Heat stability of bovine lactoferrin at acidic pH
1991
Abe, H. | Saito, H. | Miyakawa, H. | Tamura, Y. | Shimamura, S. | Nagao, E. | Tomita, M.
In order to develop a practical method for pasteurization of lactoferrin, the influence 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 11.0 and heated at various temperatures (80 to 120 degrees 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 apo-lactoferrin gelled at neutral and alkaline pH. At acidic pH, lactoferrin in the heated samples remained soluble, and solutions were clear. The HPLC pattern of apo-lactoferrin heat-treated at pH 4.0 and 100 degrees C was similar to that of unheated apo-lactoferrin. It resisted heating at pH 4.0 and 90 degrees C for 5 min without any significant losses of iron-binding capacity, antigenic acitivty, 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 100 degrees C for 5 min were suitable as a practical method for pasteurization of lactoferrin. Moreover, the possibility of using an UHT method for more effective and efficient pasteurization of lactoferrin was demonstrated. Apo-lactoferrin treated at pH 2.0 or 3.0 and 100 or 120 degrees C for 5 min was apparently degraded, but the antibacterial activity was equal to or stronger than that of unheated apo-lactoferrin. This result suggests that some of the lactoferrin fragments produced by heat under acidic conditions have antibacterial activity.
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