Refractance Window™ drying technology is a proprietary drying method that uses a heat transfer process and specific properties of water to gently remove moisture while maintaining the maximum integrity of the natural material.
When water is placed over a heating source, infrared energy is transferred throughout the water by convection. The heat energy then radiates from the water, primarily through evaporation.
When water is covered by a transparent membrane such as plastic and placed over a heating source, evaporation and its associated heat loss are blocked or "refracted", and only conduction occurs. The plastic membrane acts like a mirror reflecting the infrared energy back into the water.
But when a moist raw material is placed on the plastic membrane's surface, the water in the material creates a "window" that allows for the passage of infrared energy through the material. Heat behaves as if there were no membrane in that location, and is directly transferred to the water present in the material
In a matter of a few moments, the water in the material on the plastic membrane's surface evaporates, and the "window" of infrared energy closes and "refracts" back into the heated water source, no longer exposing the material to heat.
Refractance Window™ Drying Process
During the Refractance Window™ drying process, moist raw material (Aphanizomenon flos-aquae) is applied on the surface of the drying system's conveyor belt. The belt is a food grade Mylar (transparent polyester film) floating on the surface of a heated cistern containing circulating hot water. The heat from the cistern's water is conducted by way of a "refractance window" through the Mylar belt to the water present in the raw material laying on the belt's surface.
As the material travels down the conveyor, the water in the material evaporates through the "window" in a matter of a few moments, with the "window" closing in proportion to the rapid dissipation of water in the material. Because the Mylar conveyor belt is a poor heat conductor, once the material dries, the "refractance window" closes, and only a miniscule amount of heat is transferred to the product as it is carried to the end of the conveyor system.
Raw material dried through the Refractance Window™ process delivers a flaked product close to its natural state. This expedient drying method protects the product's delicate nutrients, color and flavor.
Because the Refractance Window™ drying process maintains the temperature of the raw material far below the temperature of the water circulating beneath the conveyor belt, its precious nutrients are protected from oxidization. During the process, heat is applied to the material at 72°C for only three to five minutes.