Food and Bioprocess Technology

, Volume 10, Issue 4, pp 687–698 | Cite as

Electromagnetic Heating for Industrial Kilning of Malt: a Feasibility Study

  • R. S. Ferrari-John
  • J. Katrib
  • E. Zerva
  • N. Davies
  • D. J. Cook
  • C. Dodds
  • S. Kingman
Original Paper


Industrial malting operations use ∼800 kWh/t of energy to produce the heat required to kiln malt. Electromagnetic heating technologies are suggested as a way to potentially improve the energy efficiency of the kilning processing. In this work, the potential for using electromagnetic heating to dry malt to commercially acceptable moisture levels whilst preserving the activity of enzymes critical for downstream brewing processes is investigated. The 2450 MHz bulk dielectric properties of malt at moisture contents consistent with those occurring at different points in the kilning process are evaluated; 12% is shown to be a critical moisture level below which drying becomes more energy intensive. Calculated penetration depths of electromagnetic energy in malt at radio frequency are 100-fold higher than at microwave frequencies, showing a significant advantage for commercial-scale batch processing. The moisture contents and alpha and beta amylase activity of malt subjected to RF heating at different temperatures, treatment times and RF energy inputs in the intermediate and bound water drying regions were determined. It is shown for the first time that whilst significantly reduced process times are attainable, significant energy efficiency improvements compared to conventional kilning can only be achieved at higher product temperatures and thus at the expense of enzyme survival. It is suggested that RF heating may be feasible where higher bulk temperatures are not critical for downstream use of the material or when used in hybrid systems.


Microwave Radio frequency Malt Kilning 



The authors would like to express their gratitude to Muntons PLC for sponsoring this work.


