Production of soy yogurt enriched with glyceollins

Abstract

Soy milk was prepared from regular soybean (M1), soybean germinated for 3 days at 25A degrees C (M2), and soybean germinated under fungal infection (M3). Rhizopus microsporus var. oligosporus ATCC 22959 was used as the elicitor for glyceollin production. Each soy milk was fermented with Streptococcus infantarius 12 and Weissella sp. 4 (1:5, v/v) for 12 h at 37A degrees C. Significant induction of glyceollins was confirmed only in M3 soy milk and glyceollins maintained stably during 12 h fermentation period. The concentration of glyceollins in M3 yogurt was 2,400.4 +/- 83 and 2,525.2 +/- 158 mu g/g dry matter (d.m.) at 0 and 12 h, respectively. The amount of daidzein was significantly higher in M3 yogurt (635.1 +/- 21) than that of M1 (417 +/- 11) and M2 (545 +/- 17 mu g/g d.m.) yogurt in 12 h (p < 0.05). M2 yogurt had the highest amount of genistein (695.3 +/- 17) followed by M3 (634.5 +/- 26) and M1 (612.5 +/- 14 mu g/g d.m.) yogurt. M3 soy yogurt also showed the highest content of total phenolic compounds (5.37 mg/g) and antioxidant activity. The results indicated that functional soy yogurt can be prepared from soybean enriched with glyceollins.