Sensory-Guided Analysis Of Afterbitter Compounds In Shaoxing Huangjiu

Huangjiu is one of the three ancient wines in the world,known as the treasure of Chinese brewing technology.Shaoxing Huangjiu is one of the most representative Huangjiu,and it is the first protected geographical indication product in China.Its brewing technology such as“low temperature slow fermentation method under natural environment”and“wine koji re-test fermentation method”is China’s intangible cultural heritage.Semi-open environment can easily lead to unstable taste quality of Shaoxing Huangjiu,resulting in too high bitterness intensity or too long duration,that is,after bitterness.In this study,Shaoxing Huangjiu fed in different environments was used as the research object（pre-wine（T1）fed before the beginning of winter,two batches of neutral wine fed half a month after the beginning of winter（T2）and one week before the winter solstice（T3）,and post-wine fed after the winter solstice（T4））.Based on the sensory-oriented method,the afterbitter substances in Shaoxing Huangjiu were analyzed,and the changes of afterbitter substances during fermentation under different ambient temperature conditions were analyzed.The main conclusions are as follows:（1）The combination of static and dynamic sensory evaluation was used to clarify the taste differences of Shaoxing Huangjiu fermented at different ambient temperatures,and the dynamic changes of after-bitterness during the drinking process of Shaoxing Huangjiu samples fermented at different ambient temperatures.The results showed that the neutral wine sample（T3）produced near the winter solstice had weaker after-bitterness intensity,more coordinated and rich taste,and less bitterness than the Shaoxing Huangjiu produced in other periods,while the post-liquor sample T4 between the winter solstice and the beginning of spring had the heaviest after-bitterness and was not easy to dissipate.Based on the results of electronic tongue and sensory evaluation,the expression of after-bitterness evaluation model establishedbypartialleastsquaresmethodwas:Y=2.669+0.021*X₁+0.399*X₂-0.018*X₃+0.156*X₄-0.537*X₅+2.801*X₆,where X₁,X₂,X₃,X₄,X₅and X₆were the electronic tongue response values of acid,bitter,umami,sweet and post-bitterness,respectively.The prediction model was stable and reliable,and the correlation coefficient reached 0.928.Based on the after-bitterness evaluation method,the taste of Shaoxing Huangjiu samples was verified.To a certain extent,it assists in the control of the flavor quality of Shaoxing Huangjiu;（2）The dynamic changes of non-volatile afterbitter substances in four batches of Shaoxing Huangjiu samples during fermentation at different ambient temperatures were analyzed by HPLC.PLS and PCA methods were used to establish the correlation between the taste-active substances and the bitterness response value after the electronic tongue.Finally,it was determined that the important non-volatile after-bitter substances in Shaoxing Huangjiu were leucine,isoleucine,valine,histidine,lactic acid,and succinic acid.Higher fermentation ambient temperature promoted the accumulation of non-volatile afterbitter substances in Shaoxing Huangjiu;at the same time,based on the method of sensory omics,HPLC,UPLC-MS combined with TDA were used to separate the important after-bitter substances in Shaoxing Huangjiu,and their molecular formulas were preliminarily inferred to be C₃₇H₆₈O₈and C₂₄H₄₄N₄O₄.（3）Based on the results of sensory evaluation in the first chapter,sample 4-2 with the heaviest bitterness was selected as the research object for GC-O analysis.Based on the results of GC-O,a total of 11 kinds of bitter volatile substances in Shaoxing Huangjiu were determined,which were 3-methyl butanol,benzaldehyde,ethyl octanoate,phenyl ethanol,octanoic acid,isobutanol,phenol,furfural,ethyl nominate,ethyl palmitate,and acetophenone.The volatile bitter substances in four batches of Shaoxing Huangjiu samples were quantitatively analyzed by GC-MS combined with the external standard method,and the importance of volatile bitter substances to the bitterness characteristics of Shaoxing Huangjiu was evaluated by OAV value.PLS and PCA were used to establish the correlation analysis between post-bitterness and volatile bitter substances in Shaoxing Huangjiu.It was determined that benzaldehyde and ethnominateate were important volatile post-bitter substances,mainly manifested as bitter almond taste and burnt bitterness.At the same time,a higher fermentation environment temperature will promote the formation of benzaldehyde and eneonateonate,thereby enhancing the perception.