Mylar is a polyethylene terephthalate . The amount of energy conducted and radiated from the Mylar layer change according to the temperature of the heating source, the thickness of the flim, the thickness of the product and the humidity of the product. RW™ is a powerful tool that allows for the Refractance Window Dryer dehydration of fruit using temperatures of 95 °C and provides a 50% reduction in drying time. 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).
Other authors have focused more on the relationship of aw with moisture and storage temperature which are very important aspects when considering food conservation12,13,39. Fat content in walnuts was observed to be in the range of 54–68% making it a major component of walnuts. Walnuts mainly contain unsaturated fatty acids, i.e. linoleic, oleic, and linolenic acids which comprise more than 90% of total fatty acids . These fatty acids make it prone to oxidation, which causes rancidity and off-flavour generation. It was observed that an increase in temperature resulted in a decrease in the level of fat content which can be attributed to lipid oxidation with an increase in lipoxygenase activity in treated samples.

In case of aromatic compounds, sample analysis showed that RW-dried strawberry purees had less esters and alcohols and more heat-induced ketones and aldehydes. Total drying time was about 4 minutes . Refractance Window™ drying uses circulating water at atmospheric pressure to carry heat to the product to be dried. Moist product is applied to the upper surface of an infrared-transparent, plastic conveyer belt that floats on the surface of the heated, circulating water. This water is continuously re-circulated and re-heated, so as to maintain temperature as heat energy is transferred to the product. Three different heat transfers occur in the Refractance Window Drying system during drying as conduction, convection and radiation.
The dendrogram Fig.7 represents the compound correlation between all the treatments of refractive window drying and indicates that the sample dried at node 4 (80 °C) and node 5 (90 °C) have a similar pattern in all the studied parameters. A similar pattern can also be observed for the samples dried at 50–60 °C indicating a cluster of nodes 1 and node 2. The dendrogram distance for both clusters were about 100 with respect to 500 for all the cases. The total phenolic content was determined as per the method followed by Amin et al. with minor modifications. The sample was mixed with 5 mL of 0.25 N Folin Ciocalteu reagent. After 3 min incubation at temperature 37 °C, 4 mL of 7.5% Na2CO3 was added to the mixture and incubated for 2 h at room temperature.
The above suggest that drying nanoemulsions at low temperatures could a more heterogeneous flake structure as the IDM values obtained for these temperatures decreased. Image analysis represents a particularly useful tool for characterising food morphology. Many food materials present highly irregular structures that elude precise quantification by conventional techniques. This methodology enables measurements to be obtained from digitalised images15,16.

The physiochemical characteristics of the dried apple slices including flavonoid content, total phenolic compounds, antioxidant activity, vitamin C content and color were measured. In addition, the energy consumption and energy efficiency of the dying methods were evaluated. Results showed that combining ultrasound and infrared with conductive hydro-drying can result in higher drying rates and lower product moisture content. Quality of UIACHD dried apple slices was close to the freeze-dried products and it was significantly better than the cabinet dried products. Moreover, the energy efficiency of UIACHD was considerably better than the cabinet dryer and the freeze-dryer. The results of this study showed that combining ultrasound and infrared with conductive hydro-drying can lead to an energy-efficient process with good quality retention ability.
One milliliters supernatant was added to a mixture containing 4.0 mL of a 10 mmol/L linoleic acid stock solution and 1.0 mL of 0.05 mol/L sodium phosphate buffer, pH 6.5, at 25 °C. The same method was used for LOX activity tests unless otherwise indicated. The absorbance was checked at a wavelength of 234 nm at 30-s intervals during a 2.5 min period in triplicates. The same thing was repeated for blank reaction mixtures where no supernatant was added.

Refractance window drying is a film-based drying technique in which for a short period food is exposed at relatively low temperatures . This technique utilizes the circulating water at different temperatures for carrying the thermal energy to the product to be dried. Here the product is generally placed on the mylar plastic films that are placed over the circulating water. There are very few methods of walnut drying. It is important to compare different methods of drying walnuts based on quality and develop an optimum and efficient drying method for walnut kernels.
The Mylar film takes the heat from the hot water (temperature below 99°C) at atmospheric pressure. The product slurry is spread over a transparent film evenly and the film permits the infrared energy at the speed of light to the product. The energy transfer due to conduction or radiation depends on the thermal resistance offered by the plastic film and the evaporation of moisture is by convection of air above the product. The air convection helps to lower the temperature during drying.
Drying for agricultural and marine products are one of the most attractive and cost-effective application of solar energy. Numerous types of solar dryers have been designed and developed in various parts of the world, yielding varying degrees of technical performance. Basically, there are four types of solar dryers; direct solar dryers, indirect solar dryers, mixed-mode dryers and hybrid solar dryers.