8. Vacuum packaging
Vacuum packaging involves the removal of air from the package and the application of a hermetic seal. The air
removal creates a vacuum inside the packs and lack of O2 in packages may minimise the oxidative deteriorative
reactions and aerobic bacterial growth. Vacuum packaging can considerably extend the viable shelf life of many
cooked foods. The use of vacuum packaging, in gas impermeable and heat stable materials, has many advantages,
which include; no or low risks of post pasteurisation contamination, ease of handling, Inhibition of growth of
aerobic spoilage organisms and inhibition or slowing of deleterious oxidative reactions in the food during storage
due to oxygen barrier properties of the packaging material.
There are number of criteria required for the films used for vacuum packaging in large scale production methods.
These requirements include: high durability, ie. ability to withstand considerable mechanical stresses during
packaging, handling and transport, retention of flexibility even at low temperatures (-2 °C to 4 °C) to enable
satisfactory handling in the packaging and refrigeration rooms, ability to withstand heating to at least 150 °C
without structural damage, leaching of potentially toxic plastics or plasticisers, impermeability to liquids, including
oils and fats and macromolecules, impermeability to gases, in particular oxygen, so that oxidative deterioration of
the packaged food stuffs is limited or inhibited, manufactured from non-toxic, food acceptable, odourless materials
and must be able to create airtight durable heat seals to close packs. Many of these criteria have been met by a range
of materials mostly multilaminated plastics.
Vacuum packed foods maintain their freshness and flavor 3 times to 5 times longer than with conventional
storage methods, because they don't come in contact with oxygen. Foods maintain their texture and appearance,
because microorganisms such as bacteria mold and yeast cannot grow in a vacuum. Freezer burn is eliminated,
because foods no longer become dehydrated from contact with cold, dry air. Moist foods won't dry out, because
there's no air to absorb the moisture from the food. Dry, solid foods, won't become hard, because they don't come in
contact with air and, therefore, can't absorb moisture from the air. Foods that are high in fats and oils won't become
rancid, because there's no oxygen coming in contact with the fats, which causes the rancid taste and smell.