Protein–protein interactions of a whey–pea protein co‐precipitate

Summary The aim of this study was to investigate the mechanisms behind protein–protein interactions in a co‐precipitate of whey protein isolate (WPI) and pea protein isolate (PPI). A co‐precipitate and blend, consisting of 80% WPI and 20% PPI, were compared. Covalent disulphide interactions were studied by blocking of free thiols with N ‐Ethylmaleimide (NEM), while electrostatic interactions were studied in systems with 0.5 m NaCl and hydrophobic interactions with 0.2% SDS. Protein solubility, stability and secondary, tertiary and quaternary protein structures were analysed. Co‐precipitation did not introduce different protein–protein interactions than the direct blending of proteins. SDS affected solubility ( P < 0.05), secondary and tertiary structure. However, the effects of NEM and NaCl were significant greater ( P < 0.05) on the same parameters and thermal stability, especially when combined ( P < 0.01). Thus, the protein–protein interactions in a whey–pea co‐precipitate and protein blend consisted of disulphide bonds and electrostatic interactions.