Ohmic Heating of Foods

Abstract

Ohmic heating is the direct passage of an electric current through food and the subsequent heating of the food due to its electrical resistance. The absence of an intermediate step between the energy source (electricity) and the food that is common in other processes provides significant energy savings and efficiencies. It is a very rapid process and therefore there is little time for heat loss from the food and environmental losses are minimised. Therefore, it can justifiably be regarded as one of the greenest food heating processes. Although the concept is simple, the application is not. Ohmic heating of foods has developed significantly over the past three decades but it has been known for significantly longer. In the 1950s and 1960s, significant research was undertaken into the process, largely at the request of electrical utility companies, rather than the food industry. Those efforts did not result in significant industrial applications, primarily because of problems with electrode design, electrode polarisation and fouling. Other difficulties include applying an electric current directly to a food consisting of food particles of conductivity differing from that of the main food matrix. Current advances in developing materials for making electrodes to conduct the electricity to the food and a better understanding of the heating process of complex foods, obtained by improved modelling and computational techniques, give this ‘green’ process a very bright future.