The Effect of Beer pH on Colloidal Stability and Stabilization�A Review and Recent Findings
Peer-Reviewed Paper
MBAA TQ doi:10.1094/TQ-47-2-0607-01 |
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Karl J. Siebert. Food Science and Technology
Department, Cornell University, Geneva, NY.
Abstract
pH has a pronounced effect on the amount of haze produced in both model
systems and beer from the same amounts of haze-active (HA) proteins and HA
polyphenols. The greatest haze intensity is seen slightly above pH 4 and
varies slightly with alcohol content. This pH promotes removal of HA
material during maturation, resulting in better beer colloidal stability.
Fining with HA proteins (gelatin or isinglass) or HA polyphenols (e.g.,
tannic acid) is similarly affected by pH, with the greatest effectiveness
near pH 4.3. Factors that influence beer pH are reviewed for their effects
on colloidal stability. Under low adsorbent dose conditions, both silica
and PVPP are slightly less effective at the pH at which proteins bind
polyphenols most strongly. This appears to be due to competition between a
stronger protein�polyphenol interaction and binding of HA material to an
adsorbent.
Keywords: adsorbent, fining, haze, polyphenol, protein
S�ntesis
El pH tiene un gran efecto sobre la cantidad de
turbieza formada (tanto en cerveza como en sistemas modelos) aun con
id�nticas concentraciones de prote�nas turbieza-activas (TA) y polifenoles
TA. La mayor intensidad de turbieza se manifiesta a
un pH ligeramente superior a cuatro y var�a un poco seg�n el contenido de
alcohol. Este pH promueve la remoci�n de material TA durante la
maduraci�n, as� mejorando la estabilidad coloidal de la cerveza. El tratamiento con prote�nas TA (gelatina o
�isinglass�) o con polifenoles TA (�cido t�nico) tambi�n es afectado por
el pH, siendo m�s eficaz cerca de un pH de 4,3. Se
discuten los factores que afectan el pH de la cerveza y como estos pueden
afectar la estabilidad coloidal. En condiciones de baja dosificaci�n de
adsorbente, tanto s�lica gel como PVPP se muestran menos efectivos a un pH
donde las prote�nas se unen m�s fuertemente a los polifenoles. Parece que
esto se debe a la competencia entre una interacci�n prote�na-polifenol muy
fuerte y la fuerza de la uni�n de un material TA a un adsorbente.
Palabras
claves: adsorbentes, polifenoles, prote�nas, tratamiento anti turbieza
coloidal, turbieza
