About Microwave Heating
How Microwave Drying Works
Microwaves are radio waves which operate in bands; they are non-ionizing and non-nuclear. Unlike all other methods of heating which dry from the surface inward, microwaves simultaneously penetrate all parts of the material, so they heat uniformly. This is called volumetric heating.
Microwaves produce heat by vibrating water molecules, almost a billion times per second. The resulting friction converts the radio energy to heat energy and vaporizes the water. Molecules of other substances, such as protein, fat, and fiber, don’t readily absorb microwave energy so they don’t heat up as much. This effect, plus evaporation of surrounding water, keeps the product cool. As a result, almost all the energy applied removes water, unlike conventional dryers where much energy is lost heating air and steel. Microwave dryers typically have 80%+ energy efficiency compared to about 50% for gas-fired rotary drum dryers.
Industrial Microwave System Components
Unlike home microwaves, industrial system separate microwave generation from the cooking/drying cavity. A system is constructed using one or more microwave generator units. The generators come in 75 KW and 100 KW (output power) models. Using special duct called waveguide, the energy is carried to one or more industrial microwave cavities. A typical cavity is about 12 feet long and five feet wide. A common conveyor belt carries the product through the cavities. A simple system may consist of one generator and one cavity, while a large system may have a dozen generators and six cavities. This inherent modularity provides great flexibility in scaling a system, or building systems which can be easily expanded in the future.
Producing Better Quality Products
Conventional gas dryers have internal temperatures of 500ºF to 1100ºF which results in significant degradation of protein and amino acids in animal feeds. Caramelization and Mailard reactions occur at a temperature of about 300 ºF. In microwave systems, product temperatures do not exceed 212ºF, well below the temperature where amino acids and proteins are degraded. The result is that the full nutritional goodness of the feed is preserved.
Additionally, Microwave can enhance the activity of enzymes applied to animal feeds. Microwave energy breaks down the structure of cellular walls which gives enzymes more attachment points on the otherwise crystalline cellulose structure. This can greatly enhance the activity of enzyme treatment. Also, it has been well established that microwave processing can destroy E. Coli, listeria, and certain other harmful microorganisms.