Processing effects on antioxidant, glucosinolate and sulforaphane contents in broccoli and red cabbage

The objective of this study is to investigate the effects of three home cooking methods traditionally used all around the world (boiling, steaming and microwaving) in two vegetables: broccoli and red cabbage. Their effects on phytochemical content (i.e., polyphenols, ascorbic acid, anthocyanins, glucosinolates and sulforaphane) and on total antioxidant capacity were investigated. Steaming and microwaving were explored to understand the effect of cooking time and/or cooking power. Nutrient and health-promoting compounds in broccoli and red cabbage are significantly affected by domestic cooking. The boiling seems to result in a very significant loss of nutritional compounds by leaching in cooking water. However, steaming and microwaving allowed the preservation of the higher quantities of bioactive compounds such as antioxidant compounds and glucosinolates. Microwave cooking significantly influenced the concentrations of bioactive compounds such as ascorbic acid, anthocyanins and sulforaphane. Sulforaphane content increased 4 or 6 times during the first minute of microwaving in the two vegetables.