Thermal Stability of the Iron–Lactoferrin Complex in Aqueous Solution is Improved by Soluble Soybean Polysaccharide

Abstract

Lactoferrin (Lf) can solubilize more than a 70-fold molar equivalent of iron in the presence of bicarbonate anions. The resulting iron–Lf complex (FeLf) is a useful food ingredient for iron fortification to prevent anemia. Although FeLf has greater thermal stability than Lf, a pasteurizing technique for FeLf has not been established. The aim of the present study was to develop a practical technique to pasteurize FeLf based on its thermal stability with the aid of a polysaccharide. FeLf [0.1 %, weight/weight (w/w) ratio] was heated at 80 °C for 3 min under various pH (5.5–8.0) and electrical conductivity (0.1–6.0 mS/cm) levels. Overall, FeLf was thermally stable and was hardly affected by pH or electrical conductivity, although aggregation and precipitation occurred when FeLf was heated at pH 6.0–7.5 in the presence of salt and electrical conductivity >3.0 mS/cm. When 0.01 %–0.4 % (w/w) of soluble soybean polysaccharide (SSPS) was added to 0.01 % (w/w) FeLf solution, the FeLf remained soluble and maintained its iron-holding property at pH 6.5, even when heated at 120 °C for 4 min. Particle charge measurements showed that the ζ-potential of FeLf-SSPS became negatively charged following the addition of SSPS, which was associated with the improved thermal stability of FeLf. These results have important implications for the use of FeLf in developing liquid-based food products.