Analysis of Aroma Components of Five Steamed Grains for Production of Nongxiangxing Baijiu by Simultaneous Distillation and Extraction Combined with Gas Chromatography-Mass Spectrometry

Simultaneous distillation and extraction (SDE) combined with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile aroma compounds of steamed five grains for the production of Nongxiangxing baijiu: sorghum, wheat, maize, glutinous rice and rice as well as their mixture. A total of 153 compounds were identified from the five grains, of which 108, 93, 93, 66 and 66 were found in sorghum, wheat, maize, glutinous rice and rice, respectively. The identified compounds were dominated by aldehydes, alcohols, ketones, aromatic compounds and esters. Totally 140 compounds were identified in the mixed grain sample by dual-column qualitative analysis. A total of 29 odor active compounds were identified by gas chromatography-olfactory-mass spectrometry (GC-O-MS). The effects of different compounds on the overall flavor of steamed grains were evaluated by using aroma extract dilution analysis (AEDA) and odor activity value (OAV). The OAVs of 17 compounds including benzylthiol, (E,E)-2,4-decadienal, (E)-2-nonenal, nonanal, hexanal, octanal, (E)-2-octenal, (E,E)-2,6-nonadienal, 1-heptanol, (E)-2-decenal, (E,E)-2,4-nonadienal, phenylacetaldehyde, 4-ethyl-2-methoxyphenol, ethyl hexanoate, geranyl acetone, ethyl octanoate and vanillin were larger than 1, which were considered as important compounds contributing to grain flavor. Benzylthiol and (E,E)-2,6-nonadienal were identified as important flavor compounds in steamed grains for the first time.