The effect of inoculum types on microbial growth, β-glucan formation and antioxidant activity during tempe fermentation

The aim of the research was to study the effect of inoculum type and fermentation time on microbial growth patterns (yeast, fungi and bacteria), β-glucan formation and antioxidant activity during soybean fermentation into tempe. The research was conducted using factorial Completely Randomized Block Design with 3 replications. The first factor was the types of inoculum: commercial inoculum of tempe, Raprima (3%), a single inoculum of S. cerevisiae (3%), a single inoculum of R. oligosporus (3%), and mixed inoculum of 1.5% S. cerevisiae and 1.5% R. oligosporus. The second factor was the length of fermentation which consisted of 0, 8, 16, 24, 32 and 40 hours at room temperature. Regarding the number of fungi, yeasts and bacteria, the observational data were presented descriptively in the form of graphs, while for the data from the analysis of β-glucan and antioxidant activity, the data obtained were analyzed for variance with analysis of variance (ANOVA) and then analyzed further by the Least Significant Difference (LSD) at the 5% significance level. The results showed that the type of inoculum and duration of fermentation had an effect on increasing the growth of fungi, yeasts and bacteria, as well as increasing β-glucan content and the antioxidant activity of tempe. Yeast growth had a more dominant effect on increasing β-glucan content and antioxidant activity compared to fungi and bacteria. Tempe inoculated with a mixed inoculum of 1.5% R. oligosporus + 1.5% S. cerevisiae, resulted in the highest β-glucan content of 0.58% and the highest antioxidant activity at 82.42%. In conclusion, a mixed inoculum of 1.5% R. oligosporus + 1.5% S. cerevisiae with 36−40 hours of fermentation produced tempe with the highest β-glucan content and antioxidant activity. Therefore, the β-glucan content causes tempe to have better potential health benefits than tempe without the addition of S. cerevisiae.