Thermal imaging & vision systems
n the food industry, it is essential to carefully control the temperature of perishable goods throughout production, transportation, storage, and sales. Repeated warnings about illnesses due to tainted and improperly cooked foods highlight the need for tighter process control. Because this almost always involves a human factor, food processors need tools that automate crucial operations in a way that helps minimise human error while holding down costs. Thermal imaging cameras are such a tool. Using FLIR thermal imaging cameras, you can make automated non-contact temperature measurements in many food processing applications. Analogue video outputs can be viewed on video monitors, and digital temperature data, including MPEG4 video outputs, can be routed to a computer via Ethernet.
I HOW IT WORKS
The main elements doing non-contact temperature measurements in the food processing industry are a thermal imaging camera and associated software. They act as “smart” non-contact sensors to perform 100 per cent inspections, measuring the temperature of equipment, refrigerated products, and cooked foods as they exit the cooking process. Thermal imaging cameras are easy to use, small, and can be positioned almost anywhere as needed. They can also be used to inspect package sealing, and improve efficiency in other food processing operations. FLIR thermal imaging cameras have firmware and communication interfaces that enable their use in automated process control. Third-party software makes it easy to incorporate these tools into automated machine vision systems without the need for extensive custom-written control code. The use of thermal imaging cameras in food processing is growing for applications such as:
Oven baked goods Microwave cooked meats
Microwave drying of parboiled rice and other grains
Inspecting ovens for proper temperature
Proper filling of frozen meal package compartments
Checking integrity of cellophane seals over microwave meals
Inspecting box flap glue of overwrap cartons
Monitoring refrigerator and freezer compartments
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THERMAL IMAGING CAMERAS IN THE FOOD INDUSTRY
contact type temperature sensors. Thus, thermal imaging cameras can help correct variability and improve quality before a lot of product is scrapped.
FLIR A310 is a fixed mounted thermal imaging camera. It can be used for all types of monitoring in the food industry
THERMOGRAPHY FOR QUALITY ASSISTANCE AND PRODUCT SAFETY Thermal imaging is first and foremost a quality assurance (QA) tool. Controlling the quality and safety of cooked meat products is an excellent use of this technology. A permanently mounted thermal imaging camera can record the temperature of, for example, chicken tenders as they exit a continuous conveyor oven.
The objective is to make sure they are done enough but not over-cooked and dried out. Reduced moisture content also represents yield loss on a weight basis. Thermal imaging cameras can also be used for inspection on microwave precooking lines. Besides improving product quality and safety, overall throughput can be increased. An additional benefit is reduced energy costs.
EQUIPMENT MONITORING
In addition to cooked food inspections, thermal imaging cameras can monitor conveyor ovens. They can even be part of a feedback loop to help control oven temperature.
Another use of thermal imaging cameras for conveyor ovens is monitoring temperature uniformity across the width of the conveyor oven cooking belt. If a heating element inside an electric oven fails, or you get uneven heating across an air impingement oven, one side of the product stream may be cooler. This can be quickly discovered with thermal imaging cameras. Quality inspections of this sort are much more difficult with conventional
April 2023 Instrumentation Monthly
PACKAGING INSPECTIONS Software is available that allows thermal imaging cameras to locate objects and patterns in the images. One application for pattern matching is in the production of frozen meals. Thermal machine vision can use pattern recognition software to check for proper filling of food tray compartments. A related application is automated 100 per cent inspection of the heat-sealed cellophane cover over finished microwave meals. A thermal imaging camera can see heat radiating from the lip of the container where the cellophane heat-seal is formed. The temperature along the entire perimeter of the package can be checked by using the thermal image with machine vision software. This type of program matches the geometric pattern in the image and its temperatures against the temperatures in a pattern stored in a computer memory. An added function in such a system could be laser marking of a poorly sealed package so it can be removed at the inspection station.
An issue affecting product safety indirectly is the integrity of cartons that overwrap and protect food containers. One of the most cost- effective ways of sealing overwrap cartons is to use heated glue spots on the carton flaps. In the past, the integrity of the spot gluing was determined by periodically doing destructive testing on several samples. This was time-consuming and costly.
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