Packaging

Anuga FoodTec: Big gains for modified atmosphere packaging

Thursday 12. March 2009 - Packing under protective gas assures quality and hygiene

Recent years have seen enormous growth in the use of modified atmosphere packaging (MAP) for fresh produce in the food retail trade. This technique optimises the internal atmosphere of product packages, thus ensuring that the goods inside retain their quality for a longer period of time. In addition, MAP offers attractive presentation opportunities at the point of sale as well as enhanced hygiene conditions. Suppliers of MAP technology will be presenting the latest developments from this field at Anuga FoodTec, which will run from 10th to 13th March 2009.

When a product is packaged with MAP, air is evacuated from the package during the packaging process and then replaced with special protective gas. The evacuation process removes air from the product as well as the package, thus minimising the oxygen remaining in the package. Only then is a special protective gas injected in order to retard the speed at which the product perishes. The composition of the protective gas depends on the foodstuff being packaged. It may consist of only one gas or be a combination of nitrogen and carbon dioxide. The injection of a protective gas into the packaging creates a new gas-filled space that resists the force of the atmospheric pressure outside. This technique is also suitable for packaging pressure-sensitive products with a long shelf life without damaging them. One of the major benefits of the MAP technique is that it does not require the use of any preservatives. Sensor tests confirm that products packaged in this way do not suffer any change in taste – provided, of course, that the right protective gas is used.

MAP is an ideal way to package many products, including pre-baked rolls and bread for warming in the oven, pasteurised foods such as pasta or ready-meals, fresh meat, sliced sausage and cheese, sausages, curd cheese and sliced fruits. The method is particularly suited for packaging fresh meat, since the protective gas not only gives the product a longer shelf life but also ensures that it retains an appetizing colour.

MAP can be produced using either thermoforming machines or tray sealers. Thermoforming machines use rolls of plastic film, which can be replaced inline. They are very efficient, operating at a high cycle rate and with very little wastage of film. The rolls of packaging film can be stored without problems.

As a rule, tray sealers work with prefabricated trays made of polypropylene, which offers outstanding protection against steam. The trays used must have a sealing edge that is even all around and sufficiently broad, be easily stackable and have a flat bottom and sealing edge, so as to ensure thorough and fully automatic machinability. In the sector for pre-prepared and convenience products, there is now a trend towards packaging trays made of CPET-based materials that can be used in the oven.

In the MAP method, the covering film is usually made of either shrink film or composite film, depending on the barrier effect required to ensure the desired shelf life. In addition to being highly transparent, these films must also display excellent antifogging properties. This prevents the formation of droplets of water on the inside the film, so the packaging does not mist up.

A trend towards thinner materials
With regard to both trays and films, the trend is now toward the use of thinner materials. Many suppliers are working hard in this field, not least because the resulting savings in materials help offset high prices for raw materials as well as conserving natural resources. For example, Anuga FoodTec will feature a new MAP tray made of polypropylene that contains 25 per cent less material than the trays normally used. Measuring 190 x 144 x 50 millimetres, it weighs a mere 10 grams.

A growing interest in biodegradable materials
There is likewise a growing interest in the use of biodegradable trays and films. Good results have already been achieved with polyactide (PLA), for example. PLA is a polymer based on lactic acid and produced from maize via biochemical processes. It is waterproof and can be thermoplastically processed. When the material first came on the market, there were problems with its machinability. In the meantime, however, there have been significant developments in this field, with the result that renewable packaging materials now present an interesting option, not least because the look of PLA materials has also substantially improved. In addition, some suppliers are now using trays made of other renewable materials, including pure wood pulp. This is particularly suitable for packaging convenience foods that can be either oven-cooked or microwaved in the tray.

Greater importance attached to look of packaging
In general, more and more attention is being paid to the appearance of packaging. With the rapid growth of the market in pre-packed meat and meat products over recent years, the issue of presentation at the point of sale has become increasingly important. Once again, the discount supermarkets have led the way here with their growing use of packaging films that are printable with a high-quality rotogravure process.

MAP also has benefits for the packaging of meat spreads and pâtés. It is now increasingly common for such products to be sold in tubs, thus enabling them to be neatly portioned until they are fully consumed. One manufacturer has now developed a MAP system that, depending on the nature of the product, reduces residual oxygen levels in the sealed packaging to 0.3 per cent or less, thus preventing undesirable discolouring. Here too, presentation at the point of sale plays a crucial role. The opportunity to create individually shaped and printed tubs and containers also generates all kinds of additional benefits for both manufacturers and consumers.

Last but not least, the use of so-called lifestyle packaging – in conjunction with, for example, “to-go” products such as triangular sandwiches – also offers interesting market opportunities. Such products look freshly made – a trend that’s appreciated by many consumers. And equally important for the retail food trade: sandwiches hermetically sealed in deep-drawn packaging with a modified atmosphere have a shelf life of up to 12 days.

A strong double act
Another special type of skin packaging developed specially for red meat features not one but two films. The first film, which is skin-wrapped around the product, fixes the meat to the tray bottom and prevents juices from escaping; the second film, which is smooth and shiny, is sealed atop the skin package in an additional sealing process that places the skin-wrapped product under a modified atmosphere with a high oxygen content. The first film is breathable and thereby allows for a controlled diffusion of oxygen, so that the meat retains its red colour. Thanks to the covering film, the packages are stackable and easy to label. Skin packages with a covering film are also ideal for marinated products. The first film encloses and fixes the product in the packaging, thus preventing any sliding or sauce spillage, while the application of a second, flexible covering film gives the tray a smooth top. If desired, product information, recipes or even other foodstuffs, such as vegetables, can be inserted between the two films. In other words, besides giving the product an attractive appearance, such packaging offers consumers further added value that may have a positive influence on their purchasing decision. Skin packaging is suitable for fresh, frozen and also convenience products such as steamable foods.