Interfacial properties of whey protein hydrolysates monitored by quartz crystal microbalance with dissipation.

Abstract

Whey protein hydrolysate (WPH) can be used to develop hypoallergenic foods. However, the stabilization mechanism of WPH-stabilized emulsion is not fully understood. Here, a real-time quartz crystal microbalance with dissipation monitoring (QCM-D) was used in conjunction with a rheometer to investigate the interfacial properties of WPH. Initially, the properties of WPH with different (6 %, 8 %, 10 %, 12 % and 14 %) degree of hydrolysis (DH) were investigated. 8 %-WPH demonstrated superior emulsifying (11.49 m²/g, 81.34 min) and foaming properties (14.00 %, 7.78 %). Subsequently, the stability of different WPH-stabilized emulsions were examined. 8 %-WPH emulsion exhibited the lowest centrifugal precipitation rate (4.50 %) and Turbiscan stability index (2.24). Additionally, the 8 %-WPH promoted the adsorption and retention of molecules at the interface, which effectively reduced the interfacial tension. QCM-D measurement further proved that the 8 %-WPH possessed excellent adsorption mass and viscoelasticity. Finally, we characterized the interface-adsorbed WPH. The 8 %-WPH exhibited the highest surface hydrophobicity (1072.60) and flexibility (0.22). Notably, the 8 %-WPH showed the highest β-sheet (41.11 %). This led to stronger interactions between neighboring interfacial WPH molecules, which protected the emulsion droplets from destabilizing factors. Nevertheless, excessive hydrolysis (10 %-14 %) caused WPH molecules aggregation, which consequently diminished the viscoelasticity of the interfacial film and the emulsion stability.