Thermal imaging in food processing

Paul Boughton

The need to accurately monitor the temperature of foods in the cooking, chilling and freezing processes has made thermal imaging the quality control method of choice for many manufacturers. Chris Brown reports.

Thermal imaging cameras are now sufficiently discrete to be mounted onto any part of the process to provide automatic temperature measurement. They have firmware and communication interfaces that enable their use in automated process control and can be incorporated into machine vision systems without the need for custom-written control codes thanks to their compatibility with third party software. This software includes a wide variety of functions that support automated food processing applications.

The cameras provide operating modes that support correct temperature measurements under various conditions. Two of the most common are spotmeter, for taking measurement at a particular point, and area measurement that provides minimum, maximum and average temperatures within a selected area.

The camera's I/O ports can be used to trigger an alarm device without additional software. However, food processing often benefits from high-level analytics available through third party software. And through the cameras' adherence to commonly used machine vision interface standards such as GigEVision and GenICam a wide range of functionality can be achieved.

Controlling the quality and safety of cooked meat products is one of the prime applications for thermal imaging. A permanently mounted camera can record the temperature of chicken, for example, as they exit the continuous conveyor oven.

The technology is also suitable for monitoring the efficiency of the conveyor oven itself. Its feedback can also assist in maintaining the optimum oven temperature. And it is equally suited to monitoring temperature uniformity across the width of the oven's cooking belt, so that any faulty element or poor heat distribution can be detected swiftly and remedial action taken.

With the pattern recognition software, thermal imaging cameras can now be used to locate objects and patterns in the thermal images. A typical application for this is checking that food tray compartments on the packing line have been properly filled.

A related application is the inspection of heat-sealed cellophane covers over microwaveable meals. A thermal imaging camera can see heat radiating from the lip of the container where the heat seal is formed.

An issue affecting product safety indirectly is the integrity of cartons that overwrap and protect food containers. One of the most popular ways of sealing the pack is to use heated glue spots on the carton flaps and checking the efficiency of this process is therefore another application for thermal imaging.n

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Chris Brown is Business Development Manager - FLIR EMEA Industrial Automation & Process Control Systems, West Malling, Kent, UK.

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