Effect of infusion time on phenolic compounds and caffeine content in black tea

Tea is a quite popular and largely consumed beverage in several continents. It is a rich source of phenolic compounds, however, few studies have addressed the availability of these compounds associating with the infusion time of the drink. The objective of this study was to determine total phenolic compounds in several types of black tea either in granule or bag form and to verify the effect of infusion time on the availability of these compounds. The infusion times were varied until 30 min and measurements were done initially at 2.5 min interval up to 10 min whereafter measurements were done at 10 min interval. Eight different brands of tea were analyzed and among these 5 were in tea bag form and 3 in granule form. The total phenolic content was determined by using Folin-Cicoalteau reagent and measurement done in a spectrophotometer. Identification and quantification of some phenolic compounds and caffeine were done in a system of High Performance Liquid Chromatography coupled with Diode Array Detector. Higher concentrations of propyl gallate (43 mg.g− 1), caffeine (67 mg.g− 1), gallic acid (0.9 mg.g− 1), catechin (48 mg.g− 1) and rutin (12 mg.g− 1) were found in Brazilian samples while chlorogenic acid (4 mg.g− 1) and p-coumaric acid (7 mg.g− 1) were found in Indian teas. Chlorogenic acid was not detected in Brazilian teas at all infusion times including the maximum of 30 min tried in this study. It was concluded that these teas are good sources of dietary phenolic compounds and the content of these compounds in the beverage is higher with the longer infusion time.

► This article monitors the effect of infusion times in black tea obtained from several countries such as Brazil, Britain and India. ► The focus is on quantification of phenolic compounds and on caffeine content. ► The paper furnishes yields of these compounds as related to the infusion times.