Rheological Properties of High Pressure Milk Cream

AbstractThe High Pressure (HP) treatment induces significant changes on the milk macromolecules (proteins, whey proteins and caseins), as well as on its functional properties, which allow its application in innovative dairy productions. The aim of this work was to setup the process condition and product formulation to produce a milk cream under pressure and evaluate and model its rheological behaviour. Some preliminary experiments (pressure level=400-500 MPa, time=5-10 min, temperature=25°C) were carried out to optimize the processing parameters inducing milk coagulation. Moreover, different milk concentrations (50%, 60%, 70%) were tested to identify the concentration values able to achieve the optimal creaminess of the high pressure milk cream. The latter information was obtained analyzing the results of rheological static and dynamic tests. According to several literature studies, preliminary results indicate that the milk coagulation occurs at a pressure level of 500 MPa and ambient temperature after 10 minutes of treatments. The dynamic rheological analysis demonstrate that the compactness of HP milk cream increases with increasing the milk concentration of the product, while the values of the G ‘and G” modules of the unprocessed concentrated milk are similar to those of the fresh milk. Therefore, as milk concentration doesn’t affect the rheological behaviour of the cream, the higher compactness observed can be attributed to milk coagulation under pressure. The stationary rheological tests, indeed, indicate that the HP milk cream behaves as a non-Newtonian pseudo-plastic fluid, whose stress-strain relationship can be described by a power law model equation. This rheological behaviour is due to the milk macromolecules, which conglomerate under pressure, tend to align and provide greater resistance to flow