Evaluation of Thermal Resistance of Refractance Window (RW) Drying System and Effect of Drying Temperature on Strawberry Powder Characteristics
DOI:
https://doi.org/10.52151/jae2025623.1951Keywords:
bulk density, color values, hygroscopicity, Mylar film, solubility, transmissivity, thermal resistanceAbstract
This study investigates the performance of an in-house fabricated Refractance Window (RW) drying system for processing strawberry puree, with a focus on heat transfer dynamics, material properties, and quality characteristics of the dried product. Spectral transmissivity of the Mylar film was measured using FTIR spectroscopy, revealing significant peaks within the wavelength ranges of 2.7-3.69, 5.29-11.16, and 12.44-15.09 µm, corresponding well with the absorption spectrum of water-rich strawberry puree. Thermal resistance components were evaluated, including resistance between water and Mylar film (R1), resistance due to Mylar film (R2), the strawberry puree (R3), and the convective resistance between puree and air (R4). R1 exhibited the highest resistance at 0.653 W⁻¹ m² K, identifying it as the primary bottleneck for heat transfer. Conversely, the strawberry puree posed minimal resistance (R3 = 0.00162 W⁻¹ m² K), facilitating efficient energy absorption. The overall heat transfer coefficient of the system was calculated to be 1.187 W m⁻² K⁻¹, indicating effective heat utilization. Results showed that powders dried at higher temperatures (85°C) exhibited greater solubility (89.04%) and hygroscopicity (17%) due to enhanced porosity from rapid water evaporation. However, this was accompanied by significant color degradation, likely due to Maillard browning and anthocyanin degradation, as evidenced by a high total color difference (∆E > 4.0). Samples dried at 65°C retained better color but exhibited lower solubility and higher moisture content. The optimal drying temperature was found to be 75°C, balancing functionality and appearance with a solubility of ~85.8%, water activity <0.46, and a perceptible color difference below critical thresholds (∆E < 3.2). This temperature effectively maintained product integrity while ensuring efficient drying.
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Abul-Fadl, M. M., & Ghanem, T. H. (2011). Effect of Refractance Window (RW) drying method on quality criteria of produced tomato powder as compared to the convection drying method. World Applied Sciences Journal, 15(7), 953-965. http://www.idosi.org/wasj/wasj15(7)11/7.pdf
Adekunte, A., Tiwari, B., Cullen, P., Scannell, A., & O'Donnell, C. (2010). Effect of sonication on colour, ascorbic acid and yeast inactivation in tomato juice. Food Chemistry, 122(3), 500–507. https://doi.org/10.1016/j.foodchem.2010.01.026
Ali, S., Narwari, I. R., & Faisal, S. (2024). Response surface optimization of refractance window drying of bitter gourd slices. Journal of Agricultural Engineering (India), 61(1), 52-66. https://doi.org/10.52151/jae2024611.1829
Anagnostou, E., & Spakowski, A. E. (1969). Transmission Effects on Plastic Films Irradiated with Ultraviolet Light, Electrons, and Protons. NASA Technical Memorandum- NASA TM X-1905. National Aeronautics and Space Administration, Washington, D. C. Avaiable at: https://ntrs.nasa.gov/api/citations/19690030954/downloads/19690030954.pdf (accessed on 03 September 2025).
AOAC. (2000). Official methods of analysis of Association of Official Analytical Chemists International (17th ed.). Gaithersburg, MD, USA:AOAC International.
