Study On Characteristic Aroma Compounds During The Process Of Fu Brick Tea

Fu brick tea is popular among consumers due to its unique flavor quality and health care function.“Fungus aroma” is the most important aroma quality feature of Fu brick tea,but at present,it is not clear what kind of substance “Fungus aroma” is composed of,which hinders the research on the forming mechanism of Fu brick tea quality flavor.In this study,samples were taken at different time points during the processing of Fu brick tea.The changes of volatile components in Fu brick tea during processing and the correlation between different aroma components and aroma types were studied by HSSPME,GC-MS,sensory quantitative description and multivariate statistical analysis.This paper reveals the key aroma active substances of Fu brick tea and the contribution of “gold flower” and “Tea of no golden flower” to the fragrance of Fu brick tea were explored.The conclusion is as follows.(1)HS-SPME extraction conditions were optimized,and the optimal extraction parameters were determined to be 1.0g tea sample with 5ml boiling water and 0.5gNaCl.The extraction temperature was 80 and the extraction time was 50 min.The qualitative results showed that a total of 72 volatile components were identified,among which ketones,alcohols,hydrocarbons and aldehydes were the main components.(2)The variation of volatile components in Fu brick tea processing was studied by GC-MS and multivariate statistical analysis The results showed that the volatile components in Fu brick tea processing presented an overall downward trend,in which the total amount of alcohol lactonates,ketones,aldehydes and phenols presented a downward trend,ester compounds presented an upward trend,and the content of heterooxygens first decreased and then increased,but the change trend of hydrocarbons and nitrogenous compounds was not significant.The results of PCA and HCA analysis showed that the processing process of Fu brick tea could be divided into four stages: raw teas stage,the early “Fahua” stage(from the stowing stage to the 6th day),the middle “Fahua” stage(the 9th day),and the late “Fahua” stage(from the 12 th day to the 22 nd day).OPLS-DA analysis of the four stages showed that: in the first and second stages,a total of 20 different components were screened,mainly fatty green mushroom flavor substances decreased.In the second and third stages,a total of 22 different components were screened.While fatty,green and mushroom flavor substances decreased,some floral and wintergreen flavor substances increased.In the third and fourth stages,a total of 18 differences were screened,with floral and wintergreen flavor substances rising.(3)The relationship between aroma components and aroma types of Fu brick tea was studied by sensory quantitative description analysis combined with OAV value and PLS regression analysis.The results showed that: in the process of Fu brick tea processing,the green continued to decrease,the mushroom and the flower continued to increase,and the woody decreased and then continued to increase after being pilefermentation.OAV analysis shows that there are 25 components contributing to aroma in Fu brick tea processing(OAV>1).The aroma components,such as Hexanal,(E)-2-Nonenal,Methyl heptenone,(E,E)-2.4-Nonenedienal and 1-Octen-3-ol,are highly correlated with green and the content of them gradually decreases in Fu brick tea processing.Linalool,Acetophenone and Methyl salicylate are highly correlated with “fungus aroma”,floral,mint and woody,and their contents increase gradually in Fu brick tea processing.This indicates that the formation of the characteristic aroma of Fu brick tea “fungus aroma” was due to the decrease of aroma components highly related to green and the increase of aroma components highly related to floral,mint and woody.Linalool,Acetophenone and Methyl salicylate are the key components of “Fungus aroma”.(4)GC-MS and OAV values were used to compare the differences of volatile components in “gold flower” and “Tea of no golden flower”,and the contribution of volatile components in “gold flower” and “Tea of no golden flower” to the “Fungus aroma” was clarified.The results showed that 59 volatile components were identified in golden flower and the tea of no golden flower.Cedrol,Linalool,Methyl salicylate,1-Octen-3-ol and β-Cyclocitral in “gold flower” contribute to Fu brick tea’s aroma of woody,floral,wintergreen,mushroom and fruity components to Fu brick tea.Hexanal,(E,E)-2.4-Nonenedienal and Dihydroactinidiolide in “Tea of no golden flower” contributes to Fu brick tea’s aroma of green,fatty and sweet components to Fu brick tea.The core component of Fu brick tea “Fungus aroma” is mainly contributed by "golden flower",and “Tea of no golden flower” tea promotes the formation of “Fungus aroma” in Fu brick tea through indirect and synergistic effects.