Testing Modified Atmospheric Packaging

Modified atmospheric packaging testing is a necessary procedure, which is used to validate the mixture of gases that exist inside a sealed container of fruit, vegetables, meat, drinks, drinks, pharmaceuticals as well as a myriad of other consumable products.

Product spoilage can be affected even by minute variations of nitrogen, oxygen, water vapor or carbon dioxide. All of the above can impact spoilage as well as product attractiveness to the consumer. It is not enough purely to provide product safety, given the importance of providing safe consumables to customers – it is necessary for packagers to test and verify the safety too.

  1. Modified Atmosphere Packaging: What Is It?
  2. How a MAP Handheld Oxygen Sensor Works
  3. Beyond MAP - Controlled Atmosphere Testing
  4. MAP During Packaging
  5. How Safe Is Modified Atmospheric Packaging?

What is Modified Atmosphere Packaging?

As we all know, food does not stay fresh forever. Whether it is a wilted lettuce, spoiled milk or strange-smelling meat, there are several factors in food spoilage. One of these, a major factor in how rapidly the food perishes, is the oxygen level inside the package. In the packaged space, oxygen can cause decay, by both oxidation as well as by the growth of molds and yeasts, and other aerobic microorganisms. One method of slowing down this process is by using modified atmosphere packaging.

To flush air from food storage containers and replace it with known-gas mixtures, modified atmosphere packaging, otherwise known in the food industry as MAP, is used. MAP permits the retention of nutritional value for fresh packaged food, as well as offering a chemical-free route towards an extended shelf-life. In addition to this, standards for brand quality and consistency will be met by packaged foods. Though this technology of modified atmosphere packaging is by no means new, over time the technology has become more refined.

The environment of MAP is generated from a carefully-chosen mixture of atmospheric gasses. First, the package is flushed with a mixture of known gases, and subsequently it is sealed. At the same time, preservation of moisture may be required to maintain the texture and taste of the product. In certain cases, vacuum packaging is used to remove virtually all the gases in the package.

Nitrogen (N2), for instance, will displace oxygen but also removes all moisture. Given that all gaseous environments seek to attain equilibrium, the displaced moisture will attempt to find this balance by substituting the displacement with moisture. Therefore, this is where a mixture of carbon dioxide (CO2) and nitrogen is used. Carbon dioxide also supports moisture while reducing the pH, this means that the residual moisture becomes more acidic. In addition, this eliminates potential foodborne illness by reducing the environment for bacterial growth. The optimal result being aimed for is a slowing of product expiration, a reduction of color loss and overall preservation of the food product in its peak and freshest condition.

The measurement of the remaining oxygen in the modified atmosphere inside the package is the common factor in all these details. A sample is taken of a very small quantity (1-5cc) of gases in the sealed package in order to test the remaining gas.

MAP Handheld Oxygen Sensor: How Does It Work?

To test handheld oxygen sensors in food or pharmaceutical packaging facilities, handheld oxygen sensors are used. Samples of the final product are selected at random from the line and then pierced with a hollow needle called a cannula. The gases inside the package are pulled through this cannula, via a vacuum, into a tube and subsequently an oxygen gas sensor. This permits for testing, inside the package, of the modified atmosphere. If the required standards for the package are not met by the oxygen level, the user can conclude that there is a problem inside the modified atmosphere packaging machinery. The line of packaging is stopped, the machinery tested, and a sample taken once again.

An example of an oxygen sensor that is used in the testing of sealed packages is the TecPen Handheld Oxygen Sensor.  Designed to verify oxygen levels in closed food packaging, it pierces the sealed packaging material and measures the oxygen level inside.

Using a technique known as fluorescent quenching by oxygen, the TecPen measures low concentrations of oxygen. A dye is illuminated by a specific wavelength of light which causes the dye to fluoresce. The fluorescence is reduced, or “quenched” if oxygen molecules touch the molecules of dye. The concentration of oxygen at the surface of the fluorescent material can be computed, if the amplitude of the emission and the decay time once the excitation source is removed is known.

This process of excitation and measurement of emission happens thousands of times per second, or in the kilohertz range. Thus, the TecPen is permitted to accurately measure oxygen levels from minute samples of gas. Additionally, TecPen can measure changes in oxygen levels which are as low as one part-per-million, or 1 ppm.

Controlled Atmosphere Testing - Beyond MAP

In the process of moving food from farms to grocery stores, there are several steps in moving food. A variation of MAP called controlled atmosphere testing (CA) storage is common during food transportation. CA maximizes storage life and minimizes spoilage by combining low temperatures and a modified Atmosphere. There are two places in which CA is used before undergoing final packaging:

1. Controlled Atmosphere Testing After Harvesting

Fruit continues to live and respire after it has been harvested, until the depletion of all its internal glucose stores. The longer this respiration continues, the longer the fruit will remain fresh.

For instance, after apples are picked, they are transported into cold storage rooms which will reduce the speed of the respiration rate. The colder the environment, the slower the respiration is, and the longer time the apples will stay fresh until they are sold. During this phase, it is essential to test the Oxygen levels, as levels need to be lowered from 21% to 1.2% to put the apples to “sleep.”

2. Controlled Atmosphere Testing During Transportation

It is common for fresh produce to travel a long way to the purchasing destination from its point of harvest. It can be sealed, during this time, within containers wherein the Oxygen levels are lowered. This is designed to keep respiration low, which requires modified atmospheric packaging.

MAP During Packaging

The food package must be sealed as soon as normal oxygenated air is taken out during the food packaging process. This applies not only to fruits, as stated above, but other goods too including vegetables, meat and poultry.

We should also note that different levels of gas in the packaging are required by different foods in order to stay fresh. For instance, ideally, fruits and vegetables should be packaged with 1-5% Oxygen, 2-15% CO2, and 80-95% Nitrogen. Contrastingly, red meat is conventionally packaged in 30% CO2 and 70% Nitrogen.  Foods such as potato chips, which are dried, are often packaged in 100% nitrogen.

The TecPen, and other modified atmospheric packaging testing equipment is a reliable way to test oxygen levels during the process of packaging, in order to protect overall consumer safety as well as surpass industry standards.

How Safe is Modified Atmospheric Packaging?

To the question, “Is Modified Atmospheric Packaging Safe?”, the answer is an unmitigated “yes”; and to the question of how safe, the answer is ‘very’. The technique of artificially managing the air in and around stored foods has been a staple of safety in food processing since the ancient Egyptian era. Without the need for chemicals, MAP facilitates the storage and transportation of fresh foods, and it is used in every food production industry in the world. Nonetheless, testing is required in order to obtain 100% efficiency, hence the need for modified atmospheric packaging testing.


This information has been sourced, reviewed and adapted from materials provided by GasLab.

For more information on this source, please visit GasLab.


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