Effect of salt on the fermentation of soybean (Glycine max) into daddawa using Bacillus subtilis as starter culture

Abstract

Previous studies showed that 1% salt improved the organoleptic attributes of traditional fermented daddawa. Also, Bacillus subtilis as a monoculture starter produced daddawa of same quality with traditional daddawa. The aim of this study was to investigate the effect of 1% salt on some biochemical changes occurring in the fermentation of soybean into daddawa using Bacillus subtilis as starter. Viable cell count of Bacillus subtilis increased with fermentation and was significantly (P<0.05) higher in 1% salted daddawa. The pH value increased with fermentation with no significant difference between the salt free and 1% salted daddawa after 24 h of fermentation. Ammonia concentration increased in both fermentations with higher values in 1% salted daddawa. Proteolytic activity which increased rapidly in the first 48 h and dropped giving higher amounts of free amino acids with fermentation was also higher in 1% salted daddawa. The total soluble sugars decreased in both fermentations with significantly lower levels in 1% salted daddawa after 24 h of fermentation. Although there was no significant difference in the organoleptic properties of salt free and 1% salted daddawa, the panelist showed preference for 1% salted daddawa. Key words: Bacillus subtilis, biochemical changes, fermentation, organoleptic quality, salt, soy-daddawa.