Liquid and supercritical CO2 extraction of fat from rendered materials

Abstract

The separation of fat from rendered materials has potential for value-added products, fuels and feed sources for animals. Current industrial processes utilize continuous screw pressing to extract fat from rendered materials, but the ability to minimize residual fat content is limited. In this work, liquid and supercritical CO2 were used to extract the remaining fat from rendered poultry meal. CO2 extraction offers high extraction yields with potential ecological and economic benefits for the rendering industry. A semi-batch extraction unit was used to investigate the effect of pressure (69–345bar), temperature (25°C, 40°C and 50°C), flow rate, and mass of CO2 on the extraction yield and the fat solubility. Maximum extraction yields between 87% and 97% were obtained which produced a remaining fat content of 1.0±0.3wt% in the extracted poultry meal. Fat solubility increased with pressure but decreased with temperature, providing liquid CO2 with the highest fat solubility (6.47g/L) at 25°C and 345bar. The Chrastil model successfully correlated the solubility data as a function of density and temperature, obtaining an AARD value of 5.56%. Gas chromatography was used to analyze the composition of fatty acids, obtaining similar results with those reported in the literature. It can be concluded that high fat extraction yields can be obtained using CO2 and that liquid CO2 is more effective than supercritical CO2 for the extraction of rendered fats under the conditions tested.