Antioxidant of green tea and pickle tea product, miang, from northern Thailand

Abstract

Consumption of tea offers health benefits attributed to phenolic compounds. In Thailand, tea mostly belongs to Camellia sinensis var. assamica which is grown in the northern region. Although, Assam tea cultivation is for tea manufacture, it is also originally grown as part of the forest and is being recognized as agroforestry system. Local northern Thais commonly use mature tea leaves to make a pickle tea product called 'miang' to chew on during working hours (similar to chewing tobacco) and as a common household guest reception snack. While this product still has low economic value, it is gradually gaining more attention from Thai researchers due to its health benefit potential. This study aims to investigate phenolic content in miang in comparison to the benchmark green tea product. A sample of freshly picked tea shoots (the first top 3 leaves) and mature tea leaves (leaves 4-6 from top) and the processed products from tea shoots and mature tea leaves (green tea and miang, respectively) from the same crop were compared in terms of total phenolic content and antioxidant activity measured by FRAP and ORAC assay. The results indicated lower content of phenolic compounds and antioxidant activity measured by both assays in mature tea leaves compared to tea shoots. However, when green tea and miang were extracted under conditions that mimic normal consumption manner, i.e., brewing for green tea and grinding for miang, the results showed that miang had a comparable amount of total phenolic content and antioxidant activity. The results from the same extraction conditions between green tea and miang is also provided in this paper.