Structural changes and functional properties of highly concentrated whey protein isolate-citrus pectin blends after defined, high temperature treatments

- Structural analyses indicate the formation of Maillard reaction products.
- Improved emulsifying capacity after temperature treatments at 120 °C and 140 °C.
- Emulsifying capacity apparently depends on fluorescence intensity.
- Physically stable emulsions over a period of 15 days.

Extrusion processing can be used for conjugation of whey proteins with citrus pectins. However, many reactions can take place simultaneously, and so far less is known about the influence of the extrusion parameters on the structural and functional properties of the reaction products. This study focuses on the influence of elevated temperatures on the structural and functional properties of highly concentrated whey protein isolate-citrus pectin blends. Defined temperature treatments were performed by using a closed-cavity rheometer. Structural changes due to non-disulfide, covalent cross-links, and the formation of fluorescent compounds were analyzed. Functional properties (e.g. viscosity, emulsifying capacity) were determined of selected samples. The results showed that the emulsifying capacity can be improved by defined temperature treatments at 120 °C and 140 °C. Samples with an improved emulsifying capacity also exhibited higher maximum fluorescence intensity indicating the formation of Maillard reaction products (e.g. conjugates).