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A huge number of the foods that people buy are contained in modified atmospheric packaging (MAP). Fruits, meats, vegetables, and baked goods are all contained in a modified atmosphere in order to prolong their shelf life. MAP means food tastes and looks fresher for a prolonged period, without any alteration of the food itself.
MAP attains this by replacing the air that would generally be trapped in the food container with an optimal blend of gases customized to the foodstuff.1
The typical gas blends that are used in the MAP are combinations of N2 and CO2, and for a few food types, O2 is also included. ‘Normal’ air contains a composition of 78% N2, 21% O2 and 1% argon alongside other trace gases.2 Of these gases, oxygen, is used most carefully as it can react with the food, or offer the necessary conditions for the growth of microorganisms that lead to food spoilage.
The MAP is extensively used in the food industry as it provides a way of prolonging shelf life without the use of any chemical additives of preservatives. For products such as salads, carefully selected MAP guarantees that the product is desirable to consumers by remaining fresh and crisp at the point of sale.
The Best Conditions for Food Preservation
In order to maximize the preservative gains from the MAP, the gas combination used is customized to the foodstuff being packaged. For instance, meats usually benefit from a MAP containing 70-80% O2, whereas shellfish and seafoods generally benefit from low O2 levels and more CO2. The requirements for bulk shipping and the final individually packaged retail products also frequently differ, with the majority of bulk packaging needing extremely high concentrations of CO2.3
The differences between the perfect gas compositions for fish and meat storage generally arise from the existence of myoglobin in the meat. Myoglobin, which is an iron-containing protein also existing in human tissue, has a deep purple color and can respond with small gas molecules to develop different complexes. When myoglobin reacts with O2, it produces oxymyoglobin, which has the bright red color related to fresh meats. However, if the myoglobin or oxymyoglobin is oxidized, it forms metmyoglobin, which is brownish in color and is associated with spoiled food.4
Whether the O2 binding reaction or the oxidation process dominates is greatly dependent on the oxygen concentration in the surrounding atmosphere. However, an O2-free environment is beneficial for most non-meat or pre-cooked products. Due to this, CO2 becomes the gas of choice. The key role of carbon dioxide is to eliminate oxygen from within the packaging, which can lead to the degradation of all types of foods (other than raw meat). At high concentrations, CO2 can also behave as an insecticide, preventing pests from attacking produce.
For cooked meats, CO2 concentrations of almost 30% are needed for preserving the meat for as long as possible. Fish, ready meals, seafood, vegetables, and pastas also benefit from similar CO2 concentrations while bakery products and harder cheeses can benefit from CO2 concentrations of around 50%.
For plant-based foods, having the potential to precisely determine the gas mixture for MAP conditions is mainly important. This is because some O2 enables the plant to respire but this will have to be balanced with an increased CO2 concentration to slow the rate of respiration and preserve the freshness for longer. However, too much CO2 concentrations can also have a detrimental effect, so the concentrations will have to be balanced exactly.
Guides are available with recommendations for optimum MAP conditions for varied products3, being able to develop such environments depends on being able to precisely monitor and determine the concentrations of the varied gases. Preferably, the gas sensors employed for the MAP will need to have the potential for real-time gas monitoring and analysis.
Sensors from Edinburgh Sensors for Modified Atmospheric Packaging
The Guardian and GasCard series of gas sensors from Edinburgh Sensors Guardian and GasCard series of real-time gas monitors excels, developed using almost four decades of expertise in gas sensor technologies. Both devices offer high-quality, highly-accurate online gas sensing capabilities for detecting CO2, ideally suited for bulk MAP requirements.
The Guardian series5 represents a complete, stand-alone gas monitor that uses infrared detection for the real-time monitoring of CO2 in conditions where concentrations range from 0 to 3000 ppm and 0 to 100% volume. With an impressively rapid 1.5 minute warm-up time, the sensor is designed with ease-of-use in mind, including an on-device display with set-up menus that can also be used for graphical display of historic readings over a user-defined period. As the sensor can work in conditions of 0 – 95% relative humidity and 0 – 45 °C, it is perfect for applications in the MAP, mainly where CO2 concentrations are of primary interest.
Whilst the Guardian series has been designed to be stand-alone sensors, Edinburgh Sensors also provides the GasCard range for use in applications where incorporation into another gas sensor device is needed.6 Besides being capable of real-time temperature and atmospheric pressure correction, the GasCard range offers detection sensitivities of 0 – 5000 ppm for CO2.
The GasCard uses RS232 communications to allow both control and real-time data logging and there is also an option for on-board LAN support where needed. It can work under atmospheric conditions, and can also be customized for detection of additional gases or incorporated with other gas sensing devices where increased versatility is needed. All GasCards are available with technical support and one-to-one customer service, including support for system integration.
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References and Further Reading
- B. Ooraikul, Modified Atmosphere Packaging of Food, Springer, 1991
- Weather and Climate Basics, https://www.eo.ucar.edu/basics/wx_1_b_1.html, (accessed January 2018)
- Modified Atmospheric Packaging Poster, https://modifiedatmospherepackaging.com/~/media/Modifiedatmospherepackaging/Brochures/MAP-Poster-Guide-2014.ashx, (accessed January 2018)
- Meat Colouring Pigments, http://msue.anr.msu.edu/news/the_color_of_meat_depends_on_myoglobin_part_1, (accessed January 2018)
- The Guardian NG, https://edinburghsensors.com/products/gas-monitors/guardian-ng/, (accessed January 2018)
- The GasCard, https://edinburghsensors.com/products/oem/gascard-ng/, (accessed January 2018)
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.
For more information on this source, please visit Edinburgh Sensors.