Why is MAP so important?

Getting optimal performance from the MAP of your food products is no longer optional. It could be essential for your future profitability.

Why? Because effective use of MAP can:

  • increase your products’ shelf-life by days or even weeks and maintain quality
  • extend your product range and open up new markets
  • stabilise output with fewer seasonal bottlenecks
  • simplify distribution with less frequent deliveries over longer distances
  • reduce spoilage and returns

Together, these benefits give companies a decisive economic advantage in today’s market where quality, freshness and choice are so valued. Individual MAP solutions can be fine-tuned to meet consumer preferences and buying patterns, informed by market research and data analysis.

Increasingly MAP is a precision tool that both raises and meets consumer expectations. As a producer, that’s a strong shot to have in your locker. And keeping your high quality products on the shelves for longer can reduce waste, boost your profitability and market share. In turn, increased market share enhances your products’ reputation among consumers. And so it goes.

Two factors dictate the effectiveness of MAP – your knowledge of which gases to use to modify the atmosphere around the food, and the quality of the packaging they’re placed within.

Whether it’s how you combine these two, or just the gases themselves, the key to growing your business using  MAP really is ‘all in the mix.

Using the right mix of atmospheric gases

From the moment it is harvested, food starts to deteriorate if left open to the atmosphere – the air we breathe every day. Whether the decay is caused by microorganisms or chemical reactions in the produce, placing the food in a sealed container, stored at the correct temperature, surrounded by carefully chosen combinations of the natural gases nitrogen, oxygen and carbon dioxide, can significantly reduce that rate of decay.

Carbon Dioxide – one of the most important gases in the MAP armoury, it’s highly effective against the most common aerobic bacteria such as mould. Less so against the growth of anaerobic microorganisms.

Nitrogen – an inert gas, primarily used to replace oxygen in MAP to prevent oxidation. Nitrogen is good at maintaining internal volume and so also helps to prevent package collapse.

Oxygen – oxygen causes chemical breakdown in foods and so in many cases MAP should contain as little oxygen as possible.

In practice, this isn’t as straightforward as one may think. Each gas has its own unique properties that affect how it interacts with foodstuffs. Sometimes using a gas can solve one problem but create another. For example, a sealed oxygen-free atmosphere will limit the growth of microorganisms. However a very unpleasant bacterium called Clostridium botulinum grows in an oxygen-free environment and, in certain circumstances, can develop on chilled food unless other safeguards are used.*

So, it’s essential that food companies get expert advice, rooted in continuous investment in research and development, to both maximise their MAP benefits and ensure the safety of consumers.

The science of packaging

The correct choice of packaging is also key to the success of MAP. There are many questions to consider. What is the best packaging to provide protection against microbial growth, oxidation or dehydration? How much barrier protection does it provide against oxygen, light and volatile substances? What is its water vapour transmission rate? And how about the material’s transparency, sealing ability, anti-fogging properties and cost? Is it safe to use inside a microwave or oven?

With the exception of fruit and vegetables, packaging for all forms of MAP treated foods should offer high barrier protection. The film used to seal the product is then adapted to suit the individual food product and the chosen packaging. Layers of several different materials are often combined in the packaging, each layer performing its own function. Various combinations can be used to achieve, for example:

  • mechanical strength
  • water vapour barriers
  • gas barriers
  • gas permeability
  • anti-fogging
  • transparency
  • a strong seal

The techniques of MAP

A number of different machines can produce MAP protected food but all work on the same principle – place the food in a container, replace the air within the container with a modified atmosphere and finally seal the package.

There are two ways of modifying the atmosphere in the package:

  • Flushing – a gas stream dilutes the air around the food before the package is sealed; a continuous, quick method
  • Vacuum extraction and then gas injection – air is extracted from the package and the vacuum broken by an injection of the modified atmosphere; a slower, two-step process but with more accurate end results

The importance of testing

As in all food processes, quality control and assurance in MAP are critical to protect public health and build trust with your customers. Something as simple as a hole the size of a pinprick could be enough to compromise food safety and expose a consumer to bacteria or toxins.

Seal integrity is one of the most important areas of MAP quality control. Particles of food may have come between the tray edge and the seal. Or the heating element that creates the thermal seal might be faulty or misaligned. There may be issues with the pressure, heat and duration of the sealing process.

So how do you check for leaks? The traditional method is to place a sample package in a sealed water bath, suck air out of the bath and watch for any bubbles escaping from the package through a break in the seal.

In a more recently developed test, you place the MAP package in a sealed airtight container and monitor for the presence of any CO2 escaping from a break in the package seal.

A third important control method is headspace analysis. The headspace is the internal volume of a MAP package that is not occupied by the food itself – in other words the atmosphere surrounding the food. A pump withdraws a small sample of headspace gas through a thin needle inserted into the package. The sample is measured for concentrations of residual oxygen or carbon dioxide in the headspace to ensure these are in line with expectations.

So what’s the best gas mix for certain foods?

Meat and meat products – bacteria grow easily on fresh meat because of its high water and nutrient content. However red meat in particular needs sufficient levels of oxygen to retain its red colour. Carbon dioxide can inhibit bacterial growth, so the right mix of gas is crucial for each type of meat packaged.

Fish and seafood – fresh fish is full of water, enzymes and has a neutral pH value. It’s a perfect storm of factors to encourage rapid microbial growth and enzymatic damage. Carbon dioxide levels of up to 50%, combined with a constant storage temperature as close to 00C as possible, can prolong shelf life by 3-5 days.

Bakery products and dry foods – foods such as crisps, powdered milk and cocoa products contain unsaturated fats and are vulnerable to oxidation. Replacing oxygen with nitrogen, carbon dioxide or a mix of the two will extend shelf life. Similarly carbon dioxide will slow the growth of mould on bread.

Dairy products – microbial growth and rancidity are the two major causes of dairy deterioration. Up to 100% carbon dioxide is used for hard cheese to prevent mould fungi. For soft cheeses, the level is reduced to 20-40%, to prevent package collapse as the CO2 dissolves into the cheese’s water content.

Prepared foods – the variety of ingredients in, say, a sandwich or a pizza presents a real challenge for the implementation of MAP. Each product presents a unique problem requiring in-depth knowledge of the best gas mix for each, usually a combination of nitrogen and carbon dioxide.

Fruit and vegetables – these present a myriad of variables to consider including the makeup of each product, their age, whether they are processed (e.g. peeled potatoes) or not, pack volume and sensitivity to light. These all contribute to the produce’s respiration rate, where fruit and vegetables take in oxygen and give out carbon dioxide. This continues after harvest, inside the MAP, so you need a film with sufficient permeability (but not too much) to keep the atmosphere around the food balanced at the optimum level for preservation.

In a nutshell, MAP requires a level of expertise and know-how. Reaching the right mix of gas and packaging for any food is achieved through experimentation and the application of specialist knowledge gathered over decades of research and practice.

It’s a world of precision, but the benefits for food producers can be game changing in preserving what makes you, you.

Read the Quick guide on Clostridium botulinum in MAP/VP chilled foods >

Buy MAPAX® Food Fresh Gas Cylinders from BOC >