Effect of Stir Frying on the Antioxidant Capacity and Aroma Components of Bok Choy (Chinese Cabbage)

Bok choy, Brassica rapa subsp. Chinensis, is a type of Chinese cabbage. Stir frying could affect antioxidant activity and aroma composition of bok choy. Antioxidant activity such as diphenyl picryl hydrazinyl radical and ferric-reducing antioxidant power of the leave and stem samples were determined. The highest ferric-reducing antioxidant power activity was obtained at 1.5 min stir-frying under 160ºC for bok choy leaves (49.7 ± 2.1 µmol FeSO₄/g dry weight). In ferric-reducing antioxidant power assay, antioxidant capacities of bok choy stem samples increased significantly after stir-frying. Dimethyl sulfide (DMS), a typical volatile organic sulfur compound with a characteristic cabbage-like odor, was only observed in leave groups. After cooking treatment, antioxidant activities of bok choy stems were higher than those of leaves in diphenyl picryl hydrazinyl radical assay. Odor-active compounds were identified using gas chromatography-olfactometry-mass spectrometry technique. Compared to stem sample data, more aroma components were quantified in leaves sample in 160, 180, and 210ºC, respectively. It was first time to detect and analysis the aroma components and antioxidant activity in different edible part of bok choy after Chinese domestic cooking.