A quick tagline about ohmic heating
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.