Experimental Measurements and Thermodynamic Modeling of CO2 Solubility at High Pressure in Model Apple Juices

High pressure carbon dioxide (HPCD) treatment can be used for the pasteurization of liquid foods. Solubility of CO2 in the liquid affects microbial inactivation. Measurement and prediction of CO2 solubility in a real or model system are of industrial relevance since the knowledge of the solubility limits will avoid the use of excess CO2. An experimental apparatus was set up to measure CO2 solubility in tertiary mixtures of water-CO2-glucose and water-CO2-malic acid and in a quaternary mixture of water-CO2-malic acid-glucose at different concentrations of malic acid (0.01 and 2.68 g in 100 g of solution, corresponding to 7.5 x 10(-5) and 0.02 mols in 100 mols of solution) and of glucose (4 and 12 g in 100 g of solution, corresponding to 0.02 and 0.07 mols in 100 mols of solution). CO2 solubility was also measured in a more complex Solution of water-malic acid-ascorbic acid-pectin-glucose-sucrose, based on apple juice composition and in a commercial apple juice. The range of pressure tested was between 7.5 and 15.0 MPa while the temperature was between 308 and 333 K. CO2 solubility was inversely proportional to the glucose and sucrose concentration. Malic and citric acids only slightly affected CO2 solubility. Slight differences in the value of CO2 Solubility were detected between the model solution and the real juice. The experimental results were compared with the equilibrium conditions evaluated using the process simulation software Aspen Plus. The vapor-liquid equilibrium was solved with the Peng-Robinson EOS, where the parameters were evaluated using Wong and Sandler mixing rules (PRWS), and the activity coefficients were defined using the functional groups with the modified UNIFAC method. The CO2 solubility values predicted by the model agreed well with the experimental data in the pressure and temperature range tested.