Why is Coffee Bitter?

Why is coffee bitter? For decades, this question has puzzled scientists.

Now, scientists have narrowed their research focus to two chemical molecules. At the annual meeting of the American Chemical Society, scientists reported that these two compounds responsible for bitterness are produced during coffee processing - a discovery that could change the coffee industry.

Thomas Hofmann from the Technical University of Munich in Germany and his colleagues separated brewed coffee once again. After analysis using mass spectrometry, Hofmann identified one of the molecules: chlorogenic acid lactone, a breakdown product of chlorogenic acid, which is found in almost all plants. Hofmann's team then prepared a series of different coffees, measuring the chlorogenic acid lactone content in each. Although in light and medium roast coffees the lactones produce only a mild bitterness, if the beans are roasted for longer, the secondary decomposition products of the lactones generate an intense bitter taste.

FrontStreet Coffee Recommendation

That finding explains a good deal of what drinkers notice in the cup: bitterness is not simply a matter of how much coffee you use, but of how the beans were roasted and processed. Light and medium roasts hold that bitterness back, which is why they taste sweeter and more rounded - a useful starting point if the bitterness in dark roasts puts you off.

FrontStreet Coffee's Brazil Queen Estate is a good first stop. It is a yellow Bourbon from Brazil, the world's largest coffee producer, and its mild, clean character roasts well at a medium level, bringing out cream peanut, chocolate, toast and sugarcane sweetness. It has enough body to feel satisfying without any harsh edge, and works as pour-over, moka pot or espresso.

If you like a sweeter cup, FrontStreet Coffee's Strawberry Candy combines a Costa Rican honey-processed coffee with a washed Panamanian Geisha and roasts it medium, so the orange-blossom honey character and a round sweetness come through whether you brew it as pour-over, cold brew or espresso.

For a gentle, tea-like profile, FrontStreet Coffee's 2013 Yunnan natural Typica is roasted medium and shows nut, brown sugar, black tea and dried apricot, with a soft balance that keeps the bitter note in check. At the classic end, FrontStreet Coffee's Jamaica Blue Mountain No.1 is also roasted medium, blending chocolate, roasted nut, cream and caramel so that acidity, bitterness and sweetness stay in proportion - the clearest illustration of the balance this research points to. Two practical notes follow: keep the water temperature moderate, since overheating a brew is one of the most common causes of a harsh, salty, bitter cup, and match the grind to the roast level, which for these medium roasts means a medium-fine setting rather than a fine one.