Academic Member of the Department of Food Science and Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran.
Tea might be considered as the most popular drink in Iran as well as some other parts of the world. Its popularity to some extent depends on its flavor and some other constituents present in its leaves or extract. Black tea samples from various agro climatic zones of northeast of Iran were evaluated for the chemical constituents, polyphenols and metal analysis that determine the quality perception. Black tea epicatechins, namely epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC) and epicatechin (EC) were also assessed by HPLC. Furthermore, for metal analysis, the level of Mn, Cu, Pb and Ni elements were evaluated in black tea from the five tea growing districts of north Iran. The results confirmed that the total polyphenol concentration in black tea varied from 17.10 g/100g to 12.20 g/100g, whereas the catechins content ranged from 17.20 mg/g to 15.80 mg/g. Furthermore, significant differences were detected in the chemicals content between different black tea samples. In general, the contents of caffeine and water extract in Lahijan sample were found to be the highest. The Mn content was found in the range of 702 and 731 mg/kg and copper ranged between 24.30 and 32.60 mg/kg. The Lead content in the samples were in the range of 0.22 and 0.35 mg/ kg. Nickel concentration in black tea leaves ranged between 2.31 and 3.67 mg/ kg. The results of the evaluation of tea confirmed that the level of elemental contents in all of the tea sample were completely lower than the acceptable limit according to the international standards. It was noted that in different black tea samples, Lahijan produced the best quality tea followed by Tonekabone.