May 27, 2021

Can we use biochemical analysis to predict coffee quality?


Across the coffee supply chain, quality is a key issue for a range of different stakeholders. Farmers often receive higher prices for better quality coffees, roasters can use them to boost their brand and improve their margins, and consumers are increasingly looking for complex cup profiles.

With the global specialty coffee market predicted to be worth US $83.5 billion by 2025, this increasing demand for quality only seems set to continue. And while we have some quality control and assurance protocols to leverage across the supply chain, researchers are always looking for new ways to identify and maximise quality during production.

One of these methods is biochemical analysis, where researchers examine coffee’s complex chemical structure against cup scores and other quality markers. To learn more about whether or not this is a viable way to predict coffee quality, I spoke to four people involved with a BREEDCAFS research project. Read on to find out what they said.

You may also like our article on tasting “forgotten” wild coffee species: an experiment

Using biochemical analysis to predict coffee quality

Thanks to decades of research, we know that the biochemical structure of coffee affects the flavours and aromas we perceive when we consume it.

Benoît Bertrand is a geneticist at French agricultural research organisation CIRAD. He says: “More than 850 biochemical compounds have been described in the aroma of roasted coffee, and more than 300 in green coffee.”

Claudine Campa is a Senior Scientist at IRD, a public research institution committed to achieving the UN’s Sustainable Development Goals. “Biochemical compounds are natural substances produced by living organisms that play an important role in their physiology and metabolism,” she explains. “Proteins, complex carbohydrates, organic acids, lipids, phenolic compounds, and alkaloids… these are all biochemical compounds made by coffee cells.”

Each compound, alone or through its combination or interaction with others, can influence the quality of green coffee. However, the biochemical composition of coffee changes when the beans are roasted. 

By activating recombination between molecules, roasting significantly heightens the presence of volatile compounds, which are associated with aroma and flavour. 

Each of these has a different relationship with coffee quality. For example, carbohydrates and lipids enhance the mouthfeel of coffee, while organic acids and phenolic derivatives increase acidity levels and fruity flavours.

Furio Suggi Liverani is the Chief Scientific Officer at illycaffè. He says: “Most of the coffee volatiles are formed during roasting by a series of complex reactions. These break down the natural components of raw green beans.

“We can find aroma compounds characterised by fruit and floral notes as well as nuts, caramel, toasted bread, and chocolate. These compounds are like individual musical instruments, combining to create an orchestra.”

However, despite the amount of research showing that biochemical compounds affect flavour, little is known about exactly how they influence coffee quality.

Why do we want to predict coffee quality? 

Across the supply chain, there are a number of different motivations for predicting coffee quality at a biochemical level.

“Scientists have dreamed of being able to determine the quality of coffee as objectively as possible for more than 200 years,” Benoît says.

In addition, climate change is already having an impact on coffee production. A better understanding of coffee quality could be of crucial importance to support producers in dealing with it.

In theory, using biochemical tests to accurately and consistently predict coffee quality could help growers identify more resilient varieties with appropriate cup profiles, which could then be grown in warmer climates.

“Wanting to predict quality based on biochemical compounds is like wanting to understand why Beethoven’s 9th Symphony is a masterful and universal work, or why one painting is a great work compared to so many others,” Benoît adds.

Today, we assess quality based on the physical and sensory characteristics of coffee, but both are subjective and require expertise or existing knowledge to carry out.

The physical quality of green coffee is evaluated by noting the number of defects in the sample, which are generally defined as notable deviations in size, colour, odour, and shape. 

Sensory quality, however, is assessed through cupping. This is when samples of roasted coffee are ground and brewed according to a strict protocol. Each sample is tasted by certified professionals, who score the coffee’s aroma, acidity, body, sweetness, and so on. 

However, these manual quality control processes are time-consuming, and require access to equipment and infrastructure. Developing a more quantitative system that relies only on biochemical analysis would not only be quicker, but also more consistent, increasing accuracy for actors along the coffee supply chain.

Which compounds influence coffee quality?

To learn more about how biochemical analysis can be used to predict quality, CIRAD has partnered with IRD, illycaffé, the Plateforme Metabolome (Univ. Bordeaux), and Eurofins (a world-leading testing laboratory).

