Biomolecules and Nutritional Quality of Soymilk Fermented with Probiotic Yeast and Bacteria

Soymilk was fermented with five isolates of probiotic lactic acid bacteria and in
combination with probiotic yeast Saccharomyces boulardii. Nutritional profile like fat,
protein, ash, pH, acidity, polyphenol, and protein hydrolysis were analyzed. Polyphenol
content decreased from 265.88 to 119 μg/ml with different cultures. Protein hydrolysis
ranged from 2.46 to 2.83 mmol l−1 with different cultures. The antioxidant activity was
assessed using different methods like 1, 1-diphenyl-2-picrylhydrazyl free radicalscavenging
assay, inhibition of ascorbate autoxidation, and measurement of reducing
activity. The activities varied with the starters used but, nevertheless, were significantly
higher than those found in unfermented soymilk. Bioconversion of the isoflavone
glucosides (daidzin+genistin) into their corresponding bioactive aglycones (daidzein+
genistein) was observed during soymilk fermentation. Total glucosides in soyamilk were
26.35 mg/100 ml. In contrast, aglycones genistein and daidzein were quantitatively lesser
accounting 2.91 mg/100 ml (genistein 1.17 mg/100 ml and daidzein 1.19 mg/100 ml).
Soymilk fermented with probiotic cultures resulted in the reduction of glycosides ranging
from 0.40 mg to 1.36 mg/100 ml and increase in aglycones ranging from 6.32 mg to
13.66 mg/100 ml.