Thermal-induced alterations in complexes based on lactoferrin and low/high methoxyl pectin: Physicochemical, structural, and functional properties

The current study investigated the interacting mechanism within lactoferrin (LF)-low methoxyl pectin (LMP) and LF-high methoxyl pectin (HMP) complexes, alongside heat-induced alterations in their physicochemical, structural, and functional properties. At pH 7, LF can form soluble complexes with pectin at mass ratios of 3:1 and 1:1. Molecular docking and Fourier transform infrared spectra revealed that LMP primarily bound LF via electrostatic interactions and hydrogen bonds, whereas HMP predominantly engaged in hydrophobic interactions. Molecular dynamic simulation further indicated that LF-HMP exhibited superior conformational stability. After being heated at 95°C for 10 min, the particle size decreased by 73%/35% to 58% in LF/LF-pectin complexes, whereas the absolute zeta potential increased by 40%/2% to 10%. Secondary structures of LF and LF-LMP become more disordered, whereas LF-HMP maintained its structural orderliness. Tertiary structures universally unfolded, with the extents dependent on degree of esterification and concentration of pectin. Thermal treatments altered the functional attributes of LF, enhancing emulsifying activity and foaming performance while compromising its antibacterial activity. Compared with LMP, HMP manifested more positive effects on LF, specifically, elevating the emulsifying activity by 43% to 46%, enhancing the foam ability by 6% to 23%, and maintaining the antibacterial activity on Escherichia coli/Staphylococcus aureus by 64% to 73%/71% to 75% post heating at 95°C for 10 min. These findings provide a theoretical basis for broadening the application of LF in food processing involving heat treatments.