Cup 'o joe

Chemistry explains why the most underrated part of coffee is so important

It all comes back to the “mouthfeel.”


Watch out coffee enthusiasts, a new specification to obsess over has just dropped — and it might totally change the beans you buy.

Whether you’re drinking a meticulously steeped pour-over or grabbing a coffee at your local drive-thru, coffee drinkers know that the “mouthfeel” of their drink can have a huge impact on how much they enjoy it. From novices to baristas, people can usually tell a pretty good coffee from a watery mess.

There are few things worse than a horrible cup of coffee, but this new scientific insight could help you avoid it.

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Coffee can typically be tweaked with sugar or dairy to make even the worst brews somewhat palatable, but the Specialty Coffee Association (SCA) specifically describes the mouthfeel, or body, of coffee as the “tactile feeling” of the drink your mouth without these amendments. This is the physical sensation that accompanies a sip — and the realization that your brew is thick and velvety, thin and delicate, or something in between.

On Tuesday at the American Chemical Society fall meeting, scientists revealed the chemical compounds responsible for causing the phenomenon.

They found small molecules, rather than sugars and lipids as believed, influence mouthfeel. The study team used a combination of chemical analysis and expert palettes to zero in on what compounds are responsible.

Just as wine lovers can attribute certain features to specific compounds, now coffee fans can do the same.

The science of “mouthfeel” — Brianne Linne, a Ph.D. candidate at The Ohio State University, is one of the co-researchers and presenters of this coffee chemistry examination.

“Mouthfeel is really the wild west... ”

Linne tells Inverse that despite how important mouthfeel is for enjoying the drink, scientists haven’t know exactly what was going on under the brew’s surface to elicit the sensation — until now.

“From a flavor chemistry standpoint, there has been a limited amount of research conducted on the mouthfeel of coffee,” Linne explains. Previously, most coffee research was focused on taste and aroma.

How you brew or grind your beans can influence mouthfeel.

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“Mouthfeel is really kind of the wild west when it comes to flavor,” she says. “I think this is largely because we have more complete and widely understood lexicons to verbalize taste and aroma attributes.”

How you brew or grind your beans can definitely influence coffee’s mouthfeel— a cup brewed from a moka pot might feel different than one brewed in a french press. In this study, Linne and colleagues focused specifically on coffee brewed in a drip coffee machine using a filter.

Why it matters — Not only does this work help answer a long-standing question for coffee chemists, but it can help consumers and roasters better understand their coffee preferences and techniques.

“Using these techniques, we can establish molecular markers that enable processors and roasters to target compounds of interest corresponding to their desired flavor profile throughout processing,” Linne says.

This may offer coffee enthusiasts a new language to describe their favorite pastime.

There is a myriad of ways to brew coffee today, but in this research, the scientists stuck with a true classic: drip coffee.


How’d they do it — The study team examined different samples of drip coffee and worked with professional coffee tasters (a job title called “cuppers”) to identify four different tactile attributes that contribute to a drink’s overall mouthfeel.

“The panel names a sensation they are perceiving and then taste through many references to select the one that most closely imparts the same sensation they are describing,” Linne explains. “Then, throughout the tasting, these references are used to remind the panel and maintain alignment on the attributes of interest.”

Those attributes include:

  • Chalkiness
  • Mouthcoating
  • Astringency
  • Thickness

Components from these samples were then isolated using chromography — a chemistry technique that separates parts of a solution using capillary action — and analyzed used mass spectrometry to determine which chemical compounds might be responsible for different parts of the taste sensation.

From this process, the team was able to pinpoint several different compounds responsible for telltale tactile sensations, including that compounds formed during roasting are responsible for the astringent component of coffee’s body.

These melanoidin compounds are caused by the Maillard reaction, which is the same reaction responsible for the caramelized-like exterior of a good steak.

What’s next — While this new work has made an important dent in these coffee questions, there are still many unknowns that the researchers hope to explore next. How do the receptors in our mouths detect these subtle compounds? How can changing the roasting of beans tweak this sensation?

“An immediate next step is actually to do some lab-scale roasting experiments to see how roasting impacts the concentration of these compounds by examining a single bean at multiple roast levels,” Linne says.

“By understanding this, we should have a fairly actionable idea of whether these compounds are higher or lower or static based on the degree of roast. At that point, it will be up to consumers to decide which they prefer.”

Abstract: Body is one of ten attributes defined by the Specialty Coffee Association (SCA) that contributes to the overall quality rating of coffee, and, consequently, to the value ascribed to coffee beans. The SCA describes coffee body as the “tactile feeling” of the liquid in the mouth. This study investigated compounds that impact tactile sensations of drip brewed coffee. A descriptive analysis (DA) panel was presented with a set of coffees receiving a range of body scores from certified Q-grade cuppers and, through multiple tastings, identified four tactile sub-attributes that allowed differentiation among presented coffees (“chalkiness”, “mouthcoating”, “astringency”, and “thickness”). A sensory-guided fractionation methodology was then employed with the highest body coffee undergoing multi-dimensional separation on a preparative-scale liquid chromatography system equipped with triple quadrupole mass spectrometry (QqQ MS) detector. After each dimension of separation, sensory analysis was conducted by the trained DA panel to screen for activity using a combined paired-comparison and intensity rating sensory evaluation protocol. Phenolic quinic acids and melanoidins were implicated in mouthcoating and astringency perceptions, respectively. Compounds were identified using authentic standards and MS/MS fragmentation analysis. Fourier-transform ion cyclotron resonance coupled with MS (FT-ICR MS) was further utilized to character the melanoidin isolate. Compound concentration ranges were quantified in coffee using standard addition and sensory recombination testing further validated contribution to tactile attributes. Psychophysical testing will follow to elucidate mechanistic underpinnings. This research provides a molecular basis through which to understand how processing and roasting conditions may impact coffee body and mouthfeel and will also contribute to the dearth of knowledge on tactile perception in the oral cavity and its relation to the food and flavor experience.
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