Curcumin-micellar casein multisite interactions elucidated by surface plasmon resonance.

Determine the thermodynamic and kinetic parameters of interaction between micellar casein (MC) and curcumin (CUR) is useful for the application of MC-CUR systems in food products. We used surface plasmon resonance (SPR) and ultraviolet-visible spectrophotometry (UV-vis) to study the complex formation between MC obtained from skimmed milk and CUR, MC carrying capacity, and thermal protection for CUR at a pH of 6.6. An MC could carry about 18,000 molecules of CUR. SPR suggested an enthalpy-driven process (∆H° = -64.63 kJ∙mol and T∆S° ranging from -42.45 to -44.46 kJ∙mol). Temperature increased reduced the rate of MC-CUR complex formation and increased its dissociation rate. The activation energy for the formation of MC-CUR activated complexes was negative for association of free MC and CUR molecules (-62.8 kJ mol) and positive for dissociation of the thermodynamically stable complexes (1.80 kJ mol). MC protected the CUR against its thermal degradation when it was subjected to different temperatures (30, 40, 50, and 60 °C for 5.5 h). This study shows the importance of characterizing MC-small molecules interactions for better application of MC as a nanocarrier.