A cup of coffee contains about 30 different chemicals.

Human beings have a long history of quoting coffee. Coffee has not only become a part of many people's lives, but also aroused the creative inspiration of many artists. For example, the German composer Bach once wrote an oratorio for coffee to describe his love of coffee.

There are about thirty different chemicals in a cup of coffee. These different compounds bring complex flavors to coffee, such as sour, astringent, bitter and so on. As early as 1930, many scientists began to study the effects of various chemical molecules in coffee on coffee flavor. But there is not much research on the bitterness of coffee.

Thomas Hofmann of Technical University of Munich in Germany decided to study the bitterness of coffee. He filtered the brewed coffee and found that some of the molecules with the smallest molecular weight tasted the bitterest. So he began a series of experiments on this point, and he found that one of the molecules was chlorogenic acid (chlorogenic acid lactone). Chlorogenic acid exists in most plants and becomes chlorogenic acid lactone after dissociation. So they analyzed a series of ​​ coffees with different roasting degrees to test the content of chlorogenic acid lactone.

They found that roasted coffee beans break down chlorogenic acid into chlorogenic acid lactone, giving the coffee a mild bitter taste. The result of further baking will decompose chlorogenic acid lactone into phenyl lindane (phenylindanes), which will produce a strong bitter taste. The findings were presented at this year's American Chemistry Annual meeting.

In addition to increasing our understanding of coffee, another source of coffee bitterness may be of more interest to coffee manufacturers. From this study, they may be able to find ways to reduce the bitterness of coffee and make it acceptable to more people.