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.