Development of method for measuring the degree of maceration of soybean fermented with Rhizopus

Abstract

The force-deformation curve of bulk-soybean fermented with Rhizopus could be described by an equation, F=C(Δε)n. The degree of maceration of fermented soybean (a measure of softness) was estimated by the n-value of the power of the equation. The degree of maceration of fermented soybean depended on the Rhizopus strain used. Of the Rhizopus strains tested, Rhizopus oligosporus (TISTR 3001, known as a dominant tempeh processing strain) and Rhizopus sp. LKN (isolated from a tempeh starter) gave high degrees of maceration corresponding to n = 1.3 (initial value of 1.8) and 1.6 (initial value of 1.8) respectively, for 60 h of fermentation of raw soybeans at 30°C. For sterilized soybeans, the Rhizopus oligosporus and Rhizopus sp. LKN gave n-values of 1.5 (initial value of 1.7) and 1.3 (initial value of 1.7) respectively, for 60 h of fermentation at 30°C. N-values less than 1.5 were considered as indicating considerably high degrees of maceration.