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Are Craft Brewers Underaerating Their Wort?

MBAA TQ vol. 45, no. 4, 2008, pp. 352-354  |  VIEW ARTICLE

Neva Parker. White Labs Inc., 7564 Trade Street, San Diego, CA 92121.

Abstract
Small-scale microbreweries and brewpubs often lack some of the expensive equipment essential for maintaining strict consistency in fermentation products. One control that is commonly overlooked is the amount of dissolved oxygen (DO) in wort prefermentation. This leads to the question, are craft brewers underaerating their wort? An investigation is described here that explores the adequacy of current DO levels in craft breweries and whether this has any correlation with fermentation issues such as long lag time and slow fermentation. The range of oxygenation levels with respect to their effects on fermentation speed and the variance in DO requirements between laboratory-grown cultures and multiple-generation brewery cultures are also addressed. The DO levels of wort from a small sampling of mid-sized craft breweries were compared with the same wort at a measured 10 ppm DO in lab-scale fermentation trials. A commercial ale yeast strain was used for all fermentations, and fermentation vessels were kept at a constant temperature in a glycol-controlled water bath. The study was designed to determine whether craft breweries are sufficiently oxygenating their wort and the impact of this on yeast performance, as well as to provide a possible approach to improve fermentation success.

Keywords: aeration, dissolved oxygen, slow fermentation, underattenuation

 

S�ntesis
A las cervecer�as artesanales frecuentemente les faltan algunos de los equipos costosos esenciales para mantener una uniformidad estricta en sus productos. Un control que por lo general se desde�a es el control de la cantidad de ox�geno disuelto (DO) en la prefermentaci�n del mosto, lo que podr�a conducir a que los cerveceros artesanales no airean suficientemente al mosto enfriado. Se estudiaron los niveles de DO en los mostos de cervecer�a artesanales para tratar de determinar si esto tendr�a alguna correlaci�n con problemas tales como un lento arranque de la fermentaci�n y/o fermentaciones lentas. Tambi�n se estudi� el efecto del nivel de ox�geno sobre la velocidad de la fermentaci�n, as� como la diferencia en los requerimientos de DO de cultivos propagados en el laboratorio y aquellas levaduras provenientes de fermentaciones anteriores. Los niveles de DO en mostos de un peque�o n�mero de cervecer�as artesanales de tama�o medio fueron comparados en fermentaciones en laboratorio con un mosto con 10 ppm DO, usando una sepa de levadura comercial tipo �ale� en mini fermentadores mantenidos a temperatura constante en ba�o de mar�a con glicol. Con esto se quiso ver si cervecer�as artesanales oxigenaban suficientemente a sus mostos y como esto afectaba el desempe�o de la levadura, como tambi�n proveer una manera de mejorar la fermentaci�n.

Palabras claves: aeraci�n, atenuaci�n pobre, fermentaci�n lenta, ox�geno disuelto

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