Refractance Window Drying: An Emerging Technology for Heat-Sensitive Food Products

In another research, time–temperature evolution of drying mango pulp surface was determined by thermography during the RW process performed with 2 mm-thick pulp and water at 95 °C. After spreading, pulp temperatures quickly increased up to 70 °C and remained almost steady during the constant drying rate period. From10 to 15 min after the RW process started the temperature began to increase in some areas, owing to their low moisture content (Zotarelli et al., 2015).
Phage Felix O1 powders were placed in sterile polypropylene falcon tubes and stored for 180 days at room temperature. D values of phage Felix O1 powders produced by freeze drying, spray Refractance Window Dryer drying and electrospraying were 11.52, 16.65 and 6.20, respectively. The highest bulk (0.68) and tapped density (0.93) values were found in powders produced by electrospraying.

The main application of drying is to convert a liquid or semi liquid product into powders, flakes or solids (Assegehegn, Fuente, Franco, & Gallegos, 2019; Maisnam, Rasane, Dey, Kaur, & Sarma, 2017; Prosapio & Norton, 2018). The dried end products should retain the physico-chemical properties and indented to produce at lower cost (Zotarelli, Carciofi, & Laurindo, 2015). The traditional drying method causes several nutritional, physical and chemical changes which makes food unacceptable to the consumer.
Color changes by different drying methods have been already demonstrated for numerous plant materials , i.e., blackcurrant , pomegranate , soya , Piper borbonense , sour cherries , blueberry , black mulberry , and, chokeberry . Heat treatment is considered to be one of the most common methods in food drying. However, the problem with this conventional method is that the texture of the food sample is often altered from its original state, just like in brown rice. Superheated steam treatment system is introduced as an effective method to remove the moisture of the sample. In order to perform process control, a programmable logic controller , which served as the main controller, is employed to automate the process. Changes in curcuminoids and chemical components of turmeric (Curcuma longa L.) under freeze-drying and low-temperature drying methods.
Improvement of phytochemical and quality characteristics of Dracocephalum kotschyi by drying methods. Figure 4.Effect of the drying method on the water activity of guava samples. The RWD technique is affected by various process parameters, including water bath temperature, mylar film thickness, loading rate, sample thickness, relative humidity, and air velocity. Among these, film thickness, air velocity, and temperature are easily controllable primary parameters, while loading rate and sample thickness are secondary parameters. Zotarelli MF, Augusto B, Carcio M, Laurindo JB. Effect of process variables on the drying rate of mango pulp by refractance window.

This might be produced by the solute moving from the inner core to the surface at high temperatures . It has been discovered that CD of food materials with low thermal conductivity decreases heat transmission to the interior of the product during the falling rate period . Dried vegetables, fruits and other food ingredients are widely used in prepared foods. Conservation of quality attributes such as aroma, color and nutrients has always been a challenge in dehydration of heat sensitive fruits and vegetables.
So, more research is needed for the drying of solid foods like meat, fruits, vegetables, etc without compromising their quality. Nowadays, efforts are done to combine RWD with other novel processing technologies like microwave, ultrasound, etc., for the pre-treatment of food products. A bottleneck to scaling up the RW drying process is the need for a wide area to dry and thermal exchange and the film’s thickness is kept  on the low side, which reduces the processing capacity.

Similarly, energy consumption decreased with decreasing temperature and thickness. However, the drying time and energy input per unit weight of product obtained were equivalent when drying at 1.5 or 3.5 mm. That is important for deciding the amount of sample to be dried as a function of operating cost and final product quality when exposed to high temperatures for a longer time.
Thermal processing induces physicochemical changes such as loss in vitamin content, reduction of available lysine content and denaturation of proteins or to produce nutritional compounds such as lactulose. A dairy powder is characterized not only by its chemical composition but also by its microbiological and physical properties. All of these characteristics depend on drying parameters, the properties of the raw materşal before drying and storage conditions. Amid, “Effect of different drying techniques on flowability characteristics and chemical properties of natural carbohydrate-protein gum from durian fruit seed,” Chemistry Central Journal, vol.
The TPC results were expressed as mg Gallic acid equivalents /g sample. Water extraction technology pioneer Mazza Innovation has received an $840,000 ($1.1 million CDN) investment from the Canadian government to install new drying technology at its plant in British Columbia. Methods of ensuring the safeness of dried meat along with their challenges.

Greater heating in HD, VD, and RWD at a temperature of 60 °C assisted the breakdown of cell components, resulting in a significant decrease in antiradical activity. Table 4 shows the R2 and RMSE values of the best drying model and ANN model. It was observed that the ANN model showed a higher R2 value and lower RMSE value when compared to the best drying model for both drying methods. The ANN model was able to predict the MR for both drying methods with a reasonable level of accuracy. Independent of the parameters used, the prediction capability of the trained ANN model was better than that of the drying models.