Basic Research On The Characteristic Aroma Components Of Hunan Black Tea

Aroma quality of tea is one of the important factors that determine the quality of tea.It plays a very important role in tea flavor,grade evaluation and public consumption orientation.The aroma quality characteristics and material basis of Hunan black tea are still unclear,which block the research on the flavor of Hunan black tea quality and the further improvement of product quality.In this paper,the characteristics and components of aroma quality of Hunan black tea of different varieties and different tenderness are analyzed through sensory evaluation,detection of aroma chemical composition and multivariate statistical methods,and the formation mechanism of aroma quality of Hunan innovative black tea is studied as well.The main research contents are as follows:(1)Sensory quality analysis of 191 black tea samples of different grades in Hunan region revealed that there are differences in the quality of black tea of different tea varieties and tenderness grades.The appearance of Hunan fine variety black tea is tight and comely,tippy and even,group varieties black tea are rich in taste,while black tea of other provinces have obvious high aroma in tea soup.The comprehensive quality of Hunan black tea shows a downward trend as the tenderness level decreases.The aroma changes from tender sweet to floral or sweet(honey);floral honey aroma and fresh sweetness flavor are the main characteristics of Hunan black tea.(2)By using HS-SPME/GC-MS in combination with sensory evaluation,odor activity value(Odor activity value,OAV)and least squares(PLS)regression method,the main characteristics and aroma components of Hunan black tea are as follow: Geraniol,phenethyl alcohol,phenylacetaldehyde,linalool and other 10 kinds of aroma components are high in content,they are the main aroma substances in Hunan black tea;the OAV value of 24 aroma substances such as geraniol is greater than 1,which are the main active aroma components of Hunan black tea aroma.Nonanal and tran-sorange tert-alcohol have a high correlation of aroma intensity of floral aroma,and benzyl alcohol and phenylethanol have a high correlation of aroma intensity of sweet honey aroma.They are the main aroma substances that constitute the characteristics of the "floral honey aroma" of Hunan black tea.(3)Through the sensory quality evaluation and aroma component analysis of Hunan's main tea varieties,group varieties,and oolong tea varieties showed that there are significant differences in the composition of aroma substances between Hunan lobular black tea and black tea of oolong tea varieties.Phenethyl alcohol,neroli alcohol,cedar alcohol,neroli aldehyde and folic acid are the characteristic aroma components of good varieties of Hunan lobular black tea.Caproic acid leaf alcohol ester,(E)-o-rolene,laurene,o-violonone,nonyl aldehyde,phenylacetonitrile,indoles are the characteristic aroma components of oolong tea varieties black tea,and the composition similarity rate of the two types of black tea varieties is low.(4)Sensory quality evaluation and aroma composition analysis are carried out on Hunan black tea standard samples,group varieties and samples of Hunan black tea with different tenderness levels.The results show that: different tenderness grade black tea has same change trend.The percentage of alcohol decreases as the tenderness level decreases,the absolute content and percentage of aldehydes and ketones increase with decreasing grade,Supper grade tea of the three groups of samples,Hydrocarbons all are the highest,while the ester compounds are different in different samples.Further analysis shows that the high and long sweet fragrance in the superfine tea is due to the highest proportion of alcohols.The contents of alcohols,aldehydes,ketones and esters in the first-grade tea samples are in the middle,so most of them show pure and strong sweet fragrance.Secondary tea samples are significantly different from each other.For example,the hydrocarbon and ester compounds in the sample are relatively high(in the standard second-level sample),and their fragrance is obvious;if they are relatively low(fine seed and neutralization group),they show pure sweetness.(5)Applying comprehensive withering innovative process is an important way to form the honey aroma of Hunan black tea.Through analyzing the main aroma components and the dynamic change of enzyme activities in each process of the innovative process,explored the formation mechanism of floral honey aroma and grass aroma of Hunan black tea.In the process of processing,the contents of total aroma substances,alcohols,aldehydes,esters and ketones show the trend of change of "?","?","n","m" and "n" respectively,In the process of processing,2-hexenal and hexanal are the main fragrant substances of "Grass aroma",decanal and geraniol are the main fragrant substances of "sweet fragrance",linalool,?-violone,trans Neroli tertiary alcohol,Neroli alcohol and Neroli aldehyde are the main fragrant substances of "flower fragrance".The activity changes of ?-glucosidase and polyphenol oxidase in each process promote the increase or decrease of the substances of grass aroma,flower fragrance and sweet fragrance,and make the aroma of the products in process change,and finally present the floral honey aroma of the finished products.