Preliminary studies on tempeh flour produced from three different Rhizopus species

Abstract

Tempeh which is culturally an Indonesian food was produced by fermenting soybeans with different Rhizopus species - Rhizopus oryzae, Rhizopus stolonifer and Rhizopus oligosporus. The tempeh was subsequently dried and milled. The tempeh flours were subjected to proximate analysis, physicochemical (total titratable acidity, pH and water absorption capacity) and microbiological tests. Selected minerals such as calcium, potassium, iron and zinc were analyzed. Vitamin contents were evaluated. Sensory evaluation was conducted in order to determine the acceptability of the samples. The statistical analysis was carried out using the Analysis of Variance (ANOVA) at 95% confidence limit and Duncan test. The pH and total titratable acidity ranged from 6.8 to 7.0 and 0.032 to 0.077 g/100 g, respectively. No significant difference existed among the water absorption capacities of the samples. The average percent crude protein was 44.27, 44.62 and 44.85% for the three samples. The fat content ranged from 16.45 to 17.12% while the % crude fibre content ranged from 0.38 to 0.42. There was no statistically significant difference in the Vitamin B2, Vitamin C and Vitamin D content of the samples while a significant difference existed in the Vitamin B1 and Niacin content among the samples. The result of the mineral content analysis revealed that the potassium, iron, zinc and calcium contents ranged from 0.14 to 0.17, 0.011 to 0.014, 0.0046 to 0.0050 and 0.19 and 0.21%, respectively. Yeast and Coliform was not detected in the samples. The total bacterial count ranged from 0.5 × 105 to 1.6 × 105cfu/g, the lactic acid bacteria ranged from 18.0 × 105 to 22.4 × 105cfu/g while the mould count ranged from 0.8 × 105 to 1.4 × 105cfu/g. There was no significant difference in the aroma and texture of the flour samples. The tempeh flour produced using R. oligosporus and the one produced using R. oryzae were compared in terms of colour and overall acceptability.