The Important Odorants Of Qingke Liquor And The Aroma Compounds In Its Fermented Grains

Qingke liquor is a kind of light aroma type liquor mainly produced in highland areas ofChina, especially in Qinghai province and Tibet region. It gives a pleasant flavor characterizeof highland barley aroma. Different from other light aroma type liquors, the main rawmaterials for Qingke liquor production is highland barley, and it produces four runs of liquorduring the fermentation process. The fresh distillates from each runs of fermented grains aredistilled out through four cleaning of steamed clean-burning technics. During thedistillation process, a portion of the heads and the ends of distillates are moved out to balancethe liquor quality. Then the fresh distillates are aged for a certain time and blended to finishedproducts. Due to its special raw materials and fermentation technics, Qingke liquor formed apeculiar flavor differing from other light aroma type liquors. At present, however, there islittle research carried out to study the aroma compounds in Qingke liquor, so it is still unclearabout its important aroma constituents. Thus leads to a lack of theoretical direction for Qingkeliquor production and also a difficulty to maintain the production stability. So, in this paper,the volatile aroma compounds of Qingke liquor and its fermented grains were analyzed. Themain contents are as follows:(1) By gas chromatography olfactometry (GC-O) and gas chromatography massspectrometry (GC-MS) techniques, a total of111aroma compounds in Qingke liquors wereidentified. Among them,20compounds such as ethyl Z-4-decenoate,(E,Z)-2,6-Nonadienal,and isophorone were not repored before, and ethyl octanoate,2-phenylethanol,3-methylbutanol, β-damascenone, butanoic acid, and3-methylbutanoic acid had the higheraroma intensities.(2) By application of the headspace solid phase microextraction (HS-SPME) and theliquid liquid microextraction (LLME) methods coupled with GC MS and gas chromatographwith flame ionization detector (GC-FID), a total of105aroma compounds were quantified inQingke liquors (including base liquors and finished liquors). Among them, esters, alcohols,and acids had greater concentrations, especially for ethyl acetate, ethyl lactate, ethyl butanoate,acetic acid,1-propanol,3-methylbutanoic acid, and acetal. In addition, aroma compounds inthe heads, middle, and ends of distillates from different runs of fermentation were furthercompared.(3) Based on the quantitative results and relevant thresholds, odor activity values (OAVs)of the aroma compounds were calculate to reveal their contributions to the overall aroma.3-Methylbutanal (OAV>10000in base liquor) and acetal (OAV>5000in finished liquor,except for bdzf-tf liquor) were confirmed as the most important aroma compounds for Qingkebase liquor and finished liquor respectively. Additionally, OAVs of ethyl butanoate, ethyloctanoate, ethyl pentanoate, ethyl3-methylbutanoate, ethyl2-methylbutanoate,1-octen-3-ol,3-methylbutyl acetate, and2-methylpropanol were higher than1000, therefore, thesecompounds had very important contributions to the overall aroma of Qingke liquor.Compounds as ethyl2-methylpropanoate, ethyl hexanoate, dimethyl trisulfide, ethyl3-phenylpropanoate, β-damascenone, acetic acid,(E,Z)-2,6-Nonadienal,3-methylbutyl butanoate and ethyl acetate had somewhat lower OAVs between100and1000, they were alsothe important aroma contributors to Qingke liquor.(4) Aroma compounds in Qingke liquor fermented grains of different fermentation timewere studied, and their content variations were analyzed, especially for the important aromacompounds determined in liquors. Acetal reached the highest concentration till the fifth day offermentation, while3-methylbutanal, ethyl butanoate, and ethyl octanoate reached the highestconcentration till the fifteenth day of fermentation.