Volatile flavor components in red fermented soybean (Glycine max) curds

Red fermented soybean (Glycine max) curds (FSC) were extracted with a simultaneous steam distillation and extraction (SDE) apparatus and analyzed by gas chromatography-mass spectrometry (GC-MS) and further evaluated by gas chromatography-mass spectrometry-flame ionization detector-olfactometry (GC-MS-FID-O). A combined total of 89 compounds were identified from three samples (A-C). The numbers of components identified (samples A-C) were 87, 85, and 81, respectively, which were divided into 10 compound classes. The quantity of 48 compounds was statistically significant (p < 0.05). Sample B generally had the lowest level, whereas sample C had the higher level of each common component among the samples. GC-MS-FID-O analyses showed that the majority of the fruity, diacetyl, cantaloupe-like odors were eluted early during the run (RI < 1100), followed by the meaty flavor, rosy, and prune-like aromas (RI > 1100). Ethyl 2-methylpropanoate, 2,3-butanedione, ethyl butanoate, ethyl 8-methylbutanoate, 3-(methylthio)propanal, benzeneacetaldehyde, and ethyl 3-phenylpropionate were found to be important common components contributing to the characteristic aroma of red FSCs.