Chemists winning the battle against bitter coffee

Coffee drinkers are a varied lot to be sure but most of them can agree that bitter coffee is bad coffee. But chemists in Germany and the United States now say they have identified the chemicals that appear to be largely responsible for coffee’s bitterness and they hope that discovery will lead to a better tasting brew. 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 unroasted beans, the researchers note.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,Research by others 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.”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 in a statement. Only 15% 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.” How you brew also plays a role in bitterness. Espresso, 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, researchers said. “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 types of beans 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.The study, one of the most detailed chemical analyses of coffee bitterness to date, was presented this week at the 234th national meeting of the American Chemical Society.Improving taste will likely only heat up the competitive coffee market where one person’s perfect cup of morning Joe in another’s cup of mud.  You may recall the stink earlier this year  when Consumer Reports, the venerable testing rag said McDonald’s coffee is better than Starbucks, Dunkin Donuts and others.     Consumer Reports said the tastings were conducted by a professional tester, and included staffers from Consumer Reports’ food-testing division. The group tasted medium cups of coffee – no cream or sugar – at two locations from each company in November. They rated McDonald’s premium brand the best, calling it “decent and moderately strong” although lacking “subtle top notes,” whatever that means. Dunkin Donuts’ coffee was called “inoffensive, but it had no oomph.” Starbucks was labeled “strong, but burnt and bitter.” Burger King’s offering resembled coffee, “but tasted more like hot water,” the magazine said.  Then there are other outlets that seem hell-bent on ruining the coffee experience.  7-Eleven earlier this year  rolled out “Fusion Energy” coffee which includes an herbal boost of ginseng, guarana and yerba mate – ingredients found in many energy drinks.  For the record, Layer 8 is a Peet’s fan.