Refractance window drying of foods: A review

Novel drying techniques emerging as outcome of laboratory-based research may yet prove to have a positive impact on the food industry in terms of scalability, energy efficiency, cost and end-product quality. Refractance window drying is one such technique that gained a lot of attention in recent years, owing to the numerous benefits it claims. The technique involves drying purees and liquids placed over a thin infrared transparent film that essentially forms a 'window' through which drying occurs. Importantly, product temperatures are kept low and rapid drying occurs as all three modes of heat transfer are involved. Refractance window drying has found several applications not only in food industries but also in pharmaceutical, nutraceutical, cosmetic and pigment handling industries. The objective of this work is to present the recent trends in refractance window drying of foods with emphasis on the underlying mechanism and effect on product quality. A case study on refractance window drying of mango pulp is presented for improve understanding on the topic. Refractance window drying has the potential to produce high quality dried slices, purees and juices. Research suggests that active aromatic and pigment compounds responsible for characteristic sensory and nutritional attributes can be retained through this technique.