Penetration of Rhizopus oligosporus into Soybeans in Tempeh.

Histological observations were made on the penetration of hyphae of Rhizopus oligosporus into soybean cotyledons in tempeh, an Indonesian soybean food. Hyphal penetrations averaged one per 1,400 mum (+/-390 mum) on the curved (outer) cotyledon surface and one per 1,010 mum (+/-340 mum) on the flat (inner) one. Hyphae infiltrated to a depth of 742 mum, or about 25% of the average width of a soybean cotyledon. This previously unreported degree of penetration offers partial explanation for the rapid physical and chemical changes in soybeans during tempeh fermentation.