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Solvent-free microwave extraction of natural products


Key words Microwave, hydrodiffusion, extraction, solvent-free, essential oils, antioxidants, colours
Latest version 2013/09/05
Completed by INRA - IATE

How does it work?

Primary objective Solvent-free extraction of metabolites from fresh plants (fruits, vegetables, herbs, spices...)

The same principle is used for Microwave drying of spice and herbs

Working principle This extraction method is performed by Microwave heating at atmospheric pressure.

The plant material, without any added solvent or water, is placed in a batch (= extraction vessel) inside the microwave oven. The internal heating of the in-situ water distends the plant cells and leads to the rupture of glands and oleiferous receptacles. The physical phenomenon, known as hydrodiffusion, allows the extract to diffuse outside the plant material. The solution is continuously cooled through a cooling system outside the microwave oven. Oils and water are separated by decantation. The excess of water is refluxed back to the extraction vessel in order to restore the in-situ water to the sample (1). For an equivalent amount of material to process, the solvent-free microwave extraction requires much less time than traditional processes. Examples: Basil, garden mint, thyme essential oils: 30 min. of extraction vs. 270 min respectively, with equivalent yields (2). Orange peels essential oils: 10 min vs. 180 min, with equivalent yield and non-oxygenated compounds amount, and a 78% rise for oxygenated compounds amount (3).

picture: 100 litre microwave extractor

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Additional effects This process can produce essential oils in concentrated form, free from any residual solvents, contaminants, or artefacts.

The extracted essential oils can be analyzed directly by GC-MS without any preliminary clean-up or solvent exchange steps (4).

Important process parameters Duration


Important product parameters Water content of the initial product

Polarity of the compound of interest

What can it be used for?

Products Extracts coming from: aromatic herbs, spices, dry seeds (4)

Juice, essential oils, colours, antioxidants (2)

Operations Extraction, distillation
Solutions for short comings Search for green extraction processes

What can it NOT be used for?

Products Only plant-based products, no petroleum solvents
Operations Only extraction or distillation, no synthesis or drying
Other limitations Capacity: from 5 litres to 100 litres
Risks or hazards Related to the elevated temperature (up to 100°C).


Maturity The method and device are patented for the European territory.

A 100 litre pilot experimental device is available by April 2012 at INRA - SQPOV (Avignon, France).

Modularity /Implementation This technology replaces the existing extraction equipment.
Consumer aspects No specific study has been carried out so far regarding consumer acceptance.

Yet there is a general trend for more natural products and eco-friendly processes.

Legal aspects European Patent, EP 1 955 749 A1, 2008.

United States Patent, US 2010/0062121, 2010. International Patent PCT, WO 089943 A1, 2008.

Environmental aspects Absence of solvent

Energy savings due to the short extraction time

Further Information

Institutes INRA - SQPOV, Université d'Avignon et des Pays de Vaucluse
Companies Milestone
  1. F. Chemat, G. Cravotto Microwave-assisted Extraction for Bioactive Compound. Springer, NewYork, 238 pages. 2013. ISBN 978-1-4614-4829-7.
  2. X. Fernandez, F. Chemat, T. Do Les huiles essentielles : vertus et applications. Vuibert, Paris, 160 pages. 2012. ISBN 978-2-311-01029-9
  3. F. Chemat Eco-Extraction du Végétal : procédés innovants et solvants alternatifs. DUNOD, Paris, 336 pages. 2011. ISBN : 978-21-005654-3-6.
  4. X. Fernandez, F. Chemat La Chimie des huiles essentielles. Vuibert, Paris, 256 pages. 2012. ISBN 978-2-311-01028-2.

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Created by Hte inra on 30 May 2013, at 10:19