Storage Temperature And Quality Changes Of Natto

Storage conditions significantly affect the quality of natto, a fermented soybean food produced with Bacillus subtilis (natto). We investigated the relationship between the quality of natto and the storage temperature. Manufactured natto samples were stored at 5-20 degrees C for 20 days, and on every 5th day we evaluated the following: 1) viable bacterial number, 2) ammonia nitrogen, 3) free amino acids, 4) gammapolyglutamic acid (gamma-PGA), 5) hardness, and 6) color of soybean grains. During storage, natto products exhibited damage, especially when stored at 20 degrees C. Natto products were scored based on these quality indicators, and natto stored at 5 degrees C for 10 days or at 10 degrees C for 5 days had similar quality scores. Overseas export of natto is gradually increasing. The quality score proposed in this study is a basic indicator that can be used to rule out inferior products, and this will help to grow the natto market worldwide and facilitate distribution through a cold chain.