Heat Stability of Bovine Lactoferrin at Acidic pH

Abstract

In order to develop a practical method for pasteurization of lactoferrin, the M uace of pH on the heat stability of bovine lactoferrin was studied. Solutions (5%; wt/vol) of iron-free lactoferrin (apo-lactoferrin) in distilled water were adjusted to various pH values from 2.0 to 11 .O and heated at various temperatures (80 to 120'C) for 5 min. The heated samples were analyzed by HPLC and assayed for iron-binding capacity, antigenic activity, and bacteriostatic effect. The heated solutions of aplactoferrin gelled at neutral and alkaline pH. At acidic pH, lactofetrb in the heated samples remained soluble, and solutions were clear. The HPLC pattern of aplactoferrin heat-treated at pH 4.0 and 1WC was similar to that of unheated aplactoferrin. It resisted heating at pH 4.0 and W C for 5 min without any signiiicant losses of iron-binding capacity, antigenic activity, or antibacterial activity. These results indicate that apolactoferrin is very stable at pH 4.0 and high temperatures. It was considered that heating conditions of pH 4.0 and temperatures of 90 to 1 W C for 5 min were suitable as a practical method for pasteurization of lactoferrin. Moreover, the possibility of using an WlT method for more effective and efficient pasteurization of lactoferrin was demonstrated. Apo-lactoferrin treated at pH 2.0 or 3.0 and 100 or 120C for 5 min was apparently degraded, but the antibacterial activity was equal to or stronger than that of