Featured Research

from universities, journals, and other organizations

UNC Chemists Figure Out What Causes "Skunky Beer"

Date:
October 18, 2001
Source:
University Of North Carolina At Chapel Hill
Summary:
Many people think beer tastes bad all the time, while others, who enjoy the alcoholic malt beverage, believe it turns "skunky" only when it isn’t handled properly. Now chemists at the University of North Carolina at Chapel Hill say they have figured out precisely what goes wrong with beer to give it that offensive "light-struck" flavor.

CHAPEL HILL – Many people think beer tastes bad all the time, while others, who enjoy the alcoholic malt beverage, believe it turns "skunky" only when it isn’t handled properly. Now chemists at the University of North Carolina at Chapel Hill say they have figured out precisely what goes wrong with beer to give it that offensive "light-struck" flavor.

Related Articles


"Historically, beer has been stored in brown or green bottles to protect hop-derived compounds from light in a process we call photodegradation," said Dr. Malcolm D. Forbes, professor of chemistry.

"Hops help flavor beer, inhibit bacterial growth and are largely responsible for the stability of the foam in the head," Forbes said. "Hops, however, are light-sensitive, and the three main compounds in them identified as being light-sensitive are called isohumulones. When attacked by either visible or ultraviolet light, these break down to make reactive intermediates known as free radicals that lead to the offensive taste and skunky odor."

Using isohumulones supplied by brewing companies and a sophisticated technique called time-resolved electron paramagnetic resonance spectroscopy, the UNC scientists and colleagues determined what happens chemically during photo degradation. Lasers served as the light source for producing the chemical reactions they studied.

"This light problem is a phenomenon that was reported in the literature as early as 1875, but until now the detailed mechanism has not been unraveled," Forbes said. "The final product of the reaction turns out to be what we call "skunky thiol," an analog of a compound found in skunk glands that produces a very bad taste and smell. This molecule has an extremely low taste and smell threshold in humans, just a few parts per trillion."

A report on the findings will appear in the Nov. 5 issue of a publication called Chemistry - A European Journal and appeared online this weeek. Besides Forbes, authors are UNC chemistry doctoral student Colin S. Burns and Dr. Denis De Keukeleire and his doctoral student Arne Heyerick of the University of Gent in Belgium.

The new paper describes how the team succeeded in creating the free radicals, working out their structure, explaining reactions that made them and learning precisely where in the isohumulone compounds photo breakdown takes place.

"Understanding mechanisms behind changes in beer tastes is important because the world beer industry is hoping to save money by storing, shipping and selling beer in less expensive clear glass," Forbes said. "Producers of Miller Genuine Draft, for example, already do that by adding a chemically modified hop compound to the beer. We have found evidence that Miller beer is still photochemically active, but it doesn’t make the same free radicals, and so those can’t lead to bad-tasting skunky thiols as quickly."

Corona beer also is sold in clear bottles, but manufacturers do not used a modified hop product, he said. Instead, they usually keep their bottles boxed to exclude light and encourage drinkers to add a slice of lime to improve the odor.

"Corona is marketed extremely cleverly," the chemist said.

Forbes’ laboratory is one of the most sophisticated in the world for studying super-fast radical reactions that take place in billionths of seconds. His Belgian collaborators have applied for a patent on a process that will alter and retard the photochemistry of beer to make the beverage easier to store and give it a longer shelf life.

The National Science Foundation, the Interbrew-Baillet Latour Foundation of Leuven, Belgium, and the UNC chemistry department supported the research.


Story Source:

The above story is based on materials provided by University Of North Carolina At Chapel Hill. Note: Materials may be edited for content and length.


Cite This Page:

University Of North Carolina At Chapel Hill. "UNC Chemists Figure Out What Causes "Skunky Beer"." ScienceDaily. ScienceDaily, 18 October 2001. <www.sciencedaily.com/releases/2001/10/011018071707.htm>.
University Of North Carolina At Chapel Hill. (2001, October 18). UNC Chemists Figure Out What Causes "Skunky Beer". ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2001/10/011018071707.htm
University Of North Carolina At Chapel Hill. "UNC Chemists Figure Out What Causes "Skunky Beer"." ScienceDaily. www.sciencedaily.com/releases/2001/10/011018071707.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Reuters - Light News Video Online (Dec. 19, 2014) Millions of monarch butterflies begin to descend onto Mexico as part of their annual migration south. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins