Selective Extraction of Phospholipids from Egg Yolk with Supercritical Co2

It is well known that supercritical CO2 (SC-CO2) is very efficient to remove neutral lipids from a variety of matrices, such as plant seeds [1]. The valuable, polar phospholipids (PL) remain behind, which is ascribed to their limited solubility in SC-CO2 [2]. Typically, they are extracted by adding a polar modifier such as methanol or ethanol to the supercritical fluid (SC-fluid) [2-4]. In a recent study, PL could be extracted from egg yolk powder without using a modifier [5]. This was accomplished by 4 subsequent extractions at 517 bar and 40C. The procedure is advantageous, because it is technically simpler and because no conventional solvents are needed. In this study, the extraction of PL from egg yolk is explored in more detail. The extraction is performed with SC-CO2, and the efficiency is examined as a function of time and process parameters such as temperature, pressure and pulsation. Furthermore, the effect of the polarity of the SC-fluid is investigated by adding ethanol as modifier. Within the processing conditions studied, the PL cannot be extracted from egg yolk powder without adding at least 5 mole% ethanol as modifier. The extraction efficiency of the PL increases with the ethanol concentration and with the pressure. The processing temperature shows only a minor effect at a low ethanol concentration.