The Chemistry of Beer Brewing
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One of the world’s oldest and most popular beverages is beer. The brewing of beer was first done by ancient civilizations such as the Egyptians and Babylonians and is considered to be one of the earliest uses of biotechnology.1 Science was not known during this time and the brewing of beer was mostly considered an art form. It was not until the discovery of fermentation during the 19th century that chemistry was first applied to the brewing of beer.1,2

Chemistry is now a large part of the beer brewing process. While the exact number is unknown, there are over 450 identified chemical compounds found in a typical beer.3,4 Like other alcoholic beverages, beer can greatly vary among its different types. Though the differences between beer types can be substantial, all beers have a set of characteristics that give them a common definition. Beer is a slightly alcoholic, bitter tasting liquid with a color ranging from light yellow to dark brown, and an acidic pH ranging from 4 to 4.5.3

The basic brewing process has remained relatively unchanged since its use in ancient civilizations. However, with applications of chemistry being used in beer brewing, beer has been improved upon in many ways. Identifying what molecules give beer its characteristics can be used to help give a higher quality product. Beer is also never at equilibrium5, making chemistry vital in the control of reactions during the brewing process. There are five main steps in the brewing of beer: malting, mashing, boiling, fermentation, and ageing.

     
      References

1.
Onishi, A.; Proudlove, M. O.; Dickie, K.; Mills, C.; Kauffman, J. A.; Morgan, M. R. A. Monoclonal Antibody Probe for Assessing Beer Foam Stabilizing Proteins. J. Agric. Food Chem. [Online] 1999, 47, 3044–3049. http://pubs.acs.org/doi/pdf/10.1021/jf9810968 (accessed Oct 7, 2012).

2. Bardt, E. P.; Koutinas, A. A.; Souploni, M. J.; Kanellaki, M. E. Immobilization of Yeast on Delignified Cellulosic Material for Low Temperature Brewing.  J. Agric. Food Chem. [Online] 1996, 44, 463–467. http://pubs.acs.org/doi/pdf/10.1021/jf9501406 (accessed Oct 7, 2012).

3. Jasminka, K. N.; Plavsic, J. V.; Marinkovic, D.; Mandic, L. M. Beer as a Teaching Aid in the Classroom and Laboratory. J. Chem. Educ. [Online] 2012, 89, 605–609. http://pubs.acs.org/doi/full/10.1021/ed200187c (accessed Oct 9, 2012).

4. Castritius, S.; Kron, A.; Shafer, T.; Radle, M.; Harms, D. Determination of Alcohol and Extract Concentration in Beer Samples Using a Combined Method of Near–Infrared (NIR) Spectroscopy and Refractometry. J. Agric. Food Chem. [Online] 2010, 58, 12634–12641. http://pubs.acs.org/doi/pdf/10.1021/jf1030604 (accessed Oct 12, 2012).

5. Stewart, G. G. The Chemistry of Beer Instability. J. Chem. Educ. [Online] 2004, 81, 963–988. http://pubs.acs.org/doi/pdf/10.1021/ed081p963 (accessed Oct 7, 2012).