Nutritional profile and antioxidant capacities of fermented millet and sorghum gruels using lactic acid bacteria and yeasts

Abstract

ABSTRACT Predominant lactic acid bacteria and yeasts isolated during the spontaneous fermentation of millet and sorghum were investigated for technological characteristics and food safety. Nutritional profile and antioxidant capacities were monitored. The pH reduced in both malted millet and sorghum slurries to 3.31 and 3.45 respectively. Lactobacillus fermentum KL4, Lb. plantarum MOBL1, Candida tropicalis OBY6 and C. tropicalis MKY6 were selected for high production of lactic acid, diacetyl, and hydrogen peroxide. These strains were safe for use as starter cultures. Starter culture fermented malted millet and sorghum slurries possessed significantly (p < .05) higher niacin and riboflavin content, total phenolics and flavonoid contents. Fermented malted millet slurry (MKC) demonstrated the highest magnesium and potassium contents of 114.2 and 212.13 mg/100 g while spontaneously fermented unmalted sorghum slurry (OBS) the least of 40.2 and 82.3 mg/100 g respectively. Fermented malted millet slurry (MKC) possessed the highest DPPH scavenging activity of 98.2%, while the unmalted spontaneous sorghum slurry (OBS) the least of 60.3%. For ferric reducing antioxidant power, the malted starter culture fermented sorghum slurry (MOBC) displayed the highest value of 998.3 mg/g AAE while unmalted spontaneous millet slurry (KS) the least of 260.2 mg/g AAE after 72 h fermentation time, respectively. Unmalted starter-produced Ogi-baba (OBC) exhibited the significantly highest overall sensory acceptability of 7.50 while the least was the spontaneous fermented malted Ogi-baba (MOBS) with a value of 5.10 (p < .05). The results indicated that Koko and Ogi-baba from whole grains are important sources of nutraceuticals and promising fermented cereal gruels.