Effect of Thermal Processing on the Nutritional Status of Soy Milks and Yoghurts Produced by Enhanced Spontaneous Fermentation

Abstract

This research was carried out to determine the effects of thermal process of boiling of soy bean seeds on the nutritional status of soy milk and soy yoghurt produced by fermentation. The soybean seeds were de-hulled, boiled and thermally processed to soymilk. Food sweetener (Glucose -D), cassava stabilizer and starter cultures were added to the samples to enhance the spontaneous fermentation. Staphylococcus aureus, Bacillus spp, Escherichia coli, Streptococcus Lactobacillus spp, Aspergillus spp and Saccharomyces spp were isolated from the fermenting samples. The proximate composition showed that the soy yoghurt had more protein content than soymilk while the soymilk had more crude fiber, moisture content, fat content, ash content and carbohydrate. The soy yoghurt was more acidic pH 3.7 than the soy milk pH 6.4. The acidic nature of the soy yoghurt together with other metabolites of Lactic acid bacteria prevented the continued growth of food borne pathogens and spoilers thus ensuring the safety of soy yoghurt. Soy yoghurt can be used as a close substitute for cow milk which is relatively expensive to the rural dwellers.