This paper brings forward a novel process for particle production named extraction and particle formation on-line (EPFO). The process comprises the hyphenated on-line association of pressurized liquid extraction (PLE) with supercritical antisolvent (SAS) precipitation performed in the same multipurpose equipment. The highlight of EPFO process stands for using the pressure energy applied in the extraction step as a useful energy for spraying and producing microparticles in the precipitation step. Performing EPFO process also prevents degrading bioactive compounds because the extract directly flows to the precipitation vessel, avoiding light and oxygen exposure. Then, we obtained dried microparticles as a fine powder from onion peels. After studying some different extraction conditions using ethanol, the more suitable one was found: 40 degrees C/120 bar for extraction step and 40 degrees C/100 bar for precipitation step. In such condition, we obtained 4.1 +/- 0.6 g microparticles/100 g of dried onion peels, the highest quercetin content in the microparticles (26 +/- 2 wt.%) and the smallest mean particle diameter (d([3,4])=119 +/- 1 mu m). Analysis of morphology showed lengthened microparticles with rod-like structures. We presented the microparticles characteristics obtained between EPFO process and conventional process (rotary evaporation), whereas EPFO process produced smaller microparticles more concentrated with quercetin. (C) 2015 Elsevier B.V. All rights reserved.