Formulation and development of peanut-based ready-to-use therapeutic foods for malnourished pregnant women in Mali

Abstract

Koji are solid-state fermentation products made by inoculating steamed grains with the spores of fungi, particularly Aspergillus spp. This research was undertaken to identify the fermentation and storage conditions optimal for the production and maintenance of selected hydrolytic enzymes, such as α-amylase and protease, in koji. Steamed rice and barley were inoculated with 2 X 10 11 Aspergillus oryzae spores per kg of grains and fermented for 118 h in a growth chamber at 28-32° C with controlled relative humidities. Samples were drawn periodically during fermentation and storage at -20, 4, or 32 °C, and α-amylase and protease activity, mold counts, aw, moisture contents, and pH of collected samples were determined. It was observed that the aw, moisture contents, and pH of the koji were influenced by the duration of fermentation and temperature of storage. The α-amylase activity of both koji increased as the populations of A. oryzae increased during the exponential growth phase. The enzyme activity of barley koji was significantly higher than that of rice koji, reaching a peak activity of 211.87 or 116.57 U at 46 and 58 h, respectively, into the fermentation process. The enzyme activity in both products started to decrease once the mold culture entered the stationary growth phase. The protease activities of both koji were low and remained relatively stable during fermentation and storage. These results suggest that rice and barley koji can be used as sources of α-amylase and desired enzyme activity can be achieved by controlling the fermentation and storage conditions.