Quality characteristics of steamed rice bread prepared with different contents of proteolytic enzyme

Abstract

The aim of this study was to investigate the quality characteristics of steamed rice bread containing the various contents of protease (0, 0.5, 1.0, and 1.5 % Flavourzyme (R)), pH, and expansion of the dough during different fermentation times (0, 20, and 30 min), and hardness after different storage times (0, 1, 2, and 3 days). When the Flavourzyme (R) contents increased, pH of the dough gradually decreased, but expansion increased up to 30 min of the fermentation. Specific loaf volume was the greatest for steamed rice bread prepared with 1.5 % Flavourzyme (R). In SDS electrophoretic patterns, the band intensity of wheat gluten (P37) decreased by 1.0 and 1.5 % Flavourzyme (R) treatments. The alpha-glutelin of rice protein clearly degraded in the samples prepared with 1.0 and 1.5 % Flavourzyme (R), whereas the band intensity of beta-glutelin decreased only in the sample with 1.5 % Flavourzyme (R). The band intensity of soy lipoxygenase and the 7S globulin fraction (P54) of soy protein decreased in the sample with 0.5 % Flavourzyme (R). The latter showed the highest water-holding capacity and the highest hardness but lowest rate of retrogradation during 3 days of storage. In microstructure of the control, pore size was the smallest and the fewest pores were observed. The greater the contents of Flavourzyme (R), the greater the size and number of pores were observed. Steamed rice bread prepared with 0.5 % Flavourzyme (R) was thought to be optimal due to retarded retrogradation because of the highest water-holding capacity, highest scores of mouthfeel, and overall quality due to greater springiness and cohesiveness.