Refractance Window Drying: Principles and Applications

Abstract

Refractance window (RW) drying is a modern drying technology that yields superior quality products. The dryer incorporates a technology that can be used to dry or evaporate both fluids and semi-fluid-like products; hence, the dryer applies to a wide range of products, such as agricultural products, herbal extracts, spices, and various food ingredients. RW technology is a low temperature (60-70 °C) short time (2-6 min) drying process that allows for the retention of quality attributes, such as color, flavor, and nutrients, as well as the preservation of bioactive compounds, such as beta carotene, ascorbic acid, and anthocyanins. The low operating temperature makes the RW dryer an appropriate drying technique for heat- sensitive products. Compared to other conventional dryers, the RW dryer has high thermal efficiency because the hot water is recovered through recirculation. RW drying technique expends approximately one-third of the freeze-drying cost and uses less than half of the energy consumed by a freeze dryer for a unit quantity of the wet material. The chapter explores the potential of this novel technology in the drying and preservation of food products.