Initial study on high pressure jet processing using a modified waterjet on physicochemical and rennet coagulation properties of pasteurized skim milk

Developments in material science and engineering have enabled high pressure jet (HPJ) processing at >500 MPa. The objective of this study was to characterize the physicochemical properties of pasteurized skim milk processed at pressures from 0 to 500 MPa using waterjet technology, to explore novel uses of this technology for milk. The apparent particle size of casein micelles increased from approximately 180–220 nm in milk processed from 0 to 200 MPa to approximately 280 nm in milk treated at 500 MPa. All milk samples were shelf-stable up to 14 days at 4 °C. The viscosity of skim milk processed at 400 and 500 MPa almost doubled (4.2 mPa s) when compared with control unprocessed milk (2.2 mPa s). Increasing HPJ processing pressure changed the structure–function properties of the casein micelles and no rennet-induced coagulation was observed for milk processed at 500 MPa.