Effect of Catechins Extract of Green Tea on Quality Protection of Black Tea-bag During Storage

Green tea is one of the richest sources of antioxidants especially catechins, which are studied most because of their health benefits. These valuable compounds may lose their activity and oxidize to thearobigin during fermentation stage or black tea processing. The main objective of this research is applying antioxidant mixtures extracted from green tea on packaging material of black tea and determining the amount of antioxidants released from the tea bags by their immersion into boiling water. The green tea extracts prepared by a two-step extraction process in water at 50°C and 80°C in four individual time periods, i.e., 10min, 10min; 10min, 20min; 20min, 10min; 20min, 20min (1). Final extract from each process was analyzed by HPLC and DPPH tests and then sprayed on the tea bag packaging material.The activity and concentration of antioxidants (catechins) released from treated tea bags were investigated immediately and after 3 months storage. Sensory properties of the tea beverage samples were also studied. The results (Tables 1, 2) show that the concentration of antioxidants increases by 66–76% as compared to control i.e., untreated black tea. Tea beverage samples were more astringent as compared to untreated black tea. Under different time/temperature conditions the best results were obtained by the sample extracted by a two-step process (20min at 50°C) and (10min at 80°C) with the highest concentration of antioxidants, lowest astringency and best stability during 3 months storage.

Keywords: Green tea, Antioxidant activity, Catechins, Black tea bag

References: 1. Labbe, D, et al. (2008) Food Chem. 111:139–143.

Table 1: Effect of extraction time on concentration/activity of the antioxidants released from treated tea bags immediately after preparation

Extraction time (min)	Total antioxidant
	Concentration (µg/mL)	Activity (%)
10,10	0.52±0.02a	71.70±0.35a
10,20	0.57±0.05a	72.58±0.51a
20,10	0.62±0.07b	72.88±1.26b
20,20	0.64±0.01b	73.34±0.35b

Table 2: Effect of extraction time on concentration/activity of the antioxidants released from treated tea bags after 3 months storage

Extraction time (min)	Total antioxidant
	Concentration (µg/mL)	Activity (%)
10,10	0.44±0.01a	67.70±0.35a
10,20	0.49±0.01a	66.67±0.42a
20,10	0.56±0.02b	70.54±0.30b
20,20	0.58±0.01b	67.83±0.38b