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Sensing solutions help ensure food safety

04 October 2021

Andy Walker explains how new sensing solutions can make it easier to keep control of critical food production processes. 

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The top priority food manufacturers must be product safety and there are many factors in the manufacturing process that can affect this. Two of the most important considerations, however, are hygiene and temperature. 

Hygiene is an essential requirement, both to ensure product purity and to minimise the risk of cross-contamination during changeover and many food processes rely on cleaning in place (CIP) to reach the necessary standards of cleanliness, while keeping the plant downtime needed for cleaning to a minimum.

CIP typically works by introducing cleaning fluids into the plant and then flushing them out again before the plant is returned to service. To work as intended, there are two key requirements. The first is that the concentration of the cleaning solution must be correct, and the second is that all traces of the solution must be flushed from the plant at the end of the cleaning cycle. Failure to satisfy either of these requirements can lead to product wastage. If the problem is not promptly detected it could result in harmful product reaching the consumer.

Rigorous procedures need to be in place to minimise the risk of these problems occurring. A more dependable approach is to directly monitor and measure what’s going on and a convenient way of doing this is to look at the conductivity of the fluids in the plant. The cleaning fluid, when at the correct concentration, will have a relatively high and known conductivity, whereas the flushing water will have a very low conductivity once all the cleaning fluid residues have been removed.

While conductivity sensors are not new, what is new is a sensor that can deliver the level of accuracy needed at high conductivity levels to confirm the correct concentration of the cleaning fluid and also at very low conductivity levels to confirm that flushing is complete. They achieve this partly throuogh advanced design and construction, and partly by using digital IO-Link signals to send data to the control system. The accuracy of signals transmitted via IO-Link  are unaffected by electrical noise and have no conversion (A-D) losses, making it possible to achieve exceptional resolution over a very wide measuring range.

As well as helping to guarantee product safety, using a conductivity sensor to monitor CIP can also boost productivity. With the sensor providing positive confirmation that all cleaning fluid has been flushed from the plant, it is no longer necessary to prolong the flushing process ‘just to be sure’. This means shorter CIP cycle time, leading to increased plant availability and higher productivity. 

Temperature is one of the most critical aspects of food processing techniques. Take, for example, pasteurisation – even marginally incorrect temperatures can lead to serious quality and safety issues. 

Temperature sensors are commonplace, but if the calibration of a temperature sensor starts to drift, how much product might be compromised before anyone notices? A serious error is likely to be noticed quickly, but even then, there may be considerable product wastage. A more subtle error may persist for some time before detection, which could mean whole batches of product have to be scrapped or even recalled.

A new type of temperature sensor incorporates two sensing elements with opposing (PTC/NTC) characteristics. The sensor constantly compares the measurements from the two sensing elements which, under normal circumstances, match very closely. If a mismatch occurs, indicating calibration drift, it is detected immediately, and the sensor provides a local visual indication as well as sending a warning to the plant control system. Like the conductivity sensors discussed earlier, these temperature sensors use IO-Link digital communication to deliver accurate data to the control system. 

These new conductivity and temperature sensors have been specifically developed for the food industry so they comply with all major national and international standards for hygienic applications. Whether used in new plant or as a retrofit upgrade to existing plant, their cost is modest but the benefits they deliver in terms of enhanced product safety and peace of mind, are invaluable. To find out more, just ask ifm electronic!

Andy Walker is product sales manager at ifm electronic.

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