Baeghbali, V., Niakousari, M., & Farahnaky, A. (2015). Refractance window drying of pomegranate juice: Quality retention and energy efficiency. LWT - Food Science and Technology, 66, 34-40. https://doi.org/10.1016/j.lwt.2015.10.017
Baini, R., & Langrish, T. (2009). Assessment of colour development in dried bananas-measurements and implications for modelling. Journal of. Food Engineering, 93(2), 177–182. https://doi.org/10.1016/j.jfoodeng.2009.01.012
Balci-Torun, F., & Ozdemir, F. (2021). Encapsulation of strawberry flavour and physicochemical characterization of the encapsulated powders. Powder Technology, 380, 602-612. https://doi.org/10.1016/j.powtec.2020.11.060
Barbosa-Canovas, G. V., Ortega-Rivas, E., Juliano, P., & Yan, H. (2005). Food Powders: Physical Properties, Processing and Functionality. Food Engineering Series (FSES), Kluwer Academic/Plenum Publishers, New York. https://doi.org/10.1007/0-387-27613-0
Cano-Chauca, M., Stringheta, P. C., Ramos, A. M., & Cal-Vidal, J. (2005). Effect of carriers on the microstructure of mango powder obtained by spray drying and its functional characterization. Innovative Food Science and Emerging Technology, 6, 420-428. https://doi.org/10.1016/j.ifset.2005.05.003
Caparino, O. A., Tang, J., Nindo, C. I., Sablani, S. S., Powers, J. R., & Fellman, J. K. (2012). Effect of drying methods on the physical properties and microstructures of mango (Philippinez 'Carabao’ var.) powder. Journal of Food Engineering, 111, 135-148. https://doi.org/10.1016/j.jfoodeng.2012.01.010
Castoldi, M., Zotarelli, M. F., Durigon, A., Carciofi, B. A. M., & Laurindo, J. B. (2015). Production of tomato powder by refractance window drying. Drying Technology, 33(12), 1463–1473 https://doi.org/10.1080/07373937.2014.989327
Chutintrasri, B., & Noomhorm, A. (2007). Color degradation kinetics of pineapple puree during thermal processing. LWT- Food Science and Technology, 40(2), 300–306. https://doi.org/10.1016/j.lwt.2005.11.003
Cordenunsi, B. R., Genovese, M. I., Oliveira DoNascimento, J. R., Aymoto Hassimotto, N. M., Jose Dos, S. R., & Lajolo, F. M. (2005). Effects of temperature on the chemicalcomposition and antioxidant activity of three strawberry cultivars. Food Chemistry, 91, 113-121. http://dx.doi.org/10.1016/j.foodchem.2004.05.054
Goddijn-Murphy, L., & Williamson, B. (2019). On thermal infrared remote sensing of plastic pollution in natural waters. Remote Sensing, 11(18), 2159. https://doi.org/10.3390/rs11182159
Jafari, S. M., Azizi, D., Mirzaei, H., & Dehnad, D. (2016). Comparing quality characteristics of oven-dried and refractance window-dried kiwifruits. Journal of Food Process and Preservation, 40, 362-372. https://doi.org/10.1111/jfpp.12613
Johnson, W. L., Van Dresar, N. T., Chato, D. J., & Demers, J. R. (2017). Transmissivity testing of multilayer insulation at cryogenic temperatures. Cryogenics, 86, 70-79. https://doi.org/10.1016/j.cryogenics.2017.07.002
Kalse, S. B., Jain, S. K., Swami, S. B., Panwar, N. L., Rajpurohit, D., Wadhwan, N., & Bhatnagar, A. (2025). A comprehensive review of mechanisms, heat transfer dynamics and the hybrid approach of Refractance Window™ drying. Food Engineering Reviews, 17, 319–343. https://doi.org/10.1007/s12393-025-09399-5
Kraus, D. (n.d.). Daniel’s XL Toolbox addin for Excel. Xltoolbox, Würzburg, Germany (www.xltoolbox.net).
Mahanti, N. K., Chakraborty, S. K., Sudhakar, A., Verma, D. K., Shankar, S., Thakur, M., Singh, S., Tripathy, S., Gupta, A. K., & Srivastav, P. P. (2021). Refractance WindowTM drying vs other drying methods and effect of different process parameters on quality of foods: A comprehensive review of trends and technological developments. Future Foods, 3, 100024. https://doi.org/10.1016/j.fufo.2021.100024
Meinel, A. B., & Meinel, M. P. (1976). Applied Solar Energy: An Introduction (4th Ed). Addison-Wesley Educational Publishers Inc.
