Determination of heat-induced effects on the particle size distribution of casein micelles by dynamic light scattering and nanoparticle tracking analysis

The change in particle size distribution of casein micellar dispersions induced by heating both in the absence and presence of whey proteins was investigated by two techniques. Whereas dynamic light scattering (DLS) is an ensemble technique that tries to recover a particle size distribution from the combined signal of all particles present in the sample, nanoparticle tracking analysis (NTA) investigates the diffusion of individual particles. Both DLS and NTA indicated that heating of casein micellar dispersions in the presence of whey proteins gave rise to a bimodal distribution. Whereas the small diameter mode was not significantly affected by heating, an additional large diameter mode was obtained. This observation indicated the increase in average particle size to be primarily a consequence of casein micellar aggregation, which in itself is a further consequence of heat-induced whey protein deposition onto the casein micelles.