Co-precipitation of whey and pea protein -indication of interactions

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The aim of this study was to investigate the mechanisms behind protein-protein interactions in a coprecipitate 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.

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