Effect of the Degree of Tossing on the Quality and Antioxidant Activity of Xinyang Tea
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Abstract:
The quality and antioxidant activity of Xinyang green tea, Xinyang black tea, and Xinyang teas with different degrees of tossing were compared using the fresh leaf raw materials (one bud and three leaves or four leaves). This provides a theoretical basis for the further development and utilization of the fresh leaves of small-leaf tea varieties in the Jiangbei tea region. The main biochemical and volatile components of the five teas were examined by spectrophotometry, liquid chromatography and GC-MS. Their antioxidant activities were evaluated by the DPPH method, followed by sensory evaluation. The results showed that the contents and composition of the main components in the Xinyang teas with different degrees of tossing differed. As the degree of tossing increased, the content of tea polyphenols decreased from 21.17% to 18.90% (P<0.05), the content of amino acids increased from 3.43% to 3.73% (P<0.05), and the content of flavonoids increased from 5.63 mg/g to 6.55 mg/g (P<0.05). The aroma components showed a steady increase trend, in particular, the contents of monoterpenes increased significantly (P<0.05) e.g. β-pinene increased from 0.13 μg/g to 0.37 μg/g, E-β-basilene increased from 0.05 μg/g to 0.15 μg/g. Sensory evaluation revealed that the quality of tea subjected to light tossing was better . The calculations of the IC50 values of DPPH radical scavenging revealed that with the rise of the degree of tossing, the IC50 value increased. The 1/IC50 value was significantly and positively correlated with the content of tea polyphenols (P<0.01). The 1/IC50 value was significantly and negatively correlated with the contents of amino acids and flavonoids (P<0.01), and significantly and negatively correlated with the contents of 19 volatile components (P<0.05). These results indicate that the quality of the Xinyang green tea made from one bud and three or four leaves can be improved by a proper tossing process.
