Combined spectroscopic, molecular docking and quantum mechanics study of β-casein and ferulic acid interactions following UHT-like treatment

Temperature induced interactions between beta-casein and ferulic acid were investigated under ultra-high temperature (UHT) conditions (140 degrees C) utilising a variety of spectroscopic methods. Fluorescence measurements indicate that structural alterations to the protein have occurred; the resulting red shift in tryptophan peak fluorescence with increasing concentrations of ferulic acid indicates that the single tryptophan residue has become more exposed to the polar environment. This evidence is further supported by Fourier transform infrared (FTIR) and circular dichroism (CD) measurements showing an increase in irregular and intermediary structural components upon addition of ferulic acid, as well as UV-vis measurements that record an increase in absorption. High performance liquid chromatography (HPLC) work strongly argues that the ferulic acid is bound covalently to the protein post heat treatment. This outcome is in agreement with molecular docking simulations and quantum mechanics calculations that indicate the formation of a covalent bond between ferulic acid and glutamine54 residue of beta-casein to create a new adduct.