Analysis Of Flavor Compounds In The Production Of Luzhou-flavor Liquor

Chinese liquor is one of the six world famous distilled liquor. Based on a unique flavor, luzhoulaojiao was well known as the model of strong aroma liquor. Fermentation and distillation were two extremely important process during the brewing of Luzhou-flavor liquor. This article used the headspace solid phase micro extraction(HS-SPME), gas chromatography mass(GC-MS) and high performance liquid chromatography(HPLC) technology to detect the changes of flavor compounds in fermented grains during the fermentation stage and volatile compounds in raw liquor during the distillation stage. Multivariate statistical analysis was used to determine the characteristic flavor compounds in fermented grains and raw liquor during different stage. This study possessed a important significance for exploring the fermentation mechanism, explaining the manufacturing process and guiding production scientifically. The main results showed as follows:In the fermentation process, the water content and the total acids(converted into lactic acid) of upper, middle and bottom layer fermented grain shown a rising trend.At the end of fermentation, the total contents of 7 organic acids in upper, middle and bottom layer fermented grains were 47.02±0.83 mg/g dry culture, 61.93±0.31 mg/g dry culture and 72.18±0.11 mg/g dry culture, respectively. Lactic acid, acetic acid and citric acid were 3 main organic acids, taking more than 94% of the total contents. The acetic acid and citric acid in upper, middle and bottom layer fermented grains shown a similar change trend.99, 98 and 98 kinds of volatile compounds were detected in upper, middle and bottom layer fermented grains during fermentation stage by using HS-SPME/GC-MS. Alcohols, acids and esters taken 99% of all volatile substance contents. At the end of fermentation, the contents of volatile compounds in upper layer were highest, that in bottom layer were lower, and that in middle layer were the least. And in the fermentation process, the changing trends of flavor compounds in upper layer fermented grain were similar with that in bottom layer.Multivariate statistical analysis was used to analyze the data from fermentation. The 15 th day was initially determined as a dividing point during fermentation stage. Ethyl acetate, ethyl butyrate, isoamyl butyrate, ethyl pentanoate, propyl hexanoate, butyl hexanoate, isopentyl hexanoate, hexyl hexanoate, ethyl heptanoate, ethyl octanoate and ethyl nonanoate were determined as the characteristic flavor compounds at the prophase of fermentation. And, ethyl lactate, diethyl butanedioate, ethyl hexanoate, ethyl caprate, ethyl oleate, ethyl linoleate, ethyl laurate, ethyl palmitate, ethyl phenylacetate and Ethyl hydrocinnamate were determined as the characteristic flavor compounds at later stage.During the distillation stage, the ethanol content of raw liquor declined from 75.6% vol of 0th min to 13.9% vol of 19 th min, and rapidly down from 15 th min.The best parameters of HS-SPME for extracting flavor conpounds in raw liquor were 5% alcohol content, and extracting at 50 celsius for 40 min. 105 kinds of volatile compounds were detected in raw liquor during distillation stage, and the most of esters concentrated in the head liquor, dropping from 1700.9 mg/L at the begaining to 320.5 mg/L at the end. Alcohols and aldehydes also shown a declining trend, while the acids raised.The 20 raw liquor samples were divided into 4 categorys: 0 min, 1~7 min, 8~15 min and 16-19 min by cluster analysis, and characteristic flavor compounds in each category were determined by principal component analysis.