| Owing to the special manufacturing process of spontaneous fermentation and distillation under solid-state conditions,so far more than 1800 volatile compounds have been detected in Baijiu.These numerous volatile compounds impart Baijiu attractive aroma,taste,and mouthfeel.Pungency is one of the most important mouthfeel characteristics for affecting the sensory quality of Baijiu,and is also the key factor for affecting the national,diversifical and international development of Baijiu.The characterization of pungency is the premise of studying the chemical basis of pungency of Baijiu,which is of great significance for improving the flavor quality of Baijiu products.However,there are few researches about the pungency sensation of Baijiu,the chemical drivers of Baijiu pungency have not been demonstrated,which leads to lack of scientific basis for regulating the sensory quality of Baijiu.In this study,the time-intensity,subqualities and dynamic characteristics of Baijiu pungency were studied by food sensory science,and the chemical basis of Baijiu pungency was analyzed by chemosensory strategy for the first time.The main research contents and results were listed as follows:(1)The modern food sensory analysis methods were used to systematically characterize the mouthfeel of Baijiu,and the first Baijiu Mouthfeel Wheel was constructed.Descriptive analysis combined with focus groups were used to describe the mouthfeel characteristics of Baijiu.The mouthfeel terms were collected and the citation frequency of each term was analyzed through online questionnaire using CATA method.The terms with more than 10%citation frequency were selected,the sensory evaluation group discussed and established clear definitions and references.Finally,the first Baijiu mouthfeel wheel was constructed,which including 38 specific terms and covering 6 categories of basic taste,other taste,pungency,texture,body and aftertaste.(2)Based on the combination strategy of multi-sensory analysis methods,the sensory method for charactering the pungency characteristics of Baijiu was established.The linear scale method combined with time intensity analysis(TI)and temporal dominance sensations(TDS)were used to comprehensively characterize the pungency characteristic,considering both intensity,subqualities,and dynamic changes.The results showed that the intensity differences of pungency were mainly in the Imax,Tmax,Vi,Vd,Ttot and AUC.The significant differences of pungency subqualities among Baijiu were mainly in the combination of dominant sub-qualities,as well as in the maximum dominance rates(DR-max)and the dominant duration(T-max)of subqualities.This established sensory method enriching our understanding about pungency of alcoholic beverages.(3)An innovative instrumental analysis technology was established to quantitatively predict the difference of pungency intensity based on the tongue surface temperatures with infrared thermal(IRT)imager.An infrared thermal(IRT)imager technique was used to measure the differences of tongue surface temperature after drink Baijiu samples,and sensory evaluation technology established before was used to evaluate the difference of pungency intensity of samples.The correlations between tongue surface temperature and pungency intensity was established by multiple linear regression analysis.The regression equation between tongue surface temperature and pungency intensity was as follows:Pungency(AUC)=133.19T Aver-9.28 Tmax-15.10 Tmin-3362.84(p<0.05),The correlation coefficient R~2between predicted value and measured value of training set sample was 0.648,the R~2 between the predicted value and the actual value of the sample in the prediction set was 0.590,indicating that the correlation between tongue surface temperature and pungency intensity was statistically significant.This instrument analysis technique is rapid,convenient and reproducible,and could be applied to predict the differences of pungency intensity of alcoholic products.(4)Based on the chemosensory strategy,the flavor chemical drivers of pungency of Baijiu were identified.The differences of pungency characteristics and the concentrations of flavor compounds in Baijiu with different aging times were analyzed.The correlation analysis between flavor compounds with significant differences and pungency was conducted by multivariate statistical analysis.Several esters,aldehydes,and acids were found to significantly correlated with pungency.Ethyl hexanoate,ethyl acetate,3-methylbutyl hexanoate,acetaldehyde,acetal,and 3-methylbutanal were confirmed to contribute to the pungency of Baijiu,and acid compounds at low concentrations were confirmed to suppress the pungency perception by two-alternative forced-choice test(2-AFC).Sensory recombination testing further revealed that esters were the most important compounds contributing to Baijiu pungency,which filled the understanding of chemical basis of pungency of Baijiu.(5)The taste interaction between organic acids and pungency was explored.The identified key flavor compounds of pungency were added to 46%ethanol aqueous to form control solution as the reference of pungency,by adding different concentrations of hexanoic acid,acetic acid,lactic acid,and butyric acid to compose of a series of model solutions.The pungency intensity and pungency sub-qualities of control and model solutions were evaluated.Results showed that medium and low concentrations(<1000 mg/L)of acetic acid and hexanoic acid decreased the pungency intensity,while high concentrations(>1000 mg/L)of acetic acid and hexanoic acid increased the pungency intensity.Lactic acid inhibited the pungency perception,while butyric acid had no significant effect on the pungency sensation.In addition,the addition of four organic acids delayed the time(Tmax)and rate(Vi)to reach the maximum intensity,and decreased the duration(Ttot)of pungency.The acids significantly affected the maximum dominance rate(DR-max)and dominance duration(T-max)of the dominant pungency sub-qualities.The order of importance of four organic acids on pungency was acetic acid>hexanoic acid>lactic acid>butanoic acid. |
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