β-Lactoglobulin and sorghum phenolic compounds molecular binding: Interaction mechanism and thermal stability impact

The mechanism of molecular interaction between (3-lactoglobulin ((3-lg) and sorghum bran phenolic compounds from 4 genotypes was studied. Catechin (CA) and ferulic acid (FA) were used as model systems. Higher affinity for (3-lg:FA interaction (Ksv ti 105 M-1) compared with (3-lg:CA interaction (Ksv ti 104 M-1) was revealed, with different preferable binding sites identified through molecular docking. Nevertheless, regarding the molecular interaction between the proteins and the complex extracts of phenolic compounds, Ksv in the magnitude order of 104 M-1 were observed. Antioxidant capacity progressively increased after protein-phenolic interaction, indicating a potential synergistic effect. Concerning the thermal stability of the phenolic compounds, epimerization as the primary response of CA to thermal treatment (90 degrees C / 10 min) was identified, but the addition of (3-lg exerted a protective effect against CA degradation (-7 % in (3-lg:CA complexes); however, proteins were not able to protect complex phenolic matrices (e.g. sorghum extracts).