Free‐Volume Changes in Flexible, Hermetic Packages Containing Respiring Produce

Abstract

To investigate free-volume changes in flexible, sealed packages containing respiring fruits and vegetables, a simple method based on the dilution of an injected gas (ethane) in the package was developed. Free-volume decreased steadily at Ϸ3 cm 3 /day after an initial transient period in lowdensity polyethylene packages (29-µm-thick film; 600-cm 2 surface area; initial free volume Ϸ285 cm 3 ) containing 40g of cut broccoli held at 0ЊC. A general transient model was developed that showed that freevolume changes in flexible packages were a function of differential film O 2 , CO 2 , and N 2 permeabilities and differential product O 2 uptake and CO 2 production rates. The model predicted that flushing packages with low permeative gases would decrease free-volume depletion rate, whereas flushing with highly permeative gases, such as CO 2 , would increase the initial rate considerably.

Development of a mathematical model for simulating gas and water vapor exchanges in modified atmosphere packaging with macroscopic perforations

“…Gas and water vapor exchanges through polymeric films follow Fick's first law of diffusion (Dirim et al, 2004;Emond et al, 1991;Talasila & Cameron, 1997). Thus, the change in the volume of gas i inside a package is expressed as…”

“…One perforation of 2 and 5 mm diameter a All are the same experiment using one perforation of 5 mm diameter at 5°C. Talasila and Cameron (1997) reported that transpiration rate may be expressed in terms of a transpiration coefficient (T 0 ) and the water vapor partial pressure difference between the fruit and the surrounding atmosphere (VPD) as…”

“…For model predictions, the initial free volume of the film package was determined indirectly by dilution of a known quantity and concentration of a gas injected into the bag (Hagger, Lee, & Yam, 1992;Talasila & Cameron, 1997). Methane gas (CH 4 ) was used due to its biological inactivity and detectability at low concentrations by GC (Talasila & Cameron, 1997).…”

“…Methane gas (CH 4 ) was used due to its biological inactivity and detectability at low concentrations by GC (Talasila & Cameron, 1997).…”

Volumetric method to determine carbon dioxide solubility and absorption rate in foods packaged in flexible or semi rigid package

“…Geometrical calculations to monitor volume change are difficult, due to the non-uniform shape of the package. A method based on the dilution of an injected gas (ethane) in the package has been developed (Talasila & Cameron, 1997), but the method requires expensive equipment. Objects submerged in water experience a buoyancy force, and Archimedes' method can be used to measure displaced volume.…”