Comparative study on the growth rate and physico-chemical properties of yeast (Saccharomyces cerevisiae) using Zea mays l. (corn) and Triticum asetivum l. (wheat) flour substrates

Abstract

Significance of yeasts in food technology as well as in human nutrition, as alternative sources of protein to cover the demands in a world of low agricultural production and rapidly increasing population, makes the production of food grade yeasts important. The comparative study on the growth rate and physicochemical properties of yeast was carried out using corn and wheat flour substrates. 50 g of wheat and corn flour each was weighed into a calibrated culture plastic rubber. 120 ml of distilled water was added with 5 ml of lemon juice. The sample was stirred and kept under room temperature at 26°C. The growth of the yeast were observed every three days for two weeks and recorded in millimetre. Yeast (Saccharomyces cerevisiae) culture grown using corn flour gave a mean growth of 12.18±0.38 for the first week and 15.24±1.21 for the second week. On the other hand, the growth of yeast produced from wheat flour gave 8.29±0.35 and 10.46±1.23 for first and second week respectively. The result also showed that yeast produced from corn flour grew rapidly than the wheat flour. The acid value of yeast produced from corn flour was 17.95 mgKOH/g, saponification value of 9.5 mgKOH/g, ester value of 164.37 mgKOH/g, iodine value of 87.63 gI2/100g, peroxide value of 16.0 mEq/kg, free fatty-acid of 9.02%, refractive index of 1.50, specific gravity of 0.902, density of 5 g/cm3 and pH of 5, while yeast produced from wheat flour had an acid value of 14.3 mgKOH/g, saponification value of 5.3 mgKOH/g, ester value of 152.1 mgKOH/g, iodine value of 66.0 gI2/100g, peroxide value of 10.1 mEq/kg, free fatty-acid of 5.2%, refractive index of 0.6, specific gravity of 0.561, density of 3.2 g/cm3 and pH of 5. The result showed that the physico-chemical properties of yeast produced from corn flour were higher than that produced from wheat flour with p value of 0.001.