Barley and Malt Starch in Brewing: A General Review
MBAA TQ vol. 40, no. 2, 2003, pp. 89-97 |
VIEW ARTICLE
Peer-Reviewed Paper
Dr. Charles W. Bamforth. University of
California, Department of Food Science & Technology, Davis, CA
95616-8598. Based on a paper presented at the 115th Convention of the
Master Brewers Association of the Americas, Austin, TX, October, 2002.
Abstract
The degradability of barley starch in malting and brewing can be addressed
(and has been reviewed) within a two-part model that comprises the
exposure of the substrate in a form accessible by enzymes, followed by the
enzyme hydrolysis itself. Recent research on the accessibility of starch
has included interference by the presence of protein (including friabilin)
and lipid. However, it is also worth revisiting older studies that
highlighted treatments such as heating that, while inducing
gelatinization, can also lead to physical changes in the starch, rendering
it less digestible. Recent studies have highlighted the limitations to
wort fermentability that previously were supposed to be due to the thermal
instability of limit dextrinase but are actually due to a shortage of
enzyme in a free and active form. Release of this enzyme is facilitated,
among other things, by reduced pH and reducing conditions.
Keywords: amylases, gelatinization, granules, heat, limit
dextrinase, lipid, protein, starch, structure
S�ntesis
La degradabilidad del almid�n de cebada en los procesos cerveceros y de
malteo puede ser visto como un modelo de dos etapas: la exposici�n del
substrato en una forma accesible a las enzimas, seguido por la hidr�lisis
enzim�tica propiamente dicho. Investigaciones recientes con respecto a la
accesibilidad del almid�n han incluido el tema de la interferencia
causada por la presencia de prote�na (incluyendo la friabilina) y
l�pidos. Vale la pena revisar estudios antiguos que investigaron
tratamientos tales como el calentamiento, que si bien induce la
gelatinizaci�n, tambi�n ocasiona cambios f�sicos en la estructura del
almid�n que lo hace menos digerible. Estudios recientes han demostrado
que las limitaciones a la fermentabilidad del mosto, que antes se supon�a
debida a la inestabilidad t�rmica de dextrinasa l�mite, en realidad se
debe a una falta de suficiente enzima en una forma libre y activa. La
liberaci�n de esta enzima es facilitada por, entre otras cosas, un pH
reducido y condiciones reductoras.
Palabras claves: amilasas, gelatinizaci�n, granulas, calor,
dextrinasa l�mite, l�pidos, prote�na, almid�n, estructura molecular
