Objective Varied compressing conditions to make tea cakes with leaves plucked from two tea cultivars were tested to optimize the physiochemical quality of the products.
Method Leaves plucked from Huangquanyin and Jinmoudan bushes were used in an orthogonal experiment designed to optimize the tea cake forming process. Conditions of cold and steam pressing under a pressure of 30, 60, 90, 120 or 150 kN, held for 20, 40, 60, 80 or 100 s, and dried at 40, 60 or 80 ℃ were implemented. Sensory evaluation, chemical analysis, and a cracking test were conducted on the tea cakes. Pearson bivariate correlations between the sensory quality and physicochemical properties were analyzed.
Result The results of orthogonal test and sensory analysis showed that the test samples with the highest sensory evaluation scores of the two cultivars had the same pressing process scheme. The resulting Huangguanyin compressed white teas received an overall sensory score of 94.75, and the Jinmudan teas 95.90. The contents of polyphenols and amino acids in the tea cakes significantly correlated to the sensory scores with r=0.358 for Huangguanyin and 0.346 for Jinmudan (P<0.05). And the mechanical rupture strength extremely significantly correlated to the sensory scores of the compressed white teas with r=0.430 (P<0.01).
Conclusion The optimized pressing process of Huangguanyin and Jinmudan compressed white teas is as follows, the steam pressing applied 60 kN compression pressure held for 40 s and dried at 40 ℃. The composition and contents of the flavoring compounds, such as tea polyphenols and amino acids, as well as the rupture strength positively affected the sensory quality of the two kinds of tea cakes.
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