Effects of Different Cooking Methods on Physicochemical and Bioactive Compounds of Selected Green Vegetables in North Eastern Region, Bangladesh

Md. Rahmatuzzaman Rana¹*, Hasan Ahmad¹, A.S.M. Sayem¹, Jakia Sultana Jothi², Md. Mozammel Hoque¹ and Mizanur Rahman¹

¹Department of Food Engineering and Tea Technology, School of Applied Sciences, Shahjalal University of Science and Technology, Sylhet Sadar, Sylhet, Bangladesh.

²Department of Food Processing and Engineering, Faculty of Food Science and Technology, Chattogram Veterinary and Animal Sciences University, Khulshi, Chattogram, Bangladesh.

Corresponding Author Email: rzaman-fet@sust.edu

This study evaluated the effects of three cooking methods, including boiling (100 oC, 5 min), steaming (7.5 min), and microwave (900 W, 1 min) on physicochemical characteristics and bioactive compounds of three widely consumed winter vegetables in Bangladesh, such as green bean (Lablab purpureus), cabbage (Brassicaoleracea var. capitata), and mustard leaf (Brassica juncea). The ascorbic acid (AA) content was decreased significantly after all cooking treatments. In general, the AA retained by different vegetables was highest after microwave cooking and lowest after boiling. Cooked vegetables contained more β-carotene than fresh vegetables, and maximum retention was observed after steaming. However, total flavonoid contents were decreased slightly for all treatments. With the exception of cabbage, both steaming and microwave cooking enhanced significantly (P<0.05) the polyphenol content (TPC) in all vegetables. The highest TPC was found in the green bean during boiling (72.5 mg GAE/100 g), and the lowest was found in cabbage with steaming (35.58 mg GAE/100 g). There is a significant increase in antioxidant activity after boiling and steaming, except microwave cooking of cabbage and mustard leaf. However, the lightness (L*) of all vegetables decreased for each cooking method, but the greenness intensity increased after microwave cooking. Overall, cooking can alter the food's physical and nutritional content but depend on vegetables and the method of cooking.

Bioactive Components; Boiling; Green Vegetables; Microwave; Steaming

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