Advertisement

Microwave-Assisted Extraction: An Introduction to Dielectric Heating

  • Cristina LeonelliEmail author
  • Paolo Veronesi
  • Giancarlo Cravotto
Chapter
Part of the Food Engineering Series book series (FSES)

Abstract

Low environmental impact and high efficiency in chemical processing and manufacturing can be attained with the use of “light” instead of conductive heating. At microwave (MW) frequencies (300 MHz–300 GHz), the electromagnetic field can be dissipated by matter in the form of heat via polarization mechanisms, magnetic interactions, and ionic conduction. The conversion is extremely rapid, and heat is volumetrically diffused into the solvents, leading to an incredibly fast temperature increase that can speed up extraction processes in a way no other technique can match. In closed systems, microwave-assisted extraction can be performed at higher temperatures, and extraction times can be reduced drastically. In fact, enhanced plant matrix swelling increases the diffusion rate and promotes faster extraction kinetics. However, the user must take into account that the temperature distribution in a solvent exposed to microwave radiation is strictly dependent on the electromagnetic field distribution in the reactor, on the dielectric properties of the material, and on the presence of mass transport phenomena such as natural convection and stirring. Shorter extraction times and shorter cooling times usually avoid material degradation and afford high-quality extracts.

Keywords

Continuous Flow Reactor Reactor Geometry Noncontact Method Electromagnetic Field Distribution Multimode Applicator 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

References

  1. 1.
    International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines: http://www.icnirp.de/
  2. 2.
    Raju GG (2003) Dielectrics in electric fields. Dekker, New YorkCrossRefGoogle Scholar
  3. 3.
    Ulaby FT (2001) Fundamentals of applied electromagnetics. Prentice Hall, Upper Saddle RiverGoogle Scholar
  4. 4.
    Pozar DM (1998) Microwave engineering. Wiley, TorontoGoogle Scholar
  5. 5.
    Metaxas AC (1996) Foundations of electroheat: a unified approach. Wiley, New YorkGoogle Scholar
  6. 6.
    Mingos DMP (2005) Theoretical aspects of microwave dielectric heating. In: Tierney JP, Lidstrom P (eds) Microwave assisted organic synthesis. Blackwell, Oxford, pp 1–22CrossRefGoogle Scholar
  7. 7.
    Gabriel C, Gabriel S, Grant HH, Halstead BSJ, Mingos MP (1998) Dielectric parameters ­relevant to microwave dielectric heating. Chem Soc Rev 27:213CrossRefGoogle Scholar
  8. 8.
    Kaufmann B, Christen P (2002) Recent extraction techniques for natural products: microwave-assisted extraction and pressurised solvent extraction. Phytochem Anal 13:105CrossRefGoogle Scholar
  9. 9.
    Mandal V, Mohan Y, Hemalatha S (2007) Microwave assisted extraction - An innovative and promising extraction tool for medicinal plant research. Pharmacogn Rev 1:7Google Scholar
  10. 10.
    Mason TJ, Chemat F, Vinatoru M (2011) The extraction of natural products using ultrasound or microwaves. Curr Org Chem 15:237CrossRefGoogle Scholar
  11. 11.
    Wang LJ, Weller CL (2006) Recent advances in extraction of nutraceuticals from plants. Trends Food Sci Technol 17:300CrossRefGoogle Scholar
  12. 12.
    Leonelli C, Mason TJ (2010) Microwave and Ultrasonic processing: now a realistic option for industry. Chem Eng Proc Process Intens 49:885CrossRefGoogle Scholar
  13. 13.
    Castera A (2011) Oleo-eco-extraction with a microwave batch reactor. In: 13th international conference on microwave and high frequency heating, AMPERE 2011, ToulouseGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  • Cristina Leonelli
    • 1
    Email author
  • Paolo Veronesi
    • 1
  • Giancarlo Cravotto
    • 2
  1. 1.Dipartimento di Ingegneria dei Materiali e dell’AmbienteUniversità di Modena e Reggio EmiliaModenaItaly
  2. 2.Dipartimento di Scienza e Tecnologia del FarmacoUniversità di TorinoTorinoItaly

Personalised recommendations