Abstract:In this study, the effects of the freezing treatment prior to withering and the combination of freezing treatment with one, two and three times shaking after withering on the formation of black tea quality were analyzed, and the optimal process conditions were determined. The results showed that the new process could significantly increase the contents of gallic acid, polyphenols, theaflavins and flavonoid glycosides in tea (P<0.05), meanwhile, the freezing treatment could significantly reduce the soluble sugar content (P<0.05) (decreased by 10.73%), and the combination of freezing and shaking could significantly reduce the theabrownine content (P<0.05) with an average decrease of 6.77%. Compared with the freezing treatment, the combination of freezing and shaking significantly reduced the content of tea polyphenols (P<0.05) with an average decrease of 3.55%, whilst increased significantly the theaflavin content (P<0.05) with an average increase of 18.06%. Among all the treatments, he combination of freezing and twice shaking led to relatively high contents of amino acids, theaflavins and cis-caproate-3-hexen ester, and relatively low contents of gallic acid, catechins, flavonoid glycosides, theabrownins and 3-octen-2-one. In the resulting black tea had a bright orange yellow, sweet aroma, mellow quality, with its total sensory score being 91.30, which was 2.40 and 2.60 points higher than the score of the control and the tea subjected to the freezing treatment, respectively. In conclusion, the combination of freezing and twice shaking was the best new process.
