Enhanced foaming and emulsifying properties of high-pressure-jet-processed skim milk

The effect of high pressure jet (HPJ) processing on foaming and emulsifying properties of skim milk was studied. Viscosity of milk significantly increased at HPJ processing pressures ≥300 MPa and particle size distribution became bimodal for milk processed at 400 or 500 MPa. Cryo-electron microscopy of milk processed at 400 or 500 MPa showed formation of non-uniform aggregates of proteins, which were distinctly larger than intact casein micelles. HPJ processing markedly increased the foam expansion index of milk. In addition, significant increases in foam volume stability index and emulsion activity index were observed for milk following HPJ processing at ≥300 MPa. It is suggested that the structural modifications occurring in the micelles due to HPJ processing are primarily responsible for the observed changes in interfacial properties. The ability to modify key functional properties of milk by HPJ processing opens opportunities for milk-based novel ingredient manufacturing.