Oil-in-water emulsion properties of egg yolk: Effect of enzymatic modification by phospholipase A2

Emulsifying properties of egg yolk were investigated after a treatment with phospholipase A2 (PLA2) where phospholipids (PLs) are converted into lyso-phospholipids. The resulting lyso-PLs are more hydrophilic and therefore show improved emulsifying activity in o/w-emulsions. However, so far no systematic study deals with the changes of egg yolk's functionality due to enzymatic treatment. Little is known about the emulsion properties particularly in different environmental conditions. Egg yolk's functional behaviour is highly dependent on pH and salt concentration used. Therefore, this study investigated four different environmental conditions. At pH 4 the pH of commercial dressings is simulated and pH 6.5 represents the pH of untreated egg yolk in its natural form. Two salt concentrations are used, where granules are in their native and their disrupted form, i.e. 0.15 and 0.52 M NaCl, respectively. Results suggest that significant differences in the emulsifying properties of untreated and modified egg yolk not primarily derive from the existence of lyso-phospholipids but from structural changes in egg yolk granules and LDL micelles.