Kinetic modelling of vitamin C loss in frozen green vegetables under variable storage conditions

A systematic kinetic study of l-ascorbic acid loss of four green vegetables was conducted in the temperature range of freezing storage. The temperature-dependence of vitamin C loss in the −3 to −20 °C range was adequately modelled by the Arrhenius equation and activation energy ranged from 98 to 112 kJ/mol for the four frozen green vegetables. The developed models were validated in fluctuating time–temperature conditions, in order to establish their applicability in the real marketing path of the commercial products. Based on the models, the nutritional level can be estimated, at any point of the freezing chain, when the full time–temperature history is available. Comparison among different green vegetables showed that the type of plant tissue significantly affects the rate of vitamin C loss. Frozen spinach was found to be the most susceptible to vitamin C degradation, peas and green beans demonstrated a moderate retention, whereas okra exhibited a substantially lower loss rate.