Abstract
Tea (Camellia sinensis) is widely sought for beverages worldwide. Heavy metals are often the main aims of the survey of teas, given that the use of agricultural fertilization is very frequent. Some of these may affect the content of bioactive compounds. Therefore, in this study, we analyzed fermented and non-fermented teas of a single plant origin from Japan, Nepal, Korea, and China, and described mutual correlations and changes in the total antioxidant capacity (TAC), and the content of polyphenols (TPC), caffeine, and heavy metals in tea leaves, in relation to the origin and fermentation process. Using UV-VIS spectrophotometry and HPLC-DAD, we determined variations in bioactive compounds’ content in relation to the fermentation process and origin and observed negative correlations between TAC and TPC. Heavy metal content followed this order: Mn > Fe > Cu > Zn > Ni > Cr > Pb > Co > Cd > Hg. Given the homogenous content of these elements in relation to fermentation, this paper also describes the possibility of using heavy metals as determinants of geographical origin. Linear Discriminant Analysis showed an accuracy of 75% for Ni, Co, Cd, Hg, and Pb, explaining 95.19% of the variability between geographical regions.
Highlights
A tea infusion prepared from Camellia sinensis is one of the most popular beverages worldwide [1,2,3]
Given the popularity of tea and limited knowledge in the area mentioned above, our research focuses on detecting the possible effect of the fermentation process on the bioactive compounds and the content of heavy metals in tea leaves originated from one plant
Based on the consistent behavior of heavy metals relative to processing, we focused on using these elements as parameters that are suitable for geographical origin identification, as well as using advanced statistical approaches
Summary
A tea infusion prepared from Camellia sinensis is one of the most popular beverages worldwide [1,2,3]. During the oxidation process connected with the fermentation of black tea, oxidation products such as theaflavins and thearubigins are produced. These represent the main difference between black and green tea. Research has shown that black tea has approximately 20–30% Camellia sinensis polyphenol content [5]. Total antioxidant capacity (TAC) has become a very popular quality parameter of food products and plant extracts because studies are establishing a link between dietary TAC, as a measure of antioxidant intake, and health [7]
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