###### Abstract  
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 \({}^{\circ}\)C, 85 \({}^{\circ}\)C and 90 \({}^{\circ}\)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 \({}^{\circ}\)C resulted in the greatest, smallest losses or the greatest increase in total polyphenol content, whereas the sous-vide method at 80 \({}^{\circ}\)C and 85 \({}^{\circ}\)C had the same effect on the antioxidant potential and polyphenols profile.  
sous-vide; steamed; HPLC; DPPH assay; Folin-Ciocalteu; beetroot; red cabbage; green pepper; red pepper; kale 2025  
1 Chair and Department of Bromatology, Poznan University of Medical Sciences, Collegium Pharmaceuticum, 3 Rokietnicka St., 60-806 Poznan, Poland; [EMAIL_ADDRESS].  
benefits, including improved metabolic health and reduced inflammation [5]. Gut microbiota may also improve the bioavailability of polyphenols by converting them into bioavailable metabolites [4; 6]. Vegetables are eaten raw and subjected to various processes, most often heat-treated, which affects their final nutritional value. Food processing methods are critical in determining the bioactivity and bioavailability of dietary polyphenols, as well as their interactions with the intestinal microbiota [7].  
Traditional heat treatments, including classical cooking, stewing, baking and steaming, cause changes in the chemical composition, mainly the content of secondary metabolites and organoleptic properties of vegetables, causing loss of nutrients and contributing to oxidative processes. The modern sous-vide (French: under vacuum) method involves cooking raw materials in a vacuum-sealed, thermostable, plastic bag in a water bath or convection steam oven at a strictly controlled temperature not exceeding 100 \({}^{\circ}\)C, the most popular temp. from 80 \({}^{\circ}\)C to 95 \({}^{\circ}\)C for a longer time than classical methods [8; 9; 10; 11; 12; 13; 14]. Vacuum sealing of the raw material prevents the transfer of valuable nutrients to the broth through osmosis [15; 16] and limits the oxidation of phenolic compounds and vitamins. Slow heat treatment also prevents the loss of moisture and volatile compounds, preserving the vegetable's delicate, juicy structure, intense flavour, aroma and colour [16; 17; 18; 19]. This process also limits the loss of vitamins and other nutrients [20], and the lack of oxygen prevents lipid oxidation [21]. Raw vegetables do not always have the highest antioxidant potential or polyphenol content compared to processed vegetables because elevated temperature and other factors can affect the bioavailability of active ingredients [22].  
The sous-vide method increases the bioavailability of vitamins, minerals and phytochemicals compared to conventional cooking methods, which may positively affect the development of various diseases, including lifestyle diseases [23; 24]. Therefore, this study determined the changes in the polyphenol total content, their profile and antioxidant properties in selected vegetables with proven high antioxidant potential subjected to steaming and sous-vide cooking at three different temperatures.