Changes in the content of health-promoting compounds and antioxidant activity of broccoli after domestic processing

Abstract

The effect of water- and steam-cooking on the content of vitamin C, polyphenols, carotenoids, tocopherols and glucosinolates, as well as on the antioxidant activity of broccoli, are reported. Flavonoids, phenolic acids, vitamins C and E, β-carotene, lutein, and glucosinolates in domestically processed broccoli were quantified using high-performance liquid chromatography (HPLC) methods; total polyphenols were determined with Folin–Ciocalteu reagent. The antioxidant capacities of broccoli extracts were evaluated using the Trolox equivalent antioxidant capacity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods. The results indicated that steam-cooking of broccoli results in an increase in polyphenols, as well as the main glucosinolates and their total content as compared with fresh broccoli, whereas cooking in water has the opposite effect. Steam-cooking of broccoli has no influence on vitamin C, whereas cooking in water significantly lowers its content. Both, water- and steam-cooking of broccoli results in an increase in β-carotene, lutein, and α- and γ-tocopherols as compared with fresh broccoli. Similar effects of steaming and water-cooking of broccoli on their antioxidant activity were observed.

Keywords:

• Broccoli
• polyphenols
• vitamin C
• carotenoids
• tocopherols
• glucosinolates
• antioxidant activity
• domestic processing

Acknowledgements

The grant from the State Committee for Scientific Research (Poland) (Grant No. PBZ-KBN-094/P06/2003, 2004–2006) is gratefully acknowledged.