Analysis Of The Characteristic Aroma Compounds Of Hunan Fu Brick Tea

Fu brick tea is a typical post-fermentation tea known for its unique flavor and special health benefits.The unique fungal flower flavor of Fu brick tea is the key factor to determine its quality,and to some extent,is also an important indicator to determine the market price.Aiming at the problem that the material basis of Fu brick tea fragrance is not clear at present,taking the samples of Fu brick tea in Hunan province as the experimental materials,this paper first made a preliminary understanding of the aroma profile of Fu brick tea by means of sensory quantitative description and electronic nose analysis.Then,headspace solid phase microextraction(HS-SPME)combined with gas chromatochromatoid-flight mass spectrometry(GC-TOF/MS-O)was used to qualitatively and quantitatively analyze the components of Fu brick tea.Finally,the key odor-active compounds of Fu brick tea were determined by aroma extraction dilution analysis(AEDA),odor activity value method(OAV)and aroma recombination omission test.The main conclusions are as follows:(1)The overall aroma profile of Fu brick tea was mainly characterized by "fungal flower","green" and "woody",which together with "fruit fragrance" and "mint fragrance" formed a unique aroma profile.With the extension of storage time,the unique fungal flower aroma of Fu brick tea gradually decreased and be replaced by the aroma of stale.(2)A total of 123 compounds were identified by HS-SPME combined with GC-TOF/MS,including 17 alcohols,31 aldehydes,30 ketones,10 esters,8 heteroxys,18 hydrocarbons,4 phenols and 5 acids.The quantitative results showed that the contents of ketones were the highest,ranging from 29.49% to 42.61%,followed by aldehydes(12.32%-30.88%),esters(13.87%-24.93%)and alcohols(5.87%-11.97%).(3)A total of 27 odor-active compounds were identified by GC-O,and the main odor-active compounds were aldehydes,ketones and alcohols.Among them,there were 15 volatile compounds with dilution factor(FD)greater than 27 and OAVs greater than 1.PLS analysis showed that 6-methyl-5-hepten-2-one,linalool,α-ionene,geranylacetone,β-ionone and cedrol were significantly positively correlated with "fungal flower" and "woody" attribute.And(E,E)-2,4-Heptadienal,(E)-2-Octenal,(E)-2-Nonenal and(E,E)-2,4-nonadien-1-al were significantly positively correlated with "green","fruity" and "mint" attribute.(4)The results of odor recombination test and omission test show that 14 compounds were determined to play a decisive role in the formation of the aroma of Fu brick tea,which were hexanal,(E,E)-2,4-Heptadienal,phenylacetaldehyde,(E)-2-octenal,(E,Z)-2,6-nonadienal,(E)-2-nonenal,(E,E)-2,4-nonadien-1-al,6-methyl-5-hepten-2-one,α-ionene,geranylacetone,β-ionone,benzyl alcohol,linalool and cedrol.