Inactivation of pectinmethylesterase (PME) and quality parameters of orange juice have been studied after high pressure carbon dioxide (HPCD) treatment. The HPCD treatment conditions covered a wide range of temperature from 2 to 40 °C, far below normal thermal treatment, while operating pressure was varied from 10 to 30 MPa and exposure time from 3 to 60 min. A decrease in PME activity was found, even at the lowest temperature studied in this work, 2 °C. Different inactivation kinetic models were used to correlate the PME residual activity: the two-fraction model, the fractional-conversion model and the Weibull model. The two-fraction model presents the lowest mean relative deviation. Some quality parameters such as colour, pH, ºBrix, turbidity, ascorbic acid, total acidity and particle size distribution (PSD) were also determined right after HPCD treatment and along storage at 4 °C up to 12 days. PSD shows that HPCD treatment results in a volume increase of small particles and a volume decrease of large particles regarding the non-treated orange juice. Calcium content was also determined before and after HPCD treatment to check for insoluble calcium carbonate formation but not significant changes were observed in calcium content after HPCD treatment.
