(677a) Liquid and Supercritical CO2 Extraction of Fat From Rendered Materials

The processing of rendered materials (RM) allows the separation of fat which results in value-added co-products for energy and up-graded feed sources for animals. The current industry utilizes steam and continuous mechanical press to extract the fat from the RM. The main objective of this work is to investigate the use of CO₂ as a solvent for the extraction of the remaining fat from RM, which will result in ecological and economic benefits for the rendering industry.

Supercritical (SCCO₂) and liquid CO₂ (LCO₂) were employed for the extraction of the fat in RM. Lipids were characterized by gas chromatography and by alkaline titration to determine the fatty acids (FA) composition and the amount of free FA, respectively. A continuous-flow extraction unit was used for the extraction. The impact of pressure, temperature, and mass of CO₂ on the extraction yield and solubility of the fat on CO₂ was studied. The solubility of the fat at the different conditions was calculated from the slopes of the extraction curves. The experimental data was fitted to the Chrastil and Modified Chrastil equations to correlate the solubility as a function of density and temperature.

A maximum extraction yield of approximately of 93% was obtained for all the conditions tested. This means that no significant difference was observed in the maximum total amount of fat extracted as an effect of temperature and pressure only. However, the mass of CO₂ used for the extraction was greatly changed due to the solubility of the fat. The highest solubility (6.47 g.L^-1) was reached at 25˚C and 5,000psi – being this the highest density used in this work. The solubility of fat significantly increased when using higher densities of CO2. This behavior was very well correlated by both models used to predict the solubility, with values of average absolute relative deviation (AARD) around 5.5%. It can be concluded that high fat extraction yields can be obtained using CO₂ in RM; and that at the same pressures, LCO₂ is more effective than SCCO₂.