ORIGINAL PAPER Phase Equilibrium Measurements of Sacha Inchi Oil (Plukenetia volubilis) and CO 2 at High Pressures Ivor M. do Prado • Willyan M. Giufrida • Vı ´ctor H. Alvarez • Vladimir F. Cabral • So ´crates Quispe-Condori • Marleny D. A. Saldan ˜a • Lucio Cardozo-Filho Received: 18 November 2010 / Revised: 11 February 2011 / Accepted: 14 February 2011 / Published online: 5 March 2011 Ó AOCS 2011 Abstract New data on phase equilibria for Sacha inchi seed oil in carbon dioxide have been measured using a variable volume cell phase equilibria system at tempera- tures of 303, 313 and 323 K and at pressures ranging from 4.3 to 27.7 MPa. The CO 2 mole fraction varied from 0.7488 to 0.9997. At the studied concentrations, phase transitions of vapor-liquid, liquid-liquid-vapor and liquid- liquid were observed. Sacha inchi oil contains 47% of omega-3 fatty acids, with a ratio of 0.76:1 for omega- 6:omega-3, which is good for human health. The Peng- Robinson equation of state was used to describe the experimental data. A qualitative agreement was obtained between experimental and calculated data for the binary system CO 2 and Sacha inchi seed oil. Keywords Carbon dioxide  Equation of state  High pressure  Omega-3  Phase equilibria  Plukenetia volubilis  Sacha inchi seed oil Introduction The addition of polyunsaturated fatty acids (PUFA) to functional food ingredients and their consumption in die- tary supplements have experienced significant increases [1]. PUFA have been associated with a variety of health benefits such as decrease risk of cardiovascular disease and prevent complications of lipotoxicity [2]. Fish and flax oils are the commonly sources of PUFA [3]. Recently, seeds of Sacha inchi (Plukenetia volubilis) from a Peruvian tree have been commercialized as an alternative source of PUFA due to its high oil (35–60%) and protein (27–33%) contents [4]. Sacha inchi is a millenarian legacy of the Inca civilization that has been cultivated to date by the native communities of the Peruvian Amazon. Sacha inchi seed oil is an excellent source of PUFA, composed mainly by lin- olenic (C18:3 x -3) and linoleic (C18:2 x-6) acids [4]. However, one of the major drawbacks of oils containing a high amount of PUFA is their low stability and rapid oxidation, which involves the formation of toxic products such as peroxides or undesirable off-flavor compounds [5]. Commercially, unrefined Sacha inchi seed oil is pro- duced by cold pressing. Although this process preserves its original composition such as PUFA content, the yield is low (38.4%) compared to Soxhlet extraction (54.3%). But, Soxhlet extraction uses high temperatures that reduce the quantity of PUFA in the oil due to oxidation by high temperature exposure [5, 6]. Therefore, supercritical fluid (SCF) extraction is another alternative process for the extraction of oils [7]. This extraction method exploits the high solvation power, low viscosity, and high diffusion coefficient offered by the supercritical fluid to increase the extraction yield. Phase equilibrium measurements of soybean or castor oil ? supercritical CO 2 and fish oil ? supercritical CO 2 have been reported earlier by Ndiaye et al. [8] and Riha and Brunner [9], respectively. These authors report only pressure transitions and the correlation of their data with equations of state (EoS). There is great interest in ther- modynamic models that are able to correlate and predict I. M. do Prado  V. H. Alvarez  S. Quispe-Condori  M. D. A. Saldan ˜a (&) Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada e-mail: marleny@ualberta.ca W. M. Giufrida  V. F. Cabral  L. Cardozo-Filho Department of Chemical Engineering, Universidade Estadual de Maringa ´, CEP 87020/900 Maringa ´, Parana ´, Brazil 123 J Am Oil Chem Soc (2011) 88:1263–1269 DOI 10.1007/s11746-011-1786-z