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Title

Detección de caseinato y suero en leche y producos lácteos mediante técnicas electrofóreticas, cromatográficas y espectroscópicas

AuthorsMiralles, Beatriz
AdvisorAmigo, Lourdes ; Ramos, Mercedes
Issue Date2001
PublisherUniversidad Complutense de Madrid
CSIC - Instituto de Fermentaciones Industriales (IFI)
Abstract[ES]: La presente memoria ha abordado el análisis de la fracción proteica de la leche y de distintos productos lácteos mediante técnicas analíticas de alta resolución. Está estructura en tres capítulos. En el primer capítulo se ha estudiado la determinacion de la relación proteína de suero/proteína total de la leche para detectar adiciones de suero. Se ha optimizado un método de espectroscopía ultravioleta de la 4ª derivada (UV 4th DS) que ha permitido detectar la adición de suero a la leche UHT en una proporción de un 5% en proteína. También se ha evaluado la determinación de la relación proteína de suero/proteína total mediante un método de electroforesis capilar en zona libre (CE) y un método de electroforesis capilar con SDS (SDS-CE) y se han comparado los resultados obtenidos mediante los métodos anteriores en muestras de leche sometidas a diferentes tratamientos térmicos, obteniéndose valores similares. En el segundo capítulo se han evaluado algunas técnicas aplicables a la detección de la adición de caseína o caseinato a quesos fundidios, Quarg y Mozzarella: Electroforesis capilar, Isoelectroenfoque en gradiente de pH inmovilizado (IPG-IEF), y cromatografía líquida de alta eficacia (HPLC). Por útlimo, en el tercer capítulo, se ha desarrollado un método de CE mediante el cual pueden cuantificarse simultáneamente la B-Lg y la para k-CN en muestras de leche y queso. La aplicación del método ha permitido separar algunos productos de degradación que aparecen en la leche cruda refigerada, atribuyéndose su presencia a la actividad proteolítica de bacterias psicrotrofas sobre la molécula de k-CN., Además, el método de CE desarrollado ha demostrado su utilidad en la caracterización de los quesos frescos por su proceso tecnológico de elaboración y en los quesos Mozzarella, además, por el tipo de leche utilizada en su elaboración.
[EN]: This thesis describes the analysis of the protein fraction of milk and different milk products by high resolution analytical techniques. It is structured in three chapters. In the first chapter the determination of the whey protein/total protein ratio in milk has been studied with the aim to detect additions of whey. A method of UV 4th derivative spectroscopy (UV 4th DS) has been optimized to determine the above mentioned ratio without influence of heat treatment or degree of proteolysis of milk. This method has permitted to detect the addition of whey to UHT milk in a proportion of 5% in protein. A capillary zone electrophoresis method (CE) and a sodium dodecyl sulphate CE method (SDS-CE) have also been evaluated to determine the whey protein/total protein ratio. The results obtained with these three methods have been compared when applied to samples of milk with different heat treatments, and similar results have been obtained. As milk proteolysis has influence on the results obtained by CE, some indicators that can be useful to determine this degradation in raw and UHT milk have been studied. In the second chapter, some of the available techniques for the detection of the addition of casein or caseinate to processed, Quarg and Mozzarella cheeses have been evaluated. The quantification of intact κ-CN has demonstrated its suitability to detect acid casein in renneted cheeses if the addition has been done after the rennet action, while it would not be useful in cheeses made with acid coagulation. In theese cheeses, however, rennet casein addition can be detected by the quantification of para-κ-CN. CE has permitted the determination of the addition of casein/caseinate to processed cheeses without influence of its content in milk powder in a proportion up to 1.2%. The results obtained by this technique and by immobilized pH gradient isoelectrofocusing (IPG-IEF) have been compared, showing the better repeatability of the CE. Other methods, such as the determination of lisinoalanine by HPLC, which was also evaluated, can be used as a qualitative index to detect the addition of caseinate to Mozzarella cheeses. In the third chapter, a CE method has been developped to simultaneously quantify β-Lg and para-κ-CN in samples of milk and cheese. The application of this method has permitted to separate some degradation products that appear in refrigerated raw milk. Their presence is attributed to the activity of psychrotrophic bacteria on the κ-CN molecule. By coupling HPLC to MS, the characterization of five triptic peptides has confirmed the formation of para-κ-CN and other related peptides by the action of the extracellular protease of Pseudomonas fluorescens B52. Moreover, the CE method developed has demonstrated its suitability for the characterization of fresh cheeses by its technological process of manufacture and, in Mozzarella cheeses, besides, by the type of milk used in its manufacture.
DescriptionMemoria para optar al grado de Doctor presentada por Beatriz Miralles Buraglia y que ha sido realizada en el Instituto de Fermentaciones Industriales del Consejo Superior de Investigaciones Científicas (CSIC).
URIhttp://hdl.handle.net/10261/101541
ISBN84-669-2014-5
Appears in Collections:(IFI) Tesis
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