Studies On Characteristic Volatile Components Of Green Tea With Chestnut Aroma

In the present work,the chestnut-like green tea was investigated by headspace solid phase microextraction(HS-SPME).the extracting parameters such as fiber type,extraction time,extraction temperature and electrolyte concentration were evaluated to obtain the optimal conditions.The volatile constitutions of green teas with three different chestnut characteristics were characterized based on gas chromatography-mass spectrometry(GC-MS)combined with multivariate statistical analysis including principal component analysis(PCA),hierarchical cluster analysis(HCA)and partial least squaresdiscriminant analysis(PLS-DA).The characteristic aroma components of three different typical chestnut-like characteristics green teas were identificated based on HS-SPME combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry(GC×GC-TOFMS)and odor active values(OAVs).The main results were as follows:1.This study explored the optimal conditions for preparing aroma of chestnut-like green tea and carried out the characteristic peak analysis of chestnut-like green tea.Results indicated that The optimal extraction conditions of chestnut-like green tea was obtained as follows: DVB/CAR/PDMS fiber,extraction temperature of 50 ?,extraction time of 50 min,electrolyte concentration of 1-3 mg/ml.Under the optimal condition,171 volatile compounds were detected and 30 peaks were identified as the common characteristic peaks of chestnut-like green tea,including 5 alcohols,4 alkenes,7 alkanes.And the RSD of relative peaks areas ?5.0%,which showed the good repeatability.The characteristic peak of chestnut-like fragran obtained by similarity analysis using angle cosine method and correlation coefficient method proved to have a good explanation ability.2.The multivariate statistical analysis results showed that PCA,PLS-DA and HCA could achieve good differentiation of three chestnut flavor green teas.In PLS-DA analysis,18 chestnut-like green tea samples were well separated according to their aroma characteristics,and the well-explained variance(R2Y=0.847)and cross-validated predictive capability(Q2=0.698)indicate the model's good feasibility.In HCA analysis,three kinds of chestnut fragrant green tea could be clearly divided into three categories at a distance of 12,of which the chestnut-like and tender-chestnut-like tea samples were more closer,matching the results of sensory evaluation.In addition,38 volatile components were identified based on variable importance in projection(VIP)score > 1,which were responsible for the discrimination of green teas with three different flavor characteristics.3.The results showed that 79 common components were identified in three kinds of chestnut-like green tea samples,including 16 terpenes,14 aldehydes,11 ketones,11 aromatic hydrocarbons,10 esters,7 olefins,4 alcohols,1 acids and 5 other compounds.Aldehydes were present with the highest proportion in green tea.In addition,12 characteristic aroma components with OAVs value larger than 1 were screened out,including 1-octen-3-ol,2-methyl-propanal,hexanal,benzeneacetaldehyde,nonanal,decanal,1-octen-3-one,linalool,trans-beta-ionone,heptanal,p-cymene,ethyl acetate,which indicated that they had a significant contribution to the characteristics of chestnut-like green tea.