Effect of substrate type and incubation time on the microbial viability of instant starter for premium tempeh

Premium tempeh starter is a tempeh starter containing a mixed inoculum of Rhizopus oligosporus and Saccharomyces cerevisiae. Previously, premium tempeh starter was made in the form of liquid culture. This study aims to produce premium tempeh starter in powder form with the best type of substrate and incubation time so that it can be used practically. In this study, the effect of substrate type and incubation time on microbial viability of instant premium tempeh starter was studied. The study was arranged in a Completely Randomized Block Design with two factors and three replications. The first factor was the type of substrate: tapioca flour and rice flour, while the second factor was the incubation time at room temperature: 0, 24, 48, 72, 96 and 120 hours. The instant premium tempeh starter was analyzed for pH value, water content, number of fungi, yeast and bacteria. The microbial viability of tempeh starter was indicated by the growth of fungi, yeast and bacteria during incubation. The data obtained were analyzed by analysis of variance and further tested with the Honest Significant Difference (HSD) test at a 5% significance level. The results showed that rice flour and incubation time of 96 hours produced the best premium tempeh instant starter with the number of fungi of 9.02 Log CFU/g, 9.17 Log CFU/g yeast, 7.81 Log CFU/g bacteria, pH 4.2 and 7.75% water content. Tempeh made using the best premium tempeh instant starter has a chemical composition in accordance with the tempeh product standard (SNI 3144:2015).