This study produced 30 whey- and casein-based cow's milk protein hydrolysates and compared their immunogenicity and sensitizing capacity in a Brown Norway rat model, testing whether the degree of hydrolysis (DH) predicts allergenic risk. Alongside DH, peptide size, thermal denaturation and surface hydrophobicity, the researchers used Flow Induced Dispersion Analysis (FIDA) on a Fida 1 instrument (Taylor Dispersion Analysis with label-free UV fluorescence) to measure the hydrodynamic radii of the hydrolysates and quantify large nano-sized aggregates. DH proved a poor predictor of sensitizing capacity, with surface hydrophobicity most associated with higher IgE. It is an example of using FIDA to size proteins and aggregates in solution, label-free.