Drying holy basil using combined microwave and hot-air technology: An analysis of drying kinetics, energy efficiency, and color retention
Article Sidebar
Main Article Content
Abstract
Holy basil (Ocimum tenuiflorum) is a perishable herb with a high moisture content. Traditional hot-air drying methods result in longer drying times, higher energy use, and reduced quality. This study investigates combined hot-air and microwave drying to improve drying efficiency, reduce energy consumption, and maintain product color. A drying method was developed to evaluate the effects of hot air temperature (60, 70, and 80 °C) and microwave power level (300, 400, and 500 W) on drying kinetics, moisture diffusivity, color retention, and energy consumption. A mathematical transport model was developed in COMSOL Multiphysics to simulate the drying process. The model showed good agreement with experimental data. The results showed that microwave-hot air drying substantially accelerated moisture removal. Higher microwave power and hot-air temperature reduced drying time and specific energy consumption while increasing the effective moisture diffusivity. Combined hot‑air and microwave drying resulted in a lower total color change. The highest effective moisture diffusion coefficient (2.79 × 10⁻¹¹ m²/s) and the lowest total specific energy consumption (529.91 MJ/kg water evaporated) were obtained at a hot-air temperature of 80 °C and a microwave power of 300 W.
Article Details
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
References
Paengkanya S, Patcharatvirakul S, Kumklam P. Drying ripe mango slices using step-down temperature far-infrared-hot air techniques. Int J Agric Biol Eng. 2025;18(6):281-9. DOI: https://doi.org/10.25165/j.ijabe.20251806.9770
Neamtang P, Nathakaranakule A, Paengkanya S, Thepa S, Soponronnarit S. Drying ripe mangoes using a step-down industrial microwave-hot air belt dryer. Dry Technol. 2024;42(15):2241-55. DOI: https://doi.org/10.1080/07373937.2024.2417982
Nathakaranakule A, Paengkanya S, Soponronnarit S. Durian chips drying using combined microwave techniques with step-down microwave power input. Food Bioprod Process. 2019;116:105-17. DOI: https://doi.org/10.1016/j.fbp.2019.04.010
Chahbani A, Fakhfakh N, Balti MA, Mabrouk M, EI-Hatmi H, Zouari N, et al. Microwave drying effects on drying kinetics, bioactive compounds and antioxidant activity of green peas (Pisum sativum L.). Food Biosci. 2018;25:32-8. DOI: https://doi.org/10.1016/j.fbio.2018.07.004
Gaikwad PS, Sunil CK, Negi A, Pare A. Effect of microwave assisted hot-air drying temperatures on drying kinetics of dried black gram papad (Indian snack food): drying characteristics of black gram papad. Appl Food Res. 2022;2(2):100144. DOI: https://doi.org/10.1016/j.afres.2022.100144
Handayani SU, Mujiarto I, Siswanto AP, Ariwibowo D, Atmanto IS, Mustikaningrum M. Drying kinetics of chilli under sun and microwave drying. Mater Today: Proc. 2022;63(S1):S153-8. DOI: https://doi.org/10.1016/j.matpr.2022.02.119
Zhang Z, Chen Y, Peng J, Huang S, Wu H, Gao X. Study on drying characteristics of combined microwave-hot air drying of paddy. Case Stud Therm Eng. 2024;64:105539. DOI: https://doi.org/10.1016/j.csite.2024.105539
Jia Y, Khalifa I, Hu L, Zhu W, Li J, Li K, et al. Influence of three different drying techniques on persimmon chips’ characteristics: a comparison study among hot-air, combined hot-air-microwave, and vacuum-freeze drying techniques. Food Bioprod Process. 2019;118:67-76. DOI: https://doi.org/10.1016/j.fbp.2019.08.018
Inla K, Bunchan S, Krittacom B, Luampon R. Drying behavior, color change and rehydration of lingzhi mushroom (Ganoderma lucidum) under convection-assisted microwave drying. Case Stud Therm Eng. 2023;49:103348. DOI: https://doi.org/10.1016/j.csite.2023.103348
Wason S, Verma T, Irmak S, Subbiah J. In-package pasteurization of dried basil leaves using radiofrequency heating. Food Control. 2022;141:109179. DOI: https://doi.org/10.1016/j.foodcont.2022.109179
Thuwapanichayanan R, Kumklam P, Soponronnarit S, Prachayawarakorn S. Mathematical model and energy utilization evaluation of a coaxial impinging stream drying system for parboiled paddy. Dry Technol. 2022;40(1):158-74. DOI: https://doi.org/10.1080/07373937.2020.1775640
Pu YY, Sun DW. Combined hot-air and microwave-vacuum drying for improving drying uniformity of mango slices based on hyperspectral imaging visualisation of moisture content distribution. Biosyst Eng. 2017;156:108-19. DOI: https://doi.org/10.1016/j.biosystemseng.2017.01.006
AOAC. Official methods of analysis. 16th ed. Washington: Association of Official Agricultural Chemists; 1995.
