Control of ammonia formation during Bacillus subtilis fermentation of legumes

The control of ammonia formation during the Bacillus subtilis fermentation of autoclaved, roasted soybean cotyledons (Glycine max) and of autoclaved African locust bean cotyledons (Parkia spp.) was investigated. Addition of NaCl, 1.5 mol (kg wet cotyledons)−1, part way through the fermentation inhibited ammonia formation and softening of the cotyledons. Addition of glycerol, 1.7 mol (kg wet cotyledons)−1 part way through the fermentation inhibited alkalinisation and ammonia formation while allowing enzymic activity and softening of the cotyledons to continue. Restriction of the oxygen supply by incubating the cotyledons in a sealed container also prevented excessive ammonia production and increase in pH value. Fermentations conducted in sealed containers with an air to cotyledons ratio of approximately 130–175 ml air (g wet cotyledons)−1 supported good microbial growth and proteolysis without the formation of detectable ammonia aroma.