It is an economical alternative to drum, spray and freeze‐drying for the production of food powders. The liquid is whipped to form stable foam, and dehydrated by thermal means.

The materials to be dried are contained in a trough-shaped conveyor belt, made from mesh, and air is blown through the bed of material. The movement of the conveyor continually turns over the material, exposing fresh surfaces to the hot air.

It is used to eliminate the moisture content from crops, vegetables, and fruits. It is also consists of a box made up of easily available and cheap material like cement, galvanized iron, brick, and plywood.

It comprises a conveyer belt which is fed with the dewatered sludge. The sludge solids are slowly transported by the belt through a stream of heated air, generally at 80-180 °C.

It is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature.

It is a batch operation performed in an air-tight vessel. Using vacuum pumps, the pressure and humidity within the chamber are reduced.

This drying process involves the atomization of a solution, slurry, or emulsion containing one or more components of the desired product into droplets by spraying followed by the rapid evaporation of the sprayed droplets into solid powder by hot air at a certain temperature and pressure.

It has come in different shapes according to the requirements of the design of the dryer. Depending on the model of dryer and locally available materials they can be made from different materials such as metal, wood, concrete, bricks, woven bamboo mats etc.

This process is based on the water sublimation effect in a low temperature and low pressure environment. It is often recommended for the drying of temperature sensitive food products, as it preserve most of the organolpetic properties.