The Study of Haze Formation in Freshly Packaged and Stored Beers
MBAA TQ vol. 44, no. 1, 2007, pp.
23-28 |
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Deborah K. Parker, Ph.D. Brewing Research
International, Lyttel Hall, Nutfield, Surrey RH1 4HY, UK.
Abstract
The mechanism of haze formation has been studied for many years,
yet in the literature, there is still uncertainty about which protein
fractions take part in haze formation. In particular, methods of haze
measurement have focused on smaller chill haze and permanent haze
particles. The formation of larger haze particles meanwhile has received
little attention, and little is known about the composition of such larger
hazes formed in beer post-packaging. This paper describes work conducted
in an investigative study to examine the formation of nonmicrobiological
haze during beer storage. Control beers were brewed and packaged without
additional processing or chillproofing aids. The control beers were
separated further into batches and treated with foam and/or haze
stabilizers. In addition, beers of differing gravities were compared.
Total haze, protein levels, and hydrophobic polypeptides were measured
following packaging and pasteurization and during storage. A method for
measuring the quantity of larger haze particles was included. Beers were
stored at three different temperatures and assessed over a 6-month period.
It must be emphasized that the work done in this study is experimental and
does not relate to current brewing procedures. The findings show that the
amount of total haze present and levels of hydrophobic polypeptide
measured in foam, beer, and haze vary depending on treatment, storage
temperature, and storage time. Observations indicate that a dynamic
equilibrium exists in beer between total protein and hydrophobic
polypeptide present in various beer fractions. A mechanism is proposed for
the formation of heat-induced haze and storage haze in beer
post-packaging.
Keywords: beer haze, polypeptide, protein hydrophobic, storage
S�ntesis
Se ha estudiado durante muchos a�os el mecanismo de la formaci�n de
turbieza, sin embargo aun subsiste en la literatura mucha incertidumbre en
cuanto a cuales son las fracciones de prote�na que afectan la formaci�n de
turbieza. Los m�todos de medici�n de turbieza se han concentrado en la
turbieza al fr�o y en las part�culas peque�as de turbieza permanente. Se
ha dedicado poca atenci�n a la formaci�n de part�culas mayores de turbieza
permanente, y poco se sabe acerca de la composici�n de estas turbiezas
mayores formadas despu�s del envasado. Aqu� se presenta un estudio para
examinar la formaci�n de turbieza no-bacteriol�gica durante el
almacenamiento de cerveza. Se elaboraron y envasaron cervezas de control
sin estabilizadores de ning�n tipo. Las cervezas de control se separaron
en lotes, tratando algunos lotes con estabilizadores coloidales y/o de
espuma. Tambi�n se compararon cervezas de diferente extracto original. Se
midi� la turbieza total, niveles de prote�na y polip�ptidos hidrof�bicos
luego del envasado y pasteurizaci�n y a lo largo del almacenaje. Se
incluy� un m�todo para medir por separado la cantidad de part�culas
grandes de turbieza. Las cervezas se almacenaron a tres diferentes
temperaturas y evaluadas a lo largo de seis meses. Se hace hincapi� que
este es un estudio experimental y no tiene que ver con la evaluaci�n de
procesos cerveceros actuales. Los resultados demuestran que la cantidad
total de turbieza presente y los niveles de polip�ptidos hidrof�bicos
medidos en la espuma, cerveza y turbieza var�a seg�n el tratamiento y el
tiempo y temperatura de almacenaje. Las observaciones indican que en la
cerveza existe un equilibrio din�mico entre prote�na total y polip�ptido
hidrof�bico presentes en diferentes fracciones de cerveza. Se propone un
mecanismo para la formaci�n en cerveza pos-envasado de turbieza inducida
por calor y turbieza debida al almacenaje.
Palabras claves:
almacenaje, polip�ptidos hidrof�bicos, prote�nas, turbieza cervecera
