Hydrogen peroxide is formed upon cooking of vegetables

Hydrogen peroxide (H2O2) is generated under autoxidation of some components of beverages including flavonoids and ascorbate, especially in tea and coffee. As polyphenols are also present in solid food, especially in vegetables, we checked whether hydrogen peroxide is generated during cooking of several common vegetables. The formation of hydrogen peroxide was found in the decoctions of all cooked vegetables studied except for potato and in the homogenates of cooked vegetables except for garlic and purple potato. The highest concentration of hydrogen peroxide in 1:2 (w/v) homogenates was found for the broad bean (73.4±9.0 µM) followed by broccoli (18.6±0.3 µM), onion (10.4±1.6 µM) and leek (10.0±0.3 µM), while the H2O2 concentration in the decoctions was the highest for broccoli (24.4±0.8 µM), then for broad bean (21.4±1.1 µM), carrot (13.2±0.2 µM) and cauliflower (12.6±1.2 µM).