REFRACTANCE WINDOWTM TECHNOLOGY

The pods contain a thick, slimy mucilage that can be extracted as viscous gum. Okra can be a good source of fiber, vitamin C, vitamin B6 and folic acid. The hydrocolloid mucilage in okra can bind and inhibit the absorption of cholesterol. Also, it can help relieve the common cold sore throat (Famurewa & Olumofin, 2015). Okra hydrocolloids are natural, inexpensive and non-toxic biopolymers which mostly consisted of acidic heteropolysaccharides (Ghori, Alba, Smith, Conway, & Kontogiorgos, 2014).
Refractance Window drying equipment performs continuous drying in 2-6 minutes and utilizes far less energy than comparable drying methods. The findings indicate better water removal with high energy efficiency, Refractance Window Dryer 3.5–5 times lower GHG emission than the thermal drying system, and better vitamin C level retention. Refractance window drying is a promising technology for heat-sensitive high moisture foods .

However, these statements were not observed in Hungarian thyme. In this particular case, as the air temperature increased, the losses decreased. This behavior was attributed to the longer processing at lower temperatures compared to the shorter times required for higher temperatures . Volatile compounds retention was observed in studies on ginger when heat pump drying was applied. This is a positive effect with respect to other driers that usually loose the volatile compounds of the product .
The spectra were corrected for baseline  in the region of 400–4000 cm−1 using Origin 2022b software . These window dryers help to keep your room organized and dries quickly. Refractance window dryers are a simple way to cool the air inside of the home, and they maintain a low amount of air inside of the room.
However, this macroscopic approach to quantify the transport of water during the first falling rate period of drying commonly involves the determination of an effective water diffusivity . Chaaban, H.; Ioannou, I.; Chebil, L.; Slimane, M.; Gérardin, C.; Paris, C.; Charbonnel, C.; Chekir, L.; Ghoul, M. Effect of heat processing on thermal stability and antioxidant activity of six flavonoids. Castoldi, M.; Zotarelli, M.F.; Durigon, A.; Carciofi, B.A.M.; Laurindo, J.B. Production of tomato powder by refractance window drying. The total flavonoid content was quantified following the colorimetric method described by Zhishen et al. , using rutin as a standard and performing spectrophotometric reading at 450 nm . The results were expressed in milligrams of rutin per 100 g of sample .

Firstly, it was assumed that the main heat transfer mechanism of RW drying system was thermal radiation via the plastic sheet through a transparent window which was created by the contact of wet material on the surface of the sheet. Another important parameter in a RW drying is air convection. Forced air convection in a RW dryer causes lower product temperature during the process and higher moisture loss values in comparison with natural convection. Recently, refractive window drying has received considerable scientific attention due to its potential to produce high-quality dried products. However, understanding the drying mechanism and comparing it with conventional drying methods are important to expand its potential applications.
The dryer 100 includes a cover 101 that provides a cover and headspace above a drying belt 110 for the dryer 100, an air supply manifold 120 that introduces conditioned air 102 into the dryer 100 and an air outlet exhaust manifold 130. In one embodiment, low pressure air is distributed through adjustable slots, or air knives, to effectively distribute the air across the entire width of the drying belt. The present drying system dries a liquid or slurry product placed on a continuous drying belt by properly directing conditioned air across the surface of the product, according to one embodiment.

This article presents the principle of Refractance Window 1 drying and highlights some results that show its potential and how it compares with other dryers for processing fruits, vegetables, and other heat-sensitive products. In the present study a batch RW system with a nozzle feeder, water temperature controller and energy meter was designed and manufactured. In this system thermal energy is transferred from running hot water to a film of puree or concentrate of fruits, vegetables or herbs sprayed on a thin sheet of specially formulated polymers in contact with water. The fast and self regulated drying process is carried out at atmospheric pressure well below the hot water temperature which means that heat damage is kept to a minimum.
The slice sample had a higher ash content than the pulp sample, with the control sample having the lowest ash content. Similar observations were made by Jaafar et al. regarding the fluctuation in total ash content of dragon fruit stem. In a study on drying of green asparagus using different methods, microwave assisted spouted bed drying was the fastest and resulted in highest retention of total antioxidant activity among the methods where heated air was used. TAA of asparagus was improved after RW and freeze-drying, with the TAA values being significantly higher than for heated air-drying methods.
Physicochemical properties including moisture content, solubility, bulk density and color parameters of samples dried  using different methods were compared. Energy consumption of the RW dryer was about one third and 1/40 of those of spray drying and freeze drying systems, respectively. Thermal drying consumes up to 25% of the industrial energy consumption in developed countries. Refractance Window is a relativelynew drying methodthat it is characterized by maintaining a relatively low temperature inside the food and short drying times.

Drying belt 630 floats above a heated medium flowing in a trough 640, according to one embodiment. According to another embodiment, one trough per chamber is used where the temperature of the water in each trough is independently controlled. The film thickness showed no influence on the drying parameters. New technologies are currently being developed and they are expected to be cost-efficient, energy-efficient, and environmentally effective. Considering these expectations, renewable energies are seen as a viable solution to help reach such requirements. In this sense, alternatives for technological development in the drying field using processes integrated with renewable energies are still scarce.