Emulsification properties of bovine milk protein isolate and associated enzymatic hydrolysates

Oil-in-water (O/W) emulsions were prepared using bovine milk protein isolate (MPI) or MPI hydrolysates containing 1.60% (w/v) protein, 3.60% (w/v) lipid blend and 7.00% (w/v) lactose. The role of enzymatic treatment of MPI with Flavourzyme™, Neutrase™ and Protamex™ at two hydrolysis time points per enzyme [ranging in degree of hydrolysis (DH) from 15.6 to 37.1%] on the emulsifying properties was determined. All emulsion samples had mean fat globule size (d₄₃) values < 1 μm after homogenisation. The hydrolysate containing emulsions displayed reduced emulsion stability under accelerated storage conditions, i.e., following an applied centrifugal force, and reduced heat stability at pH 7.0 compared with emulsions formed using intact MPI. The results demonstrated that hydrolysis reduced emulsion stability in the model system studied. Emulsion instability was hydrolytic enzyme dependent, increased with increasing DH and increasing content of peptides <1 kDa.