Abstract: In this study, whey protein isolate (WPI) was heated at 85 ℃ for 12 h under different pH conditions (pH 2.0 and 7.0) to prepare two different forms of protein aggregates, and the morphological characteristics and emulsifying properties at different pH and salt concentrations of the aggregates were evaluated. The microstructure, salt stability and thermal stability of Pickering emulsions stabilized with WPI and the two aggregates were comparatively investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS) and optical microscopy. The results showed that fibrous and spherical aggregates were obtained at pH 2.0 and 7.0, respectively. The isoelectric points (IP) of the two aggregates shifted away from that of WPI, and the emulsifying activity increased at all pHs and salt concentrations tested compared with WPI. Moreover, the Pickering emulsion stabilized by the aggregates had better stability to severe environments. Notably, the spherical aggregates had better thermal stability. This study provides a basis for the application of Pickering emulsions stabilized WPI aggregates in milk beverages.

Key words: whey protein isolation; aggregation; emulsifying properties; stability