Rhéological properties of milk derived peptides in high-concentrated casein matrices

Proteins can be hydrolyzed into peptides during food processes or storage. This hydrolysis can enhance the functional properties of food products depending on the type of peptides produced. Most knowledge on peptide functional properties currently comes from dilute solutions, in which both the composition and the protein concentration differs greatly from food products. Moreover, additional information is required to understand the self-assembly of proteins and peptides in complex matrices. Pools of peptides are usually not characterized and a fortiori it is difficult to determine how, and to which extent, the functional properties of proteins are modified due to protein hydrolysis. To answer these questions, we produced pools of peptides, from sodium caseinate, with defined physicochemical characteristics through the action of two enzymes: Trypsin and Glu-C. Three pools were obtained per enzyme, which contain peptides quantitatively and qualitatively different. Advances in sequence identification and structural determination have made possible to characterize the peptides present in the hydrolysates. Controlled amount of these peptides were incorporated into high-concentrated casein matrices in the form of: i) liquids and ii) gels. Then, rheological properties and microstructure of these matrices were studied. Under our conditions (4°C and 20°C, neutral pH, gel or liquid), specific pools of peptides, with various concentrations, modified the rheological properties and the microstructure of high-concentrated casein matrices. This innovative approach gives new ways to study the relationship between physicochemical and structural characteristics of peptides and their functional properties in matrices. This method could be enlarged to various food matrices.