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  Home > JCE Print > Journal of Chemical Education > Issues > 2004  > July  >
Chemistry for Everyone
The Chemistry of Beer Instability
Graham G. Stewart
International Centre for Brewing and Distilling, Herlot–Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
Cover
July 2004
Vol. 81 No. 7
p. 963
Abstract
Compared to most other alcoholic beverages, beer is unique because it is unstable when in the final package. This instability can be divided into biological and nonbiological instability. Nonbiological stability of beer involves a wide range of chemical processes and can be considered in a number of categories: physical, flavor, light, foam, and gushing. It is the balance between flavanoid polyphenols (tannoids) and sensitive proteins that specifically combine with polyphenols to form haze that largely dictates physical stability. The flavor stability of beer primarily depends on the oxygen concentration of packaged beer but is influenced by all stages of the brewing process. Foam stability in a glass of beer reflects the quality of the beverage. The backbone of foam is hydrophobic polypeptides. Novel brewing processes such as high-gravity brewing result in a disproportionate loss of these polypeptides and have a negative effect on the foam stability of the resulting beer. Beer is light sensitive, especially in the 350–500 nm range. Beer exposed to this wavelength range in clear or green glass containers quickly develop nauseous skunky-like off-flavors resulting from the formation of 3-methyl-2-butene-1-thiol. Methods of enhancing all of these types of beer stability are discussed.
More Information
*  Citation
 Stewart, Graham G. J. Chem. Educ. 2004 81 963.
*  Keywords
 Biochemistry; Biotechnology; Carbohydrates; Enzymes; Food Science; Oxygen; Photochemistry; Polymer Chemistry; Proteins / Peptides
*  History
 Created:
Last Updated:		 May 27, 2004
January 19, 2005
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