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The objective of this syudy was to investigate the effect of
dilution of chicken egg white (EW)(EW:H2O=1:1-1:5), water
cooking temperature and cooking time, pH and salt (sodium
chloride) concentration on the thermal aggregation of egg white.
The physiochemical properties and changes of egg white
appearance were also observed. Results showed that protein
concentration, heating conditions and pH have effects on the
degree of aggregation. That is, the higher the protein
concentration and heating temperature in egg white, the greater
the degree of aggregation. Increasing the degree of dilution,
the pH range of thermal non-coagulated egg white was also
increased. With four times diluted EW (DEW)adjust to pH 3.0, and
heated at high temperature(>90℃ ), the degree of protein
aggregation was reduced, and more likely to obtain turbid liquid
of thermal non-coagulation. With three times DEW and adjust pH
to 9.3, it is more likely to become transparent liquid of
thermal non-coagulation.The addition of NaCl at 0.01-0.35 M
affected the degree of EW aggregation. Icreeasing the
concentration of NaCl will decrease the degree of aggregation of
two times DEW at 60℃ .In addition, the molecular weight of EW
aggregate was increased and the concent of SHs and
hydrophobicity were decreased. When heated at 60 , the SH
concent of egg white decreased, and soluble aggregates were
obtained only pH 7.0(0.35 M NaCl), pH 9.0 and pH 9.5.The
hydrophobicity was varied, becausethe repulsion environment
against the ionic strength of four times DEW. When heated
athigher temperature(90℃ and 120℃ ), the increase of NaCl
concentration resulted inthe increase degree of aggregation. The
hydrophobicity interaction and SH oxidation or SH/SS exchange
resulted in the reduction of SH content and hydrophobicity. From
the variation of electrophoregram and the distribution of
molecular weight indicatingthe molecular weight of soluble
aggregates is larger. Results showed that the higher the degree
of aggregation, the lower the protein concentration, SHs content
and hydrophobicity of the thermal non-coagulated egg white. It
is proposed that egg white protein gradually changes while
heating and becomes aggregates by polynerization.First,
hydrolyze two side polypeptide bonds the polymerize with the
formation ofhigh molecular weight and viscosity of aggregates by
hydrophobicity interaction and SH oxidation. The results showed
that protein concentration, pH, SH group and hydrophobicity all
effected the degree of aggregation and transparency of
thermalnon-coagulated egg white.
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