Environmental Engineering Reference
In-Depth Information
(Mahalik and Nambiar, 2010), better communication of information is
likely and may address this problem in the future.
Upgrading the quality of a package can sometimes reduce food waste
(Williams and Williams, 2011). However, there is a trade-off between the
reduction of food waste achieved and the larger environmental footprint
of the upgraded package. Food waste also generates CO
2
: each ton of food
waste accounts for approximately 4.5 tons of the gas and also wastes
embedded energy. For foods high in GWP such as meat or cheese (e.g., 25.5
kg CO
2
-eq/kg bone-free meat), a substantial upgrading of packaging might
be justified (Wikström et al., 2013).
5.2.2 Chemical and Microbial Protection
Packaged food is often discarded because of alterations in its odor, taste,
and texture as a result of oxidation, hydrolysis, and spoilage of the contents
due to degradation by bacteria. Controlling the ingress of oxygen and water
vapor into food is therefore a key metric of protection afforded by food
packaging. The values of permeability for O
2
and water vapor for common
plastic materials are listed in
Chapter 8
. Plastics including blends,
multilayered laminates, or filled laminates (especially with nanoscale fillers
barrier properties to select from (Wani et al., 2014). For instance, polymers
such as poly(vinyl alcohol) (PVOH) or its copolymers in multilayer
constructs provide transparent film with good barrier properties. Plastic
packaging films with a thin layer of glass or ceramic surface coating
deposited using physical vapor deposition provide a nearly impermeable
andtransparentbarriertogasesandwater.However,microcrackingofglass
during handling of the glass-coated plastic film results in some leakage of
gases and water through these films.
Popularity of glass and tin cans in early packaging was due to their low cost
and because they could withstand the high temperatures encountered with
in-package sterilization. Low-temperature sterilization (peroxidetreatment,
use of short bursts of ultrahigh temperatures and gamma ray irradiation) is
used in modern sterilization to minimize the alteration of taste and aroma
of the food. Plastics can withstand all the common sterilization treatments
without significant degradation. Where transparency is not a requirement,
metallized plastic films or metal-plastic laminates offer impermeability
along with the convenience of heat sealability. Natural preservatives (such
