Abstract
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 deter- mined 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 ranges were 0-1646.5mg/100g (mean value, 319.5)in acetoin, 0-164.3 (38.1) in 2, 3-butanediol, 116.1-921.0 (378.0) in acetic acid, 1.5-14.2 (7.9) in propionic acid, 20.2-286.5 (123.5) in iso-butyric acid, 5.3-332.5 (104.4) in 2-methylbutyric acid, and trace-375.0 (77.0) in 3-methylbutyric 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.
