Quantitative understanding of Refractance Window drying
The contact surface with the processing air of individual grains, pellets or parted products separated and fluidized is much bigger and the processing time is drastically reduced. As the air is uniformly jetted from all Jet-Tubes placed regularly, a heat processing with an extremely high uniformity is realized. Overall energy efficiency of spray, freeze and RW dryers (Baeghbali et al., 2016). The present application relates in general to the drying of a product. In particular, the present disclosure is directed to a low profile design air tunnel system and method for providing uniform air flow in a refractance window dryer. The values of the temperature-dependent parameters, k and L were calculated from equations5 and 6 by using the values of the model parameters .
The average value of the radiation penetration depth in 2% CMC was 1.20 ± 0.19 mm. Although the penetration depth is known to depend on the nature of the material and temperature of the emitting source , the value obtained depended only on the material (CMC 2%) in the range of temperatures evaluated (70, 80, and 90 °C). It was, as expected, independent of the type and thickness of the films Revolutionizing Food Drying: The Advantages of Refractance Window Dryer evaluated. The radiative heat flux emitted by the water at 70, 80, and 90 °C and the radiative heat flux transmitted through the film (water–film system) determined during the first 50 s were measured . It was observed that the heat flux was significantly higher for times longer than 50 s . The heating of the film after this time increased its emissivity, causing an increase in heat flux.
Likewise, the absorbance of the puree depends on its thickness and moisture content . Yemmireddy V.K., Chinnan M.S., Kerr W.L., Hung Y.-C. Effect of drying method on drying time and physico-chemical properties of dried rabbiteye blueberries. Horuz E., Bozkurt H., Karataş H., Maskan M. Effects of hybrid (microwave-convectional) and convectional drying on drying kinetics, total phenolics, antioxidant capacity, vitamin C, color and rehydration capacity of sour cherries. Pham N.D., Martens W., Karim M.A., Joardder M.U.H. Nutritional quality of heat-sensitive food materials in intermittent microwave convective drying.
Accordingly, resonant absorption occurs in carbohydrates, which heat the water in the CMC. Subsequently, a thermal heating effect of the water occurs due to the dipole orientation in the electromagnetic field of radiation. Figure 1 shows the drying kinetics of CMC with thicknesses of 1.5, 2.5, and 3.5 mm for the three films at 90 and 70 °C.
Of the many methods, Drying is the oldest method used to delay food decomposition; other methods include the Infrared, Freeze, Convective hot-air and Natural sun-drying methods. Many of these methods are time-consuming or energy intensive and are also either too complicated or too expensive. The Refractance Window Drying technique is a new method of drying; typically used to convert liquid foods and related biomaterials into flakes, powders or sheets. However, its use in drying root tubers needs to be investigated. All the more so, in Africa and Asia, where cassava, yams and potatoes are important food crops; providing energy and food nutrients for over 500 million people. Current root tubers dehydration techniques are lengthy; usually taking a few days.
Computed results indicated that there was a 5% increase in transmission of IR radiation through the plastic sheet between a dry and wet product. A major portion of thermal energy was transferred via conduction through the plastic sheet. As a consequence, quality of the RW dried product is preserved when compared with other drying techniques (Monica Jimena Ortiz-Jerez, Gulati, Datta, & Ochoa-Martínez, 2015). Okra is a nutritious vegetable but it is highly perishable and drying is one of the best methods for its preservation.
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.
This slight difference in wavelengths for the studied temperature range explains the lack of an effect of this factor on the penetration depth. The penetration depth is defined as the depth at which the radiation intensity decays by 37% (1/e) of its initial value . Depending on the material, electromagnetic waves can travel inside the food or be absorbed on its surface . Using (Equation ), the parameters I0 and μ−1 were obtained . According to Figure 6, all films showed high transmittance to radiation, with the heat flux being similar to that of the water. These results agree with those presented by Tsilingiris for PP and LDPE films.
While conduction, convection and radiation occur at the hot water-film interface, conduction and radiation occur through the film and convection occurs at the air-film interface. In RWD systems, thermal energy is transferred from hot water to a film of fruits slices or juice spread thinly on a polyethylene membrane. Kanha, “Effects of processing conditions on powder properties of black glutinous rice (_Oryza sativa_ L.) bran anthocyanins produced by spray drying and freeze drying,” Science and Technology, vol. O. A. Caparino, J. Tang, C. I. Nindo, S. S. Sablani, J. R. Powers, and J.
The important disadvantage is the higher plastic surface area of belt required for large amount of sample for drying. Okra is extremely perishable because of its high respiratory activity and moisture content and it is necessary to use a suitable method of preservation for it (Falade & Omojola, 2008). Okra is traditionally preserved by slicing and sun drying. So, an effective way to overcome these problems is to dry the okra using more advanced drying methods (Adom, Dzogbefia, & Ellis, 1997; Doymaz, 2005). During drying, foods undergo changes in volume, shape, porosity and density that can cause shrinkage or structural collapse, thus affecting the quality of the final product . Therefore, changes in volume should be considered for the modeling of mass transfer during a drying process [7-8].
K. Sharma, “Osmo-convective dehydration kinetics of jackfruit ,” Journal of the Saudi Society of Agricultural Sciences, vol. Fractal dimension and lacunarity of jackfruit dried with different methods. The tapped density of the samples was measured by placing a 2.5 g powder sample in a 10 mL graduated measuring glass cylinder, which was gently dropped 100 times onto a mat from a height of 15 cm. The tapped density was calculated by dividing the weight of the powder by the tapped volume . Bulk density (g/mL) was determined by gently adding 2 g of jackfruit powder into an empty 10-mL graduated cylinder. The cylinder was held on a vortex mixer (SI-100 N-MRC Lab Equipment, UK) for 1 minute at the highest speed.
