Antioxidant properties of green broccoli and purple-sprouting broccoli under different cooking conditions

Abstract

Diets rich in fruit and vegetables have long been associated with reduced risk of chronic disease. Antioxidant components of fruit and vegetables have recently generated great interest in scientific research. However, few studies have explored antioxidants in food after cooking. Cooking may alter antioxidant properties by initiating destruction, release or transformation of antioxidant food components. This study has investigated the effects of boiling and microwaving on the antioxidant properties of green broccoli and purple-sprouting broccoli. Antioxidant activities of the broccoli extracts were estimated using the 2,2-diphenyl-1-picrylhydrazyl radical scavenging method, vitamin C and phenols were estimated with the Folin-Ciocalteu reagent, flavonoids were evaluated using colorimetric methods and anthocyanins were determined by a pH differential method. Results showed antioxidant components of cooked broccoli to be quite different from uncooked broccoli. The antioxidant content of broccoli was retained and/or enhanced more after microwaving than after boiling. Cooking in water caused a leaching effect of antioxidants, and this increased with cooking time. Purple-sprouting broccoli was found to contain higher contents of antioxidant compounds compared with green broccoli, but tended to show higher sensitivity to cooking treatments. Cooking methods should be carefully considered in current dietary recommendations. © 2012 The Author 2012. Published by Oxford University Press.