Evidence of low-density water to high-density water structural transformation in milk during high- pressure processing

The objective of this research was to check whether the observed low-density water (LDW) to high-density water (HDW) transformation does take place or not in a complex aqueous system like those involved in high pressure processing of food. In-situ measurements of speed-of-sound up to 640 MPa were used for this purpose. After validation of the methodology in liquid water at 25 oC, LDW-to-HDW transformation was also evidenced in sodium caseinate solution and milk samples. The transformation pressure was always observed at 275 MPa. Since water plays a key role in most biochemical transformations, the occurrence of a LDW-HDW transition should be taken into account for understanding the complex component interactions in milk and other related systems under pressure. Industrial relevance: Opportunities exist for the industry to use pressure as a tool for texturing dairy products. Process parameter choice to obtain a given texture is tricky due to the complexity of milk component interactions under pressure. As a main component in foods, water structural transformation under pressure should not be ignored by experts in the field.