Antioxidant activity of extracts from old tea leaves

The effect of methanolic extracts of old tea leaves (OTL) (leaves numbers 5-8 of the shoots) on the stability of rapeseed oil during heating at 60 degrees C and deep-fat frying of potato crisps at 180 degrees C was determined. The OTL extract was effective in retarding oil deterioration at 60 degrees C, with activity increasing with concentration in the range 0.02-0.25%. At a concentration of 0.25% the OTL extract was similar in activity to a rosemary extract added at 0.1%. The OTL extract (0.1%) was as active in retarding the deterioration of oil as a rosemary extract (0.1%) during repeat frying of potato crisps. Hence it is clear that old tea leaves, which at present are often considered as agricultural waste, contain antioxidants that may usefully be extracted and added to foods. (C) 1998 Elsevier Science Ltd. All rights reserved.