Ohmic Heating: Concept and Applications—A Review

Abstract

Ohmic heating, also known as Joule heating, electrical resistance heating, and direct electrical resistance heating, is a process of heating the food by passing electric current. In ohmic heating the energy is dissipated directly into the food. Electrical conductivity is a key parameter in the design of an effective ohmic heater. A large number of potential applications exist for ohmic heating, including blanching, evaporation, dehydration, fermentation, sterilization, pasteurization, and heating of foods. Beyond heating, applied electric field under ohmic heating causes electroporation of cell membranes, which increase extraction rates, and reduce gelatinization temperature and enthalpy. Ohmic heating results in faster heating of food along with maintenance of color and nutritional value of food. Water absorption index, water solubility index, thermal properties, and pasting properties are altered with the application of ohmic heating. Ohmic heating results in pre-gelatinized starches, which reduce energy requirement during processing. But its higher initial cost, lack of its applications in foods containing fats and oils, and less awareness limit its use.

Extraction of bioactive compounds from purple corn using emerging technologies: A review

“…It differs from the microwave technique since the electrodes are in direct contact with the food (Sastry, 2008). During its application in the extraction of bioactive compounds, ohmic heating forms an electric field causing electroporation of the cell membranes, increasing the extraction rates and reducing the enthalpy in the plant material (Kaur & Signh, 2016).…”

Ohmic Heating: An Emerging Concept in Organic Synthesis

“…As in ohmic heating the thermal energy is generated inside the medium to be heated, theoretically there is no upper limit to the temperature that can be produced. However, as previously referred, several factors influence the temperature reached by the system, such as: i) the electrical conductivity of the medium; ii) the design of the system; iii) the time used to heat the medium; iv) the thermophysical properties of the medium; v) the intensity of the electric field; and vi) the dependence of the impedance of the medium with the temperature . The current food ohmic heating systems are being specifically designed to work in a continuous mode (flow ohmic heating).…”

“…As opposed to traditional systems operating in reaction vessels (round bottom flasks or closed vessels) in batch mode, the continuous flow systems typically operate in very small microreactors, where the reactions are performed under strictly controlled conditions in a very confined space. The great innovation of the flow systems is the extraordinary efficiency of heating and mass transfer that allows the increase of the speed of the reaction and consequently the productivity of the process …”

“…However,a sp reviously referred, severalf actorsi nfluence the temperature reached by the system, such as:i )the electricalc onductivity of the medium; ii)the design of the system;i ii)the time used to heat the medium;i v) the thermophysical properties of the medium; v) the intensity of the electric field;a nd vi)the dependence of the impedance of the mediumw itht he temperature. [14] The current food ohmic heating systemsa re being specifically designed to work in ac ontinuous mode (flow ohmic heating). As opposed to traditional systems operating in reactionv essels (round bottom flasks or closed vessels) in batch mode, the continuous flow systems typically operate in very small microreactors, where the reactions are performed under strictly controlled conditions in av ery confined space.…”

“…The great innovation of the flow systems is the extraordinarye fficiency of heating and mass transfer that allows the increaseo ft he speed of the reaction and consequently the productivity of the process. [14] Several static and flow ohmic heaters for food applications have been developed with different electrode arrangement. [14] Static ohmic heaters can have an umber of electrodes inserted within ac ontainer and are most commonly employed in small scale applications such as water heaters and laboratory-scale chemicalr eactors, whilef low ohmic heaters are the most common type employed in industrial applications,d ue to the inherent advantages of flow processes.…”