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Nutrition, Vitamins & Supplements for Seniors
Chemists Say They Now Know How to Remove Bitterness
from Coffee
Great news for senior citizens who already prefer
coffee to sex
 Aug.
22, 2007 Chemists think they can make coffee taste better. Thats
staggering news to millions of senior citizens who said in a poll that
they would prefer to give up sex before their coffee. But, the
scientists claim they have discovered what makes java bitter and say
this could lead to even better tasting coffee.
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Research over the past few years has identified an
estimated 25 to 30 compounds that could contribute to the perceived
bitterness of coffee. But the main cause of coffee bitterness has
remained largely unexplored until now, the researchers say.
This study, by chemists in the U.S. and Germany,
claims to be one of the most detailed chemical analyses of coffee
bitterness to date and was presented this week at the 234th national
meeting of the American Chemical Society.
"Everybody thinks that caffeine is the main bitter
compound in coffee, but that's definitely not the case," says study
leader Thomas Hofmann, Ph.D., a professor of food chemistry and
molecular sensory science at the Technical University of Munich in
Germany.
Only 15 percent of java's perceived bitterness is
due to caffeine, he estimates, noting that caffeinated and decaffeinated
coffee both have similar bitterness qualities.
"Roasting is the key factor driving bitter taste in
coffee beans. So the stronger you roast the coffee, the more harsh it
tends to get," Hofmann says, adding that prolonged roasting triggers a
cascade of chemical reactions that lead to the formation of the most
intense bitter compounds.
Using advanced chromatography techniques and a
human sensory panel trained to detect coffee bitterness, Hofmann and his
associates found that coffee bitterness is due to two main classes of
compounds: chlorogenic acid lactones and phenylindanes,
both of which are antioxidants found in roasted coffee beans.
The compounds are not present in green (raw) beans,
the researchers note.
"We've known for some time that the chlorogenic
acid lactones are present in coffee, but their role as a source of
bitterness was not known until now," Hofmann says.
Ironically, the lactones as well as the
phenylindanes are derived from chlorogenic acid, which is not itself
bitter.
Chlorogenic acid lactones, which include about 10
different chemicals in coffee, are the dominant source of bitterness in
light to medium roast brews.
Phenylindanes, which are the chemical breakdown
products of chlorogenic acid lactones, are found at higher levels in
dark roasted coffee, including espresso. These chemicals exhibit a more
lingering, harsh taste than their precursors, which helps explain why
dark-roasted coffees are generally more bitter, Hofmann says.
The type of brewing method used can also influence
the perception of bitterness. Espresso-type coffee, which is made using
high pressure combined with high temperatures, tends to produce the
highest levels of bitter compounds. While home-brewed coffee and
standard coffee shop brews are relatively similar in their preparation
methods, their perceived bitterness can vary considerably depending on
the roasting degree of the beans, the amount of coffee used, and the
variety of beans used.
Some instant coffees are actually less bitter than
regular coffee, Hofmann says. This is because their method of
preparation, namely pressure extraction, degrades some of the bitter
compounds. In some cases, as much as 30 to 40 percent fewer chlorogenic
acid lactones are produced, leading to a reduced perception of
bitterness, he says.
"Now that we've clarified how the bitter compounds
are formed, we're trying to find ways to reduce them," Hofmann says.
He and his associates are currently exploring ways
to specially process the raw beans after harvesting to reduce their
potential for producing bitterness. They are also experimenting with
different bean varieties in an effort to improve taste. But so far, none
of these approaches - details of which are being kept confidential by
the researchers - is ready for commercialization, he notes.
But the researchers are optimistic that a better
cup of Joe is just around the corner. Perhaps no one could be happier
about the news than Hofmann, who admits that he is an avid
coffee-drinker with a passion for the dark-roasted varieties.
Editors Notes:
Funding for the study was provided by the Technical
University of Munich, the University of Muenster, and The Procter and
Gamble Company.
The American Chemical Society - the world's largest
scientific society - is a nonprofit organization chartered by the U.S.
Congress and a global leader in providing access to chemistry-related
research through its multiple databases, peer-reviewed journals and
scientific conferences. Its main offices are in Washington, D.C., and
Columbus, Ohio.
Thomas Hofmann, Ph.D., is a professor of food
chemistry and molecular sensory science at Technical University of
Munich in Germany.
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