Coacervates of lactoferrin with resistant dextrin via noncovalent interaction for enhanced thermal stability, interface characteristics and DHA encapsulation

Lactoferrin (LF), resistant dextrin (RD), and docosahexaenoic acid (DHA) are critical functional components in infant formula. However, LF exhibits thermally unstable, and DHA is susceptible to degradation from exposure to light, heat, and oxygen. The coacervation of LF with RD through the electrostatic interactions may be an effective strategy for addressing these issues. This study aimed to investigate the coacervation conditions and thermodynamic formation mechanism of LF with RD to improve the thermal stability and interfacial properties of LF, alongside assessing the feasibility of embedding DHA after LF coacervates with RD. The optimal coacervation conditions for LF with RD were identified to be pH 7.0 and an LF-to-RD mass ratio of 1:12. LF-RD complex coacervation was thermodynamically favored (ΔG < 0), attributed to entropy gain (ΔS > 0) and negative enthalpy change (ΔH < 0). Following coacervation with RD, the thermal stability of LF was improved due to noncovalent interactions. The process of complex coacervation also enhanced the surface hydrophobicity, as well as the emulsifying and foaming capabilities of LF. Optical microscopy and CLSM results indicate that, following complex coacervation, DHA droplets are uniformly dispersed within the emulsion, exhibiting a spherical shape with a denser wall forming around them. Additionally, DHA has been successfully encapsulated by LF-RD complex coacervates, with an encapsulation efficiency reaching 89.5%. This study provides a reference for enhancing the thermal stability and functionality of LF in the food industry and offers insights into the further application of LF-RD complexes and DHA microcapsules in infant formula.