Ohmic Heating - Feasibility Study

FEASIBILITY STUDY

Ohmic heating is an emerging technology which are currently being employed in some food processing industry for the many purposes such as blanching, drying, frying, fermentation etc. Although it is being used in some purposes like above mention, however its full potential has not been fully realized because of its complexity of the process and the lack of complete understanding of phenomena occurring during ohmic heating. Ohmic heating works by passing current through the food material where heat is generated internally because of electrical resistance of food. In comparison other thermal processing method usually use heater or steamer to generate heat in order to heat the food. Ohmic heating technology has great flexibility in terms of design and variety and it will only increase as the technology further mature and develop. It can be design to operate on wide range of electrical conductivities. Ohmic heater can be design in such a way so that it suite best to work in a particular individual process. One of the most important innovation that is been brought by this process is how it heat the food by generating heat internally whereas in other conventional heat processing technologies heat is generally transfer to food material either by conduction or convection. In comparison between microwave and ohmic heating, ohmic heating demonstrate more advantage since in case of microwave heating, heating can be achieved only to a certain depth of the product while in ohmic heating heat can be transfer to the whole volume whatever the size of the product is. This process of heating the food by ohmic heating differentiate it from other commercially found thermal processing technologies. Ohmic heating has the ability to heat the product rapidly and uniformly compare to many other heating technologies leading to a production of higher quality product in terms of nutritional as well as organoleptic properties. Rapid and uniform heating is of great importance in food industry because due to overheating some valuable and beneficial nutrient and flavor compounds may be lost during the process which will lower the quality of the products. The advantages of ohmic heating over conventional heating technologies include, no hot surface requirements for conduction, easier to control the process, lower chance of damaging  nutrients and other sensitive component in food, high efficiency (ohmic heater typically have efficiency of avobe 95 percent), ability to handle highly concentrate slurries ( product having 80 % particulates can be processed). Despite having all those advantages ohmic heating does aslo have few downside.  These are, cost of energy for electrical heating system, limitation on the minimum and maximum electrical conductivity values allowed for a given throughput, which will in turn limit the product type that can be processed by ohmic heating, availability of power supply from local electrical power supply system, requirements for nonconductive insulating material in order to isolate electrical components and unable to processed food having high fat globule properly. Other than above mention technical limitations the other most important limitations which have limited its further adaptation in food processing industries is its associated cost. The cost for commercially available heating system including cost of installation is as high as $9,000,000 USD, which is very costly for manufacturer. In US state of Missouri Nestle setup a food service plant which use ohmic heating system to process beef stew. The cost of processing a pound of stew at the initial stage was $0.25 to $0.49 USD. However the cost of per pound processed stew decrease after 5 year to approximately $0.21 to $0.36 USD (Rahman 1999). In contrast conventional pasteurizer cost up to $1,000,000 USD which also include installation cost and it can produce pasteurize juice products for about $0.11 to $0.17 per gallon (Stark 2008).

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