Potential of Refractance Window Technology for Value Added Processing of Fruits and Vegetables in Developing Countries

Refractance Window (RW) drying and evaporation technology is a novel method forconversion of liquid foods into valued-added powders, flakes, or concentrates. In RW dryingsystems, fresh fruits and vegetables, after pureeing or juicing, dry within a short time and under veryhygienic conditions into valued-added powders with excellent color and high retention of vitaminsand antioxidants. Both the drying and evaporation systems are simple and relatively inexpensivewhen compared with freeze-drying or vacuum evaporators that are more economical in largecommercial operations. The drying system was designed based on a novel concept where thermalenergy is transferred from hot water to a thin film of pureed product deposited on a transparentplastic conveyor belt in contact with the hot water. The evaporator, which works on the sameprinciple, can be a pre-concentration step prior to drying, thereby shortening drying times andimproving thermal efficiency. The RW drying and evaporation systems operate at atmosphericpressure and have been used to produce dehydrated foods with very high quality. This paperpresents the principle of Refractance Window drying and evaporation and some results to show itspotential for processing fruits and vegetables that usually go to waste in many developing countries.Besides solving the food loss problem, the value added and extended shelf life products can boostthe nutritional status of people in those countries. Investigations are continuing on retention ofantioxidants, changes in structure (molecular weight), and shelf stability of fruits and foodpolysaccharides processed by this technology.