A browse through a local supermarket cannot but fail to excite personnel involved in the packaging industry as to the developments and range of packaging applications being used to convey food today. One of the chief catalysts responsible for what we see in our local supermarkets is the increasing use by food manufacturers of controlled atmosphere packaging (CAP) and modified atmosphere packaging (MAP).
The control of gaseous environments surrounding food products to limit their biological activity has been around since the turn of the century. Breakthroughs and developments in barrier substrates, heat sealing and computerisation have facilitated the rising dominance of this packaging medium. The main purpose of CAP and MAP is to extend the shelf life of perishable products.
Modified atmosphere (MA) means the introduction of a gas that is different from normal air usually by evacuation or nitrogen flushing. Controlled atmosphere packaging (CAP) entails the controlling of the total gaseous environment that a product experiences. In other words, this means lowering the oxygen and raising the carbon dioxide levels and ensuring that the oxygen does not diminish to extinction while the respiratory gases are swept out.
Technically, a controlled environment would represent a dynamic action in which the atmosphere is constantly altered to meet the food shelf life demands. Although practical in bulk storage, it is something of a misnomer to refer to packs on supermarket shelves as controlled atmosphere packaging. Although there are barrier substrates on the market today that can control the entry and exit of gases through the substrate to an extent.
Because of the use of high-barrier materials, controlled atmosphere packaging is more expensive than conventional methods such as PVC film overwrapping or foamed polystyrene trays. One the other hand, the changed distribution process permits retailers to buy pre-packaged fresh products rather than having to prepare and package them in store with resulting waste and labour costs.
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For a food manufacturer wishing to explore the benefits of CAP or MAP, it would be wise to study the market first and then look at the options available with regard to materials and design alternatives and then consider the machinery. Custom made machines can be constructed if necessary. The priority would be to justify the costs and higher selling price as against a longer shelf life for the product.
Looking at the machinery available, there are choices of form, fill and seal machines, thermoforming equipment, tray sealing machines and other permutations. Basically, the machinery is either simple and straightforward or highly elaborate and expensive. The basic steps in the production of a finished pack are roughly as follows:- the pack is formed, the product is filled, the air is extracted, the gas is introduced and the pack is sealed. The main priority when choosing machinery would be to make sure it heat seals without failures and that it is fast enough to produce the quantities required.
The difficult part about going into CAP or MAP is developing, in tandem with a food technologist and a packaging consultant, the lowest cost pack with the desired shelf life. This can be very time consuming and complicated. One of the drawbacks, leaving aside environmental considerations, is the huge range of new materials and substrates that are flooding onto the market practically every week. Although price has often been a constraint to the use of new technologies, they usually win out in the end when the brand leaders take them on board.
To emphasise the importance of choosing packaging materials carefully, the following are some of the advances made during the past few years:
- Smart films which are custom made to automatically adjust their permeability according to the prevailing ambient temperature and provide an indication of temperature and even the presence of food contamination. Companies such as Landec Corp in the US are leaders in this field.
- Microwaveable films which will allow a product to be heated to a consistent temperature throughout, rather than the uneven results usually achieved.
- Metallocene polymers such as modified polypropylene and polyethylene can be specifically tailored to a product and can deliver enhanced performance in thinner gauges. OPP and LLDPE films can be used for fruit, vegetables and salads, while coextrusions can be used for dry foods, meat and cheese. It is worth checking out whether metallocenes will slow down your production machinery, especially in the area of heat sealing and printing.
- Biopolymers, such as Monsanto’s Biopol, are biodegradable materials produced from agricultural feedstocks.
- Polyethylene Napthalate (PEN) which has four to five time greater barrier to carbon dioxide, oxygen and water vapour than conventional PET as well as better UV resistance. It is useful for tray and lidding materials but very expensive.
- ‘Natural’ plastics are being developed by Durham University in the UK and Monsanto of the US. This is a method of genetically engineered oil seed rape to produce biodegradable plastic polymers in its leaves and seeds. The natural plastic can be used in the same way as oil-based polymers. Liquid crystal polymers, which are currently ten times the price of PET, offer high temperature capability, superior oxygen and water vapour barrier properties, as well as high strength and clarity. This is an excellent material that will advance if the price comes down.
Other developments to watch out for that would marry well with MAP and CAP applications are cold seal materials, edible and soluble films, oxygen scavenging materials and high gas permeability films.
Looking at the future of MAP and CAP it is possible that one of the companies developing advanced substrates will come up with a material that will keep food fresh for life.
Ireland’s Top Twenty Food Companies
|Avonmore Waterford Group
|Irish Dairy Board
|Irish Food Processors
|Dawn Meats Group
|North Connacht Farmers Co-op
|Green Isle Food Group
|Source : Company accounts and Business & Finance.
* Excludes reorganisation and merger costs. ** Sterling converted to punts.