Where does the bitterness in the coffee come from? Why is coffee bitter?

A cup of coffee is a complex drink made up of more than 30 chemicals, and it is these "compounds" that determine the taste, aroma and acidity of coffee. Since the 1930s, scientists have isolated and identified a variety of chemicals related to the sensory composition of coffee, but no one can figure out what makes coffee so bitter.

In order to solve this mystery, science continuously filters the brewed coffee. They found that a small portion of the filter products contained the lowest molecular weight and the most bitter compounds, which undoubtedly provided a goal for the research team to conduct in-depth analysis. Using mass spectrometry, the researchers determined that one of the compounds was chlorogenic lactone, a decomposition product of chlorogenic acid, which is found in almost all plants. The team then baked a range of drinks from regular coffee to bitter coffee and measured the amount of chlorogenic lactone in each coffee.

The researchers found that roasting coffee beans will produce a "continuous reaction". First, the chlorogenic acid in the coffee beans will be converted into chlorogenic acid lactone, which will be broken down into phenyl dihydrogenated indene if processing continues. Chlorogenic acid lactone can produce moderate bitterness in lightly or moderately roasted coffee, and the subsequent secondary decomposition products are the root cause of the "bitterness" of espresso.

Tips:

Although the bitterness in coffee seems inevitable, proper and correct extraction can effectively reduce the bitterness in coffee. So too bitter coffee is by no means a good cup of coffee. (this article is reproduced)