Effect of thermomechanical treatment on the aggregation behaviour and colloidal functionality of β-Lactoglobulin at high concentrations

Thermomechanical treatment of β-Lactoglobulin (βLG) protein systems at concentrations above 50% (w/w) leads to the formation of aggregates stabilised by disulphide bonds and non-disulphide covalent bonds. Although thermomechanically treated samples had lower solubility, depending on the treatment conditions, the viscosity of dispersions containing 10% untreated and treated βLG increased from 0.01 Pa·s to 300 Pa·s, respectively. Additionally, the interfacial tension at the oil-water interface decreased from 13.5 mN m⁻¹ to 11 mN m⁻¹ depending on treatment conditions, probably due to the presence of native and small water-soluble aggregates in the continuous phase. Consequently, the emulsions prepared with treated samples were more stable and showed smaller Sauter mean diameters. Furthermore, samples with high degree of aggregation showed an increased thermal stability and formed cold-set gels when dispersed in water. In contrast, heating dispersions of partially aggregated samples resulted in the formation of heat-set gels due to a second gelation process.