Unravelling of the water-binding capacity of cold-gelated whey protein microparticles

Abstract

Whey protein microparticles (CG MPs) were made with a cold gelation method. Without shearing or mixing during gelation spherical CG MPs were formed, while shearing or mixing resulted in smaller irregularly shaped CG MPs. The water-binding capacity of pellets (WBC-P) that were obtained after centrifuging CG MP dispersions was remarkably large (11–18 g water/g dry matter), though this value decreased at larger centrifugation speeds.Microscopy images hinted at the presence of two water domains in the CG MP pellets: water within and between the CG MPs. The images also imply that the amount of water within the CG MPs was determined by the centrifugation speed. The amount of water between CG MPs seemed to be defined by the amount of particle-particle interactions that were present, as suggested by the effects of the particles' size and the inhibition of the disulphide bridge formation on the WBC-P.Although microscopy images showed two water domains, only one main peak was found with time domain nuclear magnetic resonance. This was explained by water diffusion from one water domain to the other within the measuring time. This fast diffusion implies that the CG MPs had a relatively open structure. Overall, it was concluded that water-binding by CG MPs was affected by various factors and that a good understanding of the water-binding requires the use of a range of measurements.