The wonderful thing about coffee is that it delivered on its promise every time. It contributes sensation of body or mouthfeel, a tactile feeling of the liquid in the mouth.
But, what contributes to the feeling remains elusive.
Now, scientists have reported several coffee compounds that contribute to the feeling of the beverage coating the inside of the mouth and astringency and chalkiness sensations.
Scientists started by establishing a descriptive analysis panel of compounds. They then isolated the compounds responsible for coffee’s mouthfeel. They started with four different coffees evaluators. These evaluators are licensed by the Specialty Coffee Association who had given varying ratings in terms of body. A separate panel of eight experienced tasters, skilled in tactile awareness, then agreed on a set of references that illustrated the sensations differentiating each cup.
To describe coffee mouthfeel, scientists broke it down into components that allowed them to look for the compounds driving those particular sensations. Four tactile sub-attributes, namely chalkiness, mouthcoating, astringency, and thickness, were used to differentiate the coffees.
They separated the fullest-body coffee into 12 fractions using liquid chromatography, and a panel of five tasters screened each fraction. If a majority ranked a sub-attribute strongly in a fraction, it was further purified to pinpoint the exact compound responsible.
Christopher Simons, Ph.D., one of the project’s co-principal investigators, said, “We’ve known that coffee itself can impact textural sensations, and it was traditionally thought to be because of sugars and lipids. But our team finds that this feeling may be driven by small molecules, which is kind of unique.”
“This knowledge could help producers and growers make the best coffee. It also could help aficionados attribute certain features of a cup of java to specific compounds, just as wine enthusiasts do.”
Brianne Linne, a graduate student, said, “From our background reading, we found definitions of the coffee body to be very vague, and at times, contradictory, so we thought that this would be an intriguing topic for us to study.”
Scientists found that a cluster of small molecules contributes to coffee’s mouthfeel.
Peterson said, “They isolated melanoidin compounds, formed by the Maillard reaction during roasting, and for the first time associated them with astringency. Two compounds, 3- and 4-caffeoylquinic acid, correspond with mouthcoating. Unexpectedly, the sensation subsided with increased concentrations. Although biological responses are multifaceted, it is uncommon for an attribute to be perceived at low levels but not at high levels. Finally, they isolated a novel compound related to chalkiness that contains an amino acid.”
Scientists are not looking forward to determining if mechanoreceptors in the mouth detect these small molecules. They think such receptors could play a vital role in decreasing the mouthcoating sensation that increases caffeoylquinic acid.
Scientists will also know more about how coffee bean growing conditions and roasting temperatures affect the compounds. With this knowledge, growers and producers could manipulate their processes to downplay or highlight the small molecules in a cup of coffee according to consumers’ preferences.
Scientists will present their results today at the fall meeting of the American Chemical Society (ACS).