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 fieldThis work has been funded by the Spanish Ministry of Science and Innovation under project MALTA-Consolider Ingenio 2010 (CSD2007-00045), by the Spanish Ministry of Economy and Competitiveness under projects AGL2012-39756-C02-01/ALI, CTQ2015-67755-C2-1-R and MAT2015-71070-REDC, and by GRUPOS UCM 910481Peer reviewe