The aggregates in heated bovine β-lactoglobulin solutions were separated by high-performance size-exclusion chromatography, and molecular characteristics were measured on-line using multiangle laser-light scattering detection (SEC-MALLS). This technique was proven to be a very useful and valuable approach for characterization of heat-induced β-lactoglobulin aggregates. Using TSK G2000 SWXL and TSK G4000 SWXL silica gel columns connected in series, aggregates up to a molecular mass of 4 × 106 Da could be separated, and complete molecular mass distributions were derived. Up to a molecular mass of 1.5 × 106 Da the molecular masses calculated by the MALLS agreed very well with the results obtained by conventional calibration. The measured molecular mass distributions of the heat-induced β-lactoglobulin aggregates varied strongly with experimental heating conditions (β-lactoglobulin concentration, pH, heating temperature, ionic strength). The results obtained with several β-lactoglobulin concentrations at neutral pH were consistent with a kinetic aggregation model based on thiol/disulfide exchange reactions. The average molecular mass and the radius of gyration of the heat-induced β-lactoglobulin aggregates increased with increasing initial β-lactoglobulin concentration. Keywords: β-Lactoglobulin; aggregation; size-exclusion chromatography; light scattering; molecular size

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Stable and homogeneous emulsion‐filled gels were prepared by cold gelation of whey protein isolate (WPI) emulsions. A suspension of heat‐denatured WPI (soluble WPI aggregates) was mixed with a 40% (w/w) oil‐in‐water emulsion to obtain gels with varying concentrations of WPI aggregates and oil. For emulsions stabilized with native WPI, creaming was observed upon mixing of the emulsion with a suspension of WPI aggregates, likely as a result of depletion flocculation induced by the differences in size between the droplets and aggregates. For emulsions stabilized with soluble WPI aggregates, the obtained filled suspension was stable against creaming, and homogeneous emulsion‐filled gels with varying protein and oil concentrations were obtained. Large deformation properties of the emulsion‐filled cold‐set WPI gels were determined by uniaxial compression. With increasing oil concentration, the fracture stress increases slightly, whereas the fracture strain decreases slightly. Small deformation properties were determined by oscillatory rheology. The storage modulus after 16 h of acidification was taken as a measure of the gel stiffness. Experimental results were in good agreement with predictions according to van der Poel's theory for the effect of oil concentration on the stiffness of filled gels. Especially, the influence of the modulus of the matrix on the effect of the oil droplets was in good agreement with van der Poel's theory.

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