Materials and Methods
Materials
Bran from rice variety MR 219 was obtained from KBB Sekinchan, Malaysia. Commercial baker’s yeast (Eagle QS6540 2801 0001, China) was purchased from a supermarket in South City Serdang, Selangor Malaysia.
Optimization of rice bran fermentation conditions for extraction of protein concentrate
The effect of three independent variables x1 (fermentation temperature), x2 (yeast concentration) and x3 (fermentation time) on protein yield (Y1) was evaluated using response surface methodology (RSM). A central composite design (CCD) was used to study the main and combined effects of fermentation process variables on the protein yield in order to create model between the variables; and use variables to optimize rice bran fermentation conditions for extraction of protein concentrate. Twenty runs based on CCD and six center points with three independent variables were used (Table 1). The independent variables range studied were fermentation temperature (25 to 35°C), yeast concentration (1 to 5%) and fermentation time (10 to 24 h). Based on the fermentation conditions as specified in the RSM design (Table 1), 100 g of rice bran, 350 ml of water and a specific amount of baker’s yeast (based on the concentration specified in the RSM design) was mixed in a 1000 ml beaker and fermented according to the experimental design in a fermenting chamber (Binder KBF-240 Germany) to obtain yeast fermented rice bran batter. Fermented rice bran batter was dried in an air oven at 45 °C for 6 h and then ground to pass 100 μm sieve size to obtain yeast fermented rice bran flour (YFRBF).