This paper reviews the possible effects determined on polymeric food packaging films by the simultaneous application
of pressure (P) and temperature (T) in high pressure pasteurization and sterilization treatments of packaged
foodstuffs. Both theoretical modelling and experimental issues are discussed. In fact reversible and irreversible
effects that could occur in single film as well as in multilayer film structures have been reviewed and correlated
to the variation of structural andmorphological properties of the polymeric materials, under P/T conditions relevant
for the specific application. The structural changes of the amorphous and crystalline domains of polymer films could
possibly occur in response to pressure and/or temperature conditions, which, in turn, result in detectable effects on
properties of packagingmaterials. Particular attention has been devoted to addressing issues like irreversible alteration
of functional (i.e., barrier to gases and water vapor, scalping and migration phenomena) and mechanical properties
of the packaging materials in a relationship with a modification of degree of crystallinity, aging of the
amorphous phase, delamination of multilayer films, rubbery to glassy state transition promoted by pressure and
plasticization induced by absorption of low molecular weight compounds.
Industrial relevance: High pressure processing (HPP) is steadily gaining as a food preservationmethod that preserves
natural sensory and nutritional attributes of food with a minimal quality loss. In fact, packaged foods processed by
using this technique maintain most of their original texture and nutritional qualities, additionally exhibiting an
extended shelf-life.
Industrially, the selection of the proper polymeric materials as well as the packaging structure becomes extremely
importantwhen both high pressure and high temperature are employed for high pressure sterilization processes. In
this context, an important issue that is relevant for industrial applications is to predict the possible effects of treatments
on the structure and morphology of thematerials which, in turn, can determine relevant effects on mechanical,
functional (i.e., gas and vapor barrier properties) and aesthetic (e.g., see-through clarity) properties. In fact,
modification of the crystallinity level, density change of amorphous regions and possible hydrolysis phenomena
could hamper the use of the packaging material for the HPP applications. Moreover, multilayer flexible films can,
in some cases, display delamination phenomena leading to unacceptable modifications of the aspect as well as of
the integrity of the packaging structure.
© 2012 Elsevier Ltd. All rights reserved.
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