Effects of different processing conditions on the carotenoid's composition, phenolic contents, and antioxidant activities of Brassica campestris leaves

Leafy vegetables are enriched with health-promoting compounds such as carotenoids and polyphenols. Different processing treatments have been shown to affect the amounts of these compounds. In this study, mustard (Brassica campestris) leaves were subjected to various processing treatments, boiling, frying, freezing, sonication, microwaving, and blanching. Carotenoid contents were determined using HPLC-DAD while the total phenolic, flavonoids, anthocyanin, and antioxidant activities were determined using established spectroscopic protocols. It has been found that different processing treatments concentrated the lutein, flavoxanthin, and β-carotene contents of mustard leaves, while frying has been found to have deleterious effects on these compounds. During boiling the concentration of violaxanthin, antheraxanthin, flavoxanthin, and lutein was significantly increased to 87.4, 29.9, 20.4, and 340.8 μg/g respectively versus control. The total anthocyanin and phenolic contents of mustard leaves were better preserved during frying having values of 6.2 mg/L and 1281.2 mg/100g, respectively, whereas the total flavonoid contents (TFC) in the control sample was 111.8 mg/100g. Among the studied treatments the highest TFC was reported in the blanched samples (108.7 mg/100g), followed by sonication (107.1 mg/100g). During microwave and sonication, the antioxidant potential of the treated samples had significantly increased while in other treatments, it was reduced.