Abstract: In a microwave drying cavity, a thermal radiator provides infrared radiation that complements the microwave radiation in effecting a more uniform drying of a product within the cavity. The radiator includes a metal plate having apertures of a trifoliate configuration and electrical resistance-type heaters embedded in the plate. The trifoliate apertures permit microwave radiation of universal polarization to pass through the plate, so the radiator may be placed close to the product without shielding the product from the microwave radiation.

Abstract: An apparatus for drying nodular, granular and other products includes a vessel containing an evacuated chamber and an endless belt conveyor that passes through the chamber. Microwave energy is supplied to the chamber by several microwave generators, with each generator supplying energy for a different zone along the belt. The moisture-laden product is introduced into the chamber without affecting the pressure within the chamber, and is then distributed onto the conveyor belt at uniform thickness and width. The belt transports the product through the zones of microwave energy, and within each zone the strength of the field is below the breakdown point of the field for the particular pressure of the chamber, so the destructive effects of ionization are avoided. By reason of the greater moisture content in the product at the first zone, more energy can be supplied to the product in that zone, and indeed the energy supplied diminishes with each successive zone.

Abstract: A process of drying an intact whole grape having substantially the same configuration as the fresh grape is described. The dried grape has a moisture content (wet basis) of below about 10% and varies from crisp to chewy depending on the time and temperature of drying. The critical step in the process is drying in a vacuum chamber. Preferably the heating medium is microwave energy applied to the grapes in the vacuum chamber.

Abstract: This application covers a method of treating grain and packaged foodstuffs with microwave energy under vacuum to kill insects, larvae, and eggs without raising the temperature of the product being treated to an extremely high level.

Abstract: An apparatus for drying seeds and other granular products includes a drying vessel that is connected to a vacuum pump which evacuates air from its interiors. The drying vessel has an enclosing side wall and a tubular portion which is surrounded by the side wall, all such that an annular drying cavity is formed within the vessel. The tubular portion is made from a material that is transparent to microwave energy and houses waveguide-radiators, each of which is connected to a different microwave launcher that is located at the lower end of the transparent tubular portion. The launchers produce microwave energy that is directed into their respective waveguide-radiators which in turn allow the energy to escape through apertures in their side walls. This energy passes through the transparent tubular portion of the drying vessel and into the drying cavity of the vessel. Within the annular drying cavity, the vessel contains drying columns into which the granular product is directed.

Abstract: A process for removing hulls from soybeans comprises the steps of placing the soybeans in an atmosphere of reduced pressure, subjecting the beans to microwave energy while the beans are within the atmosphere of reduced pressure, removing a portion of the moisture from the beans until the moisture content of the soybeans is about 7.46 to about 10% on a wet basis, removing the soybeans from the atmosphere of reduced pressure, the temperature of the soybeans leaving the reduced pressure atmosphere being at least 110.degree. F. and less than 160.degree. F., immediately cracking the hulls of the hot soybeans without tempering, and removing the hulls from the hot soybeans.

Abstract: Seed is dried with no impairment of its germinating capabilities by subjecting the seed to microwave energy in an atmosphere of reduced pressure. The microwave energy elevates the temperature of the water within the seed to its boiling point, which is quite low because of the reduced pressure, and the water vapor which is released is condensed within the atmosphere of reduced pressure. An apparatus for practicing the process includes an upright pressure vessel, hoppers at each end of the pressure vessel, a perforated processing chute connecting the hoppers, and a control wheel at the lower end of the chute for controlling the speed at which the seed moves through the chute. It also includes a vertical wave guide surrounding the chute and external microwave power units which direct microwave energy into the wave guide and the chute within it. A condenser surrounds the wave guide within the pressure vessel.