Choi Y, Okas MR. Effect of temperature and composition on the thermal properties of foods in food engineering and process applications. In: Magnev LM, Jelen P, editors. Food Engineering and Process Applications, Vol. 1: Transport Phenomena. New York: Elsevier; 1986. p. 93-101.
Mousavi L, Rabeta MS, Murugaiyah V. Nutritional and antinutritional values of leaves and stems of Ocimum tenuiflorum L. Food Res. 2019;3(6):798-807. DOI: https://doi.org/10.26656/fr.2017.3(6).160
Costa C, Antonucci F, Pallottino F, Aguzzi J, Sun DW, Menesatti P. Shape analysis of agricultural products: a review of recent research advances and potential application to computer vision. Food Bioprocess Technol. 2011;4(5):673-92. DOI: https://doi.org/10.1007/s11947-011-0556-0
Metaxas AC, Meredith RJ. Industrial microwave heating. London: Peter Peregrinus Ltd; 1983.
Rattanadecho P. The simulation of microwave heating of wood using a rectangular wave guide: influence of frequency and sample size. Chem Eng Sci. 2006;61(14):4798-811. DOI: https://doi.org/10.1016/j.ces.2006.03.001
Shrestha BL, Wood HC, Sokhansanj S. Microwave dielectric properties of alfalfa leaves from 0.3 to 18 GHz. IEEE Trans Instrum Meas. 2011;60(8):2926-33. DOI: https://doi.org/10.1109/TIM.2011.2121270
Chauhan PD, Gadani DH, Rana VA. Effect of moisture content variation on dielectric properties of various plant leaves at microwave frequencies. Sci Rep. 2024;14(1):13204. DOI: https://doi.org/10.1038/s41598-024-64266-3
Cengel YA. Heat transfer: a practical approach. 2nd ed. New York: McGraw-Hill; 2002.
Chilton TH, Colburn AP. Mass transfer (absorption) coefficients prediction from data on heat transfer and fluid friction. Ind Eng Chem. 1934;26(11):1183-7. DOI: https://doi.org/10.1021/ie50299a012
Balaras CA, Dascalaki EG, Psarra I, Cholewa T. Primary energy factors for electricity production in Europe. Energies. 2023;16(1):93. DOI: https://doi.org/10.3390/en16010093
Wilby MR, Gonzalez ABR, Día JJV. Empirical and dynamic primary energy factors. Energy. 2014;73:771-9. DOI: https://doi.org/10.1016/j.energy.2014.06.083
Guo Q, Sun DW, Cheng JH, Han Z. Microwave processing techniques and their recent applications in the food industry. Trends Food Sci Technol. 2017;67:236-47. DOI: https://doi.org/10.1016/j.tifs.2017.07.007
Giap SGE. The hidden property of arrhenius-type relationship: viscosity as a function of temperature. J Phys Sci. 2010;21(1):29-39.
Makul N, Vongpradubchai S, Rattanadecho P. An experimental study of microwave drying under low pressure to accelerate the curing of Portland cement pastes using a combined unsymmetrical double-fed microwave and vacuum system. Int J Heat Mass Transf. 2018;127:179-92. DOI: https://doi.org/10.1016/j.ijheatmasstransfer.2018.06.119
Weemaes CA, Ooms V, Van Loey AM, Hendrickx ME. Kinetics of chlorophyll degradation and color loss in heated broccoli juice. J Agric Food Chem.1999;47(6):2404-9. DOI: https://doi.org/10.1021/jf980663o
Nanvakenari S, Movagharnejad K, Latifi A. Multi-objective optimization of hybrid microwave-fluidized bed drying conditions of rice using response surface methodology. J Stored Prod Res. 2022;97:101956. DOI: https://doi.org/10.1016/j.jspr.2022.101956
