Effect of domestic cooking methods on the total antioxidant capacity of vegetables

As well as tables of food composition, total antioxidant capacity (TAC) databases--developed in past years for investigating health effects of antioxidant-rich foods in epidemiological and nutritional studies--have been created on the basis of analytical data from raw plant material. However, most vegetables are commonly cooked before consumption. With the aim of completing a previously developed TAC database, the effect of the major domestic practices (i.e. boiling, pan-frying and deep-frying) on the TAC of commonly consumed cooked vegetables was evaluated. Based on dry weight, boiling generally resulted in positive TAC changes whereas a general negative effect on the TAC was observed in pan-fried vegetables. Deep-frying produced a TAC increase of potato, artichoke and aubergine but a TAC reduction of mushroom and onion. The present study clearly indicates that cooking is not always a detrimental process when the TAC is used as an index to evaluate the nutritional characteristics of vegetables.