Effect of hydration of microparticulated whey protein ingredients on their gelling behaviour in a non-fat milk system

•WPC and two types of MWP were added to non-fat milk and hydrated for different periods of time.•Differences in milk acidification were studied by rheology and 1H nuclear magnetic resonance.•MWP in yoghurt provided a high degree of immobilised water in the protein network as compared to WPC.•60 min hydration of small (<1 μm) microparticles led to high gel strength and water holding capacity.•Large microparticles inhibited the gelation process and weak, low viscosity yoghurt gels.

Two types of microparticulated whey protein ingredients with different particle characteristics were added to a non-fat milk system and allowed to hydrate for different periods of time prior to heat treatment. Differences during acidification of the milk systems were investigated by rheology and 1H nuclear magnetic resonance spin-spin relaxation. The amounts of more or less mobilised water were shown to differ depending on the type of microparticulated whey protein. Large protein microparticles did not actively participate in gel network formation and showed an increased fraction of more mobilised water, and thus higher syneresis upon storage. An enhanced surface reactivity was shown in small microparticles which may also be related to the increased interaction potential of the native whey proteins present.