WATER loss from fresh produce, fresh meat, fish, poultry, or other fresh or
minimally processed prepared foods as a result of normal respiration,
microbiological activity, or physical activity can occur as a result of evaporation
from the product followed by permeation through the package material
when the package material does not provide an adequate water-vapor barrier.
The use of polyethylene film carton and case liners for fresh produce, meat,
poultry, fish, and prepared food often satisfies the short-term commercial
moisture-barrier requirement but may not provide sufficient packaging if temperature
cycling occurs during the distribution of the product. When the temperature
of the product drops slightly, condensation of water-vapor deposits
liquid water on the inside of the liner. If the water-vapor content of the package
headspace is buffered to a relative humidity substantially below the approximately
95% level generated by respiration of fresh product, a safety margin
exists before condensation occurs. This feature is a characteristic of recent research
on paperboard carton coating in which the product is kept away from a
hydrophilic polymer carton liner by means of a porous polymer. Water vapor
can pass from the headspace atmosphere into the hydrophilic polymer as the
temperature varies during distribution