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(Chem) Beer

 
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adedios
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PostPosted: Sun Dec 16, 2007 8:38 am    Post subject: (Chem) Beer Reply with quote

Raymond Gephart, Georgetown University
December 15, 2007

Composition of Beer by H1 NMR spectroscopy

Beer is the oldest alcoholic beverage known in the world's history. Beer is labeled an alcoholic beverage due to the ethanol content. Ethanol is classified as an alcohol in chemistry, and this is where the term alcoholic beverage is derived from. Alcohol has been used in history for a variety of reasons. Most have used it because of its sedative nature. Alcohol is also considered the source of inspiration for art as well as an aphrodisiac. Beer was the main alcoholic beverage in man's early history and is still widely used in today's society for the same reasons.

The quality of beer is rooted in its chemical composition. Where a beer is brewed, for how long, and the ingredients that are used all contribute to the quality of beer that is produced. Some of the key ingredients are water quality, malt, hop, yeast and timing. These factors affect the beer's appearance, flavor and aroma but there is no understanding of how or why. A study of the composition of beer through NMR spetroscopy has led to a better understanding of what is in various beers from different breweries at different dates.

Nuclear magnetic resonance (NMR) spectroscopy is an instrument used in chemistry to analyze the component of a chemical. NMR is a tool that measures the effect of a strong magnet on a sample. The nucleus of the sample will spin at a frequency that is a characteristic of that nucleus in that environment. This tool allows chemists the ability to determine what chemical or chemicals are present in a given sample. An NMR experiment produces a spectrum that consists of peaks at various points from a standard. These peaks show what frequency the nucleus is spinning at. These peaks can be analysed to determine what chemical is present. For one research group, this tool is used to determine what chemicals are present in beer.

This study has been able to identify various components in beer including lactic acid, pyruvic acid, amino acids, and nucleosides. In order to identify these chemicals, water and ethanol needed to be removed from the spectrum. Water and ethanol are present in high quantities in beer and their peaks would overshadow the peaks from the other chemicals in the solution, making the small peaks dificult to observe. A technique called principal component analysis (PCA) was used to eliminate the information from water and ethanol. PCA takes a spectrum that is obtained from several NMR experiments to determine what peaks are due to the presence of ethanol and water and then subtracts them out of the spectrum.

The information obtained from the NMR and PCA experiments has allowed this research group to find differences between samples from different sites and different dates. The differences in the components in the beer samples has been attributed to quality of yeast and conditions during malting. The differences in brewing have resulted in difference levels of lactic, pyruvic acids, adenosine, uridine, tyrosine, and 2-phenylethanol, and carbohydrate composition. So far, no links have been made between these differences and the quality of the beer brewed. These researchers are encouraged that there may be a new technique that can help improve the quality of beer produced by looking at its chemical composition.




For more information:

Almeida, C. et. al., J. of Agricultural and Food Chemistry, 2004, 54, 700-706.

Beer history:
http://www.drinkfocus.com/arti...../index.php

Alcoholic beverage:
http://en.wikipedia.org/wiki/Alcoholic_beverage

NMR:
http://www.cis.rit.edu/htbooks/nmr/

PCA:
http://www.doe-mbi.ucla.edu/~p.....ar/pca.htm

Amino acid:
http://web.indstate.edu/thcme/.....acids.html

Nucleoside:
http://en.wikipedia.org/wiki/Nucleoside

Carbohydrate:
http://en.wikipedia.org/wiki/Carbohydrate

Malting:
http://en.wikipedia.org/wiki/Malt
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adedios
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PostPosted: Sat Dec 29, 2007 9:17 am    Post subject: Beer Brewed Long Ago by Native Americans Reply with quote

Beer Brewed Long Ago by Native Americans
By Heather Whipps, Special to LiveScience

posted: 28 December 2007 01:15 pm ET

Ancient Pueblo Indians brewed their own brand of corn beer, a new study suggests, contradicting claims that the group remained dry until their first meeting with the Europeans.

Archaeologists recently found that 800-year-old potsherds belonging to the Pueblos of the American Southwest contained bits of fermented residue typical in beer production.

For the full article:

http://www.livescience.com/his.....-beer.html
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adedios
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PostPosted: Mon Jun 02, 2008 12:14 pm    Post subject: Keeping beer fresher Reply with quote

Keeping beer fresher
Journal of Agricultural and Food Chemistry


Scientists in Venezuela are reporting an advance in the centuries-old effort to preserve the fresh taste that beer drinkers value more than any other characteristic of that popular beverage. Their study, which identifies key substances involved in giving beer an aged or "oxidized" flavor, is scheduled for the May 28 issue of ACS’ Journal of Agricultural and Food Chemistry, a bi-weekly publication.

In the new study, Adriana Bravo and colleagues point out that past efforts to keep beer fresh have focused on protecting beer from contact with the air throughout the brewing process. That focus, however, has resulted in only a relatively small improvement in flavor stability.

The research identified a group of poorly understood substances called alpha-carbonyls as important culprits in the decline in fresh flavor that occurs as beer ages. It also showed that levels of some of these substances could be reduced by adding ingredients that block their formation, thus making beer taste fresher longer. — MTS

ARTICLE #2 FOR IMMEDIATE RELEASE
“Formation of alpha-Dicarbonyl Compounds in Beer during Storage of Pilsner”

DOWNLOAD FULL TEXT ARTICLE
http://dx.doi.org/10.1021/jf703696p
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