ABSTRACTFresh produce packaged in polymeric films represents a dynamic respiration‐permeation model. Control of equilibrium concentrations of respiratory gases is an important variable in extending the shelf life if critical vectors of quality deterioration and transport properties of packaging materials are known.Fresh peaches were stored at 5 × 1° C under various modified atmospheres for a period of up to thirty days. Samples were removed at ten day intervals for chemical and physical analyses of vulnerable quality factors. Parameters evaluated include soluble solids, titratable acidity, and texture and profile parameters such as hardness, elasticity, and cohesiveness.An internal atmosphere of 10 to 15% O2and 15 to 25% CO2inside the package provided better retention of quality attributes such as hardness and cohesiveness than any other treatments. Springiness did not provide any significant index of quality. Soluble solids decreased over time as did the amount of acid present in the fruit. Anaerobic fermentation did not occur under any storage conditions.Subsequent to establishing the optimal gaseous concentrations, respiration rates were determined as a function of time and gas composition. Permeability of polymeric films were determined using ASTM method. Analytical equations were employed to optimize packaging parameters or to estimate transient and equilibrium gas concentrations in polymeric packages. Equations were set up to estimate transient and steady state time values for oxygen and carbon dioxide concentrations inside a package. This approach is applicable in extending the storage quality of other fresh prod