Milano, A. C., & Rojas, M. L. (2024). Drying strategies of spent coffee grounds using refractance window method. Food Research International, 178, 114007. https://doi.org/10.1016/j.foodres.2024.114007
Minjares-Fuentes, R., Femenia, A., Comas-Serra, F., Rosselló, C., Rodríguez-Gonzalez, V. M., Gonzalez-Laredo, R. F., Gallegos-Infante, J. A., & Medina-Torres, L. (2016). Effect of different drying procedures on physicochemical properties and flowbehavior of Aloevera (Aloe barbadensis Miller) gel. LWT-Food Science and Technology, 74, 378–386. https://doi.org/10.1016/j.lwt.2016.07.060
Nindo, C. I., & Tang, J. (2007). Refractance Window dehydration technology: A novel contact drying method. Drying Technology, 25, 37- 48. https://doi.org/10.1080/07373930601152673
Nindo, C. I., Feng, H., Shen, G. Q., Tang, J., & Kang, D. H. (2003). Energy utilization and microbial reduction in a new film drying system. Journal Food Processing and Preservation, 27, 117–136. https://doi.org/10.1111/j.1745-4549.2003.tb00506.x
Ochoa-Martínez, C. I., Quintero, P. T., Ayala, A. A., & Ortiz, M. J. (2012). Drying characteristics of mango slices using the Refractance Window™ technique. Journal of Food Engineering, 109(1), 69 -75. https://doi.org/10.1016/j.jfoodeng.2011.09.032
Ortiz-Jerez, M. J., Gulati, T., Datta, A. K., Ochoa-Martínez, C. I. (2015). Quantitative understanding of Refractance Window™ drying. Food and Bioproducts Processing, 95, 237–253. https://doi.org/10.1016/j.fbp.2015.05.010
Ortiz-Jerez, M. J., Sánchez, A. F., & Montoya, J. E. Z. (2022). Drying kinetics and sensory characteristics of dehydrated pumpkin seeds (Cucurbita moschata) obtained by refractance window drying. Heliyon, 8(10), e10947. https://doi.org/10.1016/j.heliyon.2022.e10947
Pangavhane, D. R., Sawhney, R. L., & Sarsavadia, P. N. (2002). Design, development and performance testing of a new natural convection solar dryer. Energy, 27(6), 579-590. https://doi.org/10.1016/S0360-5442(02)00005-1
Pathare, P. B., Opara, U. L., & Al-Said, F. A. J. (2013). Colour measurementand analysis in fresh and processed foods: A review. Food and Bioprocess Technology, 6(1), 36–60. https://doi.org/10.1007/s11947-012-0867-9
Prajapati, S., Shah, M. & Srivastava, S. (2024). Experimental characterization and thin-layer convective drying modeling of Jamun (Indian Blackberry) slices. Sādhanā, 49(4), 272. https://doi.org/10.1007/s12046-024-02618-5
Puente-Díaz, L., Spolmann, O., Nocetti, D., Zura-Bravo, L., & Lemus-Mondaca, R. (2020). Effects of infrared-assisted Refractance Window drying on the drying kinetics, microstructure, and color of physalis fruit puree. Foods, 9(3), 343. https://doi.org/10.3390/foods9030343
Raghavi, L. M., Moses, J. A., & Anandharamakrishnan, C. (2018). Refractance window drying of foods: A review. Journal of Food Engineering, 222, 267-275. https://doi.org/10.1016/j.jfoodeng.2017.11.032
Ratti, C., & Mujumdar, A. S. (2006). Infrared drying. In: A. S. Mujumdar (Ed.), Handbook of industrial drying (4th Ed.) (Chapter 19). CRC Press, Boca Raton, Florida, US. https://doi.org/10.1201/b17208
Sandu, C. (1986). Infrared radiative drying in food engineering: A process analysis. Biotechnology Progress, 2(3), 109-119. https://doi.org/10.1002/btpr.5420020305
Seres, Z., Glaonsky, A., Leki Kruse, J. J., & Zecher, P. D. (1994). Optical transmission of Mylar and Teflon films. Optical Engineering, 33(9), 3031-3033. https://doi.org/10.1117/12.177513
Shah, M., & Srivastava, S. (2024). Physio-chemical analysis of turmeric rhizomes (Curcuma longa L.) preserved through non-thermal technique: Electrohydrodynamic drying. African Journal of Biomedical Research, 27(4S), 1691–1701. https://doi.org/10.53555/AJBR.v27i4S.3920
Shah, M., & Srivastava, S. (2025). Scanning electron microscope analysis of turmeric slices dried through electrohydrodynamic drying: A morphological and structural evaluation. Journal of Basic Science and Engineering, 22(1), 245–264. https://doie.org/10.10399/JBSE.2025533119
Shende, D., & Datta, A. K. (2019). Refractance window drying of fruits and vegetables: A Review. Journal of the Science of Food and Agriculture, 99(4), 1449–1456. https://doi.org/10.1002/jsfa.9356
Shivmurti, S., Rinkita, P., Harshit, P., & Smit, P. (2014). Ohmic heating is an alternative preservation technique-A review. Global Journal of Science Frontier Research, 14(4), 1-10.
