Drying Pandan Leaves Using Step-Down Microwave Power: Approach for Drying Efficiency, Color Quality, and Energy Consumption

Wanchalee Pengpongsa; Weera Sriariyakul; Poomirat Nawarat; Ponlakrit Kumklam

doi:10.65763/jfhb.2026.e270214

Authors

Wanchalee Pengpongsa Department of Manufacturing Engineering and Energy Management, Faculty of Science, Chandrakasem Rajabhat University, Bangkok, 10900 Thailand
Weera Sriariyakul Department of Power Engineering Technology, College of Industrial Technology, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800 Thailand
Poomirat Nawarat Division of Industrial Materials Science, Faculty of Science and Technology, Rajamangala University of Technology Phra Nakhon, Bangkok, 10800 Thailand
Ponlakrit Kumklam Division of Industrial Materials Science, Faculty of Science and Technology, Rajamangala University of Technology Phra Nakhon, Bangkok, 10800 Thailand

DOI:

https://doi.org/10.65763/jfhb.2026.e270214

Keywords:

Pandan leaf, Step-down microwave drying, Drying kinetics, Specific energy consumption

Abstract

This study investigated the application of a step-down microwave (MW) power technique for drying pandan leaves (Pandanus amaryllifolius), assessing its performance against constant-power drying across a range of 100–800 W. Key parameters evaluated included drying kinetics, color quality, specific energy consumption, and effective moisture diffusivity. The results indicated that while constant high MW power of 800 W achieved the shortest drying time of 8 min, it caused significant chlorophyll degradation (a* = –1.63) and high energy use. In contrast, the step-down protocol at MW power of 450 W for 10 min, followed by 200 W, effectively combined rapid initial moisture removal with a gentler finishing phase. This approach yielded a competitive drying time of 16 min, significantly better color preservation, and a 54% reduction in specific energy consumption compared to constant MW power drying at 800 W. The maximum effective moisture diffusivity for the step-down method was calculated to be 7.911×10^-14 m²/s. The prediction model based on the Arrhenius equation confirmed that effective moisture diffusivity is a temperature-activated process. Therefore, the step-down MW technique is recommended as an efficient, energy-saving, and quality-preserving method for drying pandan leaves.

References

Adus, A., & Wisdom, E. (2024). Activation energy and effective moisture diffusivity determination on some agricultural biomaterials: A review. International Journal of Innovative Mathematics, Statistics & Energy Policies, 12(1), 33–42.

Akpinar, E.K. (2006). Mathematical modelling of thin layer drying process under open sun of some aromatic plants. Journal of Food Engineering, 77(4), 864–870. https://doi.org/10.1016/j.jfoodeng.2005.08.014

An, N.-N., Sun, W., Li, D., Wang, L.-J., & Wang, Y. (2024). Effect of microwave-assisted hot air drying on drying kinetics, water migration, dielectric properties, and microstructure of corn. Food Chemistry, 455, 139913. https://doi.org/10.1016/j.foodchem.2024.139913

Balaras, C.A., Droutsa, K.G., Dascalaki, E.G., Psarra, I., & Cholewa, T. (2023). Primary energy factors for electricity production in Europe. Energies, 16(1), 93. https://doi.org/10.3390/en16010093

Chen, C., Venkitasamy, C., Zhang, W., Deng, L., Meng, X., & Pan, Z. (2020). Effect of step-down temperature drying on energy consumption and product quality of walnuts. Journal of Food Engineering, 285, 110105. https://doi.org/10.1016/j.jfoodeng.2020.110105

Crank, J. (1975). The mathematics of diffusion (2nd ed.). Oxford University Press.

Darvishi, H., Farhudi, Z., & Behroozi-Khazaei, N. (2017). Mass transfer parameters and modeling of hot air drying kinetics of dill leaves. Chemical Product and Process Modeling, 12(2), 20150079. https://doi.org/10.1515/cppm-2015-0079

Dev, S.R.S., Geetha, P., Orsat, V., Gariépy, Y., & Raghavan, G.S.V. (2011). Effects of microwave-assisted hot air drying and conventional hot air drying on the drying kinetics, color, rehydration, and volatiles of Moringa oleifera. Drying Technology, 29(12), 1452–1458. https://doi.org/10.1080/07373937.2011.587926

