Analysis Of Volatile Compounds Of Strong-flavor Base Liquor And Study On Grade Recognition

Chinese liquor has a long history and is indispensable in people's life.There are four main steps in liquor processing that includes fermentation,distillation,aging,and blending.Base liquor is the cooling liquid which obtained from distillation of the fermented grains.Generally,the quality of the base liquor is preliminarily divided by in time division and segmentation in the distillation process.After that,the grades of the base liquor were further determined by the sensory evaluation and physico-chemical testing,which barely provided rapid detection and real-time information.Therefore,it is necessary to establish an accurate and rapid method to identity the grades of base liquor.Base liquor with different grades has different qualities and flavors,which is mainly ascribed to the volatile compounds(~2%)in base liquor.However,the exact constituents of the substances are unclear.This study,the Strong-flavor base liquor as the objective,analyses in qualitative and quantitative of the volatile components in different grades base liquor,investigate to establish a datebase of volatile components in base liquor,provide research foundation for relative research of liquor qualityand investigate to establish a novel standard for fast and accurate grading of base liquor.The main research contents are as follows:(1)The headspace-solid phase microextraction(HS-SPME)was used to extract the volatile components in different grades base liquor,while the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry(GC×GC-TOFMS)was used to separated and identified volatile components.A total of 458 kinds of volatile constituents(ethanol excluding)were identified in Strong-flavor base liquor,including alcohols(139 species),carbonyl compounds(including ketones,aldehydes and acetals)(71 species),nitrogen-containing compounds(38 species),sulfur-containing compounds(19 species),furan(25 species),ether(9 species)and Other substances(66 species).The results showed that Strong-flavor base liquor contains a wide variety of volatile constituents.(2)A total of 132 volatile constituents(excluding ethanol)in Strong-flavor base liquor were detected by HS-SPME combined with gas chromatography-mass spectrometry(GC-MS).The content of the constituents was calculated using three internal standards.The results showed that the content of ester was the most predominant,accounted for more than 68.66% of the volatile constituent in the Strong-flavor base liquor.The esters content decreased with the decrease of liquor grade,while the content of aromatic substances increased with the decrease of liquor grade.(3)The odor activity value(OAV)of the volatile compounds was calculated by the quantitative result combined with the sniffing threshold.There were 51 volatile constituents in the Strong-flavor base liquor that contributed to the whole flavor(OAVs ?1).Among them,10 volatile constituents(ethyl acetate and ethyl phenylacetate,etc.)contributed predominantly to the whole flavor of Strong-flavor base liquor.Their OAV values were related to the grades of base liquor,and it can be used as acharacteristic volatile substance of Strong-flavor base liquor.(4)The smell analysis of different grades of Strong-flavor liquor based on aroma extraction and dilution analysis(AEDA)combined with Gas Chromatography-Olfactometry(GC-O).There were 65 kinds of aroma active constituents that were detected,including 8 unknowns.Among them,ethyl caproate,ethyl caprylate,dimethyl trisulfide,ethyl butyrate,ethyl valerate,isoamyl hexanoate and hexanoic acid(with FD factor?256)were the greatest contributors to the aroma of the Strong-flavor base liquor.(5)The headspace-solid phase microextraction-mass spectrometry(HS-SPME-MS)was combined with various chemometric methods to discriminate the quality grades of the Strong-flavor base liquor and quantify the main esters.After normalization and dimensionality reduction by principal component(PCA),it was found that the recognition rates of training set and test set of the linear discriminant analysis(LDA)model were 98.00% and 92.00% respectively,which was better than the back propagation neural network(BPANN)and random forest.(RF).Competitive adaptive heavy-weighted sampling-partial least squares(CRAS-PLS)models were established to predict the content of the four major esters in Strong-flavor base liquor,namely ethyl acetate,ethyl butyrate,ethyl caproate,and ethyl lactate.The correlation coefficients of CARS-PLS model were all higher than 0.9174.The results indicated that CRAS-PLS model could meet the detection requirements of ester substanceduring liquor production.