Improved Approaches to Separate High-Value Phospholipids from Egg Yolk

Egg yolk contains approximately 10% (w/w) phospholipids (PL), of which about 70% is phosphatidylcholine (PC). Conventional methods of PL extraction from egg yolk involve using hazardous organic solvents. Supercritical carbon dioxide (SC-CO2), as a "green" solvent, had been applied for the extraction of PL from egg yolk but resulted in limited success due to low recovery and purity of the final extracted PL.;Low-density lipoproteins (LDL) contain about 90% of PL from egg yolk. Possible interaction between egg yolk components and polysaccharides can be a potential technique for LDL separation. A simple method was proposed to isolate LDL from egg yolk using 0.2% to 0.6% xanthan gum at egg yolk natural pH. The mechanism of LDL separation with xanthan gum was suggested to be a combination of different interactions such initial electrostatic and hydrophobic forces and physical properties of the polysaccharide and its complex with egg yolk LDL such as shear thinning behaviour of xanthan gum solution and density difference of LDL-xanthan gum complexes. PL is a high-value component from egg yolk with potential applications in pharmaceutical and nutraceutical industries. Developing methods to improve the recovery and purity of PC and PL from egg yolk while eliminating hazardous organic solvents use will help to protect the environment and enhance food safety.;Hydrolysis of egg yolk after soluble proteins removal, referred to as pellet, by a combination of protease and Lipase AY30 reduced emulsion stability evident by larger oil droplets size and higher coalescence index. A cream fraction obtained from Protease P and Lipase AY30 treated egg yolk pellet was subjected to PL extraction using SC-CO2 in the presence of 8% ethanol as a co-solvent. The enzymatic treatment with Protease P and Lipase AY30 significantly improved the recovery of PC from 47% in dry yolk to 85%, 70% and 61% for dry, intermediate-moisture cream (20%), and “as is” cream (45% moisture), respectively, based on initial yolk weight. A higher purity of PC and PL (84% and 103%) was obtained by using hydrolysed pellet with the intermediate moisture content (20%), compared to dried egg yolk sample.