"Souring and starch behaviour during co -fermentation of cassava and soybean into gari ‘farina’"

Abstract

Investigations were conducted to determine changes in souring/acidification and starch behaviour during co-fermentation of cassava and soybean into gari, ‘farina’ an African fermented product. A 3 x 4 factorial experiment was performed with fermentation time (0, 24 and 48 h) and soybean concentration (0, 10, 20 and 30%) as variables. Titratable acidity, pH and starch content were studied using standard analytical methods. Starch breakdown and pasting characteristics were also evaluated. The results revealed that pH decreased with concomitant increases in titratable acidity during co-fermentation of the cassava dough. Soy - fortification up to 30% caused significant (p<0.05) effects on the pH, titratable acidity and starch content during the fermentation period with only minimal and insignificant (p<0.05) effect noted at 20% soy level. Fermentation caused significant differences (p<0.05) in the pH, titratable acidity and starch concentration. Starch content decreased from 69.8% to 60.4% within the 48 h fermentation time in the unfortified sample with similar trends noted at all levels of fortification. Starch pasting characteristics showed that the pasting temperature significantly increased with increasing fermentation time and soybean concentration. Contrary to this, viscosity at 95°C and at 50°C HOLD decreased with increasing fermentation time and soybean concentration. Peak viscosity decreased from 1150 BU to 820 BU and 750 BU after 48 hours of fermentation, with 0% and 30% soybean levels respectively. Cassava could be co-fermented with soybean up to 20% concentration during gari processing, without significant effect on its process and product quality characteristics.