October 12, 2017

Understanding How a Coffee Tastes – Through a Microscope’s Lens


The first time I cupped coffee, like many, I struggled to understand acidity. I didn’t understand where all the aromas were coming from. And I certainly wasn’t giving accurate scores.

Nowadays, as a Q-grader, I love the experience of cupping coffee – but as a researcher, I’m also interested in objective methods for flavor and aroma analysis that can support the specialty coffee industry.

I’ve been using spectroscopy, chromatography, and chemometrics to research how we can use these scientific methods to produce the same results as a cupping session. In other words, can we link specific chemical compounds to all the aromas and flavors found in coffee? Can we use machinery to map different levels of sweetness, acidity, body, and bitterness in coffee? And can we understand a coffee’s quality from just its molecules?

Spanish Version: Entendiendo Cómo Sabe un Café – A Través del Lente de un Microscopio

coffee wheel

The coffee taster’s flavor wheel. Credit: Dakota Sims for Bodhi Leaf Coffee Traders

Combining Scientific & Sensory Analysis

First of all, I do not see this as a competition between sensory and scientific analysis. I’m often asked if we can understand a coffee’s quality without cuppers, or how my research will affect cuppers’ roles. The truth is that science improves our knowledge about cupping – but it doesn’t replace it.

My research is into techniques that are valuable for their speed and precision. They can be used to analyze large volumes of different specialty coffees or suggest quality improvements. They also help us to better understand cupping and coffee quality.

coffee science

Reproduction of a cupping in a lab in preparation for beverage extraction for chromatography analysis. Credit: Verônica Belchior

Mid-Infrared Spectroscopy Uncovers Coffee Flavors

My research is based on the use of mid-infrared spectrometers. When we apply the infrared region of the electromagnetic spectra in our sample, it excites molecules. We can then analyze the way light interacts with those molecules, and this in turn provides a spectrum of the chemical composition of a coffee.

This, in turn, can indicate that coffee’s taste and aroma.

coffee science

The infrared range of an electromagnetic spectrum. Credit: Clemente Ibarra-Castanedo @ Canada Research Chair in Multipolar Infrared Vision – MiViM via Wikimedia Commons, CC BY-SA 3.0

For example, we know that volatile compounds are responsible for aroma. Flavor, aftertaste, and body are usually affected by carbohydrates (sugars), proteins, melanoidins (those large molecules that give roasted coffee its brown color and also add texture), lipids (oils), and more. And acidity can be measured by the variation in the composition of organic acids (citric, malic, lactic, tartaric…) and chlorogenic acids (mainly responsible for coffee’s astringency).

With mid-infrared spectrometry, we can see the chemical breakdown of the coffee and understand which flavors will dominate in the cup. It allows us to understand attributes like acidity in a different way. Instead of measuring the feeling on our tongue, or asking ourselves if a coffee is more like mandarin or peach, we can look at the proportions of acids inside the beans.

Of course, our analytical equipment may be accurate enough to map the molecules present in coffee. But everything we know today about, say, volatile compounds and their sensory profiles is thanks to human noses. Science and cupping work together, not against each other.

coffee science

Recording data from mid-infrared spectroscopy at the Universidade Federal de Minas Gerais, Brazil. Credit: Verônica Belchior

SEE ALSO: Coffee Science: Everything You Need to Know About Milk

Cupping By Science: The Benefits

Sensory analysis is a pleasure, but it’s also time-consuming. What’s more, it requires trained professionals. For a small roastery, these points may not be issues. But for large cooperatives, coffee associations, and more, cupping new crops can represent a huge investment of time and personnel. In some regions, cupping new crops can take days of intense work.

Mid-infrared spectrometers are relatively inexpensive pieces of equipment. They require less treatment and sample preparation than other machines for chemical analysis, and can analyze several samples per day.

The big issue, of course, is that this method still requires trained professionals to operate the equipment and interpret the results. These professionals must not only have knowledge specific to this technique but also be good with statistics.

And I must emphasize, again, that this scientific analysis does not change the fact that we also need Q-graders.

However, it can be useful to have a range of analytical techniques, including mid-infrared spectroscopy, that can be applied to coffee quality analysis.

coffee science

Q-graders prepare to cup coffees from Barina’s Farm in Cerrado Mineiro, Brazil. Credit: Lucas Hallel

Quality Improvements Based on Science

Moreover, the results open up doors to research and innovation. We essentially create mathematical models capable of predicting the quality attributes of samples. At the same time, coffee associations and producers can build a collection of data on different crops.

Combining these pieces of information, along with data on coffee processing, can allow us to understand the efficacy of small technological or methodological changes in production and processing – and to rule out the impact of other variables.

The scientific analysis of coffee allows us to speak with confidence on the impact of farming practices. We don’t have to rely on correlation, anecdotes, or small sample sizes. We can rule out outliers and more. We can gather information that can be used for further research and analysis.

A scientific analysis of coffee quality based on its chemical composition has the power to support cuppers, roasters, and producers in the constant journey towards better coffee.

Perfect Daily Grind

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