Research On Flavor Characteristics And The Key Aroma Compounds Of Hong Qu Huangjiu

Huangjiu,which has a long history and wide variety,shows its own characteristics from different regions,and Hong Qu Huangjiu produced in Fujian is one of the important branches.The unique technology of adding Hong Qu endows Hong Qu Huangjiu with a distinct flavor as well as functional components such as amino acids,peptides,and phenolics,which makes it popular among consumers.However,as there is a lack of research on the flavor of Hong Qu Huangjiu,it is difficult to improve the quality of Hong Qu Huangjiu and to meet the higher popular demand.This study focused on the flavor characteristics and key aroma compounds of Hong Qu Huangjiu,and further analyzed the influence of the type and aging time of Hong Qu on the flavor and aroma compounds,which will help to further improve the quality of Hong Qu Huangjiu.The main research contents and results of this thesis are as follows:(1)The flavor characteristics of Hong Qu Huangjiu were studied by quantitative sensory description analysis.Firstly,50 sensory descriptors of Hong Qu Huangjiu in terms of aroma,taste,flavor,and aftertaste were obtained,and classified to construct an overall flavor wheel.Further,24 main sensory attributes were filtered by geometric mean and cluster analysis.The flavor characteristics of Hong Qu Huangjiu were analyzed,and we found that Hong Qu Huangjiu was mainly characterized by mellow and elegant aroma,with complex aromas of Qu,cheese,fruit and herbs,textures of soft and pure,a wine body of harmonious and smooth,aftertastes of clean and crisp and a typical style.Different types of Hong Qu Huangjiu showed differences in some of aroma and taste properties.Based on the flavor wheel and flavor profile analysis,13 sensory quality scores for color,aroma,taste and style were established and applied for quality assessment.The samples were successfully distinguished,indicating that the method can effectively assess the sensory quality of Hong Qu Huangjiu.A single-factor optimization experiment was carried out to optimize the preparation of the reference sample for the key aroma,Qu aroma,of Hong Qu Huangjiu.The optimum parameters for the preparation of the reference samples of Qu aroma were an ethanol content of 60%,a material-to-liquid of 1:10,and an extraction time of 3 h.The applicability test proved that the reference samples of Qu aroma prepared under these conditions could distinguish different wine samples.(2)The volatile compounds in Hong Qu Huangjiu were comprehensively analyzed by Comprehensive Two-Dimensional Gas Chromatography-Time of Flight Mass Spectrometry(GC×GC-TOFMS),and 284 volatile compounds such as alcohols,esters,acids,aldehydes and furans were identified.In addition,40 new compounds were newly-found in Huangjiu.Among them,the cheese aroma,presented by methyl(2-methyl-3-furyl)disulfide,and the herbal aroma,presented by 1,3-dimethoxybenzene,were consistent with the characteristic aroma in Hong Qu Huangjiu.(3)The key aroma compounds and their interactions between characteristic aromas of Hong Qu Huangjiu were investigated.Gas Chromatography-Olfactometry(GC-O)was used to sniff the Hong Qu Huangjiu,and 67 volatile compounds with high aroma intensity were obtained,and the compounds were further quantified by establishing standard curves.The ratio of compounds concentration to threshold value was calculated to obtain the Odor Activity Value(OAV),and the aroma compounds contributing to the Hong Qu Huangjiu were obtained by comparing OAV values.11 key aroma compounds of Hong Qu Huangjiu were confirmed by aroma reconstruction and deletion experiments,namely isovaleric acid,phenylacetaldehyde,isovaleraldehyde,ethyl acetate,phenethyl alcohol,ethyl isobutyrate,ethyl isovalerate,dimethyl trisulfide,vanillin,hexanal and butyric acid.The interactions among the eight compounds corresponding to the cheese,fruit and herbal aromas were explored by the σ-τ intensity method.The results showed that among the 28 groups of aroma effects,there were 5 groups of synergistic effects,9 groups of additive effects,3 groups of complete additive effects,9 groups of compromising effects and 2 groups of masking effects.Finally,multivariate statistical analysis showed significant differences in the volatile compounds contents of different Hong Qu Huangjiu,and the correlation analysis between aroma attributes and volatile compounds verified the results of sensory analysis,qualitation and quantification.(4)The effects of Hong Qu type and aging time on the aromas and volatile compounds of Hong Qu Huangjiu were investigated by sensory and quantitative means.Significant differences existed between Gutian Hong Qu Huangjiu and Wuyi Hong Qu Huangjiu in the intensity of cheese,Qu and herbal aromas.There were also differences in the concentration of aroma compounds in Gutian Hong Qu and Wuyi Hong Qu,with the overall alcohol,ester,acid and aldehyde contents of Gutian Hong Qu being higher than that of Wuyi Hong Qu.Multivariate statistical analysis revealed that the differential compounds in between Gutian Hong Qu and Wuyi Hong Qu were hexanal,ethyl caproate and ethyl propionate,among which hexanal and ethyl caproate were also differential compounds between Gutian Hong Qu Huangjiu and Wuyi Hong Qu Huangjiu,so the differences of these two compounds in Hong Qu Huangjiu might be resulted from Hong Qu.Differences in aroma and volatile compounds were also more significant in Hong Qu Huangjiu of different aging years.The intensity of aromatic properties such as Qu and mushroom aromas decreases with age,and the taste becomes softer and more harmonious with age.The compounds content of Hong Qu Huangjiu in different aging years was also different.The content of alcohols increased and then decreased;the content of acids decreased and then increased;the content of aldehydes did not change significantly in the early stage of aging but increased significantly in the later stage.The content of isovaleric acid,a key substance,increased with aging time.At the same time,the differential compounds of Hong Qu Huangjiu in different aging years were ethyl benzoate,ethyl butyrate,phenethyl acetate,benzyl alcohol,isoamyl acetate,caprylic acid,hexanal,ethyl caprylate,ethyl 2-hydroxy-4-methyl-valeric acid,and ethyl lactate.The results of cluster heatmap showed Hong Qu Huangjiu of different aging years could be well distinguished on the basis of compound contents.This also showed that the effect of aging year on the aroma compounds content of Hong Qu Huangjiu was significant.