Kinetics of beta-lactoglobulin (beta-Ig) thermal aggregation at pH 3.35, 85 degrees C, and 2-8% w/w protein concentration was studied using high performance liquid chromatography (HPLC) coupled with multi-angle laser light scattering (MALS) and rheology. Rate of beta-Ig aggregation was found to be of first order with respect to the initial protein concentration, and the conversion of native-like beta-Ig monomers/dimers (< 36 kDa) to aggregates increased with initial concentration and heating times. The size of the aggregates formed during heating was dependent on the initial protein concentration. A simple nucleation and growth model was described for the beta-Ig aggregation at pH 3.35, where nucleation was found to be a rate limiting step below the previously identified critical concentration, C(c) similar to 6.4% protein. Above the C(c), nucleation occurred quickly and was not rate limiting. Critical size of the nucleus varied with protein concentration, with larger critical size needed at lower protein concentrations. (C) 2011 Elsevier Ltd. All rights reserved.