Development of WEPO - Water Extraction and Particle formation On-line

Abstract: There are many valuable substances present in nature such as antioxidants. The conventional method for extracting the antioxidants employs organic solvents. Subcritical Water Extraction (SWE) is a sustainable method for extraction of high valuable compounds. This method uses subcritical water as a solvent instead of organic solvents but leaves the compounds in a water solution. Keeping the antioxidants in water can decrease their stability and to remove water from a solution is harder then to remove an organic solvent. It is not environmentally friendly to transport a large amount of solvent so the water has to be removed and in a way that avoids decomposition of the valuable compounds. The process developed in this project, WEPO, extracts the antioxidants with subcritical water and mixes the extract with SC-CO2 to form an emulsion that when led to atmospheric pressure forms an aerosol that can be dried quickly with hot N2 giving particles. The compound extracted in the project is quercetin, an antioxidant that can be extracted from onion. To evaluate the efficiency of the process the particles formed were analysed to determine the water content, size and morphology, antioxidant capacity and concentration of antioxidants. For comparison the same analysis were done on extracts dried with freeze-drying. Antioxidant capacity measured with a DPPH method showed about the same capacity for the particles produced by WEPO and the freeze-dried extract. SEM pictures taken of the extracts showed hollow spheres from the WEPO particles in the size range of 250 nm – 4 μm. For the freeze-dried extracts no particles were observed. The WEPO particles and the freeze-dried extracts were analysed with an HPLC-UV method and showed about the same concentrations of quercetin species. For particle formation of the extracts the WEPO process is superior to freeze-drying the extracts and matches it in antioxidant activity and concentration of quercetin and derivates.