Probing the binding between norbixin and dairy proteins by spectroscopy methods

► Complex formation was observed between norbixin (annatto) and dairy proteins. ► Norbixin had higher binding affinity with sodium caseinate than with WPI. ► The effects of pH on binding between norbixin and dairy proteins were not apparent. ► Binding affinity was the strongest for BSA-norbixin and kappa-casein-norbixin among whey proteins and caseins, respectively. ► Complexation by norbixin changed the conformation of dairy proteins, with varying extent and trend for each protein.