Analysis of Main Quality Components of Guizhou Tencha Collected in Different Picking Periods
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Abstract:
In order to investigate the quality difference of tencha collected in different picking seasons under the same shading conditions, the fresh leaves of the same grade Fuding Dabai tea collected in late spring, early summer and midsummer were used as the objects in this study. Relevant biochemical components were detected and analyzed after the teas being processed by the same tencha process. The results showed that with the picking period being moved to a later time, the contents of water extract, tea polyphenols, total chlorophyll, chlorophyll b, TDF, IDF and SDF, the phenol-ammonia ratio and the IDF/SDF ratio increased significantly (P<0.05), and the total free amino acid content, Vc content and the chlorophyll a/chlorophyll b ratio decreased significantly (P<0.05). Principal component analysis showed that the cumulative variance contribution rate of total free amino acids, water extract, SDF, chlorophyll a, soluble sugar and GCG contents reached 95.73%, which could be used as a characteristic component of the quality of tencha. The soluble sugar content (3.00%), total free amino acid content (4.40%), caffeine content (2.57%), Vc content (5.25 mg/g), gallic acid content (1.10%), EGCG content (6.74%), content of total ester-type catechins (9.02%), and content of total catechins (10.40 %) of the tencha N1 harvested at the end of spring were the highest, whilst the tea’s polyphenol content (10.94 %), catechin bitterness and astringency index (16.59), phenol-ammonia ratio (2.49) and IDF/SDF ratio (4.84) were the lowest, thus, the overall quality was the best. Therefore, the quality of tencha processed in late spring was the best, whilst the quality of tencha processed in early summer or mid-summer was relatively poor. This study can provide a scientific theoretical basis for the production and processing technology and quality improvement of Guizhou tencha and matcha.
