The influence of sodium caseinate and β-casein concentrate on the physicochemical properties of casein micelles and the role of tea polyphenols in mediating these interactions
Tessa M. van de Langerijt, James A. O’Mahony, Shane V. Crowley
Abstract
The influence of different casein-based ingredients on the physicochemical properties of native casein micelles (CMs) was studied. Sodium caseinate (SCN) and β-casein concentrate (BCC) were mixed with milk protein concentrate (MPC) at different ratios (1:3, 1:1, 3:1), at a total protein concentration of 20 g/L. Tea polyphenols (TPP) were added to select samples to investigate their effect on CM-SCN and CM-BCC interactions. The results demonstrated decreasing structural integrity of CMs and increased levels of non-micellar casein, due to addition of SCN to MPC, which led to a decreasing turbidity over time and an increase in surface hydrophobicity. Addition of BCC to MPC resulted in an increase in turbidity over time and a decrease in surface hydrophobicity of the system. TEM images suggested that small micelles from BCC interacted with the surface of CMs. The SDS-PAGE results show that CMs in samples with TPP dissociated less, indicating that TPP stabilized the CMs structure. In conclusion, the two casein ingredients, SCN and BCC, have a different effect on the colloidal and physicochemical properties of CMs in MPC suspensions. This study will contribute to a greater understanding of the effect of mixed protein formulation strategies on the functional properties of beverage systems.