Temperature Control in Food Processing Applications

While thermocouples often can be found in small-scale, low volume, commercial restaurant-grade appliances, they also can be found as part of the food production process. Typical industrial process cooking equipment that employs temperature sensing probes include ovens, warmers, fryers, toasters and grills.

Temperature sensors for the food industry need to provide consistent temperature readings to ensure precise cooking, frying or heating and protect food from being over-or undercooked. In addition to cooking equipment, it is not uncommon to find thermocouples in food packaging equipment.

We provide custom tailored temperature sensing solutions to meet the unique requirements of the food service equipment OEM. It is our goal to supply our sensor assemblies promptly and cost effectively. Our company provides various types of temperature sensors to several food service equipment manufacturers that include restaurant equipment and food inspection systems.

Dpstar Group specializes in the design and manufacture of customized thermocouples, RTDs, thermowells, and other temperature sensing device assemblies used in the food industry. We can supply accurately calibrated thermocouple sensors, cable and instrumentation which will meet the food industry’s demanding requirements for clean and safe processes. We have many years of experience working within the stringent quality requirements of the food service industry and would be eager to support your requirements.

Food Processing Applications

Deep Fat Fryers

Fryers contain a reservoir of oil into which wire baskets are lowered or through which a wire conveyor is drawn. Most systems use electric heaters either mounted around the outside or immersed into the tank. The thermocouple is immersed in the oil through the side of the tank or suspended over it. Occasionally, the probe is tacked to the frying vessel wall to reduce damage.

Pastry Ovens

Smaller pastry ovens require simple controllers usually a non-indicating type. As the pastry oven chamber size increases, the features on the controller normally improve. Larger pastry oven systems typically use natural gas because of the lower operating cost, so controllers for these larger gas-fired systems will be either differential (deadband) or fully proportional (4 to 20 mA) type.

Cookers, Steam-Jacketed Kettles and other Electrical Heater Configurations

This type of cooking equipment usually consists of a kettle with an exterior jacket though which steam flows to heat the kettle contents. The sensor normally is inserted into the process, but it also may be strapped to the outside of the vessel. Stirring the process mixture in the kettle provides more even heating and a more consistent temperature. Electric heaters also can be used to heat kettles or tanks. Typically, they are mounted either on the outside of the tank, inserted through the side or hung from the top. The temperature sensor is placed in the process mixture.

Walk-In Type Cold Storage

Food manufacturers and some drug manufacturers frequently require a large cold room for storage of products before shipment. These systems normally need cooling only (on-off type), but they also may use heat in certain geographic locations. The temperature sensors are located in the storage space.

Chocolate Tempering

Chocolate tempering melters and automatic coating systems require more accurate temperature control than most industrial and food processes. Because tolerances of ±0.5°F (0.2778°C) are required, an RTD sensor normally is used. Typically, electric heat with an SCR or solid-state relay is best suited to this type of localized heating. Other areas of the chocolate, fudge and candy market use low cost thermostats in melting and cooking kettles.

Shrink Film Packaging Systems

Heating tunnels with various styles of heaters are used to shrink plastic film around food packages. Sensor placement can be either in the airstream or on the heater. In addition, often a film-tacking assembly is placed before the heating tunnel. That equipment typically will utilize controller or other low cost temperature device.

Blister Packaging

Hard plastic protective covers are formed via vacuum-forming machines, which require a heat source to soften the plastic sheeting before a vacuum “pulls” it to the mold and forms the final shape.

Heated presses also are used to form blister packaging. Products are placed on cards, usually cardboard, covered with a “plastic bubble,” placed in a press and sealed. The press may or may not use heat. Wherever there is a heated surface in the system, there will be a thermocouple located on or in that surface to measure the temperature.

Thermoforming

In thermoforming, structured foam and plastic sheeting are heated and pressed into molded shapes to be used for food packaging. This type of package is common in egg cartons and fast food containers. Heat is used in the preheat section and can be used on the mold itself. Wherever heat is being applied in the process, a thermocouple is used to measure the temperature and feed that reading into the process control loop.

Horizontal Form/Fill/Seal Machines

These general-purpose packaging machines are well adapted to food products packaged in plastic film. Such normally solid items — pastry cakes, blocks of cheese, frozen items and the like — can be moved on a horizontal conveyor without separating. Heat is required in two places:

• The back fin seal, which is along the back of the package.
• The end seal bars, which form the package ends. This is also where the packages are cut apart.

Slip-rings normally are used on form, fill and seal (FFS) machines to bring power as well as the sensor or thermocouple leads out of the rotating seal bars.

Snack Foods Packaging

This segment of the food market includes packaging products such as potato chips, candy bars and pretzels. Two machine formats handle the majority of this market — horizontal and vertical form factors — and both use similar sealing techniques. These include the back seam, which seals the ends of the package and separates it from the next package. Solid snacks such as candy bars and individual packs of crackers are sealed on a horizontal FFS machine. The horizontal machines use rotary seal bars with the sensor and power leads brought out through slip-rings.

Products that are sold by volume usually are packaged in a vertical FFS machine. The vertical format takes advantage of gravity to pull the product into the package. The vertical machines use fixed back-seam and end-seam seal bars that close, pull the package down, open, move up and close again repetitively.

Regardless of format, temperature-sensing probes and heaters are located in the seal bars. The more sophisticated machine models integrate all machine functions into a single microprocessor with a screen to display readings, settings and menus. Even in such systems, thermocouples or RTD sensors are used for measuring the temperature readings.

Pizza Ovens

Pizza ovens can range from conveyor systems to batch ovens and can use a variety of heating fuels. Typically, all use a Type J thermocouple and a simple controller to maintain the temperature.

By helping to optimize temperature control during the manufacturing process, thermocouples and RTDs help create better end products.

We Are Ready To Help You Select The Right Product For Your Application!

Dpstar Group has extensive knowledge and experience in temperature management and process control. We provide advice, design, repair, and fabrication to our clients on a wide range of industries, uses, and capabilities of temperature management.

Dpstar Group engineers are available to consult on various stages of any project, from the development and planning of a new project to modifying or upgrading an existing facility. Our staff is here to provide you with assistance and recommendations to ensure the best outcome and value.

Dpstar Group
No 35, Jalan OP ½, Pusat Perdagangan One Puchong,
Off Jalan Puchong, 47160 Puchong,
Selangor Darul Ehsan, Malaysia.
Email: [email protected]