Physicochemical, emulsifying, and interfacial properties of different whey protein aggregates obtained by thermal treatment

Abstract

To date, few studies are found to compare the interfacial properties of protein aggregates with different structures and characteristics. In this research, different whey protein isolate (WPI) aggregates (native, nanoparticles, and nanofibrils) were fabricated, and characterized, and the emulsifying, and interfacial properties of WPI (native), its nanoparticle, and nanofibril as a function of pH values and salt concentrations were systematically investigated. The Z-average diameters of WPI (native), its nanoparticle, and nanofibril were 10, 355, and 122 nm, respectively. The isoelectric point (IEP) of native WPI was found to be approximately 5.0, whereas IEP of nanoparticles was decreased to 4.7, but increased to 5.5 for nanofibrils. WPI nanofibrils exhibited highest emulsifying activity index (EAI) and emulsifying stability index (ESI) at pH 3.0, whereas WPI nanoparticle had the highest EAI and ESI at pH 7.0. Low salt concentrations can increase the EAI and ESI of proteins. The EAI and ESI were highly correlated with the particle size, zeta-potential, and surface hydrophobicity of protein molecules. A negative correlation between interfacial tension of protein molecules and EAIs was observed regardless of protein types.