Conjugation between okra polysaccharide and lactoferrin and its inhibition effect on thermal aggregation of lactoferrin at neutral pH

This study investigated the effect of okra polysaccharides (OP) on the thermal stability of lactoferrin (Lf). Zetasizer and turbidity were used to provide insight about the stability of Lf/OP complexes, structural properties were measured by fluorescence spectroscopy and circular dichroism. The results revealed that OP interacts with Lf through electrostatic attraction. OP prevented heat-induced denaturation and aggregation of Lf molecule while the turbidity and zeta potential decreased with elevated OP concentration. Correspondingly, the average size of Lf aggregates decreased from 470 nm to 180 nm when OP concentration increased from 0.005% to 0.0125%. The internal structure of Lf was significantly influenced by the existence of OP. At low concentrations (<0.0075%), OP resulted in the loss of secondary and tertiary structure of Lf. While at high concentrations (>0.0075%), the secondary and tertiary structure of Lf can be protected after heating. The minimum OP concentration to prevent 0.05% Lf from thermal aggregation was 0.0075%. In conclusion, Lf/OP complexes could enhance the usage of Lf as emulsifying and encapsulation agents in food and pharmaceutical fields.