Electrostatic complexation of β-lactoglobulin aggregates with κ-carrageenan and the resulting emulsifying and foaming properties

The electrostatic complexation of protein and polysaccharide and the functional properties of the complexes are significantly affected by the structure of protein aggregates and are important in the development of new food ingredients. In this work, natural globular β-lactoglobulin (NGBLG), β-lactoglobulin nanoparticles (BLGNP), and β-lactoglobulin fibrils (BLGF) were prepared and complexed with κ-carrageenan (κ-car). Phase diagrams of the NGBLG–, BLGNP–, and BLGF–κ-car systems were established and divided into 4 regions: mixed soluble polymers (I), intramolecular soluble complex (II), intermolecular soluble complex (III), and intermolecular insoluble complex (IV). Aggregation shifted the boundaries of regions III and IV of BLGF– or BLGNP–κ-car to lower pH and higher protein aggregates/κ-car weight ratio (r), especially for BLGF–κ-car. The emulsifying and foaming properties of the 3 mixed systems were investigated in regions I and II. Complexes in region II had significantly better emulsifying properties than the corresponding mixtures in region I and the pure protein aggregates. Interestingly, phase separation resulted in different effects on the foaming properties of the 3 BLG–κ-car complexes, in which BLGF–κ-car complexation in region II decreased the foaming properties in region I but the complexation of NGBLG–κ-car and BLGNP–κ-car in region II increased the foaming properties. The BLGF–κ-car complex in regions I and II provided the best emulsifying and foaming properties. Interfacial data both on oil–water and air–water interfaces overall explained the emulsifying and foaming properties of the complexes.