PREDICTION OF PH IN MODEL SYSTEMS PRESSURIZED WITH CARBON-DIOXIDE

Mathematical models were developed to predict the pH of model liquid food systems (pure water, ascorbic acid-water, citric acid-water, and ascorbic acid-citric acid-water) pressurized with carbon dioxide, as functions of pressure (0-34.50 MPa), temperature (32, 37, and 42-degrees-C), and component concentrations [(0-1.107) x 10(-3) M for ascorbic acid, (0 to 6.080) x 10(-4) M for citric acid]. For all simulation systems, predicted pH values closely followed experimentally measured pH values. In the pure water-CO2 system, pH was a strong function of pressure but a weak function of temperature. In ascorbic acid-water-CO2, citric acid-water-CO2, and ascorbic acid-citric acid-water-CO2 systems, pH was relatively insensitive to CO2 pressure and was a strong function of acid concentrations. This method could be a first step toward predicting the pH of orange juice and other liquid food systems under pressurized CO2.