Development of natto fermented soybean milk andevaluation on its quality

• Main Authors: Hsin-Jung Ho, 何幸容
• Other Authors: Chi-Fai Chau
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/66557929906444016912

碩士 === 國立中興大學 === 食品暨應用生物科技學系 === 97 === Soybean has been used for thousand years because it is cheap and nutritious. The nutrition value and utilization of soybean could be improved by fermentation with B. subtilis var. natto which is famous for its health benefits. In this study, 3 commercially available B. subtilis var. natto (BSN W8, BSN E7, and BSN 520) were used to ferment soybean milk. The appearance of colony, bacterial count, source of material, optimum carbon amount, and physicochemical properties were evaluated. Besides the abovementioned, the changes in nutritional values and functional by-products such as free amino acid, isoflavone, nattokinase, γ-GABA, and vitamin B2 were analyzed in this study. The quality of fermented soybean milk was also evaluated during storage under suitable condition. In this study, it was aimed to develop a novel soybean milk with health benefits. Three commercially available B. subtilis var. natto (BSN W8, BSN E7, and BSN 520) were identified by VITEK. Our results showed that BSN W8 could provide the highest bacterial count, mild pH drops, less production of acids, and the most acceptable taste by using suitable soybean medium (inoculation dosage at 0.025%(w/v) and 5% sugar(w/w) and being fermented at 40。C for 12 hr. Comparing the analytical results of the fermented soybean milks prepared by different B. subtilis var. natto (BSN W8, BSN E7, and BSN 520), there was no significant difference in their nutritional values. However, apparent differences in the functional by-products among different strains were noted. Regarding the free amino acid, 16 amino acids (9 of them were essential one) were found in the three fermented soybean milks, with BSN W8 having with the highest amount of total free amino acids (54.2 mg/100 g). For the γ-GABA, no apparent difference was observed between the soybean milks before and after fermentation. The total isoflavone was 35.6 mg/100 g before fermentation, but it was changed to a level of 24.7-34.8 mg/100 g depending on the strains after fermentation. The amounts of nattokinase formed by the three B. subtilis var. natto after fermentationr were about 6.19-6.72 FU/100 g. with BSN W8 having the highest nattokinase content (6.72 FU/mL) In summary, our results demoustrated that, BSN W8 had a better performance among the three B. subtilis var. natto. In the shelf life test (stored at 5。C for 18 days), the results showed that pH dropped to 5.11. During storage, sour taste was found to be increased without unpleasant flavor. The bacterial population was 7.92 log CFU/mL after being stored.