Thermal imaging cameras in the food industry
In the food industry, it’s 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 minimize 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. Analog
video outputs can be viewed on video monitors, and digital temperature
data, including MPEG4 video outputs, can be routed to a computer via
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% inspections, measuring the temperature of equipment,
refrigerated products, and cooked foods as they exit the cooking
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
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.
FLIR A310 is a fixed mounted thermal imaging camera. It can be used for all types of monitoring in the food industry.
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
An IR temperature measurement and thermographic image are used to locate undercooked chicken tenders and stop the line so undercooked ones can be removed.
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.
This thermal image shows bottles being filled automatically, so bottles that are over-or under-filled can be removed. If a bottle or jar is made of dark colored glass or plastic thermal imaging cameras are much more effective than visible light cameras.
Thermal image for checking hamburger doneness by measuring temperature.
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 contact type temperature sensors. Thus,
thermal imaging cameras can help correct variability and improve quality
before a lot of product is scrapped.
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% 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.
Typical Go/No-Go inspection system using thermal imaging cameras.
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.
Because the glue is heated, a thermal imaging
camera can “see” through the cardboard to check the pattern and size of
the applied glue spots. The camera can be set up to look at predefined
areas of the flaps where glue should be applied, and verify spot sizes
and their temperatures.
The digital data collected is used for a
pass/fail decision on each box, so bad boxes can be immediately removed
from the production line. The data is automatically logged into the QA
system for trend analysis, so a warning can be generated if an excessive
number of boxes begin to fail.
Process monitoring of production line.
Yet another application for thermal imaging
cameras is monitoring container filling operations. Although this is
seldom a product safety issue, it does affect yield and compliance with
regulations. Different areas on the bottle can be defined and used to
trigger an alarm and remove bottles that are over-or under-filled.
Thermal imaging cameras are a better alternative to visible light
cameras when a bottle or jar is made of dark colored glass or plastic.
Application software currently available for
thermal imaging cameras includes a wide variety of functions that
support automated food processing applications. This software
complements and works in conjunction with firmware built into thermal
imaging cameras. The imaging tools and libraries in these packages are
hardware- and language-independent, making it easy for food processing
engineers to quickly implement thermal monitoring and control systems.
Thermal imaging cameras themselves provide the
user with different operating modes that support correct temperature
measurements under various conditions. Two functions commonly found in
these cameras are a spotmeter and area measurements.
The spotmeter finds the temperature at a
particular point. The area function isolates a selected area of an
object or scene and usually provides the maximum, minimum, and average
temperatures inside that area. The temperature measurement range
typically is selectable by the user. As an adjunct to the temperature
range selection, most cameras allow a user to set up a color scale or
gray scale to optimize the camera image.
The data is automatically logged into the QA system for trend analysis,
so a warning can be generated if an excessive number of boxes begin to
The camera can be set up to look at predefined areas of the flaps where glue should be applied, and verify spot sizes and their temperatures.
In conveyor oven applications, the area
function is typically used because pieces of cooked product are often
randomly located on the conveyor. The camera can be programmed to find
and measure the minimum and maximum temperatures within the defined
area. If one of those setpoint temperatures were to fall outside the
user-defined limits, an application program running on a PC or PLC would
instantly trigger an alarm, alerting the operator to check the thermal
image on a video monitor or PC to find and remove the bad product,
and/or adjust the cooking temperature.
In the case of local monitoring, an IR camera’s
digital I/O can be used to directly trigger an alarm device without
additional software. However, food processing often benefits from higher
level analytics that are available in third-party software that runs on
These out-of-the-box solutions do not require
the writing of application source code. By adhering to commonly used
machine vision interface standards such as GigE Vision® and GenICam,™ a
wide range of functionality is supported by this software.
A simplified block diagram of conveyor
monitoring is shown. One thermal imaging camera is adequate for many
applications, or a thermal imaging camera may be combined with a visible
light camera to record other target object attributes, such as color.