A semi-batch fractionation of a synthetic mixture of fatty acids ethyl esters was carried out by means of supercritical carbon dioxide. The feed was composed of five ethyl esters of fatty acids of different chain length (from C14 to C22), chosen in order to represent a typical product derived from esterification of sardine oil. C20 and C22 classes were represented by EPA and DHA, which are the two major v-3 fatty acids. The results obtained show that the process is capable of producing a raffinate rich in EPA and DHA. A modellization of the process based on the Peng-Robinson equation of state was developed. Two binary parameters related to interactions between CO2 and ethyl esters were used.

Production of long chain polyunsaturated fatty acids (PUFA) of the v-3 series has become a very important issue because of their increasing commercial interest in recent years. In fact, since many researches have pointed out that the typical Western diet is characterised by a high ratio v-6/v-3 that leads to several health diseases, production of foods artificially enriched in v-3 and dietary supplements based on v-3 have concerned food and nutraceutical industries. Furthermore, v-3 PUFA are under investigations for their potential application in the pharmaceutical industry because they have been proved to have a pharmacological action with respect to several health diseases. From this point of view, the eicosapentaenoic acid (EPA) and the docosahexaenoic acid (DHA) are the focus of many clinical and biochemical researches. One of their most promising fields of application is the treatment of some cardiovascular diseases, as it was recently confirmed by a clinical study on this subject. The main source of EPA and DHA are mixtures of ethyl esters derived from transesterification of fish oils. EPA and DHA enrichment of these mixtures can be obtained by conventional processes (such as vacuum distillation, urea crystallisation and hexane extraction) but they are liable to produce low quality products because of PUFA thermal degradation or because of the presence of some residual solvent in the final product. On the other hand, it has been shown that supercritical carbon dioxide is an effective solvent for ethyl esters, showing a selectivity that mainly depends on the length of the carbon chain. Due to the demand of high quality products, fractionation by means of supercritical carbon dioxide appears to be more suitable than conventional processes because of the low temperatures required and the complete solvent separation from the final product that can be achieved. In this work, a semi-batch fractionation of a synthetic mixture of fatty acids ethyl esters (FAEE) was performed by means of supercritical carbon dioxide. The data obtained were used to check the capability of the Peng and Robinson equation of state (PREOS) for simulating the supercritical process. This study, focused on the thermodynamic characterisation of a synthetic feed and on the modellization of a single-stage process, is intended as an intermediate step in order to develop a simulation of a multistage process on a natural feed derived from fish oils.