KINETICS AND COMPUTER SIMULATION OF ASCORBIC ACID STABILITY OF TOMATO JUICE AS FUNCTIONS OF TEMPERATURE, pH AND METAL CATALYST

Abstract

ABSTRACT The rates of ascorbic acid destruction in tomato juice were determined as functions of storage temperature, pH and copper concentration. Ascorbic acid destruction under anaerobic conditions was confirmed to be a first‐order reaction with respect to ascorbic acid concentration. The effect of storage temperature on the rate of ascorbic acid destruction was accounted for by the Arrhenius equation. The activation energy of anaerobic destruction of ascorbic acid was 3.3 kcal/mol at pH 4.06, and was shown to change with changes in pH. The rate of ascorbic acid destruction was influenced by pH, reaching a maximum near the pKa of ascorbic acid. The rate of copper‐catalysed destruction of ascorbic acid increased as copper concentration in tomato juice increased, and was affected by pH. A mathematical model, which described the rate of ascorbic acid destruction as functions of storage temperature, pH and copper, was developed based on the experimentally derived equations. A computer simulation program was developed using the mathematical model to predict ascorbic acid stability in tomato juice. The computer‐aided predictions of ascorbic acid stability in tomato juice was in good agreement with the results obtained from the shelf‐life tests.