The microwave steam diffusion (MSDf) apparatus for extraction of essential oils from orange peel (byproducts)
was studied. MSDf has been compared with conventional steam diffusion (SDf). A response surface
methodology (RSM) was realised to investigate the influence of process variables by a central composite
design (CCD) approach. The statistical analysis revealed that the optimal conditions for the
extraction of orange essential oil were a steam mass flow rate of 25 g min1 and a microwave power
of 200 W. Cytohistological investigations using light microscopy provided evidences for rapid and pronounced
cell and tissue alterations of oil glands with MSDf in comparison with SDf. The essential oils
extracted by MSDf for 12 min were quantitatively (yield) and qualitatively (aromatic profile) similar to
those obtained by SDf for 40 min. Extraction of essential oils from orange peel with MSDf was better than
SDf in terms of energy saving, cleanliness and reduced waste water.