3.2. Testing Material

The research material was juice made from frozen blackcurrants (Ribes nigrum L.) of the Tisel cultivar, which is of Polish origin and bought from the local wholesaler. To produce blackcurrant juice, the fruit was enzymatically treated with a pectinolytic preparation (Klerzyme 150, DSM, Lille, France) for 1.5 h at 45 °C, and then squeezed in a hydraulic layer press (Tako, Czestochowa, Poland). The juice was transferred into 250 mL glass bottles and divided into six portions. The first was left without further processing (FJ). The second was heated to 45 °C for 10 min (T45), the third was pasteurized at 85 °C for 10 min (T85), both thermal processes were carried out in a laboratory pasteurizer (Labo Play, Bytom, Poland). The next portions were treated with supercritical carbon dioxide in the batch system using a Spe-ed SFE 4 (Applied Separations, Allentown, PA, USA). The method consists of placing the sample in a thermostatic pressure chamber, to pump CO₂ at the applicable pressure, and then leave it for a specified period of time to ensure penetration. Three pressure variants were applied: 10, 30, and 60 MPa for 10 min, at 45 °C (SCCD10, SCCD30, SCCD60). Selected pressure parameters cover the entire operating range of the device, from minimum to maximum, with the optimal duration time of the process. Pasteurization carried out at 85 °C for 10 min is a widely used method of preserving fruit products in bath pasteurization. Mild heat treatment at 45 °C was used to exclude the influence of temperature in the treatment using SCCD. The samples were frozen before carrying out further research. Samples not subjected to digestion were considered to be control samples.