The average value of the radiation penetration depth in 2% CMC was 1.20 ± 0.19 mm. Although the penetration depth is known to depend on the nature of the material and temperature of the emitting source , the value obtained depended only on the material (CMC 2%) in the range of temperatures evaluated (70, 80, and 90 °C). It was, as expected, independent of the type and thickness of the films Revolutionizing Food Drying: The Advantages of Refractance Window Dryer evaluated. The radiative heat flux emitted by the water at 70, 80, and 90 °C and the radiative heat flux transmitted through the film (water–film system) determined during the first 50 s were measured . It was observed that the heat flux was significantly higher for times longer than 50 s . The heating of the film after this time increased its emissivity, causing an increase in heat flux.
Likewise, the absorbance of the puree depends on its thickness and moisture content . Yemmireddy V.K., Chinnan M.S., Kerr W.L., Hung Y.-C. Effect of drying method on drying time and physico-chemical properties of dried rabbiteye blueberries. Horuz E., Bozkurt H., Karataş H., Maskan M. Effects of hybrid (microwave-convectional) and convectional drying on drying kinetics, total phenolics, antioxidant capacity, vitamin C, color and rehydration capacity of sour cherries. Pham N.D., Martens W., Karim M.A., Joardder M.U.H. Nutritional quality of heat-sensitive food materials in intermittent microwave convective drying.
Accordingly, resonant absorption occurs in carbohydrates, which heat the water in the CMC. Subsequently, a thermal heating effect of the water occurs due to the dipole orientation in the electromagnetic field of radiation. Figure 1 shows the drying kinetics of CMC with thicknesses of 1.5, 2.5, and 3.5 mm for the three films at 90 and 70 °C.
Of the many methods, Drying is the oldest method used to delay food decomposition; other methods include the Infrared, Freeze, Convective hot-air and Natural sun-drying methods. Many of these methods are time-consuming or energy intensive and are also either too complicated or too expensive. The Refractance Window Drying technique is a new method of drying; typically used to convert liquid foods and related biomaterials into flakes, powders or sheets. However, its use in drying root tubers needs to be investigated. All the more so, in Africa and Asia, where cassava, yams and potatoes are important food crops; providing energy and food nutrients for over 500 million people. Current root tubers dehydration techniques are lengthy; usually taking a few days.
Computed results indicated that there was a 5% increase in transmission of IR radiation through the plastic sheet between a dry and wet product. A major portion of thermal energy was transferred via conduction through the plastic sheet. As a consequence, quality of the RW dried product is preserved when compared with other drying techniques (Monica Jimena Ortiz-Jerez, Gulati, Datta, & Ochoa-Martínez, 2015). Okra is a nutritious vegetable but it is highly perishable and drying is one of the best methods for its preservation.
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.
This slight difference in wavelengths for the studied temperature range explains the lack of an effect of this factor on the penetration depth. The penetration depth is defined as the depth at which the radiation intensity decays by 37% (1/e) of its initial value . Depending on the material, electromagnetic waves can travel inside the food or be absorbed on its surface . Using (Equation ), the parameters I0 and μ−1 were obtained . According to Figure 6, all films showed high transmittance to radiation, with the heat flux being similar to that of the water. These results agree with those presented by Tsilingiris for PP and LDPE films.
While conduction, convection and radiation occur at the hot water-film interface, conduction and radiation occur through the film and convection occurs at the air-film interface. In RWD systems, thermal energy is transferred from hot water to a film of fruits slices or juice spread thinly on a polyethylene membrane. Kanha, “Effects of processing conditions on powder properties of black glutinous rice (_Oryza sativa_ L.) bran anthocyanins produced by spray drying and freeze drying,” Science and Technology, vol. O. A. Caparino, J. Tang, C. I. Nindo, S. S. Sablani, J. R. Powers, and J.
The important disadvantage is the higher plastic surface area of belt required for large amount of sample for drying. Okra is extremely perishable because of its high respiratory activity and moisture content and it is necessary to use a suitable method of preservation for it (Falade & Omojola, 2008). Okra is traditionally preserved by slicing and sun drying. So, an effective way to overcome these problems is to dry the okra using more advanced drying methods (Adom, Dzogbefia, & Ellis, 1997; Doymaz, 2005). During drying, foods undergo changes in volume, shape, porosity and density that can cause shrinkage or structural collapse, thus affecting the quality of the final product . Therefore, changes in volume should be considered for the modeling of mass transfer during a drying process [7-8].
K. Sharma, “Osmo-convective dehydration kinetics of jackfruit ,” Journal of the Saudi Society of Agricultural Sciences, vol. Fractal dimension and lacunarity of jackfruit dried with different methods. The tapped density of the samples was measured by placing a 2.5 g powder sample in a 10 mL graduated measuring glass cylinder, which was gently dropped 100 times onto a mat from a height of 15 cm. The tapped density was calculated by dividing the weight of the powder by the tapped volume . Bulk density (g/mL) was determined by gently adding 2 g of jackfruit powder into an empty 10-mL graduated cylinder. The cylinder was held on a vortex mixer (SI-100 N-MRC Lab Equipment, UK) for 1 minute at the highest speed.
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