Influence of temperature and brewing time on the total polyphenol content in tea

In a standard daily diet tea is a crucial source of antioxidant compounds - polyphenols. On average, Poles drink 2-3 cups of tea each day. Its regular consumption may prevent cardiovascular and metabolic disorders. The objective of the study was to compare the total polyphenol content (TPC) in various types of tea infusions, prepared at different temperatures (T=70/100°C) and brewing time (t=2/10 minutes). Black and green teas in both options, organic and conventional, were tested. TPC was measured using the Folin-Ciocalteu spectrophotometric method and expressed as gallic acid equivalents (mg GAE/g of the sample). Each tea extract was assayed three times independently. In the organic types of teas, the highest TPC was found in green tea (95.65±3.96 mg GAE/g of the sample) brewed at 100°C for 10 minutes, while the lowest in black tea (51.65±2.39 mg GAE/g of sample) brewed at 70°C for 2 minutes. Among conventional teas the highest TPC was noted also in a green tea (91.83±2.29 mg GAE/g of the sample) brewed at 100°C/10 minutes and the lowest in black tea (48.88±2.20 mg GAE/g of the sample) at 70°C/2 minutes. Longer brewing time increased TPC in organic teas (in both, black and green) and in conventional black tea (p<0.05), whereas higher temperature increased TPC only in organic teas (black and green) (p<0.01).