Abstract
The objective of this study was to determine the relationship between the plucking periods and the major constituents and the antioxidant activity in green tea. Green tea was prepared from leaves plucked from the end of April 2013 to the end of May 2013 at intervals of one week or longer. The contents of theanine, theobromine, caffeine, catechin (C), and gallocatechin gallate (GCg) were significantly decreased, whereas those of epicatechin (EC), epigallocatechin gallate (EGCg) and epigallocatechin (EGC) were significantly increased along with the period of tea leaf plucking. In addition, antioxidant activity of green tea and standard catechins was investigated using ABTS, FRAP and DPPH assays. The highest antioxidant activity was observed in relatively the oldest leaf, regardless of the assay methods used. Additionally, the order of antioxidant activity of standard catechins was as follows: EGCg ≥ GCg ≥ ECg > EGC ≥ GC ≥ EC ≥ C. Moreover, the cis-catechins contents were the key factor affecting the antioxidant activity of green tea in all assays employed (ABTS, r = 0.731, p < 0.01; FRAP, r = 0.886, p < 0.01; DPPH, r = 0.778, p < 0.01).
Highlights
Tea, derived from leaves of the plant Camellia sinensis, is the most widely consumed beverage in the world and can be categorized into three main types depending on the level of oxidation: green, oolong and black tea [1]
The gallated catechins are derived as the sum of epigallocatechin gallate (EGCg), gallocatechin gallate (GCg) and epicatechin gallate (ECg)
These values were found to be very influenced by the components making up that parameter, and especially EGCg and ECg have an important role in the content of parameters
Summary
Tea, derived from leaves of the plant Camellia sinensis, is the most widely consumed beverage in the world and can be categorized into three main types depending on the level of oxidation: green (unfermented), oolong (partially fermented) and black (fermented) tea [1]. Some factors are more important than others; for example, the highest quality green teas are plucked during the first flush in late April and early May and quality declines in later harvests [5]. The buds and the first two to three leaves are plucked by hand or a mechanical tea plucker for processing. This process is generally repeated every one to two weeks. These basic types of tea have different quality characteristics, including appearance, flavor, taste, and color [6]
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