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Response surface methodology (RSM) was used to evaluate the processing parameters’ effects of three extraction processes namely: steam-distillation (SD), steam-diffusion (SDiff) and hydro-distillation (HD) on the extraction of thyme essential oil. The tested parameters are the mass of vegetable, the extraction time and the water vapour flow; the response is the essential oil yield. According to the method of statistics, a second order polynomial function was assumed to approximate the extraction yield of the essential oil. The models’ matching test, estimated by the determinant coefficient R2 (93.42 % for SD, 80.46 % for SDiff and 94.73 % for HD), revealed a quite matching between experimental and predictive values. When compared, the effectiveness of the three processes according to the extraction duration showed that SD and SDiff are the most powerful with a value that exceeds 80 % time wise. Analysis highlighted that the oils were characterised by a high amount of oxygenated monoterpenes and c...

Analysis of the essential oil of Origanum glandulosum (Desf.) from Algeria, by GC and GC-MS made it possible to identify 33 components, representing 92.7 % of the oil. The major components were thymol (38.8 %) followed by carvacrol (32.9 %), p-cymene (7.9 %) and γ-terpinene (5.1 %).

International audience; A microwave steam distillation (MSD) of essential oils from fresh citrus by-products (orange peels) was studied. The effectiveness of this innovative method in extraction of citrus essential oils have been evaluated and compared to conventional steam distillation. MSD offers important advantages like shorter extraction time (6 min), cleaner features and provides an essential oil with better sensory properties (better reproduction of natural fresh fruit aroma of the citrus essential oil) at optimized power (500 W). Results from chemical and cytological approaches confirm the effectiveness of this new technique, that allows substantial savings in terms of time and energy. Industrial relevance: The treatment of by-products represents a strong demand for industrial fruits processing, which produces tonnages of waste material such as peels, seeds and fibers. The disposal of these materials usually represents an industrial legal restriction problem. Moreover, the waste treatment represents significant costs and is often misjudged by companies. Transformation of waste products with high value-added allows companies to reduce the global treatment costs, sometimes even to take some profits and thus improve their competitiveness. Moreover, the recovery process of by-products is part of the current existing sustainable development and environmental protection.

International audience; Steam distillation (SD) is routinely used by analysts for the isolation of essential oils from herbs, flowers and spices prior to gas chromatographic analysis. In this work, a new process design and operation for an improved microwave steam distillation (MSD) of essential oils from aromatic natural products was developed. To demonstrate its feasibility, MSD was compared with the conventional technique, SD, for the analysis of volatile compounds from dry lavender flowers (Lavandula angustifolia Mill., Lamiaceae). Essential oils isolated by MSD were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by SD, but MSD was better than SD in terms of rapidity (6 min versus 30 min for lavender flowers), thereby allowing substantial savings of costs in terms of time and energy. Lavender flowers treated by MSD and SD were observed by scanning electron microscopy. Micrographs provide evidence of more rapid opening of essential oil glands treated by MSD, in contrast to conventional SD