Evaluation of Physicochemical and Nutritional Contents in Soybean Fermented Food Tempeh by Rhizopus oligosporus

Abstract

Evaluation of Physicochemical and Nutritional Contents in Soybean Fermented Food Tempeh by Rhizopus oligosporus Rhizopus oligosporus is considered as most preferred species in tempeh fermentation among the tempeh culture on top of it is most widely used and one of the known molds in vegetal substrates fermentation. A fermented product “Tempeh” was prepared using mixed culture fermentation of soaked and cooked soybeans or cereal grains by means of diverse group of microflora like bacteria, yeasts and molds. Rhizopus oligosporus, NRRL-2710 was used for the preparation of tempeh. The culture was maintained on potato dextrose agar media prepared by adding 3.8 grams PDA in 100 ml distilled water followed by heating. The culture was incubated at 30-37ºC in an oven for 24 hours and then stored in refrigerator at 4ºC. Soya beans soaked overnight were boiled for 10-15 minutes. The hot beans were spread in a thin layer and cooled to room temperature then they were inoculated with a spore suspension of R. oligosporus. The inoculated soya beans were packed firmly in perforated plastic bags, and incubated at 30ºC for 24 h, yielding fresh tempeh. The physicochemical characteristics and nutritional content in soybean fermented food tempeh were then assessed. Filamentous fungi are used in the preparation of fermented foods to improve the taste and the nutritional value of the product. The aim of the study was to verify the viability of Rhizopus oligosporus in soybean fermented food tempeh. Tempeh is a striking product from sensual, health and cost-effective points of view. The present work determined the sensory analysis and nutritional viability evaluated the effects of pH, temperature, relative humidity, aeration, moisture and ash contents, inoculums size, shelf life and its mineral values including protein, carbohydrate and lipid content. The mold growth was rapid at 30ºC. When R. oligosporus was inoculated at approximately 104 spores/g moist substrate, a tempeh cake with dense mycelial growth was obtained.