Study: it's not caffeine that makes coffee bitter

Chemical analyses and taste tests by humans have revealed -- contrary to popular belief -- that only 15 percent of the bitter taste in dark-roasted coffees comes from caffeine.

Study: it's not caffeine that makes coffee bitter

Chemical analyses and taste tests by humans have revealed -- contrary to popular belief -- that only 15 percent of the bitter taste in dark-roasted coffees comes from caffeine.

"Everybody thinks that caffeine is the main bitter compound in coffee, but that's definitely not the case," said study leader Thomas Hofmann, a professor of food chemistry and molecular sensory science at the Technical University of Munich in Germany, who presented his findings Tuesday at a meeting of the American Chemical Society in Boston.

Hofmann and his colleagues found two classes of compounds give coffee the bulk of its bitterness. Both are antioxidants found in roasted coffee beans, not in the green (raw) beans.

One class, called chlorogenic acid lactones, is present at high levels in light- to medium-roast brews. Dark roasts, such as espresso, showed high levels of phenylindanes, which form when the chlorogenic acid lactones break down and give a more lingering, harsh taste than their precursors, Hofmann said.

"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 explained. He added that prolonged roasting leads to the formation of the most intense bitter compounds found in dark roasts.

The scientists also discovered that how the beans are brewed affects bitterness. The high pressures and temperatures used for brewing espresso-type coffees produce the highest levels of bitter compounds.

"Now that we've clarified how the bitter compounds are formed, we're trying to find ways to reduce them," Hofmann said.

Agencies

Last Mod: 23 Ağustos 2007, 13:16
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