Gas Sensors for the Development of Modified Atmospheric Packaging

A huge number of the foods we buy are contained in modified atmospheric packaging (MAP). Fruits, vegetables, meats and baked goods are all contained in a modified atmosphere to extend their shelf life. MAP means food tastes and looks fresher for longer, without any modification of the food itself.

MAP achieves this by replacing the air that would normally be trapped in the food container with an optimal blend of gases tailored to the foodstuff.

The Best Conditions for Food Preservation

In order to maximise the preservative gains from MAP, the gas combination used is tailored to the foodstuff being packaged. For example, meats generally benefit from a MAP containing 70-80 % O₂, whereas seafoods and shellfish usually benefit from low O₂ levels and more CO₂. The requirements for bulk shipping and the final individually packaged retail products also often differ, with the majority of bulk packaging requiring very high CO₂ concentrations.

The differences between the ideal gas compositions for meat and fish storage largely arise from the presence of myoglobin in the meat. If it reacts with O₂, it forms oxymyoglobin, which has the bright red colour associated with fresh meats. However, if the oxymyoglobin or myoglobin is oxidised, it forms metmyoglobin, which is brownish in colour and is associated with food that has spoiled.

Whether the O₂ binding reaction or the oxidation process dominates is highly dependent on the oxygen concentration in the surrounding atmosphere. However, for most pre-cooked or non-meat products, an O₂-free environment is advantageous. As a result, CO₂ becomes the gas of choice. Carbon dioxides main role is to exclude oxygen from inside the packaging, which can result in the degradation of any foods (other than raw meat). At high concentrations CO₂ can also act as an insecticide, preventing pests from attacking produce.

For plant-based foods, being able to precisely determine the gas mixture for MAP conditions is particularly important. This is because some O₂ helps the plant to respire but this needs to be balanced with an increased CO₂ concentration to slow the rate of respiration and preserve the freshness for longer. However, excessive CO₂ concentrations can also have a determinantal effect, so the concentrations need to be balanced exactly.

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 nearly 40 years of expertise in gas sensor technologies. Both devices offer highly-accurate, high quality online gas sensing capabilities for the detection of 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 – 3000 ppm and 0 – 100 % volume. With an impressively quick 1.5 minute warm-up time, the sensor is designed with ease-of-use in mind, featuring 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 operate in conditions of 0 – 95 % relative humidity and 0 – 45 °C, it is ideal for applications in MAP, particularly where CO₂ concentrations are of primary interest.

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