Enzymatic Hydrolysis Enhances the Stability of Mannoprotein-Stabilized O/W Emulsion and the Protective Effect on β-carotene

Yeast mannoprotein (MP), an important constituent of the yeast cell wall, is a glycoprotein composed of protein and mannan and can be applied as a protein-polysaccharide-based emulsifier. In this study, based on the high content of mannan of MP, the mannan in MP was hydrolyzed to different degrees using Pullulanase to generate MP hydrolysates (DH1, DH2, and DH3) with varying degrees of hydrolysis of 28.178%, 55.482%, and 72.454%, respectively. The relative emulsions (DH1-E, DH2-E, and DH3-E) were prepared, and the effects of different hydrolysis degrees on the emulsion stability, microstructure, and protective effect on β-carotene (BC) were explored. The results showed that enzymatic hydrolysis increased the electrostatic repulsion between emulsion droplets and increased the average particle size of the droplets. The BC-loaded DH2-E (DH2-BCE) had the highest apparent viscosity. In addition, compared with NH-BCE and DH1-BCE, the bioavailability and retention of BC were significantly higher in both DH2-BCE (66.657% and 15.576%) and DH3-BCE (64.361% and 12.921%) (p < 0.05). This study demonstrates that a certain enzymatic hydrolysis can help stabilize MP emulsion and protect β-carotene, which will provide a theoretical basis for applying MP in stabilizing bioactive molecules.