Investigations on the emulsifying properties of egg white protein : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand. EMBARGOED until 31 December 2019
Egg white proteins (EWP) have excellent foaming and gelling functional properties.
However, their emulsifying properties are considered poor when compared to soy proteins
or milk proteins. Some studies have attributed the poor emulsifying properties to the
hydrophobic amino acid groups buried deeply in the interior of the protein conformational
structure which is crucial for emulsification. Several methods, such as heat treatment,
acid/acid-heat treatment, Maillard reaction, phosphorylation and enzymatic hydrolysis,
have been used by some researchers to improve the emulsifying properties of EWP.
Preliminary experiments carried out in this study showed that oil-in-water (O/W) emulsions
prepared with egg white liquid (EWL) generated lots of visible large aggregates, which no
other study has reported. Therefore, it was important to investigate the factors responsible
for the formation of these aggregates. Investigations into improving EWP's emulsifying
properties could offer opportunities in developing unique and well-defined egg white-based
The objective of this research project was to produce egg white emulsions with little or no
aggregates. This thesis comprises three main parts. The first part focused on the effects of
pH and heat treatment on protein aggregation and partial denaturation of proteins in EWL.
The second part investigated the effects of heat treatment, oil concentration and protein
concentration on the reduction of large visible aggregates in emulsions prepared with EWL.
The third part studied the effect of enzymatic hydrolysis on the degree of hydrolysis and
emulsifying properties of EWP hydrolysates. The emulsifying properties of original EWP
and EWP hydrolysates were characterised in terms of size and zeta (ζ)-potential of emulsion
droplets and emulsion stability (e.g. turbidity, microscopic examination and phase