Biomedical Engineering Reference
In-Depth Information
Table 3.1
Primary functions of commonly used packaging materials for food applications
Packaging material
Abbreviation
Primary function
Aluminium
Al
High barrier
Glass
-
High barrier
Low density polyethylene
PE-LD
Sealing layers
High density polyethylene
PE-HD
Moisture barrier, rigidity,
microwave capability, sealing layers
Oriented polyamide
OPA
Gas barrier
Amorphous polyester
APET
Rigidity, gas barrier
Crystallized polyethylene
terephthalate
CPET
Rigidity, high temperature
resistance, gas barrier
Ethylene-vinyl acetate
EVA
Sealing layers
Ethylene-vinyl alcohol
EVOH
Gas barrier
Oriented
polyethylene-terephthalate
OPET
High temperature resistance,
fl exibility, puncture resistance, gas
barrier
Oriented polypropylene
OPP
Moisture barrier, fl exibility,
puncture resistance
Polyamide (nylon)
PA
Temperature resistance, fl exibility,
toughness, partial gas barrier
Poly acrylonitrile
PAN
Gas barrier
Polyethylene terephthalate
(polyester)
PET
Rigidity, some gas barrier
Polypropylene
PP
Moisture barrier, rigidity
Polystyrene
PS
Rigidity
Polyvinyl chloride
PVC
Rigidity, gas barrier
Polyvinylidene chloride
PVdC
Moisture barrier, gas barrier
3.2.1
Mass Transfer of Packaging Materials
Oxygen and water vapour permeability has signifi cant importance for the mainte-
nance of quality and safety for packed convenience foods. An illustration depicting
the interactions of food, the package and the environment and the possible changes
in food are shown in Fig.
3.1
. Glass and metals are practically impermeable to gases
and vapors, so these provide an effi cient barrier against material exchange between
the atmosphere inside the package and the outside environment. This virtually per-
fect barrier, desired for many durable food products, however, is often not needed or
even negative for many of the products discussed below. polymers and paper are
permeable to gases and vapors to various degrees, and their barrier properties cer-
tainly constitute the chief criterion in estimating their suitability to serve as packag-
ing materials in a given application. Gases and vapors may pass through packaging
materials either dissolved by solution-diffusion or by gaseous through holes and
pores. Minimally processed foods, the main subject of this chapter, are diverse in