Fitri, N.R., Taufik, R.A., Ula, R.A., & Puspasari, I. (2023). Effect of air temperature on the drying kinetics of pandan leaves (Pandanus amaryllifolius) in a fluidized bed dryer. Chemical Engineering Transactions, 106, 1321–1326. https://doi.org/10.3303/CET23106221

Haq, R., Kumar, P., & Prasad, K. (2018). Effect of microwave treatment on dehydration kinetics and moisture diffusivity of Asiatic Himalayan black carrot. Journal of the Saudi Society of Agricultural Sciences, 17(4), 463–470. https://doi.org/10.1016/j.jssas.2016.11.003

Kadam, D.M., Goyal, R.K., Singh, K.K., & Gupta, M.K. (2011). Thin layer convective drying of mint leaves. Journal of Medicinal Plants Research, 5(2), 164–170.

Kusuma, H.S., Izzah, D.N., & Linggajati, I.W.L. (2023). Microwave-assisted drying of Ocimum sanctum leaves: Analysis of moisture content, drying kinetic model, and techno-economics. Applied Food Research, 3(2), 100337. https://doi.org/10.1016/j.afres.2023.100337

Łyczko, J., Masztalerz, K., Lipan, L., Iwiński, H., Lech, K., Carbonell-Barrachina, Á.A., & Szumny, A. (2021). Coriandrum sativum L.—Effect of multiple drying techniques on volatile and sensory profile. Foods, 10(2), 403. https://doi.org/10.3390/foods10020403

Makul, N., Vongpradubchai, S., & Rattanadecho, P. (2018). 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. International Journal of Heat and Mass Transfer, 127, 179–192. https://doi.org/10.1016/j.ijheatmasstransfer.2018.06.108

Maskan, M. (2000). Microwave/air and microwave finish drying of banana. Journal of Food Engineering, 44(2), 71–78. https://doi.org/10.1016/S0260-8774(99)00167-3

Nathakaranakule, A., Paengkanya, S., & Soponronnarit, S. (2019). Durian chips drying using combined microwave techniques with step-down microwave power input. Food and Bioproducts Processing, 116, 105–117. https://doi.org/10.1016/j.fbp.2019.04.013

Neamtang, P., Nathakaranakule, A., Paengkanya, S., Thepa, S., & Soponronnarit, S. (2024). Drying ripe mangoes using a step-down industrial microwave-hot air belt dryer. Drying Technology, 42(15), 2241–2255. https://doi.org/10.1080/07373937.2024.2384795

Ozkan, I.A., Akbudak, B., & Akbudak, N. (2007). Microwave drying characteristics of spinach. Journal of Food Engineering, 78(2), 577–583. https://doi.org/10.1016/j.jfoodeng.2005.10.026

Paengkanya, S., & Nathakaranakule, A. (2025). Anchovy drying using step-down microwave technique. Food Science and Biotechnology, 34(15), 3271–3281. https://doi.org/10.1007/s10068-025-01931-1

Rayaguru, K., & Routray, W. (2011). Microwave drying kinetics and quality characteristics of aromatic Pandanus amaryllifolius leaves. International Food Research Journal, 18(3), 1035–1042.

Skendi, A., Bouloumpasi, E., Chatzopoulou, P., Biliaderis, C.G., & Irakli, M. (2023). Comparison of drying methods for the retention of phenolic antioxidants in post-distillation solid residues of aromatic plants. LWT - Food Science and Technology, 189, 115463. https://doi.org/10.1016/j.lwt.2023.115463

Soysal, Y. (2004). Microwave drying characteristics of parsley. Biosystems Engineering, 89(2), 167–173. https://doi.org/10.1016/j.biosystemseng.2004.07.008

Sultana, A., & Ghosh, U. (2021). Estimation of effective moisture diffusivity of red amaranth leaves (Amaranthus tricolor L.) for thin-layer drying technology. International Journal of Agricultural Technology, 17(2), 737–752.

Van Loey, A.M., Ooms, V., Weemaes, C.A., & Hendrickx, M.E. (1999). Kinetics of chlorophyll degradation and color loss in heated broccoli juice. Journal of Agricultural and Food Chemistry, 47(6), 2404–2409. https://doi.org/10.1021/jf981146a

Wilby, M.R., Rodríguez González, A.B., & Vinagre Díaz, J.J. (2014). Empirical and dynamic primary energy factors. Energy, 73, 771–779. https://doi.org/10.1016/j.energy.2014.06.082