Enhanced thermal stability of lactoferrin through electrostatic complexation with low-methoxyl pectin

Lactoferrin (LF) possesses diverse bioactivities, but its application in food systems is limited due to environmental sensitivity and heat-induced denaturation. To improve its thermal stability, electrostatic complexes of LF with low-methoxyl pectin (LMP) were prepared, and their heat resistance was systematically investigated. Based on titration curves, soluble LF-LMP complexes at various mass ratios of 6:1, 4:1, and 2:1 (pH 6 and 7) were created. These complexes showed improved thermal stability when heated at 70°C or 95°C for 10 min, with protection efficacy varying by pH and mass ratio. Samples at pH 6 exhibited greater thermal stability compared with those maintained at pH 7, as evidenced by attenuated turbidity increases, smaller particle size variations, and suppressed fluorescence intensity shifts in general. Higher LMP ratios (2:1) conferred more effective thermal protection. Circular dichroism and Fourier-transform infrared analyses indicated that LF-LMP complexes at 2:1 maintained a relatively small structural changes following heat treatment. Differential scanning calorimetry revealed increased peak temperatures for LF-LMP complexes compared with LF alone, with further enhancement at higher LMP ratios and lower pH. Sodium dodecyl sulfate-PAGE demonstrated higher LF retention in complexes post-heating. Data suggest that LF-LMP complexation may be a promising strategy to improve the thermal stability of LF, facilitating its application in heat-processed functional foods.