Optimizing process of black soybean natto

• Main Authors: Sue-Tzu Kuo, 郭淑姿
• Other Authors: Kai-Ts''''ung Yang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/36284153072148379522

碩士 === 中國文化大學 === 生活應用科學研究所 === 91 === Natto is a traditional fermented soybean food in Japan, which is made by fermenting steamed soybean with Bacillus natto. It is characterized by unique viscous material and flavor, and has various physiological functions. In this study, we used green-cotylendon black soybean (Tainan No. 3) as row material which is better than soybean at biological activities, and using response surface methodology (RSM) to determine the physical properties (hardness, viscosity and color), nitrogen compounds (TCA-soluble nitrogen, ammonia nitrogen, solubilization ratio of protein and hydrolysis ratio of protein) and antioxidative properties (DPPH free radical scavenging activity, total polyphenols and anthocyanin content) of the black soybean natto at different cooking time (40~120 min), inoculated bacteria populations (101~109 cells/100g) and fermentation time (12~36 hr) to obtain the optimum process of black soybean natto. Furthermore, manufacturing black soybean natto with the optimizing process to investigate the effects of processing steps (soaking, cooking and fermenting) on original soybean. In addition, comparing the black soybean natto with commercial natto to understand the differences between both of them. These results were as follows: 1. The optimizing process of black soybean natto is: Cooking time for 110 minutes, bacteria inoculated populations at 102~ 103 cells/100g, fermentation time for 30~33 hours. 2. The physical properties of natto--hardness, viscosity and redness were affected by cooking time, inoculated bacteria populations and fermentation time at the same time. The hardness decreased with cooking time prolonged, but increased at inadequate or excessive degree of fermentation. It is thought that the variation was influenced by the fermentation stage it had reached. The viscosity is maximum at the longer cooking time and fermentation time, and the less inoculated bacteria populations. However, viscosity decreased at excessive degree of fermentation. As the changes of color, cooking for 80 minutes appeared the maximum redness, but decreased at inadequate or excessive degree of cooking. 3. The TCA-soluble nitrogen of natto changed remarkably during fermentation stage with different processing condition, and was affected by the inoculated bacteria populations. It is thought that the content was affected by the degree of bacteria growth by using soybean composition. However, the solubilization ratio of protein is maximum at longer cooking time and fermentation time, but the change of the hydrolysis ratio of protein was insignificant. 4. About the antioxidative properties of black soybean natto, the DPPH free radical scavenging activity appeared the best at suitable cooking time and fermentation time, and with the more inoculated bacteria populations. 5. Natto made from the green-cotylendon black soybean by fermentation compared with original black soybean, soaked black soybean and cooked black soybean has higher moisture, viscosity, brightness(L value), redness (+a value) and yellowness(+b value). 6. The black soybean natto had higher TCA-soluble nitrogen, ammonia nitrogen and solubilization ratio of protein than unfermented cooked black soybean, but were lower than the commercial natto product. However, during fermentation process bacteria probably acted on the water-soluble nitrogen material and caused the TCA-soluble nitrogen and ammonia nitrogen increase, and furthermore affected the pH value of natto and to appear the color of redness and yellowness of black soybean natto. 7. Natto made from the green-cotylendon black soybean by fermentation increased the DPPH free radical scavenging activity under the condition that total polyphenol and anthocyanin content did not increase. It is thought that the non-water-soluble nitrogen and non-protein nitrogen of natto product are directly or indirectly beneficial to promote the DPPH radical scavenging activity.