Tiny sample volume and ultra fast response CO2 sensor enables new generation of MAP analysers

Modified Atmosphere Packaging (MAP) is used to prolong the shelf life of fruits, vegetables and salads with a specific level of CO2 to keep the produce fresher for longer.  The optimal level varies widely according to the product*.  On the production line, sample packs are taken at regular intervals and the CO2 levels checked by inserting a hollow needle into the pack and drawing out a sample of the gases for analysis.

However, standard CO2 sensors take several minutes to stablise on a reading — during which time many bags can progress along a high-speed line.  The longer the read time, the more bags are made with potentially the wrong CO2 level, which wastes product and money.  In addition, packages that ship with the wrong CO2 levels can spoil before the use by date, resulting in claims against the producer by the supermarkets.

Storage Control Systems (SCS) wanted to create a portable gas analyser that would provide an accurate CO2 reading in seconds, and only need a small sample volume. The sensor that they had been using in their products has a very high power consumption, which limits the operational life for a battery powered portable device, and was not fast enough in providing a reading for this application. To achieve the performance specifications of the new class of analyser that they wanted to create for MAP application, the company used a SprintIR®-W infrared CO2 sensor from Gas Sensing Solutions. The SprintIR®-W sensor can provide 20 readings per second from only a 3ml sample due to its patented design.  This means that the analyser only has to sample 30ml of gases in order for the sensor to obtain a clear reading of the gas composition. This amount is greater than that required by the actual sensor because of the volume of tubing used to obtain the sample gases that needs to be purged.

Another key benefit of using the GSS CO2 sensor is its very low power requirement (3.5mW). SprintIR®-W uses a specially developed LED as a light source for the NDIR absorption.  It only needs a fraction of the power of competitor InfraRed CO2 sensors, so it can be easily battery powered.

Kevin Johnson, Production Manager at SCS, said, “Our customers told us that there was a market need for a new class of gas analyser for MAP that could provide a reading within seconds, so that they can save money on the production line by taking swift corrective action when CO2 levels are outside the requirements.  The innovative technology of the GSS sensor has enabled us to create a solution for this need that no other CO2 sensor could.  The result is our new SCS354 Dual Gas Analyser and we have sold 60 already.”

He added that, “The level of CO2 required for optimal shelf life varies according to the type of product being packaged.  This analyser measures levels of CO2 from 0 to 20% with great accuracy, ensuring that the use by date is achieved.  Customers are so impressed with it that they are asking us to make a version that covers from 0 to 50%.  GSS is helping us with this new design, and we have already received pre-production orders for this model. Having a GSS sensor at the heart of our new designs has enabled us to create the next generation of products to address a whole new market.  We can now offer rapid response, handheld CO2 analysers for Modified Atmosphere Packaging that are easy use and save customers money through improved quality control.”

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