Degradation of Beta-Glucan Gel in Model Systems and Unfiltered Beer Due to
High Hydrostatic Pressure Treatment
MBAA TQ vol. 42, no. 1, 2005, pp.
21-24 |
VIEW ARTICLE
Steffen Fischer, Winfried Russ, and Roland Meyer-Pittroff. Lehrstuhl f�r
Energie- und Umwelttechnik der Lebensmittelindustrie, Technische Universit�t
M�nchen, Center of Life and Food Sciences Weihenstephan, Weihenstephaner Steig
20, Freising, Weihenstephan, Bavaria 85350 Germany.
Abstract
The objective of this study was to work out the mechanisms of high-pressure�induced
degradation of beta-glucan gel. The first step was to investigate the state of
beta-glucan after high-pressure treatment. The content and viscosity of
beta-glucan
gel and beta-glucan itself were measured, and nuclear magnetic resonance
experiments were carried out. These determinations lead to the conclusion that
dissolved molecules arise from the gel because of its decreasing viscosity and
the increasing content of free water. The second step was to investigate at
which phase of high-pressure treatment the degradation of the gel occurs. The
content of beta-glucan was, therefore, measured on-line in an optical cell. It
turned out that beta-glucan gel degrades in two different steps. The first step is
independent of time but depends on the impact of deforming forces taking place
during increasing pressure. The second step is dependent on time after reaching
a certain pressure plateau because of the pressure sensitivity of the bonds. The
second step only occurs at pressures greater than 300 MPa.
Keywords: beta-glucan gel, filterability, high-pressure treatment, polymeric
chemistry
S�ntesis
El objetivo de este estudio fue elucidar los mecanismos de la degradaci�n
del gel de beta-glucano inducida por altas presiones. Primero se investig� el
estado en que se encontraba el beta-glucano despu�s de ser tratado con presiones
altas. Se midi� el contenido y la viscosidad de beta-glucano y su gel, adem�s de
realizar experimentos de resonancia magn�tica nuclear. Los resultados llevaron
a la conclusi�n que se producen mol�culas disueltas del gel debido a la
reducci�n de la viscosidad y el aumento del contenido de agua libre. Despu�s
se investig� en qu� fase del tratamiento a presi�n alta ocurre la
degradaci�n del gel. Al medir el contenido de beta-glucano en una celda �ptica
directamente en l�nea, se pudo establecer que la degradaci�n del beta-glucano
ocurre en dos pasos. El primero es independiente del tiempo y depende en la
magnitud del impacto de las fuerzas de deformaci�n que ocurren durante el
aumento de presi�n. El segundo paso depende del tiempo recorrido despu�s de
alcanzar una cierta presi�n, debido a la sensibilidad de los enlaces a dicha
presi�n. Este segundo paso s�lo ocurre a presiones mayores de 300 mPa.
Palabras claves: gel de beta-glucano, filtrabilidad, tratamiento a presi�n alta,
qu�mica polim�rica
