Effect of fermentation on proximate composition, physicochemical and microbial characteristics of pearl millet (Pennisetum glaucum (L.) R. Br.) and Acha (Digitaria exilis (Kippist) Stapf) flour blends

Abstract

The objective of this study was to determine the effect of spontaneous fermentation on proximate composition, physicochemical and microbial characteristics of sprouted millet-acha blends with the aim of producing fermented flour blends for traditional beverage. Pearl millet and acha grains were sprouted, milled and blended into different ratios. The blends were mixed with water, fermented for 72 h and dried in an air-oven. Proximate composition, pH, titratable acidity and microbial profile were determined using suitable methods. Moisture contents ranged from 5.60 to 5.94% and 10.44 to 13.33% for unfermented and fermented flour blends, respectively. Increase in pearl millet proportions significantly decreased (p ≤ 0.05) crude fat, ash, fibre and protein contents of the blends. In contrast, carbohydrate contents increased with increase in pearl millet proportion. Fermentation decreased significantly (p ≤ 0.05) the fat, fibre and carbohydrate contents of the flour blends; whereas ash and protein contents were significantly increased (p ≤ 0.05) with fermentation. pH values decreased with simultaneous increase in titratable acidity during fermentation. A total of 13 bacteria were isolated during fermentation, namely, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus leichmonnii, Lactobacillus cellobiosus, Lactobacillus casei, Pediococcus sp., Streptococcus thermophilus, Micrococcus luteus, Bacillus subtillis, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris. Fermentation has a potential to improve protein and mineral contents of pearl millet-acha flour blends for beverage preparation.