Modified Atmosphere Packaging

Beverage | Food Freezing & Chilling | Modified Atmosphere Packaging (MAP) | Freshline

 Gases, equipment and advice for the right Modified Atmosphere Packaging (MAP) In South Africa, FRESHLINE™ is Air Products’ complete offering to suppliers, of MAP packed food products. It provides the best way to ensure that food products are safely packaged in order to reach the consumer in optimum condition.

Every product, even complex food products, has its own ideal atmosphere – Oxygen, Nitrogen or Carbon Dioxide – and usually a carefully controlled mixture of these gases. In South Africa, our FRESHLINE™ specialists – experienced in all aspects of MAP – will advise you on the correct mixtures and the most appropriate equipment for your particular product.

In some cases, the nitrogen may be supplied most economically at the customer’s site through the use of membranes or other non-cryogenic air separation techniques (non-cryogenic on-site systems).

CO2 inhibits the growth of most bacteria and moulds

N2 is used to exclude air, and in particular Oxygen

  • prevents the collapse of packs for high-moisture and fat-containing foods

O2 maintains fresh, natural colour (in red meats for example)

  • maintains respiration (in fruits and vegetables)
  • inhibits the growth of anaerobic organics (in some types of fish and in vegetables)

MAP Offers Many Benefits Including: Ability to access new markets

  • Extension of shelf-life
  • Minimisation of waste
  • Enhanced appearance and presentation
  • Higher productivity
  • Reduced need for artificial preservatives

What is MAP?

MAP is food packaging in which the earth’s normal breathable atmosphere has been modified in some way. Usually combined with lowered temperatures, it is a highly effective method for extending the shelf-life of food.
Shelf-life is prolonged in some applications by creating a simple vacuum in the package (vacuum packaging) and in these cases there is almost a complete absence of gas. In others, special permeable films allow naturally respiring produce to form its own atmosphere without the addition of external gases.
Once a fruit, vegetable or animal product is harvested or slaughtered it remains a suitable environment for bacteria which continue to function using the available carbohydrate, protein, fat and nutrients. These continuing processes lead to degradation including undesirable colour changes, loss of flavour and poor texture. The action of enzymes also causes deterioration of foods. In Europe, MAP mainly involves the use of three gases – carbon dioxide, nitrogen and oxygen, although other gases are used where regionally acceptable. Products are packed in a single gas or a combination of these three gases depending on the physical and chemical properties of the food.

History of MAP

The use of gases in the preservation of food products is by no means a new process. Much of the original work was carried out in the early 1930s with the shipment of beef and lamb carcasses from Australia and New Zealand to the UK under carbon dioxide storage. During the 1940s and 1950s, sealed controlled atmosphere storage warehouses were constructed to prolong the effective shelf-life of fresh apples under refrigeration. Hence the commercial applications of gas preservation were largely confined to the controlled atmosphere storage and transport of bulk commodities such as meat and fruit. Now you see MAP used to package anything from fresh salads and individual meat portions, to sandwiches and snacks. Today it is a sophisticated technique with ever-increasing benefits to both supplier and customer.

MAP – adding value to food

Food, glorious food – in all its natural, eye-catching colour – is what the customer expects from the food industry. And week in, week out, Modified Atmosphere Packaging techniques help the retailer to deliver. Extended shelf-life, greater choice and a reduction in food-related health hazards are some of the valuable benefits of MAP but are not so apparent to the shopper as the presentation of the food itself. This is where MAP adds even more value for the retailer enabling food to look better for longer.

Why use MAP?

In the last 25 years, the change from an industrialised base to a service economy has seen the emergence of new family structures and work patterns which, in turn, has led the demand for more convenient food.
The creation of nationwide, European and international supermarket chains, has led to a highly competitive trading environment, forcing quality up and operational costs down.
For the food industry, one of the important effects of these significant social, economic and business changes has been to open the door to MAP. Hundreds of food businesses have stepped through, using MAP to form valuable new trading relationships with the multiples and other, smaller chains and independents. Because Modified Atmosphere techniques are ever changing and improving, that door of opportunity remains open. There is a great deal of advice and support available from equipment and film manufacturers, specialist gas suppliers such as Air Products, and research bodies such as Campden & Chorleywood Food Research Association and Leatherhead Food International.

