Ohmic Heating Technology for Food Applications, From Ohmic Systems to Moderate Electric Fields and Pulsed Electric Fields

Abstract

Ohmic heating (OH) of food has been investigated for many years as an alternative to conventional heating because it allows fast and homogeneous heating. The processing parameters that influence the most uniformity of the heating in OH are the electric field strength and the frequency. Therefore, recent trends have focused on studying the application of frequencies in the order of kHz and electric fields higher than 100 V/cm. In this regard, and considering only the applied field strength in a way to easily differentiate them, three ohmic systems could be distinguished: OH (< 100 V/cm), moderated electric fields (MEF) (100–1000 V/cm), and ohmic-pulsed electric fields (ohmic-PEF) (> 1000 V/cm). The advantages of applying higher electric fields (MEF and ohmic-PEF) over OH are, on the one hand, their much higher heating rate and, on the other hand, their capability to electroporate cells, causing the release of intracellular ionic compounds, and therefore, uniformizing the electrical conductivity of the product. This strategy is especially interesting for large solid foods where conventional heating applications lead to large temperature gradients and quality losses due to surface overtreatment. Therefore, the aim of this work is to review the state of the art of OH technologies, focusing on MEF and ohmic-PEF. The advantages and disadvantages of MEF and ohmic-PEF compared to OH and their potential for improving processes in the food industry are also discussed.