Evaluation of a Batch Refractance Window Dryer in Drying of Some Heat Sensitive Food Stuff

Refractance window system is a novel moisture elimination system for production of high quality, dried or concentrated food products. Refractance window dryer can turn purees, juices and extracts of fruits, vegetables and herbs in to dried powders or flakes in a short time, using relatively low amount of energy and with minimum thermal damage. In this study an electric batch Refractance window dryer equipped with a thermostat, feed nozzle and a digital single phase kWh meter with 0.01 kWh accuracy, was made and its functionality was investigated.
Refractance Window system utilizes thermal energy of hot water through a polymeric film as a means to carry thermal energy to materials to be dehydrated. Dehydration process in this system is quick, self-regulating and under atmospheric pressure and it happens in temperatures below the temperature of the hot water used in the system so the thermal damage to the product is minimized. Water vapors are removed using an electric fan. To evaluate the dryer in this study, samples of carrot puree, aloe-vera gel, catchup souse and tomato juice was dehydrated using the Refractance window dryer and a laboratory freeze dryer and the dried products were compared. Results showed that Refractance window dryer can produce high-quality products with equal or higher quality than freeze dryer, using less energy and with higher energy efficiency and therefore less undesirable environmental impact.