The key to successful food packaging is to identify the packaging needs of the product. These relate to the nature of the product, the intended market, shelf life, distribution and storage, point of sale to the ultimate consumer and the
use and eventual disposal of the packaging. The choice should take account of environmental and waste management issues. Ensuring food safety with respect to biological risks and needs relating to flavour, colour and texture is essential. Packaging needs can be considered in terms of:
• protection of the product – quality, safety etc.
• appearance – sales promotion, pack design etc.
• production – extrusion, forming, printing, packing etc.
Having decided that a type of plastic pack selected from the range of possible choices, such as a film sachet, lidded tray, bottle etc., the next decision concerns the type of plastic or combination of plastics necessary to meet the
functional needs. Performance is related to the structural design of the pack and whether it is made from film, sheet, moulding or expanded plastic. As we have seen, there are many plastics, each offering a range of properties, and
within each packaging type there are differences.
All plastics provide barriers to the ingress of gaseous and volatile materials from the external environment into a hermetically sealed pack and from the food product both into and through the pack into the external environment.
The extent to which these effects occur will depend on the food product and on the type of plastic(s), its thickness and on the temperature and RH ranges to be experienced during the life of the product. Some plastics are heat sealable so that packs can be sealed; some are also heat resistant to meet defined needs, e.g. reheating by microwave, radiant heat and retort sterilization. Some are suitable for storage in deep freeze. Many specific needs can be met within the defined conditions of use. In a chapter of this type, we can make readers aware of the choices and provide a basis for meaningful discussions between technologists whether they be suppliers or users of plastic packaging. The following Tables 7.1 to 7.3 give some guidance in terms of ranking for moisture vapour permeability,
Table 7.1 Ranking of various films with respect to specified properties
gas permeability, optical properties, packing machine performance and heat sealability.
The commercial consideration of cost must also be considered. Run lengths and lead times are also important. It is not unknown for there to be run length cost differences, where at one point a particular solution is cost effective relative to an alternative solution and for the position to be reversed at a different