EVALUATION OF 4 TYPES OF INHIBITION FOR MODELING THE INFLUENCE OF CARBON-DIOXIDE ON OXYGEN-CONSUMPTION OF FRUITS AND VEGETABLES

High carbon dioxide (CO2) concentrations can reduce the oxygen (O-2) c onsumption rate of a number of fruits and vegetables. This reduction c an be modelled by four types of inhibition in an enzyme kinetics model : (1) the competitive type; (2) the uncompetitive type; (3) a combinat ion of both previous types; and (4) the non-competitive type. These di fferent types of inhibition were tested for describing the CO2 influen ce on O-2 consumption using experimental data supplemented with data f rom literature. The gas exchange rates of apples (cv. Golden Delicious and Elstar), asparagus, broccoli, mungbean sprouts and cut chicory we re measured under a wide range of O-2 and CO2 concentrations. With the range of CO2 concentrations used, no influence was found on gas excha nge rates of apples. There was a clear influence of high CO2 on the ga s exchange rates of the other produce. A good estimation of O-2 consum ption could be obtained with the inhibition models. This supports the use of Michaelis-Menten kinetics for modelling O-2 consumption. Depend ing on the product the statistical analysis gave good results for the competitive and the uncompetitive type of inhibition. Based on gas exc hange data only, no distinction between the competitive and uncompetit ive type of inhibition could be made. It suggests the simultaneous exi stence of both types of inhibition. The idea is that the combined inhi bition equation is most closely related to what is actually occurring in plant tissues. However, for reasons of simplicity the non-competiti ve type of inhibition is preferred, showing similar results to the com bined inhibition, and giving good results for all the products tested.