Time domain nuclear magnetic resonance as a method to determine and characterize the water-binding capacity of whey protein microparticles

Water-binding capacity (WBC) is commonly measured with a centrifugation method in which a sample is hydrated in excess water and the pellet weight after centrifugation defines the WBC. When a dispersion is being analyzed, here containing whey protein microparticles (MPs), the pellet consists of swollen particles and water between the particles. These two water domains in MP pellets were distinguished using time domain nuclear magnetic resonance (TD NMR). This distinction showed that an increase in WBC from 2 to 5.5 g water/g dry matter was mainly due to an increase in water between the MPs. Besides, it was found that TD NMR-measurements could be used to provide accurate values of the amount of water in both water domains in MP pellets. This makes TD NMR therefore a more accurate method to determine the WBC of the whole pellet than weighing the pellet after centrifugation.