Abstract: Interactions among pectin, bovine serum albumin (BSA) and chiooligosaccharide (COS), and their effects on the loading efficiency of BSA were investigated through the determination of the turbidity and macroscopic and microscopic properties of binary and ternary polyelectrolyte complex (PEC) solutions of these three compounds, PEC yield, the complexation and loading rate of BSA, and the ultrastructure and Fourier transform infrared (FTIR) spectrum of PEC. The results showed that complexation methods significantly affected the turbidity, structure and state of PEC. The three compounds interacted with each other mainly through electrostatic interactions and COS competed with BSA for interacting with pectin. Pectin preferred to form complexes with a reticular structure with COS, resulting in a lower loading efficiency of PEC for BSA. The secondary structures of BSA changed due to the conformational changes of pectin during complexation in the presence of COS.

Key words: pectin; bovine serum albumin; chitooligosaccharide; electrostatic interaction; competition; loading