Interfacial Behaviour of Egg Yolk Extracts

Egg yolk, due to its emulsifying properties has a long – term tradition in food technology applications. Additionally, egg yolk extracts obtained through simple procedures were proved to be an attractive alternative to highly purified phospholipids. The aim of this work was to analyse the interfacial behaviour of previously described extracts in relation to liposomes preparation. The extracts underwent analysis of surface properties: the π-A isotherm, dilatational and stress rheology experiments as well as surface potential analysis with the use of Langmuir trough. It was proved that EA, MA and HE films were characterized by the highest collapse pressure during compression, but revealed relatively large hysteresis, suggesting irreversibility. CE extract showed minor hysteresis and high reversibility of orientation changes. The most important factor determining the elastic response on area deformation is the content of phospholipids. The lysophosphatidylcholine/phospholipids ratio is also the important factor. The balance between polar and non-polar fraction of lipids and high content of phopsholipds fraction in the film are conducive for solid-like response on shear stress whereas the presence of lysophosphatidylethanolamine induce fluid-like behaviour of this complex film. Minor film constituents significantly affect properties of the film too. MA and EA extracts revealed the highest similarity. CE and HE extracts also showed significant similarity to each other, whereas H extract differed from each.