PARIS, France – Across the coffee supply chain, quality is a key issue for a number 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. The global specialty coffee market is predicted to be worth US $83.5 billion by 2025; the increasing demand for quality only seems set to continue.
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.
Understanding coffee quality
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.
Using biochemical analysis to predict coffee quality
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.”
However, despite the amount of research showing that biochemical compounds affect flavour, little is known about exactly how they influence coffee quality.
“Scientists have dreamed of being able to determine the quality of coffee as objectively as possible for more than 200 years,” Benoît says.
“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.”
Breedcafs Project
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).
“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’,” Benoît explains.
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.
“To highlight these biochemical markers, different laboratories joined forces to use different techniques,” Claudine 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.
“Each green coffee has a unique biochemical signature,” Claudine explains. “We can authenticate one origin from another using this signature.”
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
“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,” Claudine 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.
