Changes in the contents of fat-soluble vitamins and provitamins during tempe fermentation

The content and formation of fat-soluble vitamins and provitamins during tempe fermentation was studied with 14 different strains of Rhizopus sp. All strains investigated form carotenoids in small amounts during fermentation, but beta-carotene formation was only found in fermentations with six Rhizopus strains. The highest increase of beta-carotene production was to be seen from 34 to 48 h of fermentation. Soybean seeds did not contain ergosterol in detectable amounts. Ergosterol was produced by all Rhizopus strains in concentrations of up to 750 microg g(-1) tempe dry weight (dw) during a 34 h fermentation period and of up to 1610 microg g(-1) tempe dw during a 96 h fermentation period. The amounts of gamma-tocopherol in soybeans ranged from 192.4 to 231.8 microg g(-1) dw. Soybean seeds contained only free, not esterified tocopherols. During fermentation the total amount of vitamin E remained constant but the content of free tocopherols decreased. The content of vitamin K1 in soybeans is not strongly effected by tempe fermentation with pure cultures of Rhizopus sp.