Effect of high pressure carbon dioxide (HPCD) treatment on enzyme inactivation and other properties of tomato juice

Abstract

Among the recent non-thermal technologies developed, HPCD treatment has been shown to be effective for the inactivation of microorganisms and enzymes avoiding food exposure to the adverse effects of high temperatures. Processing of tomato juice can result in a modification of its consistency and a decrease of its viscosity due to the activity of enzymes such as pectinmethylesterase (PME), polygalacturonase (PG). Peroxidase (POD) catalyzes oxidation reactions related to the production of undesirable flavours and colours. The main objective of this work was to study the effect of the HPCD technology on tomato juice. The influence of HPCD process parameters such as pressure (8.5 - 20 MPa) and temperature (35 and 45 ºC) on the inactivation kinetics of PME, PG and POD and physical parameters such as pH and particle size distribution was evaluated. Results showed that increasing pressure and temperature decreased the residual activity of the enzymes evaluated. The results obtained showed a higher efficiency of the HPCD technology regarding the high pressure processing (HPP) technology since the pressure required to achieve enzymatic inactivation by HPCD (8.5 – 20 MPa) are well below the pressure required by HPP (600-800 MPa) for the same purpose. HPCD technology uses much softer processing conditions that modify the tomato juice to a lesser extent and achieve a greater degree of enzymatic inactivation. The tomato juice pH value (4.1 ± 0.1) did not change significantly (p ≤ 0.05) before and after HPCD treatment. The particle size distribution (PSD) of the tomato juice was bimodal, with a particle diameter that shifted towards lower sizes after HPCD treatment, indicating that homogenization is favoured by this treatment.