Microwave volumetric heating (MVH) is a method of using

microwaves Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...

to evenly heat the entire volume of a flowing

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspend ...

or semi-solid. The process is known as MVH because the microwaves penetrate uniformly throughout the volume of the product being heated, thus delivering energy evenly into the body of the material. This is in contrast to traditional

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

processing, which relies on

conduction Conductor or conduction may refer to: Music * Conductor (music), a person who leads a musical ensemble, such as an orchestra. * Conductor (album), ''Conductor'' (album), an album by indie rock band The Comas * Conduction, a type of structured f ...

and

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

from hot surfaces to deliver energy into the product. Liquids, suspensions, or semi-solids heated by MVH do not come into contact with hot surfaces; this minimizes thermal damage to functional components, and allows thick and viscous products to be heated without fouling. Processing temperatures can be very accurately controlled by varying the flow rate of the product through the MVH treatment chamber. The slower the flow, the higher the final product temperature. Flowing liquids move continuously through a unique treatment chamber, thereby heating the product.

Thermal processing using microwaves

The

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

accepts that microwaves can be used to heat food for commercial use,

pasteurization Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. The ...

and sterilization. The main mechanism of microbial inactivation by microwaves is due to thermal effect; the phenomenon of lethality due to 'non-thermal effect' is controversial, and the mechanisms suggested include selective heating of micro-organisms, electroporation, cell membrane rupture, and cell lysis due to electromagnetic energy coupling. Because

transfer electromagnetic energy at a molecular level, and the vibration of the molecules creates heat through friction, it is difficult to properly check for this highly localized 'micro'-thermal effect or create conditions where study of the putative 'athermal' effect is possible.

Processes

Pasteurization Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. The ...

Flash pasteurization Flash pasteurization, also called "high-temperature short-time" (HTST) processing, is a method of heat pasteurization of perishable beverages like fruit and vegetable juices, beer, wine, and some dairy products such as milk. Compared with other ...

Food preservation Food preservation includes processes that make food more resistant to microorganism growth and slow the oxidation of fats. This slows down the decomposition and rancidification process. Food preservation may also include processes that inhibit ...

Microwave chemistry Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent ...

Dielectric heating Dielectric heating, also known as electronic heating, radio frequency heating, and high-frequency heating, is the process in which a radio frequency (RF) alternating electric field, or radio wave or microwave electromagnetic radiation heats a diel ...

References

{{reflist Microwave technology