Heat-induced interaction between egg white protein and wheat gluten

Some wheat-based food systems, such as cakes and cookies, include mixtures of gluten and egg white protein (EWP) and are processed under heating conditions. Changes in these proteins during processing can affect the quality of the end product. This study investigated protein polymerization during heating of (mixtures of) wheat gluten and EWP. Chemical changes were studied by size-exclusion high performance liquid chromatography (SE-HPLC), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), thiol (SH) measurement and Fourier transform infrared (FTIR). During heating, protein polymerization was observed in the mixtures of gluten, glutenin, gliadin and EWP according to SE-HPLC profiles and results of SDS-extractable protein. The results of SDS-PAGE profiles of different proteins were in accordance with SE-HPLC. The number of SH groups in the majority of proteins showed a significant decrease, implying that disulfide (SS) bonds contributed to the extractability loss. In addition, changes of secondary structure tested by FTIR indicated protein aggregation.