Nutraceutical Properties of Dioscorea opposita Thunb. (Yam) Fermented by Lactobacillus bulgaricus and Streptococcus thermophilus

This study was performed to determine by the ability of the mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus to ferment Dioscorea opposita Thunb. (yam) and to evaluate the nutraceutical value of fermented yam. The titratable acidity (TA) value increased from 2 to 6% with increased concentrations in both raw yam and extracted lactic acid bacteria (LAB) fermented yam (LFY). The viable cell counts and the allantoin and diosgenin contents were higher in raw LFY at large concentrations (6%) than in extracted LFY samples at all fermentation periods up to 32 h. Based on these data, it confirmed that raw yam fermented by the combination culture of L. bulgaricus and S. thermophilus for various fermentation periods favors the symbiotic growth of LAB and results in higher nutraceutical content.