Packaging Considerations - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 139

Clear PET and PP bottles and jars are being used for hot-fill and hold, shelf stable
acid foods (pH <4.6), and pasteurized low acid foods (pH

4.6) stored below 4°C
for extended periods of time. These containers have increased consumer appeal in
comparison to the opaque crystalline structures developed in the past. 36

≥

Aroma and Flavor Transfer

Aromas and flavors are composed of volatile organic compounds. The packaging of
products containing these volatiles can lead to a loss of aromas and flavors (scalping)
or, conversely, the gain of off-flavors due to permeation. Flavor and aroma scalping
is an increasing concern as more food products are being packaged in plastic
packages. 14 Citrus juices, especially orange, have been the subject of considerable
research interest with respect to flavor (limonene) scalping. 37,38
The transport of most aroma and flavor permeants through plastic packaging
materials has not been investigated as thoroughly as gas transport because of the
complexity of these compounds in foods and their interaction with various polymers.
In addition, the presence of co-permeant organic compounds can greatly influence
permeability values compared to those values obtained for pure compounds. 22 In
general, aroma and flavor compounds follow the same permeation principles in
plastic materials as described previously for gases and vapors. However, determina-
tion of transmission rates is more complicated because the solubility coefficients of
these organic compounds are pressure-dependent and the diffusion coefficients are
concentration-dependent. 1

Distribution and Handling

Temperature plays a key role in the rate of deteriorative reactions. Excessively high
temperatures during food distribution and handling of perishable foods can accelerate
deteriorative reactions and permit microbial growth. On the other hand, low tem-
peratures can be detrimental to some fruits and vegetables that are susceptible to
chilling injury, as described in Chapter 2. The development of food packaging
systems that could maintain the temperature of products within a specified range
would be desirable. This goal has been shown to be feasible through research on
the use of phase-changing materials (such as water/ice or saturated salt solutions)
that serve as a heat sink or source, by undergoing thermophysical transitions which
can effectively absorb or release heat with little change in temperature. 39,40 Packaging
considerations in temperature control are particularly important for refrigerated
foods. Refrigerated or chilled foods include a wide range of prepared foods that
require refrigeration for safety and an extended shelf life. A major challenge to the
food industry is to develop strategies for maintaining a high quality temperature
controlled distribution system for these perishable foods. 41 Time-temperature indi-
cators (TTI) have the potential to be used in monitoring or predicting safety and
shelf life of refrigerated foods. 42,43 These devices, either placed on food packages
or on shipping containers, monitor the combination of time and temperature to which
they are exposed and exhibit a visible change (e.g., color) in response to the tem-
perature exposure history.