Navarro F, Harouna S, Calvo M, Pérez M D, Sánchez L
Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
J Dairy Sci. 2015 Jul;98(7):4328-37. doi: 10.3168/jds.2015-9403. Epub 2015 May 7.
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.
乳铁蛋白是一种具有重要生物学功能的蛋白质，可从牛奶及乳制品工业的副产品（如乳清）中获取。尽管牛乳铁蛋白已得到广泛研究，但羊乳铁蛋白却不太为人所知。在本研究中，已对从羊奶中分离出的乳铁蛋白在66至75°C温度范围内于3种不同介质中进行的几种热处理效果进行了研究。通过测量乳铁蛋白与特异性多克隆抗体的免疫反应性来确定其变性情况。所获得的动力学和热力学参数表明，乳铁蛋白在乳清中比在磷酸盐缓冲液或牛奶中受热变性更快。在乳清中处理时乳铁蛋白变性过程的活化能值（390kJ/mol）高于在牛奶（194kJ/mol）或磷酸盐缓冲液（179kJ/mol）中获得的值。这表明启动羊乳铁蛋白变性需要大量能量，这可能是由于该蛋白质与其他乳清蛋白的相互作用所致。热处理后乳铁蛋白疏水性的变化通过使用丙烯酰胺的荧光测量来确定。在66至75°C处理长达20分钟时，疏水性常数的降低非常小，这表明乳铁蛋白的构象没有发生很大变化。本研究获得的结果有助于预测羊乳铁蛋白在几种热处理下的行为，并表明高温短时巴氏杀菌（72°C，15秒）不会导致其免疫反应性丧失，因此不会影响其构象和生物活性。