  1. Bala, B. K. (1983). Deep bed drying of malt. Faculty of Science: Agriculture and Engineering Newcastle University.Google Scholar
  2. Bathgate, G. (1973). Biochemistry of malt kilning. Brewers digest., 48, 60–65.Google Scholar
  3. Beddington J (2009) Food, energy, water and the climate: a perfect storm of global events. In: Lecture to Sustainable Development UK 09 Conference.Google Scholar
  4. Betz, F. (2003). Managing technological innovation: competitive advantage from change. John Wiley & Sons.Google Scholar
  5. Briggs, D., Hough, J., Stevens, R., & Young, T. (1981). Malting and brewing science: malt and sweet wort (Vol. 1, Springer US).Google Scholar
  6. Buttress, A., Jones, A., & Kingman, S. (2015). Microwave processing of cement and concrete materials—towards an industrial reality? Cement and Concrete Research., 68, 112–123.CrossRefGoogle Scholar
  7. CarbonTrust (2011) Maltings industrial energy efficiency. In: Industrial energy efficiency accelerator. vol CTG053. p^pp.Google Scholar
  8. Clarke RN, Gregory AP, Cannell D, Patrick M, Wylie S, Youngs I & Hill G (2003) A guide to the characterisation of dielectric materials at RF and microwave frequencies. Institute of Measurement and Control, National Physical LaboratoryGoogle Scholar
  9. DEFRA (2013) Industry agree stretching energy efficiency targets with government. Available at
  10. Engen, G. F., & Hoer, C. A. (1979). Thru-reflect-line: an improved technique for calibrating the dual six-port automatic network analyzer. Microwave Theory and Techniques, IEEE Transactions on., 27(12), 987–993.CrossRefGoogle Scholar
  11. European Brewery Convention (2000) Malting technology. Getränke-Fachverlag Hans Carl,Google Scholar
  12. Filly, A., Fernandez, X., Minuti, M., Visinoni, F., Cravotto, G., & Chemat, F. (2014). Solvent-free microwave extraction of essential oil from aromatic herbs: from laboratory to pilot and industrial scale. Food Chemistry., 150, 193–198.CrossRefGoogle Scholar
  13. Gebremariam, M. M., Zarnkow, M., & Becker, T. (2012). Effect of drying temperature and time on alpha-amylase, beta-amylase, limit dextrinase activities and dimethyl sulphide level of teff (Eragrostis tef) malt. Food and Bioprocess Technology., 6(12), 3462–3472.CrossRefGoogle Scholar
  14. Hardwick W (1994) Handbook of brewing. CRCGoogle Scholar
  15. Henry, F., Gaudillat, M., Costa, L. C., & Lakkis, F. (2003). Free and/or bound water by dielectric measurements. Food Chemistry., 82(1), 29–34.CrossRefGoogle Scholar
  16. Jones, D. A., Lelyveld, T. P., Mavrofidis, S. D., Kingman, S. W., & Miles, N. J. (2002). Microwave heating applications in environmental engineering—a review. Resources, Conservation and Recycling., 34(2), 75–90.CrossRefGoogle Scholar
  17. Kaatze, U. (1989). Complex permittivity of water as a function of frequency and temperature. Journal of Chemical and Engineering Data., 34(4), 371–374.CrossRefGoogle Scholar
  18. Kappe, C. O. (2013). Microwave effects in organic synthesis: myth or reality? Angewandte Chemie International Edition., 52(4), 1088–1094.CrossRefGoogle Scholar
  19. Kraszewski, A., & Nelson, S. (1989). Composite model of the complex permittivity of cereal grain. Journal of Agricultural Engineering Research., 43, 211–219.CrossRefGoogle Scholar
  20. Kunze, W., Wainwright, T., & Mieth, H. (1999). Technology brewing and malting (Vol. 669). Germany: Vlb Berlin.Google Scholar
  21. Lu, Z., Lanagan, M., Manias, E., & Macdonald, D. D. (2009). Two-port transmission line technique for dielectric property characterization of polymer electrolyte membranes. The Journal of Physical Chemistry B., 113(41), 13551–13559.CrossRefGoogle Scholar
  22. Mehdizadeh M (2015) Microwave/RF applicators and probes: for material heating, sensing, and plasma generation. William Andrew,Google Scholar
  23. Meredith RJ (1998) Engineers’ handbook of industrial microwave heating. Institution of Electrical Engineers,Google Scholar
  24. Metaxas AA & Meredith RJ (1983) Industrial microwave heating.Google Scholar
  25. Muller, R. (2000). A mathematical model of the formation of fermentable sugars from starch hydrolysis during high-temperature mashing. Enzyme and microbial technology., 27(3), 337–344.CrossRefGoogle Scholar
  26. Nelson, S. (2008). Dielectric properties of agricultural products and some applications. Research in Agricultural Engineering., 54(2), 104–112.Google Scholar
  27. Nelson, S. O., & Stetson, L. E. (1976). Frequency and moisture dependence of the dielectric properties of hard red winter wheat. Journal of Agricultural Engineering Research., 21(2), 181–192.CrossRefGoogle Scholar
  28. Nelson, S. O., & Trabelsi, S. (2006). Dielectric spectroscopy of wheat from 10 MHz to 1.8 GHz. Measurement Science and Technology., 17(8), 2294.CrossRefGoogle Scholar
  29. O’Rourke, T. (2002). Malt specifications & brewing performance. Brew Int., 2(10), 27–30.Google Scholar
  30. Pethig, R., & Kell, D. B. (1987). The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology. Physics in medicine and biology., 32(8), 933.CrossRefGoogle Scholar
  31. Raghavan, G., Rennie, T., Sunjka, P., Orsat, V., Phaphuangwittayakul, W., & Terdtoon, P. (2005). Overview of new techniques for drying biological materials with emphasis on energy aspects. Brazilian Journal of Chemical Engineering., 22(2), 195–201.CrossRefGoogle Scholar
  32. Serdyuk, V. M. (2008). Dielectric study of bound water in grain at radio and microwave frequencies. Progress In Electromagnetics Research., 84, 379–406.CrossRefGoogle Scholar
  33. Sopanen, T., & Laurière, C. (1989). Release and activity of bound β-amylase in a germinating barley grain. Plant Physiology., 89(1), 244–249.CrossRefGoogle Scholar
  34. Tassou, S. A., Kolokotroni, M., Gowreesunker, B., Stojceska, V., Azapagic, A., Fryer, P., & Bakalis, S. (2014). Energy demand and reduction opportunities in the UK food chain. Proceedings of the ICE-Energy., 167(3), 162–170.Google Scholar
  35. Thostenson, E., & Chou, T.-W. (1999). Microwave processing: fundamentals and applications. Composites Part A: Applied Science and Manufacturing., 30(9), 1055–1071.CrossRefGoogle Scholar
  36. Trabelsi, S., Kraszewski, A. W., & Nelson, S. O. (2001). New calibration technique for microwave moisture sensors. Instrumentation and Measurement, IEEE Transactions on., 50(4), 877–881.CrossRefGoogle Scholar
  37. Trabelsi, S., & Nelson, S. O. (2003). Free-space measurement of dielectric properties of cereal grain and oilseed at microwave frequencies. Measurement Science and Technology., 14(5), 589.CrossRefGoogle Scholar
  38. Trabelsi, S., & Nelson, S. O. (2006). Temperature-dependent behaviour of dielectric properties of bound water in grain at microwave frequencies. Measurement Science and Technology., 17(8), 2289.CrossRefGoogle Scholar
  39. Trabelsi, S., & Nelson, S. O. (2007). Unified microwave moisture sensing technique for grain and seed. Measurement Science and Technology., 18(4), 997.CrossRefGoogle Scholar
  40. Venkatesh, M., & Raghavan, G. (2005). An overview of dielectric properties measuring techniques. Canadian biosystems engineering., 47(7), 15–30.Google Scholar
  41. Weir, W. B. (1974). Automatic measurement of complex dielectric constant and permeability at microwave frequencies. Proceedings of the IEEE., 62(1), 33–36.CrossRefGoogle Scholar
  42. Whitehurst RJ & Van Oort M (2010) Enzymes in food technology, vol 388. Wiley Online Library,Google Scholar

Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • R. S. Ferrari-John
    • 1
  • J. Katrib
    • 1
  • E. Zerva
    • 1
    • 2
  • N. Davies
    • 3
  • D. J. Cook
    • 2
  • C. Dodds
    • 1
  • S. Kingman
    • 1
  1. 1.Department of Chemical and Environmental EngineeringThe University of NottinghamNottinghamUK
  2. 2.Division of Food SciencesThe University of NottinghamLoughboroughUK
  3. 3.MuntonsStowmarketUK

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