Abstract:
The effects of selenium (Se), aluminum (AI) at concentrations of 0, 50, 500 ppm and chitosan at 0,
5, 10, 20 ppm, pH of 4.5, 5.5, 6.5 were conducted in preharvested Assam tea to obtain high quality
of catechins and its derivatives. Results revealed that Se and AI could promote the plant height,
number of leaves, leaf area, ascorbic acid, total chlorophyll, chlorophyll a, b, carotenoids, phenolics,
and proline contents of tea leaves subjected with Se and AI, compared with the control. Catechins
and eight derivatives; gallocatechin (GC), (-)-epigallocatechin (EGC), catechin (C), (-)-epicatechin
(EC), (-)-epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), (-)-epicatechin gallate(ECG),
and catechin gallate (CG), and theanine of tea treated with Se were greater than tea treated with AI.
Major volatile compounds of tea treated with Se and Al were phthaline, pentanoic acid and
trimethoxyoctane, but acetaldehyde was found abundant in the control. However, effect of chitosan
and pH on catechins, its derivatives and quality of preharvested tea was shown that application of
chitosan at 5 ppm, pH 4.5-5.5 increased greater growth, qualities, and eight catechin derivatives
(GC, EGC, C, EC, EGCG, GCG, ECG, and CG). Major volatiles of tea subjected to chitosan were
propane, prapanoic acid, and phthalic acid. In the postharvested treatment with Se, AI, and chitosan,
results obtained were similarly to the preharvested treatments of which catechins varied among
soaking times of Assam tea in Se, Al and chitosan solutions.