The Interaction Between Malt Protein Quality and Brewing Conditions and Their Impact on Beer Colloidal Stability
Peer-Reviewed Paper
MBAA TQ vol. 41, no. 4, 2004, pp. 353-362 |
VIEW ARTICLE
Louise H. Robinson (1), D. Evan Evans (2), Anu Kaukovirta-Norja (3), Arvi Vilpola (3), Peter Aldred (4), and Silja Home (3). 1. School of Agriculture and Wine, University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia. 2. TIAR, Private Bag 54, University of Tasmania, Hobart, TAS 7001, Australia. 3. VTT Biotechnology, P.O. Box 1500, FIN-02044 VTT, Finland. 4. School of Science and Engineering, University of Ballarat, P.O. Box 663, Ballarat, VIC 3353, Australia.
Abstract
In bright beers, the formation of permanent haze is a serious quality problem that places limitations on the storage life of the product. From silica gel, used for the colloidal stabilization of beer, a silica eluent (SE) protein fraction was isolated and an antibody raised against this fraction. Sodium dodecyl sulfate�polyacrylamide gel electrophoresis (SDS-PAGE) immunoblot analysis using the SE antiserum detected a range of protein bands in barley, malt, beer, and haze. Interestingly, a polymorphism was observed in some barley varieties that contained an ~12,000-molecular-weight band (SE +ve), while in other varieties, this band was absent (SE �ve). Pilot brewing trials found that beer brewed from SE �ve varieties formed less haze in haze force testing trials (5 days at 55�C/1 day at 0�C) than did beer produced from SE +ve varieties. The interaction between the presence/absence of the SE protein and controlled-atmosphere brewing by brewing under nitrogen or air was also investigated. Surprisingly, the application of a nitrogen-rich atmosphere produced beer that was less stable compared with that produced when brewing under a normal atmosphere. Filtration trials showed that the colloidal stability of beer could be influenced by the filtration process. The removal of the SE protein and other proteins during filtration from beer brewed with an SE +ve malt variety, along with a reduction in the level of total protein as measured by Bradford, resulted in improved colloidal stability. Combined, these investigations are discussed in terms of brewers� options for extending the colloidal stability of their beer and optimizing the colloidal stabilization treatments.
Keywords: beer aging, brewing, colloidal stability, filtration, haze, malt, protein
S�ntesis
La formaci�n de una turbidez permanente en cervezas claras l�mpidas es un problema serio de calidad que impone limitaciones sobre la vida de estante del producto. Se ha podido aislar una fracci�n prote�nica eluente de s�lica (ES) del s�lica gel utilizado para la estabilizaci�n coloidal de una cerveza y se ha podido desarrollar un anticuerpo contra dicha fracci�n. El an�lisis de imunosecante de electroforesis de gel de sodio dodecil sulfato poliacrilamida, utilizando el antisuero ES, sirvi� para detectar una serie de franjas proteicas en cebada, malta, cerveza y materia turbia. Es interesante notar que se observ� un polimorfismo en algunas variedades de cebada que conten�an una franja con un peso molecular de circa 12,000 (ES +ve), mientras que en otras variedades esta franja estaba ausente (ES �ve). Pruebas de planta piloto demostraron que cervezas elaboradas con variedades ES �ve formaban menos turbidez en pruebas forzadas (5 d�as a 55�C/1 d�a a 0�C) que cervezas elaboradas con variedades ES +ve. Tambi�n se investig� la interacci�n entre la presencia/ausencia de la prote�na ES y la elaboraci�n en una atm�sfera controlada (nitr�geno o aire). Sorpresivamente, el uso de una atm�sfera enriquecida con nitr�geno result� en una cerveza menos estable que aquella elaborada normalmente. Pruebas de filtraci�n demostraron que la estabilidad coloidal de cerveza puede ser influenciada por el proceso de filtraci�n. La remoci�n de la prote�na ES (y otras prote�nas) en la filtraci�n de cervezas elaboradas con una malta ES +ve, junto con la reducci�n de la prote�na total medido seg�n Bradford, dio una mejora en la estabilidad. Se discute, a la luz de estos estudios, cuales son las opciones que tienen los cerveceros para extender la estabilidad coloidal de sus cervezas y para la optimizaci�n de sus tratamientos de estabilizaci�n coloidal.
Palabras claves: envejecimiento de cerveza, elaboraci�n, estabilidad coloidal, filtraci�n, turbidez, malta, prote�na
