Analysis of Different Parts of Broccoli (Brassica oleracea var. italica) Leaves and Retention of Functional Compounds Under Different Cooking Methods.

The disposal of broccoli by-products, such as broccoli leaves and stems, can potentially have harmful impacts on the environment. However, these by-products may contain substantial amounts of phytochemical compounds with potential health benefits. In this study, the phytochemical composition and antioxidant activities of different parts of broccoli leaves, such as leaf blades and petioles, were analyzed to identify their potential use as functional food materials. Ten glucosinolates, 1 nitrile, 1 isothiocyanate, 14 hydroxycinnamic acids, 3 benzoic acids, 5 flavonoids, and 1 lignan were detected in the broccoli leaf blades, whereas 10 glucosinolates, 1 nitrile, 1 isothiocyanate, 11 hydroxycinnamic acids, 3 benzoic acids, 0 flavonoid, and 1 lignan were detected in the petioles. Antioxidant activity was consistently high in the leaf blades, indicating greater accumulation of bioactive compounds in the blades. Furthermore, broccoli leaf blades were subjected to different cooking methods (boiling, steaming, and sous-vide) to assess changes in antioxidant activities, and sulforaphane content. Significant differences were observed depending on the cooking method, with steaming and sous-vide methods demonstrating greater antioxidant activity than that of boiling. Although both boiling and steaming resulted in a reduction in sulforaphane content compared with that of the raw samples, the sous-vide method led to an increase in sulforaphane content. In conclusion, broccoli leaf blades have superior phytochemical composition and antioxidant activities, and when broccoli leaf blades are cooked sous-vide, the retention of bioactive compounds is the highest, suggesting that health functional foods can be developed through food upcycling.