Hydrodistillation and in situ microwave-generated hydrodistillation of fresh and dried mint leaves: a comparison study.
BACKGROUND
Hydrodistillation (HD) has been used since ancient times for the extraction of essential oils (EO). Despite the intrinsic limitations of this technique, it remains the most common method both in the laboratory and on an industrial scale. The main drawbacks are the long extraction time involved and the risk of thermal degradation. Over the last decade, microwave-assisted extraction (MAE) and in situ microwave-generated hydrodistillation (MGH) have been shown to be the most promising techniques in improving plant extraction and hydrodistillation.


RESULTS
In this study we compare HD with MGH in the extraction of several mint species cultivated in Piedmont: Mentha spicata L. var. rubra, Mentha spicata L. var. viridis and Mentha piperita L. MGH requires either fresh plant or rehydrated material, it is extremely fast and allows a reduction in energy consumption and overall cost. All the EO have been analyzed by gas chromatography-mass spectrometry. A mechanism of microwave-generated essential oil extraction has been proposed to explain the differences in the composition of the oil obtained from this environmentally friendly technique.


CONCLUSIONS
The yields and composition percentages of the EO obtained by HD and in situ MGH of fresh and dried mint leaves lie in a relatively narrow range, although MGH is faster. MW polarization effects and the water solubility of the components influence extract composition.
Dipartimento di Scienza e Tecnologia del Farmaco, University of Torino, Torino, Italy.
Laura
L
Orio
Giancarlo
G
Cravotto
Arianna
A
Binello
Giuseppe
G
Pignata
Silvana
S
Nicola
Farid
F
Chemat
D003890:Desiccation; D057168:Distillation / Q000379:methods*; D005511:Food Handling / Q000379:methods*; D027541:Mentha / Q000737:chemistry*; D008872:Microwaves; D009822:Oils, Volatile / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*
D009822:Oils, Volatile; D010936:Plant Extracts