Assessment of active ingredients in pickled tea

Abstract

Miang (pickled tea) is a favourite light-meal for some people in certain areas of Thailand, particularly the north, and it has been found to play a role in various native cultures. In order to develop Lampang miang products for a wider market, relationships between processing conditions and quality of miang were studied. Apart from substances affecting miang flavour and appearance, phenolic compounds [EGCG (epigallo-catechin-gallate), EGC (epigallo- cathechin) and cathechin] and caffeine were reported as the most important functional substances in fermented tea products and also having significant impact on the product’s final quality. Assam and Oolong tea leaves; fresh, steamed and fermented Assam tea leaves (miang); from Pa Miang Village, Jae Son Sub-district, Jae Hom District, Lampang Province were examined to determine EGCG, EGC and caffeine contents using high performance liquid chromatography (HPLC), together with total phenolic compound determination using spectrophotometry. Small amounts of cathechin (1.34-8.71mg/g) were found in all miang samples while relatively high EGCG contents (range from 18.50 to 37.24 mg/g) were found to vary among treatments with total phenolic compounds around 26.24 – 48.76 mg/g. A higher EGCG and EGC content was presented in miang produced from younger fresh (50.53 mg/g) and steamed tea leaves (94.78 mg/g), compared with older fresh ones (48.12 mg/g). Both higher phenolic compounds and caffeine were found in Assam tea leaves compared with Oolong leaves. The miang produced from steamed tea leaves was found to contain more caffeine than from fresh leaves. It could be concluded that EGCG is the obvious phenolic compound in miang products and the conditions that increase the phenolic compound contents appear to affect the caffeine contents in the same manner