Quality Analysis of a New Tea Line '606' Oolong Tea in Different Seasons

In order to better understand the impact of the different seasons on the characteristic of oolong tea '606', ultra-high performance liquid chromatography triple quadrupole tandem mass spectrometry (UPLC-QqQ MS) targeted metabonomics, headspace solid phase microextraction combined with gas chromatography time of flight mass spectrometry (HS-SPME-GC-TOF-MS) technology and electronic nose technology were used to determine qualitatively and quantitatively the new line '606' oolong tea's quality, and the group differences of tea samples in different seasons were obtained by partial least squares discriminant analysis (PLS-DA). Results had showed that the total amount of amino acids in tea samples made by different seasons had a downward trend from spring to autumn to summer. Flavor amino acid in oolong tea made by spring buds was especially higher-content than autumn and summer oolong tea (P<0.05), and high level of total bitter amino acid was observed in summer oolong tea. The autumn and summer oolong tea contained higher content of total catechin than spring oolong tea, which carried out that the differences of amino acids and catechins played a strong role in the formation of flavor and quality characteristics of spring, summer and autumn tea. 86 main characteristic volatile substances in total were identified in new line '606' oolong tea in spring, summer and autumn, and among these volatile components were the contents of alcohols and hydrocarbons higher. Ketones were the characteristic aroma components of spring tea. α- Farnesene was the characteristic aroma component of summer tea. Trans Neroli tertiary alcohol, indole and hexanoate were the characteristic aroma components of autumn tea. 23 key compounds for identifying the new line '606' oolong tea in different seasons were determined, which utilized the established PLS-DA model clearly differentiating the tea samples in these three seasons. Electronic nose sensors S1, S2, S6, S7 and S10 made a difference to distinguish the new line '606' oolong tea in different seasons. Nitrogen compound and hydrocarbons were the important material for identifying tea samples in different seasons.