B-group vitamin and mineral contents of soybeans during kinema production

Concentrations of several B-group vitamins, determined by high-performance liquid chromatography (HPLC), and minerals, determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), in soybeans during different kinema production stages were compared. After soaking soybeans in water, thiamine (B₁) content decreased, whereas riboflavin (B₂) content remained unchanged. Cooking had no influence on the B₁ content, but it enhanced the level of B₂ and niacin (B₃). Incubation of beans at 37°C for 48 h, when mixed with Bacillus subtilis, caused an increase in concentration of both B₁ and B₂. Vitamin B₁ levels decreased when either Enterococcus faecium accompanied B subtilis or the temperature was elevated for 18 h fermentation. Traditionally prepared kinema contained 8 mg B₁, 12 mg B₂, 45 mg B₃, 683 mg Ca, 4 mg Cu, 18 mg Fe, 494 mg Mg, 10 mg Mn, 1257 mg P, 2077 mg K, 13 mg Zn and <0·5 mg of Cd, Cr, Pb, Ni and Na per kg dry matter. While the vitamin B₁ content was significantly (P<0·05) higher, the contents of vitamins B₂ and B₃ were significantly (P<0·05) lower in raw soybeans than those in kinema. Mineral concentrations were 3·1–8·3 times higher in raw soybeans than in kinema. © 1998 Society of Chemical Industry.