Extension of shelf-life

Depending on product, shelf-life can be usefully extended by between 50% and 500% using MAP techniques. This means that waste is minimised and re-stocking and ordering can become more flexible.
As an example, a store turning over 100% of its shoppers every 10 days will be able to offer a non-MAP food item with a shelf-life of three days to just 30% of its customers. But the same food item packaged with a suitable Modified Atmosphere to give it a 10-day shelf-life will be available for purchase by ALL the store’s shoppers.

Minimisation of waste

If there is a greater chance that a product will be sold, there is obviously less chance of it being thrown away. Even with today’s sophisticated management systems it is still not possible to accurately predict a supermarket’s daily throughput. So having a greater shelf-life available enables a store to order more efficiently and to reduce wastage.

Quality

There are obvious quality advantages for both retailer and consumer in having food that deteriorates at a much slower rate on its journey from production area to store, and then onward to the domestic kitchen, refrigerator or freezer.
Presentation is another vital quality aspect. Because MAP products cannot just be wrapped in cling film (they have to be encased, usually in a tray which lends itself to an element of design on its surface) retailers have taken the opportunity to package their food stuffs more attractively. The visual appeal of food is another key quality area and here the industry’s experience with red meat makes an interesting case study. After slaughter and ageing, red meat quickly becomes a dullish, brown colour which is unattractive to customers. Fresh, red colour is maintained longer using a mixture of between 70% and 80% oxygen, (depending on the meat), and carbon dioxide for the balance. Its remarkable effect on red meat is undeniable. In the early days it was the introduction of this technique by Marks & Spencer to its range of red meats that kick-started the use of MAP in the UK. Today, with red meat coming under scrutiny by some consumers actively pursuing a healthier lifestyle, the role of MAP is central to its survival on store butchery shelves.

Reduced need for artificial preservatives

In a world which is becoming increasingly “green” in its outlook, a world where every consumer is a watchdog for the environment, there are points to be earned by the retailer who can get rid of as many additives as possible and show that its food is basically fresh and natural. In some cases, MAP means that artificial preservatives are no longer required to achieve a reasonable shelf-life.

Increased distribution possibilities

Because of the extended product shelf-life, increased distribution is one of those areas in which the introduction of MAP is more than just “another benefit”. For companies with the right product, the potential to increase the range of delivery can produce exciting changes and opens the door to a global market.

MAP gases – the basics

Freshline® Food Grade gases from Air Products are a range of high purity gases delivered either as a liquid in stainless steel microbulk or bulk containers or as a gas in high pressure cylinders all dedicated for use only in the food industry.
Before choosing a gas mixture, many factors should be considered. A product trial is the most effective method of identifying the optimum gas mixture for your process. Contact one of our Freshline® specialists for more information.
The effects of each gas on food products are as follows:

Carbon dioxide (CO2)

Carbon dioxide inhibits the growth of most aerobic bacteria and moulds. Generally speaking, the higher the level of CO2, the longer the achievable shelf-life. However, CO2 is readily absorbed by fats and water – therefore, most foods will absorb CO2. Excess levels of CO2 in MAP can cause flavour tainting, drip loss and pack collapse. It is important, therefore, that a balance is struck between the commercially desirable shelf-life of a product and the degree to which any negative effects can be tolerated. When CO2 is required to control bacterial and mould growth, a minimum of 20% is recommended.

Nitrogen (N2)

Nitrogen is an inert gas and is used to exclude air and, in particular, oxygen. It is also used as a balance gas (filler gas) to make up the difference in a gas mixture, to prevent the collapse of packs containing high-moisture and fat-containing foods, caused by the tendency of these foods to absorb carbon dioxide from the atmosphere. For modified atmosphere packaging of dried snack products 100% nitrogen is used to prevent oxidative rancidity.

