Establishment Of Quantitative Method And Determination Of Skeletal Volatile Components Of Six Types Of Tea

The characteristic compounds of tea aroma,as known as the skeleton compounds,are important volatile compounds that can reflect the sensory characteristics of tea aroma.The confirmation of the characteristic compounds of tea aroma helps to further understand the effects of processing technology on the formation of tea aroma,thus providing references for the regulation of the quality of tea aroma.This not only improves the processing technology of tea,but also provides solutions for distinguishing different types of tea.However,due to the qualitative and quantitative detection of tea aroma is affected by sample preparation,standards,quantitative correction factors,etc,the results of detection are unstable which can not reflect the sensory characteristics of the actual tea aroma.In this study,we compared the impact of three methods including Tenax TA adsorption tube,stir bar sorptive extraction and solid-phase microextraction on volatile compounds of tea to select the best method.The quantitative correction factors of the standard substance for 106 volatile compounds of tea were determined to complete the optimization of quantitative detection methods for tea aroma compounds.On this basis,the aromatic skeleton compounds of six types of tea were filtered by combining the relative content with odor active value.Finally,the results of aromatic skeleton compounds of six types of tea were verified by chemometrics method to confirm that the results of screening skeleton compounds are reasonable.The experimental results were as follows:(1)The Tenax TA adsorption tube,stir bar sorptive extraction,solid-phase microextraction combined with gas chromatography/mass spectrometry were used to compare aroma compounds in 18 samples of six types of tea.It showed that the total peak area of volatile compounds adsorbed by Tenax TA adsorption tube method was significantly higher than stir bar sorptive extraction,solid-phase microextraction method(P<0.05),and it adsorbed both the number and relative content of short carbon chain compounds were significantly higher than other methods(P<0.05).(2)The standard substance for 106 volatile compounds of tea were determined by gas chromatography/flame ionization detector.The consistency between determined value and theory calculated value were compared.The results showed thatthe quantitative correction factors of determined value was quite different from the theory calculated value.Among them,there were 11 compounds with deviation of 21%-40%,14 compounds with 41%-60%,10 compounds with 61%-100%,and 5 compounds with deviation of more than 100%.(3)The aroma conpounds of 140 samples of six types of tea were analysed by the Tenax TA adsorption tube method,gas chromatography/flame ionization detector.A total of 34 aromaticskeleton compounds insix types of tea were selected by the quantitative results of tea aroma combined with odor active value,and 1-penten-3-ol,linalool,propanal,2-methyl-,hexanal,pentanal,2-methylbutanal,3-methylbutanal,ionone,2,3-butanedione are common skeleton compounds in six types of tea.(4)The quantitative results of tea aroma combined with chemometrics were used to classify 140 tea samples.The results of both principal component analysis and heatmap analysis showed that the compounds that had higher contributions were basically consistent with 34 aromatic skeleton compounds that were filtered.