Protection effect of sodium alginate against heat-induced structural changes of lactoferrin molecules at neutral pH

Abstract The objective of this research was to characterize the inhibition effect of sodium alginate on heat-induced instability of lactoferrin (Lf). The results showed that sodium alginate can interact with Lf through electrostatic attraction. The formation of Lf-sodium alginate complexes increased the heat stability of Lf at concentrations higher than 0.03%. The heat stability is related to the zeta potential of the complexes, which need to achieve −20 mV to form stable systems. Heating at 90 °C resulted in irreversible changes of Lf and significant exposure of hydrophobic groups at all concentrations. At sodium alginate concentration of 0.03%, only about 54% secondary structure can be maintained and the complexes have much higher size of 289 ± 14 nm. On the other hand, much smaller sizes (69 ± 2 and 41 ± 0.4 nm) were obtained at concentrations of 0.04% and 0.05% and more than 80% of the secondary structure of the Lf can be protected.