Deodorization and deacidification of edible oils with dense carbon dioxide

Abstract

AbstractNear‐critical carbon dioxide shows potential for extraction of free fatty acids, off‐odors or flavors from edible fats and oils. Deacidification and deodorization of a simulated, roasted peanut oil with dense CO2 was performed at various temperatures, pressures and extraction factors in a pilot‐scale, packed extraction column with an i.d. of 2.86 cm and a height of 162 cm. Pyrazine and its derivatives are major components of roasted peanut aroma. At constant temperature and pressure, the distribution coefficient (m) for pyrazine derivatives was inversely related to the degree of substitution of methyl groups (molecular weight) and boiling point, that is, the solubility was directly related to the compounds volatility. CO2 fluid‐phase density alone could not explain the equilibrium solubility behavior of either fatty acids or pyrazines. At constant fluid‐phase density, m for pyrazine derivatives decreased with increasing pressure and temperature, while that for fatty acids increased. At 20 MPa pressure, increasing the temperature from 47 to 57°C increased m for pyrazines, but decreased m for fatty acids, indicating that the system was within the retrograde region for fatty acids. Free fatty acid solubility was inversely related to chainlength and, in the supercritical region, directly related to the degree of unsaturation. Deodorization is mass‐transfer‐controlled, and deacidification is thermodynamically constrained. The efficient deodorization and deacidification of an actual crude oil pressed from roasted peanuts was accomplished by extraction with CO2 at 47°C and 20 MPa. Extraction with carbon dioxide may be particularly useful for deacidifying expensive specialty fats with high initial acidity, or where the quality and purity of the extracted components are of importance.