An ohmic heater also known as a joule heater is an electrical heating device that uses the electrical resistance of the liquids to generate heat, that is produced directly within the fluid itself by Joule effect, as alternated electric current passes through a conductive material. This has the result of transform energy causing a temperature rise. The most commonly used heating techniques for liquids rely on heat transfer from a hot surface. This heat can be generated directly from an electrical heating element or indirectly from a hot means of transportation (e.g. steam) via a heat exchanger (e.g. shell and tube ,plate). These methods require a temperature gradient to transfer the heat to the process liquid, therefore, the surfaces are at a higher temperature than the product.
This can cause fouling of the surfaces for certain products which become burnt on to the hot surfaces, reducing heat transfer rates and adversely affecting the product. A further issue with heat transfer is found when heating very viscous fluid and fluids with particulates, where a uniform heat transfer is difficult to achieve. Ohmic heaters address the aforementioned problems by removing hot surfaces from the heating of the fluids.
Our ohmic heating process is used in food industry for over 20 years. Emmepiemme is highly specialized and offers various types of installations and technical solutions to ensure a reliable and efficient process.
Various types of ohmic heaters have been developed over the past two decades, using new materials and advanced technology solutions, it was possible to build plants for heating treatments, pasteurization, sterilization, HTST (high temperature short time) for various categories of products, including:
- Fruit puree (peach, pear, strawberry)
- Fruit pieces (peach, pear, strawberry, pineapple, apricot)
- Vegetable cream
- Whole or pieces of vegetables
- Spreads and stringy paste cheese
- Egg products
- Dairy cream
- Creamy and vegetable sauces
Due to the above reasons, the ohmic heater can process, uniformly and in short times (from 10 to 90 sec), both homogeneous and heterogeneous products. For the latter some precautions must be taken as regards the composition of the carrying fluid, which electrical properties should be similar to the ones of the solid particles.
Ohmic processing approaches to some extent the HTST (High Temperature Short Time) concept, therefore the thermal damage of the product is remarkably reduced in comparison to conventional heating methods.
Sensory parameters in particular, like color, consistence and flavor are very satisfactory compared with the incoming fresh material.
Apart from the reported quality improvements, the industrial applications of Emmepiemme ohmic heater pointed out some further benefits in comparison with conventional heating methods, which are mentioned below.
In case the possibility is forecasted and requested in advance, a single equipment can be designed so as to be able to process both homogeneous products and products containing particulates. The processing of products containing diversified electrical properties is also possible in the range 1 to 30 times .
Absence of hot walls and quick heating make it possible to stop and restart operation without particular problems, and with very little product damage or loss, which is impossible with conventional systems and particularly with aseptic plants.
Emmepiemme ohmic heater is designed on a modular base. The single module is a 60 KW power unit; therefore it is possible, within limits, to increase a plant power and capacity by simply installing additional modules.
The overall dimensions of Emmepiemme ohmic heater are very reduced, thus it can be easily inserted even in existing lines, without problems as for layout and utilities.
The technology allows to adopt large pipe sections (from 50 to 100 mm), so that the product pumping is improved, especially for continuous plants, thus remarkably reducing the mechanical spoilage of products due to displacement.
As regards to specifically products containing particulates, this peculiarity allows to obtain finished products with very large pieces (20 and even 25 mm) that are unlikely to achieve in conventional systems, as well as products with very high drained weight, up to 80-90% (depending on the product).
Because of the improved sensory qualities and of the possibilities given by the aforementioned features, it is possible to put highly competitive and even innovative products on the market, not only in comparison to conventional processes , but with frozen products (IQF) as well.