Rehydration of whey protein isolate: Effect of temperature, water activity, and storage time

Hydration properties of Whey Protein Isolate (WPI) powder is important in food and pharmaceutical applications. However, the understanding of hydration properties of whey protein powders is limited. The present study focused on WPI at high concentrations and high solids systems. Amorphous WPI were humidified over a wide water activity, aw, range (0.11–0.85aw). WPI aqueous dispersions were prepared at 5, 10, 20, 30, and 40% (mass). The rehydration/hydration transition of WPI was time- and temperature-dependent. Variation in protein hydration resulted in aw hysteresis during the dynamic heating and cooling steps. The physical flow behaviour of WPI dispersions was significantly higher at ≤35 °C, corresponding to increased protein hydration at low temperatures in agreement with DSC data. The loss of viscosity of protein dispersions around 35 °C was related to changes in protein conformation. Our results suggest that dehydration of WPI occurred at increasing temperature. •The hydration transition of whey protein isolate is time-and temperature dependent.•The rehydration of whey protein isolate powder is effective at ≤35 °C.•Changes in protein conformation around 35 °C is associated to protein rehydration.