IMPROVING THE NUTRITIONAL AND FUNCTIONAL QUALITIES OF FERMENTED SOYMILK BY LACTOBACILLUS RHAMNOSUS

Fermentation is widely used to enhance the nutritional and functional qualities of soy products. This study evaluated the improvements in soymilk fermented by Lactobacillus rhamnosus Yoba. Soymilk was fermented at 40°C for 16 hours, and samples were analyzed for proximate and anti-nutrient composition. The amino acid and phenolic acid profiles were evaluated using Gas Chromatography techniques, while the gamma-aminobutyric acid (GABA) and the isoflavone content were evaluated using High Performance Liquid Chromatography. Results showed that fermentation significantly increased fiber (0.89% to 1.48%), protein (3.15% to 5.25%), and carbohydrate (0.46% to 10.64%) contents, while moisture (88.73% to 75.86%) and ash (and 3.24% to 3.00%) contents decreased (p < 0.05). The concentration of six out of the ten anti-nutrients examined namely: Oxalate, Cardiac Glycoside, Phytate, Hemagglutinin, anthocyanin and Cyanogenic glycoside significantly decreased from 0.51mg/g to 0.39mg/g, 6.36% to 5.94%, 0.54% to 0.12%, 0.08mg/kg to 0.05mg/kg, 3.43% to 1.94% and 4.05mg to 3.24mg respectively. Nutritionally, fermentation enhanced six out of the nine essential amino acids namely: histidine, isoleucine, lysine, methionine, threonine, and tryptophan. Fermentation improved GABA from 1.34g/100g to 3.79g/100g. Most free phenolic acids increased, while the glucoside forms of isoflavones were significantly reduced. These findings suggest that fermentation with Lactobacillus rhamnosus substantially improves the nutritional and functional qualities of soymilk, supporting the incorporation of well-documented probiotics into food matrices for health benefits.