What is Refractance Window Drying?
Refractance Window Drying is a gentle method of dehydrating fresh whole food. It gently removes water from our foods while protecting the vitamins, minerals and micro-nutrients.
Refractance Window Drying does not directly expose the food to extreme hot or cold temperatures. Instead, it relies on the transfer of thermal energy from warm water to the food. It does this up until a precise point of dehydration, at which point the drying process automatically ceases.
Since Refractance Window Drying is a kinder, gentler process, it offers several advantages over other common dehydration methods such as spray or freeze drying. Because the foods are only briefly exposed to non-damaging temperatures and are never subjected to pressure or shear force, the dried food retains all the nutritional attributes of its fresh, raw-food equivalent.
How does it work?
Science! Water is a fantastic conductor of energy – ever grab a pan out of the oven with an oven mitt that’s gotten damp? Hot stuff!
In Refractance Window Drying, we use this same principal to dry our foods. The wet Food State Nutrient is placed on a mylar belt above a body of warm water. As the thermal energy from the water below the belt travels upwards, the water content of the foods conducts this energy through the belt and thus the food, allowing for its own water content to evaporate. As the food continues to travel down the belt, the amount of water in it decreases until it reaches about 3%. At this point, there is no longer enough water in the food to conduct the thermal energy from the water below the belt, and the “window” closes. The belt refracts the thermal energy back into the water rather than through the food until it reaches the end of the line. And there you have it – food gently dried to the perfect level of dehydration!
A slurry of liquid product is evenly applied to the top surface of a continuous sheet of transparent plastic. This impervious conveyor belt floats on a surface of hot water (210° F / 99° C or less).
Our proprietary process allows infrared energy (inherent in the circulating water beneath the belt) to pass at the speed of light directly into the liquid slurry. The “window” allowing the rapid transfer of infrared energy closes as the product loses moisture. Heat is also conducted through the belt, which aids to evaporate moisture in the product, especially when the product is nearly dry. Infrared energy and conducted heat permit rapid drying at atmospheric pressure rather than under a vacuum. This rapid, yet gentle process provides superior retention of a product’s beneficial properties, including its nutrition, flavour, colour and aroma.
Energy efficient and with low water use, Refractance Window® drying preserves air quality in and around the drying facility because little product essence is lost. In addition, the process does not generate exhaust dust, a significant pollution problem.
Many factors affect drying characteristics and rates. It is important to test-dry a product utilizing our Test and Contract Processing services.
Applications of Refractance Window Drying
➢ Pureed fruit and vegetable
➢ Herbal formulations
➢ Egg mixtures Meat powder
➢ Nutraceutical Cosmetics
Advantages of Refractance Window Drying
➢ Lower operation costs
➢ Shorter drying times
➢ No cross-contamination occurs
➢ Requires 50–70% less capital and 50%less energy than the freeze drier
➢ Reduction from 4 to 6 decades of microbial load Better quality of dried products