Effects of Fermentation on Nutritional and Functional Properties of Soybean, Maize, and Germinated Sorghum Composite Flour

Abstract

Sorghum germination resulted in a substantial tannin loss (95.7 %). Proximate composition, titratable acidity, pasting properties, in vitro protein digestibility, and protein solubility were studied post fermentation (Saccharomyces Cerevisiae) of the blended soybean, maize, and germinated sorghum flours. The pH progressively decreased with fermentation time, while titratable acidity increased from 0.029 to 0.118 ml/ml. Crude protein content increased with fermentation (251.7-274.8 mg/g) as a result of a shift in the dry matter composition. In-vitro protein digestibility markedly increased (12 %) as a result of fermentation. Protein solubility curves were above 30% of which highest for both fermented (12 and 24 hours) and unfermented composite flours were at pH 12 (51.77-77.64%) and lowest at pH 4 (30.31-35.98%). SDS-PAGE showed that protein hydrolysis occurred during fermentation over 12 and 24 hours. Unfermented composite flour was potentially stable as food ingredient due to its pasting stability, but the fermented flour low viscosity potential was preferred in this study as more flour will be used during porridge making, hence giving a food with a high nutrient density.