High-Pressure Treatment of Sea Buckthorn Syrups

The U 4,000 high-pressure vessel (volume of 0.75 L, Unipress, Warsaw, Poland) was used for the high-pressure treatment of the sea buckthorn syrups (600 MPa, initial temperature: 35°C, holding times: 4 and 8 min). Process parameters were chosen based on the industrial standard as well as on expected microbial reduction based on scientific literature (37 (link), 40 (link), 41 (link)). Before treatment, the plastic bags (polyethylene and polyamide layer; Luckfield and Mann GmbH, Kiel, Germany) containing the syrup (300 mL) were vacuum sealed (Plus Vac 23, KOMET Maschinenfabrik GmbH, Plochingen, Germany) and stored at 8°C until processing. Prior to the treatment, the samples were placed in the pressure chamber and a mixture of water and 1,2-propanediol (1:1, v/v; Carl Roth GmbH and Co. KG, Karlsruhe, Germany) served as the pressure-transmitting medium. When 600 MPa were reached, the time measurement began. The temperature rise in the high-pressure vessel caused by the adiabatic heat of compression was max. 20°C, i.e., the final temperature of the syrup never exceeded 35°C. At the end of the holding time, the pressure was automatically released, and the bags were removed. The treated samples were cooled immediately.