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Research finds new compounds that explain coffee mouthfeel

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New research from The Ohio State University has discovered several compounds that contribute to the sensation or ‘mouthfeel’ when drinking coffee.

These compounds can explain why the beverage coats the inside of one’s mouth, and has astringent and chalky textures.

“We’ve known that coffee itself can impact textural sensations, and it was traditionally thought to be because of sugars and lipids,” says Dr. Christopher Simons, a co-co-principal project investigator.

“But our team finds that this feeling may actually be driven by small molecules, which is kind of unique.”

According to the American Chemical Society (ACS) these novel findings have the potential to change speciality coffee processing and roasting.

Christopher says that this knowledge could also help producers and growers to create the best cup of coffee, and help coffee aficionados to attribute certain features in a cup of java to specific compounds, like wine enthusiasts are able to do.

Until now, says the ACS, these specific compounds that contribute to this sensation have not been well defined.

Brianne Linne, a student who is working on the project with Christopher and co-principal investigator Dr. Devin Peterson says, “From our background reading, we found definitions of coffee body to be very vague, and at times, contradictory, so we thought that this would be an intriguing topic for us to study.”

The team isolated the compounds responsible for the coffee’s mouthfeel by first creating a descriptive analysis panel. They began with four different coffees that evaluators had licensed from the Specialty Coffee Association. These all had varying ratings in regard to body.

A separate panel of eight coffee tasters with “skilled tactile awareness” then agreed on a set of references that illustrated the sensations when differentiating between each cup.

“To better define the term ‘body,’ we broke it down into components that would allow us to look for the compounds driving those particular sensations,” says Christopher.

Four tactile sub-attributes were created to differentiate the coffees. These include chalkiness, mouthcoating, astringency, and thickness. The team then split the fullest-body coffee into 12 fractions using liquid chromatography and a panel of five tasters screened each fraction.

If a majority ranked the sub-attribute strongly in a fraction, it was further purified to pinpoint the exact compound responsible. Through this method, the researchers were able to find a cluster of small molecules that contributed to coffee’s mouthfeel.

Co-principal investigator Dr. Devin Peterson says the team isolated melanoidin compounds, formed by the Maillard reaction during roasting, and for the first time associated them with astringency.

Two of the compounds, the three and four caffeoylquinic acids, corresponded with mouthcoating, however, it was found that the sensation subsided with increased concentration.

Although biological responses are multi-faceted, Peterson says it is uncommon for an attribute to be perceived at low levels, but not at high levels. In the final stages, the team then isolated a novel compound related to chalkiness that contains an amino acid.

The team is now interested in whether there are mechanoreceptors in the mouth that detect these small molecules. Devin says if so, such receptors could be responsible for the decreased mouthcoating sensation that happens with increasing caffeoylquinic acid.

In the future, the team also wants to study how coffee bean growing conditions and roasting temperatures can affect these compounds. With this knowledge, the team reasons that coffee growers and producers could manipulate coffee processes or highlight small molecules in a cup of coffee, dependent on consumer preferences.

These findings were presented at the ACS Fall 2021 hybrid meeting that ran from 22 to 26 August. On-demand content will be available from 30 August to 30 September with the meeting encompassing more than 7000 presentations across a range of science topics.

The researcher acknowledge support and funding from the OSU Flavor Research and Education Center.

For more information, visit www.acs.org/content/acs/en.html

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