Analysis Of Aging Aromas And Study On Age Discrimination Of Chinese Rice Wine Based On Omics Technology

“Pottery storage,and more aging,more flavors”is one of the most typical characteristics for Chinese rice wine?rice wine?,which suggests that there exist a close relationship between“aging time or age”and“aging aroma”in rice wine.Moreover,the aging time or age,as an important standard of the quality of rice wine,is also a major reference for consumers to purchase the good rice wine.Therefore,it is of great value to analyze the aging aroma in rice wine and its close relationship with the aging time scientifically to improve the quality standards of rice wine.To clarify the aging aroma and its role in age discrimination of rice wine,the non-targeted metabolomics and the targeted strategy of flavor chemistry-oriented were mainly implemented by a variety of methods and from a variety of perspectives,such as metabolomics,flavoromics,instrument analysis technology and multivariate statistical analysis so on.And the main contents in this study are as follows:?1?Here it was the first to apply the GC/MS untargeted metabolomics strategy combined with partial least squares regression?PLSR?to analyze the aging aromas and their roles in age discrimination in 7 different aged rice wines from a molecular level and statistical perspective.A total 104 feature groups and 94 aging markers?including unknowns?were respectively isolated preliminarily identified as aging markers from all optimized candidate peaks,and their statistical relationships with seven ages from 0 to 15 years were summarized as follows:alcohols,ethyl palmitate,ethyl oleate and trans-ethyl oleate played important roles in distinguishing the 0 year-ageds from others,and 3-methylthiopropanol was only extracted in 0year-aged samples;At the age of 1 year,the number of alcohol aging-markers decreased significantly,while the phenolic and oxidized aging-markers increased significantly,and2,3,5,6-tetramethylpyrazine also appeared;In this period of 2?5 aged-years,aromatics began to appear;Aromatics had been the main body of aging markers in the period of 10?15 aged-years,and the number of furans increased significantly.Moreover,acids began to play some roles in discriminating the age of 10?15 years.Meanwhile,the changes of the identified 94aging markers showed that the aging markers,which could discriminate significantly the age of 0?3 years,decreased during the aging,and all the aging markers with uptrends during the aging played important roles in discriminating the age of 5?15 years,especially 10 and 15 years.?2?Based on the preliminary identification and aroma characteristics analysis of 74 key aromas in unstored and aged rice wines by flavoromics technology of GC-O/AEDA,a quantitative analysis of 85 aromas about their concentrations,changes and odor activity values?OAVs?was further conducted from three different brands and 14 aged rice wines with different ages by a quantitative multi-method strategy.Finally,a total of 60 potential aging markers with a significant trend during aging?*p?0.05?,49 potential key aging-aromas with a high OAV or factor dilution?FD?value and 31potential key aging-markers with both a significant trend during aging?*p?0.05?and a high OAV or FD value were respectively extracted.Therein,these 60 aging markers?I?had the close relationships with the ages,and the 49 key aging-aromas were the key contributors for the aroma characteristics during aging.Accordingly,these 31 key aging-markers were the key data objects for the flavor-oriented age discrimination.?3?Based on this result that seven different ages from 0 to 15 years were divided into these four time periods of 0 aged-year,1?2 aged-years,3?5 aged-years and 10?15 aged-years by principal component analysis?PCA?and cluster analysis?CA?of 49 potential aging markers in Guyuelongshan-rice wines,a further PCA analysis of 29 potential key aging-markers?**p?0.01?and a description of their OAV profiles were performed,and the aging status characterizations of rice wine in four aging time periods were further analyzed and discussed from both statistical and flavor perspectives.A total of 18 key aging-markers had the higher OAVs?OAV?1?during a certain aging period,where 6 key aging-markers of dimethyl sulfide,3-methylthiopropanol,3-methylthiopropionaldehyde,4-vinylguaiacol,4-ethylguaiacol and isobutanol had the highest OAVs in the 0Y-ageds,and statistical roles in distinguishing the 0Y-ageds from others;Compared with the 0Y-ageds,the number of key aging-markers with significant aroma intensity?OAV?1?in this period of 1?2 aged-years increased,such as phenol,ethyl isobutyrate,acetophenone and 2-phenyl-2-butenal;In the period of 3?5 aged-years,the number of key aging-markers with significant aroma intensity?OAV?1?increased,but also decreased,when3-methylthiopropanol,3-methylthiopropionaldehyde and isobutanol had insignificant aroma intensity?OAV<1?,but cinnamaldehyde,trans-cinnamic acid,sotolon,?-decalactone and benzyl alcohol began to have significant aroma intensity;In the period of 10?15 aged-years,the aroma intensity of these 12 key aging-markers with an upward trend,such as acetophenone,2-phenyl-2-butenal,cinnamaldehyde,sotolon,ethyl nicotinate and furfural so on,had completely exceeded that of 6 key aging-markers with a downward trend in the 0Y-ageds.Correspondingly,the other 11 key aging-markers with OAV?1,such as benzaldehyde,ethyl isovalerate and isovaleric acid so on,had important aroma contributions during the whole aging process from 0 to 15 years.However,the above study on the aging characteristics of Guyuelongshan-rice wine in these four time periods was to be further verified by sensory experiments;?4?Based on PLSR and multiple linear regression?MLR?of 29 key aging-markers,the study on the approach of age discrimination showed that 99.82%and 99.91%accuracy for the prediction of Guyuelongshan-rice wine ages could be separately achieved by both PLSR and MLR.However,the PLSR model was more accurate than the MLR model for the prediction of0 year-aged samples.In contrast,the MLR model was more accurate for the prediction of 1?15years-aged samples.Moreover,the MLR model could be successfully established by fewer variables or only five key aging-markers of 4-vinylguaiacol,dimethyl disulfide,sotolon,3-methylthiopropanol and?-decalactone;?5?The quantitative result by network reconstruction?NR?and SPME-GC/MS method showed that the condition II of one,three and five oxygen supplements would help the aging markers for the natural trends.However,a frequent oxygen supplement?such as five oxygen supplements?would make alcohols fluctuate greatly.Finally,the changes of 15 aging markers during aging would tend to be natural under the condition II of a constant temperature of 37?and three oxygen supplements in 70 days/10 weeks.Meanwhile,here a prediction was made that a higher initial concentration of O₂ would make the“aging aroma”thicker,and an appropriate supplement of oxygen in the middle and early stages of storage would facilitate the control in the stainless steel tank.In addition,a high temperature would accelerate the changes of aging markers.