Study On Off-flavor Compounds In Moutai-aroma Type Baijiu

Moutai-Aroma Type Baijiu is an unique flavor among the major aroma type baijiu in China,and about 1 to 3 % of flavor compounds have an important effect on the style characteristics of the wine.However,the quality and industry development of Moutai-aroma type Baijiu have been seriously affected and restricted by several off-flavor compounds.By integrating with the research reports for the flavor of baijiu,we found the study on decomposition the off-flavor liquor in Moutai-aroma type Baijiu is an important prerequisite and way.However,the research in the field still unclear,and most studies lack pertinence and systematicness.Furthermore,the formation of flavor in Moutai-aroma type Baijiu was accidental,which making the research on the off-flavor compounds in Moutai-aroma type Baijiu still objective.Therefore,it's difficult to dissect the formation mechanism of off-flavor compounds.To understand the structure and characteristics of off-flavor compounds comprehensively and systematically in Moutai-aroma type Baijiu.In present study,offflavor liquor in Moutai-aroma type Baijiu(257 samples)that are common in Moutaiaroma type Baijiu were selected as the research objects.First of all,the flavor structure module of Moutai-aroma type Baijiu was built,which was used as a reference for sensory,and the sensory structure module of Moutai-aroma defect-type baijiu was established.Then,the various defect-types(burnt,rancid,musty,mud,oil,bitter,and raw mood)of flavor structure and characteristics of the wine was comprehensively dissected based on sensomics and metabolomics.Finally,the off-flavor compounds in Moutai-aroma type Baijiu was identified based on metabolomics analysis methods.The main results of this study are as follows:(1)A sensory “flavor wheel” description term system for the normal flavor wine and the off-flavor wine of Moutai-aroma type Baijiu was established by sensory descriptive analysis that was based on the of olfaction,taste and overall sense organ dimensions.A total of 100 descriptive vocabulary words were identified in the normal flavor wine,including 63 olfactory descriptive vocabulary,24 taste descriptive vocabulary and 14 overall sensory descriptive vocabulary.In the off-flavor wine,a total of 66 descriptive vocabulary words were identifed,including 38 olfactory descriptive vocabulary,15 taste descriptive vocabulary and 13 overall sensory descriptive vocabulary.(2)The sensory characteristics and differences in various Moutai-aroma defecttype wine were clarified by sensory descriptive analysis.The results showed that the common off-flavor in Moutai-aroma type Baijiu were mainly characterized by seven major types,inclouding burnt,rancid,musty,mud,oil,bitter,and raw mood flavors.The further sensory quantitative analysis of the defect-type wine showed that there were27 defect-type wine samples with strong off-flavor characteristics,among of them,the defect-type of rancid havs most wine samples(7 defect-type wine samples).(3)The seven of common defect-type wines(20 samples)were first selected as the research object.Then,the low-temperature vacuum distillation,liquid-liquid extraction and C18 solid phase extraction and other pretreatment methods were applied based on the sensory flavor results to extract and separatthe off-flavor compounds in the wine.The results showed that the off-flavor compounds existed in different components according to their volatile properties in the Moutai-aroma type of defective wine.Specifically,the rancid,oil and raw mood flavors mainly exists in N / BF component;the bitter taste mainly exists in W component;the musty and burnt flavors exists in S and N / BF components,and they also exists in the non-volatile component ? and?/?respectively.In addition,the strong aroma-like components separated from the muddy wine mainly exists in N / BF;the sour components separated from the rancid wine is mainly present in the non-volatile component ?.(4)A total of 587 kinds of flavor compounds were qualitatively quantified among20 volatile off-flavor components and 9 volatile normal-flavor components based on the decomposition of 165 GC-MS spectra,including 154 esters,61 alcohols,28 organic acids,41 ketones,11 furans,51 aromatics,29 pyrazines,and several heterocyclics,alkanes and other compounds.(5)A total of 135 flavor compounds were qualitatively quantified among 14 nonvolatile off-flavor components and 9 non-volatile normal-flavor components based on the decomposition of 69 UPLC-MS spectra,including 24 esters,23 organic acids,and31 nitrogen-containing compounds,20 benzene ring,13 polyhydroxyl and 24 other compounds.(6)A comprehensive analysis of the flavor structure in the volatile and non-volatile off-flavor components was performed by the non-targeted metabolomics methods based on GC-MS and UPLC-MS.The results show that the compounds by detected in the different off-flavor components were mainly esters,alcohols,benzene rings and nitrogen-containing compounds,which further suggested that these substances may be the skeleton components in Moutai-aroma type Baijiu.In addition,we found that the different quantitative ratios of flavor compounds in different off-flavor components are the main factors affecting the formation of wine flavor by multivariate statistical analysis.(7)Thecomparative statistical analysis of the compound concentration was performed based on the marked difference between the off-flavor components and normal components.The results showed that the volatile potentially off-flavor compounds were ethyl linoleate,ethyl palmitate,ethyl lactate,ethyl caproate,1,3-propanediol monoethyl ether,ethyl 2-furoate,DL-2-Ethyl hexanoate,crotyl alcohol,DL-leucine ethyl ester,etc.Non-volatile potentially off-flavor compounds were mainly diethyl succinate,methyl palmitate,D-panthenol,2-acetylpyridine,choline,crosslinked polyvinylpyrrolidone,2-hydroxyethylpyridine and tris N-butylamine,and several compounds that are not completely accurate,etc.