Characterization of alginate–lactoferrin beads prepared by extrusion gelation method

Abstract

The potential use of lactoferrin (Lf) as a food ingredient is attracting increasing attention. Encapsulation of Lf in alginate gel beads can potentially enhance its stability and safe delivery. It is therefore important to understand the properties of alginate–Lf beads in order to develop a successful encapsulation method. Three different forms (apo-, native- and holo-) of bovine Lactoferrin (Lf) were encapsulated in alginate beads by the gel entrapment method using calcium as the cross-linking ion. A minimum of 40% alginate was required in the beading mixture to retain the form of a bead. Higher proportion of alginate reduced the water holding capacity and calcium uptake by the beads and these effects were similar for all forms of Lf. Longer cross-linking time led a greater amount of Lf and iron leaching from the beads and this was most pronounced for holo-Lf compared to apo- and native-Lf. The elastic modulus was affected by the composition (mixing ratio) of beads and not by the forms of Lf with decreasing elasticity of the beads with increasing alginate content which was attributed to the decreasing crosslinking density. The stability of the encapsulated Lf was evaluated based on the amount leached into pH adjusted Millipore water and was affected by pH (4 and 7) for holo-Lf but not for apo- and native-Lf. The relative rate of Lf leaching at pH 4 for the different forms of Lf was found not to directly correlate with the pI of the different forms of Lf.