Improvement of emulsifying and loading properties of whey protein isolate via ultrasound-assisted alkali pretreatment and carboxymethyl cellulose interaction

Whey protein isolate (WPI) is a by-product of the dairy industry. It exists as compact globular structure that always limits its wide applications. This research aimed to improve the emulsifying and loading properties of WPI through ultrasound-assisted alkali pretreatment and carboxymethyl cellulose (CMC) interaction. The results demonstrated enhanced solubility and reduced size of WPI following the pretreatment of ultrasound-assisted alkali. Circular dichroism spectra showed that alpha-helix content decreased from 14.8% to 12.8%, and the number of random coils increased from 30.6% to 37.2% (P < 0.05). Fluorescence spectra showed more hydrophobic amino acids were exposed. When WPI underwent ultrasound-assisted 0.01 mol L-1 NaOH and was complexed with CMC (4:1, w/w), the resulting emulsifying properties were improved compared to the control. The emulsions stabilized by modified WPI/CMC composites had greater encapsulation efficiency on curcumin, resulting in improved protection against UV light and thermal degradation. This study confirmed that ultrasound-assisted alkali pretreatment and CMC complexation could improve the emulsifying and loading ability of WPI.