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C-Tech Innovation has more than 30 years experience in design and build of specialised Ohmic Heating equipment for a wide variety of applications. Ohmic heating, developed by C-Tech Innovation, is an energy efficient and high quality method of heating either a continuous flow or batch quantity of wet or moist material.

The mechanisms by which heat is generated in the product varies with the operating frequency of the electric field: at low frequencies (less than 104 Hz) and radio frequencies (104 to 108 Hz) the effects are primarily due to resistive heating caused by the movement of ions / electrons in the electric field. At higher frequencies (e.g. microwave heating (108 to 1011 Hz) molecular dipole rotation is the main heating mechanism, whereas at higher frequencies still (e.g. infra-red (IR)) the dominant mechanism is one of molecular vibration, and at visible frequencies is by the elevation of electrons to higher energy levels. As the frequency of the electromagnetic field increases so the energy penetrates less deeply into the product. At IR and visible frequencies, for most food products, the energy will be absorbed very rapidly as it enters the product resulting in essentially surface heating; though for other materials, e.g. some polymers, IR heating can provide volumetric heating.

Typical volumetric heating technologies of use in the food processing industries include microwave, radio frequency and Ohmic heating. Common to these volumetric heating methods is the fact that they do not require hot surfaces, or rely on conductive or convective heat transfer through a product.

Ohmic heating is a proven technology for processing high quality fluid food products. It can be used to pasteurize, sterilize or cook foodstuffs ranging from juice and dairy products to soups and stews. With Ohmic heating, as for all volumetric heating techniques, the absence of hot surfaces in contact with the product leads to reduced thermal degradation and thus improved product quality. It is also capable of extremely rapid heating and is a very efficient heating technique. This makes Ohmic heaters a good choice in areas where traditional heat exchangers can cause problems, such as fouling and product quality reduction from overheating, and where products are difficult to heat because of a large solid content or the product contains delicate particulates. Ohmic heating involves passing an alternating (AC) current (typically 50 Hz to 100 kHz) through the product being processed. Due to the electrical resistance of the product, this current flow then causes ‘Ohmic’ heating throughout, giving a uniform temperature profile. Any conductive and pumpable product can be successfully heated including most food products. The rapid and uniform heating made possible with the technology lends itself to high temperature short time (HTST) processes with potential benefits in terms of product taste, colour and texture.

Ohmic Heating Benefits

  • Volumetric and uniform heating
  • Both liquid and solid particulates can be heated
  • Equally applicable in batch and flow-through systems
  • Reductions in process time and increased throughput
  • Energy efficient processing >95% power utilisation

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Applications

An induction-heated mixer

Advanced Induction Heating

While induction heating in industrial applications has been in widespread use for many years, particularly within the metal processing industries, there is now increasing interest in this versatile technology for other heating applications. Induction heating can be particularly useful for products which might be sensitive to excess heating, thereby creating a spoiled product, or in applications where heat is required to be applied in difficult geometries. C-Tech Innovation has extensive design and build capabilities for this kind of specialist induction heating equipment.

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Batch Ohmic Heater

Food processing using ohmic heating reduces the need for preservatives and results in superior taste and texture compared to other thermal treatment methods such as jacketed vessels, heat exchanges or steam injection. The Qulom OBA-26 is an ideal tool for R&D and recipe development at temperatures up to 100ºC. For higher temperatures we offer a prerssurised batch unit the Qulom OBP-26, capable of operating at up to 150ºC. Read More

Food cooking

Conventional cooking of foods relies on conduction from hot surfaces into the food. This can limit the rate of cooking, especially in products with large solid particles. By using the food’s own electrical resistance to generate the heat using C-Tech Innovation’s Ohmic Heaters, food can be heated evenly from within. The result is greatly increased cooking rates whilst maintaining the highest product quality. Read More

Silent Kettles

The benefits of ohmic heating are currently being transferred into everyday items. Miniaturised, the technology can be employed in a kettle, offering a completely silent boil. Ohmic heating also resists the effects of scale. it has been shown to greatly prolong the life of a kettle in hard water areas compared to conventional elements. Likewise, electrically heated showers will not lose performance due to scale build up. Other items such as steam irons and instant water heaters are in development.
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Normal Maloney, Advanced Thermal Processing Group Leader

Norman Maloney

Principal Engineer, Advanced Thermal Processing

Have a question about ohmic heating?

Contact Norman