title: Kinetic and thermodynamic parameters for thermal denaturation of ovine milk lactoferrin determined by its loss of immunoreactivity.
abstract: Lactoferrin is a protein with important biological functions that can be obtained from milk and by-products derived from the dairy industry, such as whey. Although bovine lactoferrin has been extensively studied, ovine lactoferrin is not quite as well known. In the present study, the effect of several heat treatments in 3 different media, over a temperature range from 66 to 75°C, has been studied on lactoferrin isolated from sheep milk. Denaturation of lactoferrin was determined by measuring its immunoreactivity with specific polyclonal antibodies. Kinetic and thermodynamic parameters obtained indicate that lactoferrin denatures by heat more rapidly in whey than in phosphate buffer or milk. The value of activation energy found for the denaturation process of lactoferrin when treated in whey is higher (390kJ/mol) than that obtained in milk (194kJ/mol) or phosphate buffer (179kJ/mol). This indicates that a great amount of energy is necessary to start denaturation of ovine lactoferrin, probably due to the interaction of this protein with other whey proteins. The changes in the hydrophobicity of lactoferrin after heat treatments were determined by fluorescence measurement using acrylamide. The decrease in the hydrophobicity constant was very small for the treatments from 66 to 75°C, up to 20min, which indicates that lactoferrin conformation did not experienced a great change. The results obtained in this study permit the prediction of behavior of ovine lactoferrin under several heat treatments and show that high-temperature, short-time pasteurization (72°C, 15 s) does not cause loss of its immunoreactivity and, consequently, would not affect its conformation and biological activity.
authors.affiliation: Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Navarro
authors.affiliation: Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Harouna
authors.affiliation: Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Calvo
authors.affiliation: Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
authors.forename: M D
authors.initials: MD
authors.lastname: Pérez
authors.affiliation: Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain. Electronic address: lousanchez@unizar.es.
authors.forename: L
authors.initials: L
authors.lastname: Sánchez
mesh_terms: D000818:Animals; D002021:Buffers; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D007781:Lactoferrin / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D011489:Protein Denaturation; D012756:Sheep; D013816:Thermodynamics; D000067796:Whey / Q000737:chemistry
chemical_list: D002021:Buffers; D010710:Phosphates; D007781:Lactoferrin
keywords: ovine lactoferrin; sheep milk; thermal denaturation; whey