Oxygen (O2)

Oxygen causes oxidative deterioration of foods and is required for the growth of aerobic micro-organisms.
Generally, oxygen should be excluded but there are often good reasons for it to be present in controlled quantities including:

  • Maintain fresh, natural colour (in red meats for example)
  • To maintain respiration (in fruit and vegetables)
  • To inhibit the growth of anaerobic organisms (in some types of fish and in vegetables)

Shelf-life

No matter how effectively Modified Atmosphere technology is applied to food, no product can remain on the supermarket shelf indefinitely. Over time, food spoilage inevitably sets in and the rate at which it occurs depends on the physical structure and properties of the food itself, the type of micro-organisms present and the environment the food is kept in. The acidity of food, its respiration rate, nutrient content, natural resistance to micro-organisms and its biological structure are among the factors which affect the rate of decay.
By carefully matching individual Modified Atmospheres to specific food products, adopting appropriate manufacturing, handling and packaging methods and observing recommended storage and display conditions, a retailer can successfully extend the shelf-life of most foodstuffs.

What is shelf-life

The shelf-life of a product is the time after production during which it remains acceptable for consumption. The end of the shelf-life is, therefore, the point at which it becomes unacceptable.
A more detailed definition (IFST, 1993) of shelf-life is the time during which the food product will:

  • Remain safe
  • Be certain to retain desired sensory, chemical, physical and microbiological characteristics
  • Comply with any label declaration of nutritional data when stored and handled under the recommended condition

What influences shelf-life?

The shelf-life will be influenced by many aspects of Good Manufacturing Practice and product formulation, e.g. pH (acidity), salt level or water activity and preservatives. Combinations of these factors are often used together to achieve stability, known as hurdle technology.
It is recommended that product shelf-life is determined by following a Shelf-life Evaluation Sequence as described in CCFRA Guideline No 46. The process involves a logical sequence from product concept to full scale production and it is important to identify early in the sequence what characteristics of the food and method of production and storage, will influence the shelf-life. For example, factors to consider include:

  • Raw materials
  • Product formulation
  • Processing
  • Packaging, including gas atmosphere
  • Hygiene
  • Distribution
  • Storage
  • Consumer handling

These factors exert their effects on microbiological, chemical and physical parameters within the food, which often result in a loss of sensory quality. The point at which these effects influence the product, such that the change becomes noticeable or the product unacceptable, is the end-point. It is the time taken to reach the end-point that has to be determined when assessing product shelf-life. The packaging format often has a significant influence on the acceptable, durable life of chilled foods. Consideration needs to be given, particularly to products designed as multi-portion or bulk commodity packs, to the effect of opening the pack on product durability. It may be necessary to qualify any shelf-life coding (Use By/Best Before) with clear instructions on the packaging limiting the time available from opening to consumption and indicating, where necessary, any specific handling instructions to the consumer.

End of shelf-life

For most perishable chilled food products, the end-point will depend on a number of factors. In some cases, the end-point may be defined by levels of micro-organisms present based on recommended guidance (PHLS, 2000; IFST, 1999). In other cases, the end of life may be determined by sensory or biochemical deterioration. The emphasis on the specific end-point criteria will vary between different products and must be defined during the shelf-life evaluation process.

Shelf-life testing methods

There are a number of methods for determining the shelf-life of different food products including microbiological, chemical and by sensory evaluation. Different factors will affect the end of shelf-life depending on the product, packaging and conditions surrounding the product. Shelf-life testing can be carried out during development and pilot scale production of the product but should always be carried out once full scale production has been reached.

Microbiological testing

The type of product and gas mixture used will influence the growth of specific groups of micro-organisms. Packing in an oxygen free environment will allow anaerobic organisms to grow whereas products packed in the presence of oxygen will permit the growth of aerobic micro-organisms. Sampling should be carried out regularly during shelf-life testing on a minimum of three to five samples per sampling date per pack format.

Biochemical testing

Colorimeters can be used to measure colour changes with different food products. A colorimeter may pick up slight changes not noticed by the human eye. Chromatography can be used to measure changes of the volatile compounds in the food product during storage. Changes in nutritional content can be measured during shelf-life to determine if there are any significant changes.

Sensory evaluation

There are a number of different formats for carrying out sensory evaluation on products. The product can be assessed for appearance, odour, texture and flavour to determine end of shelf-life. Specific individual attributes of the product such as ripeness, degree of fermentation, juiciness, strength, acidity and moistness can be observed by trained sensory assessors.