High pressure treatment of dairy products

From 200 MPa onwards, brining of Gouda cheese by high pressure leads to a p H-shift, which becomes smaller during ripening. This pH-shift was also foun d in the serum that was pressed from the cheeses brined at 0.1 and 300 MPa. A higher dry matter content in the serum was observed, which was due to a higher non-protein and protein nitrogen content. Disruption of the paracase in network was found yielding more proteins, especially beta-casein and pep tides in the serum. In order to study the effects of high pressure treatment on the proteolysis and rheological properties of Gouda cheese cylinders, a central composite design was used varying pressure (50-400 MPa), holding time (20-100 min) an d ripening time after pressure release (0-42 days). Pressure treatment didn 't influence the pH 4.6-soluble nitrogen and phosphotungstic acid soluble n itrogen content, while the free amino acid content was slightly decreased, especially at higher pressures. Hence, the proteolysis by chymosin and plas min is not influenced by pressure; while the proteinase, peptidase system o f the starter is slightly retarded at higher pressures. From 225 MPa onward s, pressure treated samples had a lower storage and loss modulus, and a hig her phase angle. Also, by pressure treatment, the cheese gets less solid-li ke and more viscoelastic. In addition, pressure treated cheese had less res istance to flow at longer times. After 42 days of ripening, however, no dif ferences could still be observed between pressure treated and not-pressure treated cheese.