Comparative Study of Manufacturing Process Differentiation of Volatile Components in Kenya Purple Tea Variety TRFK 306/1

Abstract

Background: Purple tea variety tea is a kind of special tea germplasm resource, which attracts attention due to its rich anthocyanins, unique leaf color and health care. Methods: This study clarified characteristic volatile components among different tea categories made from Kenya's purple tea variety. As raw materials, one bud and two or three leaves of Kenya purple tea variety (TRFK306/1) were utilized. Then, the fresh tea leaves were processed into green tea (PG), white tea (PW) and black tea (PB) based on different manufacturing processes. Volatile compounds in different categories of tea were detected and analyzed qualitatively and quantitatively by Head Space-Solid Phase Micro Extractions- Gas Chromatography-Mass Spectrometry (HS-SPEM-GC-MS), in combination with principal component analysis (PCA), partial least squares (PLS) analysis. Moreover, variance verification and tea sensory evaluation analysis were also conducted to explore characteristic metabolites. Results: The result showed that 45 kinds of volatile components were identified in green and black tea, and 38 kinds were identified in white tea. The volatile components could be divided into six categories, including alcohols, ketones, aldehydes, esters, hydrocarbons and nitrogen-containing compounds. The number of volatile components among teas is 5(PG_vs_PB), 6(PG_vs_PW), and 9 (PW_vs_PB), respectively. There was a significant difference between PB and PW in the first principal component (R2X1=0.571), and PG was in between. It was found by PLS model analysis that there were 12 potential characteristic components with variable importance factor (VIP) greater than 1.0. Conclusion: The result showed that trans-β-Ocimene, nonanal and 6-Methyl-5-heptene-2- one as characteristic volatile components in PG, and β-ionone and trans-geraniol were characteristic aroma components of white tea and black tea, respectively.