Controlling the aggregation and gelation of ß-lactoglobulin by the addition of its peptides

In this thesis the effects of peptides, or protein hydrolysates on the heat-induced aggregation and gelation of (concentrated) protein systems were studied. First, it was investigated if specific peptides could influence the heat-induced denaturation and aggregation of intact proteins solutions, and which peptide properties dominated the different interactions. Next, the effects of the peptides on the heat-induced gelation of intact proteins as a model for a potential high protein food system were studied.

It was found that certain peptides in the hydrolysate show binding to native proteins, and some additional peptides bind to unfolded proteins. Since the same peptides were shown to bind to not only β-lactoglobulin, but also other to proteins, it is concluded that the binding does not depend on specific molecular details of the protein. The hydrophobicity and charge were found to be important in determining the binding and the effect on aggregation. With the hydrolysates, as well as with two synthesized peptides (modelled on those found in the hydrolysate) it was confirmed that the addition of these binding peptides has significant effects on the heat-induced aggregation. In the gelation experiments performed in this study a dominant effect was found for peptides containing free SH groups. While it is expected that the changes in aggregation behaviour, induced by the binding of non-cysteine-containing peptides also affects the gel properties, this was not found with the techniques used. Finally, disulfide-containing peptides were found to reduce the presence of sulfurous volatiles formed after heating of β-lactoglobulin, WPI and lysozyme.

Since only certain peptides exhibit binding to intact proteins, it is expected that control over the hydrolysis process and, thereby the concentrations of such specific peptides, can be used to produce hydrolysates with specific functionalities in this respect.