A respiration model, based on enzyme kinetics, was proposed for predicting respiration rates of fresh produce as a function of O2 and COZ concentrations. In this model, the dependence of respiration on O2 was assumed to follow a Michaelis-Menten type equation (r = V,[O,]/{K,,, + [O,]}), and the effect of CO2 on respiration to follow an uncompetitive inhibition model (r = V,[O,]/{& + (1 + [COZ]/ Ki) [O,]}). The model predictions agreed well with published data for a variety of commodities and with experimental data for cut broccoli.Fresh produce respiration rates (0, consumption or CO2 evolution) at various O2 and CO* concentrations, as well as transient and equilibrium gas concentrations within permeable packages, could be accurately predicted with the model equations.

The permeabilities of t w o commercial ceramic-filled LDPE films were measured and compared with those of a plain LDPE film. The ceramic films have higher oxygen (0,), carbon dioxide (CO,) and ethylene (C2H4) permeabilities, higher C 0 2 to 0, permeability ratio, and higher C2H4 to 0, permeability ratio. The temperature dependence of the permeability was found t o follow the Arrhenius relationship. The data suggest that these ceramic films are more suitable than plain LDPE film for packaging fresh produce of high respiration rate.