Shrivastav, S., Ganorkar, P. M., Prajapati, K. M., & Patel, D. B. (2021). Drying kinetics, heat quantities, and physio-chemical characteristics of strawberrypuree by Refractance Window drying system. Journal of Food Process Engineering, 44(9), 13776. https://doi.org/10.1111/jfpe.13776
Sojak, M. J., Jaros, M., & Głowacki, S. (2014). Analysis of giant pumpkin (Cucurbitamaxima) quality parameters in various technologies of convective drying afterlong-term storage. Drying Technology, 32(1), 106-116. https://doi.org/10.1080/07373937.2013.816854
Srivastav, S., Shah, M., Ganorkar, P. M., & Kumar, K. (2024). Modelling of electrohydrodynamic drying kinetics for carrot at varying electrode distance. Journal of Food Science and Technology, 61(1), 139-149. https://doi.org/10.1007/s13197-023-05829-6
Sternglanz, H. (1956). Using water as an infrared solvent. Journal of Applied Spectroscopy, 10(2),77-82. https://doi.org/10.1366/000370256774633818
Subrahmanyam, K., Gul, K., Paridala, S., Sehrawat, R., More, K. S., Dwivedi, M., & Jaddu, S. (2024). Effect of cold plasma pretreatment on drying kinetics and quality attributes of apple slices in Refractance window drying. Innovative Food Science & Emerging Technologies, 92, 103594. https://doi.org/10.1016/j.ifset.2024.103594
Sweat, V. E. (1974). Experimental values of thermal conductivity of selected fruits and vegetables. Journal of Food Science, 39(6), 1080-1083. https://doi.org/10.1111/j.1365-2621.1974.tb07323.x
Tonon, V. R., Brabet, C., & Hubinger, M. D. (2008). Influence of process conditions on the physicochemical properties of acai (Euterpe oleraceae Mart.) powder produced by spray drying. Journal of Food Engineering, 88(3), 411–418. https://doi.org/10.1016/j.jfoodeng.2008.02.029
Vega-Mercado, H., Góngora-Nieto, M. M., & Barbosa-Cánovas, G. V. (2001). Advances in dehydration of foods. Journal of Food Engineering, 49(4), 271-289. https://doi.org/10.1016/S0260-8774(00)00224-7
Vo, T. Q., & Kim, B. (2015). Interface thermal resistance between liquid water and various metallic surfaces. International Journal of Precision Engineering and Manufacturing, 16(7), 1341-1346. https://doi.org/10.1007/s12541-015-0176-0
Yoha, K. S., Moses, J. A., & Anandharamakrishnan, C. (2023). Refractance window drying: principles, applications, and emerging innovations. In: S. M. Jafari, & N. Malekjani (Eds.), Drying technology in food processing (Chapter 13, pp. 417-455). Woodhead Publishing. https://doi.org/10.1016/B978-0-12-819895-7.00008-0
Zotarelli, M. F., Carciofi, B. A. M., & Laurindo, J. B. (2015). Effect of process variables on the drying rate of mango pulp by Refractance Window. Food Research International, 69, 410-417. https://doi.org/10.1016/j.foodres.2015.01.013
