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Dynamic adsorption and interfacial rheology of whey protein isolate at oil-water interfaces: Effects of protein concentration, pH and heat treatment
Zhou, Beibei Tobin, John T. Drusch, Stephan Hogan, Sean A.
Zhou, Beibei
Tobin, John T.
Drusch, Stephan
Hogan, Sean A.
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2021-07
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Beibei Zhou, John T. Tobin, Stephan Drusch, Sean A. Hogan, Dynamic adsorption and interfacial rheology of whey protein isolate at oil-water interfaces: Effects of protein concentration, pH and heat treatment, Food Hydrocolloids, Volume 116, 2021, 106640, ISSN 0268-005X, https://doi.org/10.1016/j.foodhyd.2021.106640.
Abstract
The effects of bulk protein concentration, Cp, (0.01, 0.1, 1 wt%), pH (3, 4.7 and 7) and heat treatment (unheated or 95 °C for 30 min) on whey protein isolate (WPI) stabilized interfaces were examined. The interfacial pressure and shear rheology of WPI-stabilized sunflower oil-water (o/w) interfaces were characterized using a pendant drop tensiometer and a rheometer equipped with a Du Nöuy ring. The rate of WPI adsorption was faster at higer Cp and pH 3. Heat-enhanced surface activity was more pronounced at pH 7 compared to pH 3 as a result of greater heat stability of WPI at acidic pH. The elastic modulus of WPI stabilized interfaces increased with Cp (≤0.1 wt%). A further increase in Cp (to 1 wt%) resulted in monolayer collapse and weaker films. Non-heated (NHT) WPI formed less elastic interfacial films at pH 3 than at pH7. Heat treatment enhanced the elastic behavior of interfacial films with longer relaxation times. This may be associated with the formation of intermolecular β-sheets. The knowledge gained on the nature of WPI-stabilized interfaces can be used to better understand the stability of dairy emulsions during subsequent processing, digestion or storage.