Changes in the Volatile Components of "Natto" during Manufacturing and Storage (Studies on "Natto", Part IV) Akishige KANNO* and Haruki TAKAMATSU* * Asahi Shokuhin Co ., Ltd 180-2, Wado, Ushibori-machi, Namehata-gun, Ibaraki, 311-24 Acetoin and 2, 3-butanediol were found to accumulate and reach a maximum in "natto"
A study was undertaken to determine the effects of Natto and steamed soybeans on body growth and the intestinal microflora of rats. Male Wistar rats (5 weeks of age and weighting 80g) were fed a control diet containing no Natto and steamed soybeans and an experimental diet containing either 10% Natto or 8.9% steamed soybeans for 31 days. Protein levels in the 3 groups were the same (15%). The results obtained were as follows: 1) Body weight gain during 31 days did not differ among the groups fed the various diets.2) The retroperitoneal fat tissue weight per carcass weight (%) in the Natto and steamed soybean groups decreased.3) The nitrogen balance of the Natto and steamed soybean groups increased. 4) The Natto and steamed soybean groups showed a tendency to increase in the length of the small intestine and thiamin content in the cecum. In the cecum, the pH and number of E. coli per g were decreased in the Natto and steamed soybean groups.
Acetoin, 2, 3-butanediol, acetic acid, propionic acid, iso-butyric acid, 2-methylbutyric acid and 3-methylbutyric acid in 34 samples of "natto" (fermentated soybean food by Bacillus natto) and 11 samples of "hikiwari-natto" (a variety of "natto" made of soybean grits) from 8 makers were determined by gas chromatographic analysis. Neutral compounds were extracted by Extrelut pre-packed column 20 with methylacetate: ethyl alcohol (9:1) from the extract of "natto" with a cupric sulfate solution. Volatile acids were collected by steam distilation under acidic condition with tartaric acid from the extract.The extract efficiencies of volatile components were above 90% when prepared with these methods.The contents of those compounds were varied among the samples, and the butyric acid on dry base, respectively. High positive correlation coefficients (up to 0.82) were observed between acetoin and 2, 3-butanediol contents, and among those of the three branched chain acids. 2-methylbutyric acid which newly detected in "natto" was identified as S-(+)-2-methylbutyric acid by the polarimetric analysis.
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