A central composite design approach was used to optimize the supercritical carbon dioxide (SCCO2) extraction of Italian Walnut oil, considering the effect of pressure (from 82.3 to 317.6 bar), temperature (from 309.7 to 326.5 K) and process time (from 1.5 to 6.5 h) on extraction yield, fatty acid composition and sitosterol content. A multiple regression analysis indicated pressure and time as major parameters influencing the extraction yield. Those parameters also induced changes in the extract compositions giving the opportunity to obtain enriched fractions of polyunsaturated fatty acid (PUFA). Increased PUFA yields were obtained with higher pressure values but, for longer process times, extracts stated augmented amounts of saturated fatty acids. The different solubility behavior of PUFA and other lipids in SCCO2 could be exploited for the production of walnut oil fractions with high PUFA contents that can be considered as starting materials for the development of food supplements or functional foods.
