An Evaluation of Shelf Life of Fermented Soybean (Soy “Daddawa”) Under Different Storage Conditions

Abstract

Fresh fermented soybean cake (soy ’’Daddawa’’) is highly perishable, limiting its shelf life, consumer acceptability and commercialization. This study evaluated the effects of different storage environments on the shelf life and quality of soy ‘’Daddawa’’. Two laboratory-produced samples (one inoculated with Bacillus subtilis and one uninoculated control) and a commercially purchased sample were investigated. Following fermentation, proximate composition was determined, and samples were stored in an oven (low-moisture) and humid conditions for 12 days. Temperature, relative humidity, pH, aerobic mesophilic bacterial count, sensory quality, and bacterial contaminants were monitored throughout storage. The oven maintained a constant temperature of 27 ± 0.00°C throughout the 12-day storage period, whereas the ambient storage temperature gradually increased to 28.33 ± 0.33°C by day six of storage. No significant differences (p > 0.05) were observed in proximate composition among the fermented samples; however, the B. subtilis-inoculated sample had the highest protein content (45.28%). Relative humidity decreased from 21% to 10% under oven storage and from 48.33% to 40.67% under humid conditions, while pH increased progressively, reaching 8.17 in oven-stored samples. Aerobic mesophilic bacterial counts increased during storage without significant differences (p > 0.05) among treatments. Freshly fermented laboratory-produced samples achieved 100% consumer acceptance, with the inoculated sample receiving the highest sensory score (8.6 ± 0.6). Sensory acceptability declined markedly after 6 days and was completely lost by day 12. Escherichia coli, Staphylococcus aureus, and Salmonella spp. were detected in stored samples. These findings show that Moisture-free storage prevents “Daddawa” spoilage.