Abstract
Natto, a traditional Japanese food product, was prepared from cooked soybeans by fermentation and its odor concentrate was obtained with a simultaneous distillation and extraction system. It was compared to those obtained from soybeans cooked for 0-3, 3-5.5 and 5.5-8hr, respectively, by gas chromatography and gas chromatography-mass spectrometry. In the odor concentrates of the cooked soybeans, hexanal, (E)-2-hexenal and hexanol contributing to the green and grassy odor of soybeans disappeared or decreased while the cooking was in progress. 2-Pentylfuran and l-octen-3-ol contributing to the beany odor remained even if the soybeans were cooked for 8 hr and were fermented into Natto. In the odor concentrate of Natto, pyrazines and sulfur containing compounds were important contributors to the characteristic odor of Natto. As the beany odor was not detected for Natto, it was concluded that the pyrazines and sulfur containing compounds cause the characteristic odor of Natto and mask the beany odor.
