Characterization of important sulfur and nitrogen compounds in Lang baijiu by application of gas chromatography-olfactometry, flame photometric detection, nitrogen phosphorus detector and odor activity value

The volatile compounds in three Lang baijiu (Honghualangshi, Y1, Langjiulangge, Y2, and Laolangjiu, Y3) were identified by gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), flame photometric detection (FPD), and nitrogen phosphorus detector (NPD) with the aid of stir bar sorptive extraction (SBSE). The results showed that a total of 60, 62, and 61 compounds with aroma contribution were present in samples Y1, Y2, and Y3, respectively. Additionally, the odor activity value (OAV) was used to evaluate the important compounds. The results indicated that 2-methyl-3-furanthiol (OAV: 20-30), 3-mercaporhexyl acetate (OAV: 13-20), beta-damascenone (OAV: 30-57), (E)-2-nonenal (OAV: 9-22), heptanal (OAV: 4-13), hexanal (OAV: 9-12) and 2-isopropyl-3-methoxypyrazine (OAV: 4-14) contributed to the aroma of Lang baijiu. Finally, six compounds (ethyl hexanoate, 2-methyl-3-furanthiol, (E)-2-decenal, guaiacol, 3-mercaporhexyl acetate, and 2-isopropyl-3-methoxypyrazine) with different OAVs were used to determine the effect on the threshold of aromatic reconstitution (AR). It can be seen that ethyl hexanoate, 2-methyl-3-furanthiol, 3-mercaporhexyl acetate, and 2-isopropyl-3-methoxypyrazine could significantly decrease the threshold of AR. The possible reason was that these four compounds had synergistic effects with the aroma compounds in AR. Compared to ethyl hexanoate and 2-methyl-3-furanthiol, the threshold of AR had a slight difference in the presence of (E)-2-decenal in AR. After the addition of guaiacol, the threshold value of AR was significantly increased, indicating a masking effect between guaiacol and the original aroma compounds in AR.