Physicochemical and functional properties of lactoferrin-hyaluronic acid complexes: Effect of non-covalent and covalent interactions

The molecular characteristics and functional properties of lactoferrin (LF)-hyalumnic acid (HA) non-covalent complexes and conjugates formed by physical mixing and chemical conjugation were compared. LF and HA interactions were characterized using phase behavior, particle size, zeta-potential and isothermal titration calorimetry (ITC) analysis. The physicochemical and functional properties of the LF-HA complexes and conjugates were also measured, including their foaming, emulsifying, and antioxidant capacities. LF and HA formed molecular complexes over a wide range of pH values, resulting in changes in particle size, charge and structure. The net charge and thermal stability of the proteins in the LF-HA complexes and conjugates were higher than that of free proteins. Covalently attaching HA to LF significantly (p < 0.05) improved its emulsifying capacity, with the highest emulsifying activity index (47.7 +/- 0.1 m(2)/g) and emulsion stability index (83.2 +/- 0.4 min) being obtained, but it did not improve its foaming properties. The antioxidant capacity of LF in complexes and conjugates was increased by around 9% and 10%, respectively. This study showed that the functional performance of LF could be enhanced by forming complexes or conjugates with HA, which may extend its use in a variety of food applications.