58. The kinetics and chemistry of beer aging—A critical review
Margaux Huismann (1), Fraser Gormley (2); (1) International Centre for Brewing and Distilling, Edinburgh, U.K.; (2) BrewDog, Ellon, U.K.
Technical Session 17: Beer Aging
Tuesday, August 16 • 3:30–5:15 p.m.
Plaza Building, Concourse Level, Governor’s Square 14
Beer is a complex beverage, consisting of thousands of dissolved
molecules and chemical compounds. These molecules and compounds are not
in a stable state of equilibrium. Therefore, changes to sensory and
colloidal stability occur as beer ages. This review will examine the
chemistry of these beer-aging reactions in light of current beer aging
research. A survey of well-known, as well as lesser-known, beer aging
reactions will be presented and discussed. This paper will consider both
oxidative and non-oxidative processes. Methods of modeling beer
reaction kinetics will be discussed and elucidated. Diacetyl, trans-2-nonenal,
haze and even free radical levels have been proposed to be useful
indicators when investigating beer stability. The unique fate and state
of these compounds during aging will be illustrated. For example, in the
past trans-2-nonenal formation, specifically in packaging, has
been (rather simply) considered a result of oxidation. However, recent
publications have sparked controversy regarding this issue.
Additionally, hydroxyl radicals are reactive oxygen species and are
thought to be major components in the formation of beer aging compounds.
However, much remains to be discovered between antioxidant levels and
total packaged oxygen present during the “ESR lag time” of aging. This
lag time refers to the time when the formation of free radicals are
limited by antioxidant quenching reactions. By modeling the kinetics of
this lag time in relation to reactive oxygen species, beer stability and
aging can be better understood. This paper will also discuss how
brewing processes and packaging affect aging reactions and beer quality.
Particular reference will be made to craft brewing operations. Recent
ongoing experiments conducted both at BrewDog and The International
Centre of Brewing and Distilling will also be referenced in this review.
Our aim will be to illustrate the dynamic nature of beer aging and
promote our understanding of aging reactions, which are crucial to beer quality.
Margaux Huismann received a B.S. degree in microbiology from the University of Wisconsin-La Crosse in 2014. Over the course of 2014-2015, she completed her M.S. degree in brewing and distilling at Heriot-Watt University at the International Centre for Brewing and Distilling (ICBD) in Edinburgh. During her master’s studies, she was employed at Stewart Brewing and Barney’s Beer. She created the inaugural year of “The Spirited Botanists” with a team of ICBD master’s students, which created Edinburgh Gin’s Seaside Gin. She is currently a Ph.D. student with the ICBD and BrewDog, studying the chemistry of dry-hopping, and sits on the Institute of Brewing and Distilling Scottish Section Committee as a young member representative.
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