Shelf-Life Studies of Vitamin C During Food Storage: Prediction of L-Ascorbic Acid Retention in Dehydrated Tomato Juice

The purpose of this study was to develop a method for predicting the extent of deterioration in dehydrated foods. The specific deterioration process studied was the loss of vitamin C in dehydrated tomato juice, as affected by environmental changes of temperature, water activity, and oxygen. Degradation of ascorbic acid (AA) was found to follow first-order reaction kinetics. The effects of temperature on the reaction rate could be described by the Arrhenius equation. Water activity had a strong effect on the reaction rate constant and on the activation energy. The effects of oxygen in this system were negligible. The rates of dehydroascorbic acid deterioration were similar to those of AA. Mathematical modeling of the retention of AA as a function of time, temperature and water activity was developed using theoretical, empirical and statistical considerations. This model was combined with equations describing the transport of water to the food, utilizing experimentally obtained mass transport parameters for the packages, and sorption characteristics of the food. By solving these equations numerically with the aid of a computer, AA retention was simulated for various conditions. Retention was also experimentally determined by storage tests. There was reasonable agreement between experimentally observed losses of AA and those predicted by the computer simulation program.