Comparative study of the effect of high pressure processing on the residual activity of milk coagulants in buffer and in ultrafiltered cheese

- In the same HIP processing, enzymes in UCF showed 74.4% lower activity than in STFS.
- Low pressures (<275 MPa) increased activity (15-43%) of the all enzymes.
- Higher pressures (450MPa/16min/25 °C) reduced the coagulants activity to < 0.1%.
- Porcine pepsin was the most sensitive coagulant, both in cheese and buffer.

This study aimed to evaluated how the high isostatic pressure (HIP) affects the milk coagulation activity (MCA) of different coagulants in Ultrafiltered (UF) cheese and in a sodium phosphate (SP) buffer solution when processed at 25 °C at different pressures (100-450 MPa) and time (2-16 min). Results showed that all the enzymes had greater sensitivity to HIP when processed in UF cheese (inactivation up to 74.4% higher) than in SP buffer solution, being the maximum condition evaluated (450 MPa/16 min) able to reduces the residual activity of all the enzymes up to 94% and 60% in UF cheese and SP buffer, respectively. In terms of activity increase, higher increase in MCA occurred in UF cheese at pressures up to 275 MPa for recombinant chymosin (20%), calf rennet (24%) and R. miehei protease (17%) and at pressure up to 151 MPa for porcine pepsin (6%) and bovine rennet (8%). Therefore, the results highlight the importance of the media in the consequence of the HIP effects on enzyme and that HIP processing could be an interesting alternative to accelerate proteolysis in matured cheeses (using activity increase conditions) or to allows extension of the shelf life in fresh cheeses (using inactivation conditions), reducing undesirable changes caused by residual coagulant activity.