Kinetic modelling of polyphenol oxidase, peroxidase, pectin esterase, polygalacturonase, degradation of the main pigments and polyphenols in beetroot juice during high pressure carbon dioxide treatment

Supercritical carbon dioxide (SCCD) was applied for the inactivation of tissue enzymes in beetroot juice. The SCCD process parameters had a significant effect on the inactivation kinetics of polyphenol oxidase (PPO), peroxidase (POD), pectin esterase (PE) and polygalacturonase (PG). The use of traditional pasteurization (TP) resulted in a higher level of inactivation of the tested enzymes than SCCD. The lowest decimal reduction time was noted for PG and the highest for POD. The PG, PE, PPO and POD inactivation kinetic constants were calculated as 0.90, 0.85, 0.82 and 0.6 x 10(-2) min(-1) for k-values and 256, 271, 281 and 384 min for D-values, respectively, based on the first order kinetic model. The highest degradation of bethacyanins, bethaxanthins and polyphenols occurred at 60 MPa at 55 degrees C, for 30 min: 58, 32 and 30%, respectively. Overall, SCCD treatment is a promising technique to obtain high quality non-acidified beetroot juice but further studies should concentrate on additional factors affecting the inactivation of tissue enzymes. (C) 2016 Elsevier Ltd. All rights reserved.