Impact of high hydrostatic pressure on the micellar structures and physicochemical stability of casein nanoemulsion loading quercetin

Natural casein is a highly structured protein and the characteristic of self-assembly makes the formation of micelles, thus negatively limiting the applications. High hydrostatic pressure (HHP), as a novel non-thermal process, can modify the structures of protein and improve the related functionalities. In this study, micellar casein was subjected to HHP treatment from 100 to 500 MPa, which then loaded quercetin and formed the nanoemulsion. The thermal, pH, ions and physical stability of nanoemulsion were comprehensively investigated. The results showed 300–500 MPa could effectively disintegrate the micellar structures of natural casein by dissociating colloidal calcium phosphate, which significantly improved the emulsifying activity and encapsulation efficiency. However, 500 MPa caused the nanoemulsion loading most quercetin and subsequently showed the better physical and ions stability in comparison with control and 100–400 MPa. Therefore, HHP is expected to modify the high-order structure of casein, which becomes the ideal nano-vehicles for hydrophobic bioactive substances.