Development of a visual test kit for estimation of total polyphenols in tea

Regarding the tea quality, the International Organization for Standardization (ISO) has established recently the levels of minimum concentrations of total polyphenols in tea. Because of this standard, the commercial exploitation of tea demands the investigation of the levels of total polyphenols. However, it is quite difficult for most producers and traders to implement because this test is laborious, time consuming, required instruments and trained technicians. Therefore, a visual test kit for the estimation of total polyphenols was systematically developed and evaluated. The estimation was accomplished by reacting tea extract with Folin–Ciocalteu reagent in alkaline medium to produce a colored compound that was measured visually using a color strip. The results obtained demonstrated that the test kit method was simple, rapid, reliable and comparable with that of the standard method. It can be stated that the test kit is suitable for the estimating of total polyphenols in tea. Since no special equipment is required, the test can be performed at the production site or the tea market even by tea processing workers or tea traders.