Benoît tells me that part of the research involves identifying the biochemical compounds that negatively affect coffee quality.

“We hope to be able to circumscribe a certain number of rules based on harmony, balance, [and] certain flavours universally recognised as pleasant, and to be able to eliminate the ‘false notes’,” he explains.

However, alongside this, the BREEDCAFS project is also exploring how some compounds, generally volatiles, indicate increased quality. 

Pyrazines and furans, for example, are associated with roastier flavours and caramel-like tasting notes, which are often desirable in the cup and improve scores.

What can we predict using biochemical analysis?

The BREEDCAFS project tested a “blind” lot of green coffee selected from an agronomic trial. Its origin, variety, and cup quality were all undisclosed. 

This sample was shared between CIRAD, IRD, illycaffè, the Metabolome Plateforme, and Eurofins for testing. The project’s aim was to not just predict the coffee’s quality, however, but also to see if it was possible to identify its origin.

Claudine tells me more about how the various research partners conducted their analyses for this project.

“To highlight these biochemical markers, different laboratories joined forces to use different techniques,” she explains. “This made it possible to analyse as many compounds as we could in the lot of green coffee.”

The analysis sought to determine the origin of the coffee (which had been hidden from researchers) and to serve as a prediction of overall cup quality.

Predicting origin

IRD used liquid chromatography to separate and quantify the different compounds in the coffee. This highlighted caffeine and chlorogenic acid levels, creating a specific initial signature for the bean.

IRD’s research found that wild accessions and specific coffee cultivars could be identified using this technique.

In contrast, research at the Plateforme Metabolome used gas chromatography instead of liquid chromatography. This allowed researchers to separate and quantify the fatty acids in green coffee.

After this, Claudine says that the researchers could combine the two results to outline a biochemical “fingerprint” for the coffee in question.

 “Each green coffee has a unique biochemical signature,” Claudine explains. “We can authenticate one origin from another using this signature.”

However, to further define the coffee’s unique “fingerprint”, the project worked with a Eurofins partner laboratory in France.

Freddy Thomas is the Research & Development Authenticity Manager for Eurofins Analytics France. He explains that Eurofins used a technique called nuclear magnetic resonance (NMR) imaging to learn more about the biochemical markers in the coffee.

“NMR is a quantitative technique,” Freddy says. “The intensity of each signal is proportional to the concentration of a specific molecule. This allows us to calculate the concentration of organic compounds (sugars, amino acids, organic acids…) at the same time.”

This analysis requires little preparation, and takes around 30 minutes in total to complete. This means around 50 samples can be tested every day. Much like the gas and liquid chromatography, NMR imaging produces a unique “fingerprint” for each coffee. 

It also allows different coffees to be grouped according to their shared biochemical characteristics, allowing researchers to identify which coffees come from the same or similar areas.

Predicting quality

Although predicting coffee quality from biochemical markers is an unbelievably complex process, Claudine tells me that some progress has been made.

“By comparing biochemical characteristics of the green beans and the sensory properties of the coffee [once cupped], we will be able to highlight biochemical markers of quality,” she says.

“Most of the previous studies have shown that the concentration of these compounds in green coffee is dependent on the variety being used, as well as environmental conditions like elevation and sunlight intensity.”

While IRD conducted research using chromatography and Eurofins relied on NMR imaging, Claudine tells me that illycaffè carried out a full sensory analysis on the selected coffees.

This analysis allowed the project to isolate specific volatile compounds as responsible for certain desirable and undesirable flavours. 

Alongside the biochemical analysis, this, in theory, allows researchers to predict coffee quality.

While more research is needed, the quest to identify coffee quality using biochemical analysis is well underway.

“It is important for the whole coffee sector and for the consumers, but also for the producers,” Benoit concludes. “The final objective is to increase quality.”

Amid volatile C market prices, climate change, and an increasing global demand for higher quality coffee, finding a solution has never been more important.

Enjoyed this? Then read our article on nature vs nurture: what has the greatest effect on coffee quality?

Photo credits: Illycaffè SpA Italy, Claudine Campa, Cécile Abdallah, Benoit Bertrand

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Please note: CIRAD is a sponsor of Perfect Daily Grind.

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