properties as measured by the whipping test are presented in Figure 4. Foam expansion was improved slightly by short-time shearing, whereas there was no significant difference in foam stability and foam liquid stability. The results from the longer shearing treatments were consistent with that from the sparging test but the trends were more noticeable. Foam expansion decreased when shearing time was longer than 1 min, and after 3-min shearing both foam stability and foam liquid stability also significantly decreased.
High-speed stirring may partially denature the egg white protein by exposing its interior hydrophobic core, therefore, may show a stronger protein– protein interaction. Over-shearing may cause reduced foaming due to total denaturation of protein, causing protein coagulation and precipitation due to strong intermolecular hydrophobic interaction. Our study quantified the effect of shearing that was suggested by other researchers (Henry and Barbour 1933).