Hibiscusleaves for the manufacture of usar, a traditional inoculum for tempe

Abstract

AbstractTempe is an Indonesian proteinaecous food produced from soya beans by fermentation mainly byRhizopus spp. A common traditional inoculum for this fermentation is usar, consisting of heavily sporulatedRhizopusspp of which the mycelium, grown on added and inoculated soya beans, adheres to leaves of the waru tree (Hibiscusspp). A description of various waru trees is given together with their suitability for usar making. The epiphytic fungi on waru trees of various geographical origins (Indonesia, Africa, The Netherlands) were investigated.Cladosporiumspp were present on all the leaves sampled. However,Rhizopusspp predominated over the other fungi encountered on the Indonesian leaves. Experimental incubation of leaves with and without added soya beans showed that the epiphytic fungi are less competitive thanRhizopusspp and will not interfere if normal usar‐making conditions are observed. Experiments with alternative attachment surfaces (paper, a textile) indicated that the waru leaves do not provide environmental selectivity through growth‐inhibiting substances, but that they serve mainly as a convenient attachment surface with moisture‐retaining capacity while providing adequate aeration for fungal development.