Improvement of lactoferrin thermal stability by complex coacervation using soy soluble polysaccharides

Lactoferrin (LF) is a multifunctional protein in the transferrin family that has been widely used in food and pharmaceutical products. However, it is susceptible to denaturation during thermal processing, which can diminish the functionality and bioavailability of LF in the final product. Coacervation of LF with biopolymers has been demonstrated as a promising approach to protect LF from thermal denaturation. This work aims to study the formation conditions, structural characteristics, and interaction mechanisms of soy soluble polysaccharides (SSP) and lactoferrin coacervate complex (SSP-LF), and to investigate the effect of the SSP-LF complex on the structural changes and antimicrobial capacity of LF before and after thermal treatment. Either soluble and insoluble SSP-LF complexes could be formed depending on the pH (4–7) and ratios (SSP: LF = 8:1 to 1:16), according to the turbidity, zeta-potential, and particle size analysis. Electrophoresis, SEM, FTIR, and CD spectra measurement suggested that the SSP-LF complex could maintain the secondary structures of LF. Quartz crystal microbalance with dissipation (QCM-D) was used to elucidate the real-time interactions between SSP and LF, showing that the major driving force to form complexes was electrostatic interaction. The SSP-LF complex was able to prevent the aggregation/denaturation of LF and the loss of the α-helix during thermal treatment at neutral pH. The SSP-LF complex maintained the antimicrobial capacity of LF after thermal treatment. The improved thermal stability and functionality of the SSP-LF complex could facilitate the application of LF in various commercial products.