Changes in Polyphenolic Profile and Antioxidant Properties of Selected Raw and Processed Vegetables Under Different Cooking Methods

The polyphenol profile and antioxidant potential in five raw vegetables (beetroot, red cabbage, red pepper, green pepper, kale) were determined after steaming and sous-vide (SV) at different temperatures (80 °C, 85 °C and 90 °C). The total polyphenol content was determined by spectrophotometry using the Folin–Ciocalteu reagent, the antioxidant properties using the DPPH radical, and the polyphenol profile by HPLC–UV–VIS. The sous-vide method at 85 °C resulted in the greatest, smallest losses or the greatest increase in total polyphenol content, whereas the sous-vide method at 80 °C and 85 °C had the same effect on the antioxidant potential and polyphenols profile.