The Endoproteinases of Barley and Malt and Their Endogenous Inhibitors
MBAA TQ vol. 45, no. 3, 2008, pp.
279-282 |
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Berne L. Jones. 316 Battle Ridge Road, Kooskia, ID 83539.
Abstract
Research in the area of soluble protein of malt has always been of interest
to brewers. During the malting and brewing processes, a portion of the barley
proteins must be degraded to amino acids and small peptides. Among other
problems, if too little protein hydrolysis occurs, there will be insufficient
low molecular weight nitrogenous compounds in the wort for optimal yeast
nourishment. Alternatively, too much hydrolysis will deplete the wort of
proteins that are necessary for good beer foam formation, mouthfeel, etc. The
endoproteinases of barley and malt are the enzymes that initially catalyze the
hydrolysis of insoluble barley storage proteins and, thus, play major roles in
determining whether a given barley variety will be useful for malting and
brewing. The four common types of proteinases (cysteine, aspartic, serine, and
metalloproteinase) are discussed in this paper. Additionally, after it was
discovered that the pH values and redox states of mashes strongly affect their
proteolytic activities, quantitative studies were carried out to measure how
these variables affect the protein solubilization that occurs during mashing.
Keywords: endoproteinases, malt proteinases, soluble protein of malt
S�ntesis
Las investigaciones con respecto a la prote�na soluble en malta siempre han
sido de inter�s al cervecero. Una porci�n de las prote�nas de la cebada debe ser
degradada a amino �cidos y a peque�as mol�culas pept�dicas durante los procesos
de malteo y elaboraci�n de cerveza. Hay que notar que una hidr�lisis excesiva
eliminar�a prote�nas del mosto necesarias para una buena formaci�n y estabilidad
de la espuma, as� como para la sensaci�n bucal (�cuerpo�) y otros par�metros de
calidad. Las endoprote�nasas de cebada y malta son las enzimas que inicialmente
catalizan la hidr�lisis de prote�nas insolubles de almacenamiento de la cebada,
por lo que juegan un importante papel al determinar si una dada variedad de
cebada ser�a �til para el malteo y para la elaboraci�n de cerveza. Se eval�an
los cuatro tipos m�s comunes de proteinasas (cyste�n, asp�rtica, ser�n, y
metaloproteinasa). Despu�s de descubrir que el estado de reducci�n/oxidaci�n y
el pH de la maceraci�n afectan las actividades proteol�ticas, se hizo un estudio
para medir las variables que afectan la solubilizaci�n de prote�nas que ocurren
durante la maceraci�n.
Palabras claves: endoproteinasas, proteinasas de malta, prote�na soluble de
la malta
