OPTIMIZATION PROCESS OF ROASTED BROKEN BLACK SOYBEAN NATTO USING RESPONSE SURFACE METHODOLOGY

ABSTRACT Response surface methodology (RSM) was used to determine the optimum combinations of three factors, roasting time (0–8 min), inoculated bacteria populations (101–105 cells/100 g) and fermentation time (6–30 h), for producing roasted broken black soybean natto. All of the responses (hardness, viscosity and ammonia content) were significantly affected by the three factors. Fermentation time was the most important factor affecting the quality of roasted broken black soybean natto. Optimum combinations were roasting time 1.6–4.0 min, inoculated bacteria populations 103 cells/100 g and fermentation time 23.4–27.0 h. PRACTICAL APPLICATIONS Natto is a traditional Japanese fermentation food. Black soybean is a black hulled soybean with seed coats containing anthocyanin. Recently, the physiological properties of natto and black soybean were noticed by the scientist. RSM enables reducing the number of experimental trials needed to evaluate multiple parameters and has been widely applied for optimizing processes in the food industry. Natto studies had been done by many researchers but roasted broken black soybean natto had not been researched by other laboratories. As the natto produce has a characteristic odor and musty flavor which was disliked by people, roasted broken beans will have better sensory characteristics and higher antioxidant activity. In this work, we have established the optimum conditions (roasting time, inoculated bacteria populations and fermentation time) for processing roasted broken black soybean natto using RSM. The results provide useful information for the industrial application of natto and black soybean.