose and glucose plus galactose increased. Introduction of bifidobacteria with lactic acid bacteria as the starter culture affected significantly the sugar and acid contents of the fermented soymilk. A further reduction in the content of stachyose and raffinose and a higher content of sucrose, fructose, glucose plus galactose and acetic acid were found in soymilk fermented with mixed cultures of bifidobacteria and lactic acid bacteria than that fermented with single culture of the respective lactic acid bacteria.