FREE-VOLUME CHANGES IN FLEXIBLE, HERMETIC PACKAGES CONTAINING RESPIRING PRODUCE

To investigate free-volume changes in flexible, sealed packages contai ning respiring fruits and vegetables, a simple method based on the dil ution of an injected gas (ethane) in the package was developed. Free-v olume decreased steadily at approximate to 3 cm(3)/day after an initia l transient period in low-density polyethylene packages (29-mu m-thick film; 600-cm(2) surface area; initial free Volume approximate to 285 cm(3)) containing 40g of cut broccoli held at 0 degrees C. A general t ransient model was developed that showed that free-volume changes in f lexible packages were a function of differential film O-2, CO2, and N- 2 permeabilities and differential product O-2 uptake and CO2 productio n rates. The model predicted that flushing packages with low permeativ e gases would decrease free-volume depletion rate, whereas flushing wi th highly permeative gases, such as CO2, would increase the initial ra te considerably.