Raspberries: they’re celebrated as one of those simple and delicious delights of summer. We’re familiar with some of their more romantic qualities: the soft plump skin, sweet red liquid, and burst of fruity flavor.
But what exactly is a raspberry?
The concept of a raspberry can exist in many shapes and forms, and all of them can yield slightly different flavors. One can experience fresh raspberries, frozen raspberries, artificial raspberries, or even raspberry-flavored Jolly Ranchers.
But the definition of a raspberry, according to the World Coffee Research Sensory Lexicon, is very clear. The Lexicon states that raspberry is a dry gelatin powder with lightly sweet, fruity, floral, slightly sour taste and musty aromatic, a flavor intensity of 6.5, served in a 1-ounce cup, and covered with a plastic lid.
In other words: it’s the recipe for Raspberry Jell-O.
A defined recipe for a raspberry might seem like a basic idea, but it’s the reason that the redesigned Coffee Taster's Flavor Wheel that was introduced in 2016 is such a valuable resource for specialty coffee.
Scott Frost is a postdoctoral researcher at the University of California-Davis Coffee Center who specializes in examining sensory chemistry relationships. He said that the Flavor Wheel allows every coffee professional, no matter which role they play or country they live in, to be truly aligned when discussing flavors in a coffee.
“The Wheel is so important because it gives a foundation for us to have a common language,” Frost said. “You can look at any descriptor on the Wheel, and that descriptor has a specific recipe you can make to reproduce it. So then I can make it, and you can make it, and we can have a discussion about it. It anchors everybody on the same page.”
For his PhD, Frost studied various treatments of wine-making and how the chemical signature of those treatments relates to flavor profiles. He is currently working on a research initiative related to the parameters of drip coffee brewing with Peter Giuliano of the Specialty Coffee Association.
Giuliano was the catalyst for the development of the new Flavor Wheel. As he described in a lecture at the 2016 Re:co Symposium in Dublin, the original Flavor Wheel created in 1995 was not well-suited for evaluating the different attributes of coffee from new coffee processing techniques that he was developing in Rwanda.
These experiments on processing techniques that were coordinated by Guiliano and Dr. Tim Schilling blossomed into the organization called World Coffee Research (WCR). It was evident to WCR that in order to fully assess the findings of future coffee research, an updated Coffee Taster's Flavor Wheel was essential.
How the Coffee Taster's Flavor Wheel Was Redesigned
The first step in the Wheel’s creation was to establish a common vocabulary to describe coffee attributes. This was done by using a Sensory Descriptive Analysis, one of the most quantitative, sophisticated and extensively-used methods in sensory science.
The analysis was conducted with a sensory panel at Kansas State University tasting hundreds of coffee samples and documented all the flavors they perceived in the coffees. The panel ended up with a list of 110 words that could be verified and repeatable in tasting coffee. These words are the flavor, aroma and texture attributes that make up the WCR Sensory Lexicon.
In addition to the Lexicon being the foundation of the Flavor Wheel, it is also a recipe book of instructions for preparing reference standards for all of the descriptors. Like the recipe for Raspberry Jell-O as the reference standard for Raspberry.
Frost said the definitions of the coffee attributes in the Lexicon are arguably the most important benefit of this research.
“The words aren’t esoteric,” Frost said. “They’re defined, they have a recipe of what they are. We know what they smell like and you could make them again. It leads to scientific reproducibility of an experiment.”
Once the Lexicon was established, the SCAA worked with a PhD candidate in sensory science at UC-Davis, Molly Spencer, to arrange the words of the Lexicon in a way that was useful for coffee Taster's. Spencer built a computer program for both a sensory panel group and a group of coffee Taster's to arrange the words in a way that was statistically sound.
The final stage of research was to provide color to the Wheel, since humans have a biologically strong association between the perception of color and taste. The SCAA worked with a design agency in London called One Darnley Road to match each descriptor on the Wheel with the precise color.
How the Flavor Wheel Is Used
World Coffee Research has stated that the primary purpose for the development of the Wheel is for future research. Measuring coffee’s flavors and aromas is the necessary first step to understanding what causes coffee to taste, smell, and feel the way it does.
The first example to demonstrate the Lexicon and the Wheel’s value was during the Colombia Sensory Trial, a controlled comparison of the Castillo and Caturra varieties from the Narino region of Colombia. The Castillo variety is being heavily subsidized and incentivized by the Colombian government because it is rust resistant, but it has a bad reputation from coffee buyers looking for high quality.
But the trial proved that sensory scientists at the Sensory Analysis Center at Kansas State were better able to identify differences between the two varieties than experienced coffee cuppers using CQI’s Q protocols. There was no objective difference in quality of the two varieties, but they were able to show distinguishing factors in tasting attributes: Castillo was fruity but not citric, with notes of dark chocolate and roasted nuts, while Caturra was floral with coca and caramel notes.
But the value of the Wheel goes well beyond controlled experiments in a lab. Roasters with multiple roasting facilities around the world can use the terminology from the Wheel to create an identical roast profile for each location.
The Wheel is also a valuable tool for coffee cuppers and baristas. It’s even organized in tiers in what’s called ‘center-out methodology,’ which allows Taster's to narrow down the descriptor they are tasting. For example, the Wheel can guide a taster from the inner part of the Wheel to the more specific outer layers: from “fruity” (a general flavor) to “citrus fruit” (an umbrella term) to “grapefruit” (a specific descriptor).
Winston Thomas is a two-time barista champion of South Africa and Urnex Ambassador. The redesigned Flavor Wheel has helped him as an independent barista and coffee trainer in structuring the identity of a coffee with specific characteristics to translate to peers and customers.
“The biggest challenge I've experienced as a coffee professional is the ability to taste and identify flavor and the coffee Wheel has made this a lot easier,” Thomas said. “I always have it on hand for cupping, but also for dial-in with baristas at start of shift as well as different training courses. It's helpful in that it provides guidance and clarity when tasting.”
To him, it’s important to accurately describe attributes of a coffee because of how many different factors are at play with the taste of the final brew.
“The flavor of a specific coffee can change so dramatically from the cupping table at origin to the consumers kitchen counter. It becomes important to establish a very specific vocabulary in terms of flavor and characteristics to assist in making a buying or brewing decision.”
The creation of the new Coffee Taster's Flavor Wheel was a groundbreaking piece of research that combined the efforts of two scientific studies, three institutions and hundreds of coffee Taster's. But in a way, the Wheel took the artistic component out of tasting coffee. There will always be a scientifically correct answer when evaluating the flavors of a coffee.
But Tandem Coffee Roasters in Portland, Maine sets a fine example of how to translate the science of coffee into originality. In addition to listing the flavor attributes on its packages of coffee, it offers a song title to more imaginatively describe the ‘genre’ of coffee. Like their Stoker coffee, which contains notes of dark chocolate, burnt honey, cherry, and "L.A. Woman" by The Doors.
As long as there are brilliant and creative people in both the academic and business ends of the specialty coffee industry, coffee will always be a balance of science and art.
For more posts on coffee theory, read Coffee Extraction and the Ideal Brew.
We'd like to give a special thank you to Scott Frost for his contribution to this post!