REAP Conference 2024 registration is open
Book tickets, feature in the technology exhibition or apply for a REAP bursary - available for farmers and those in full-time agriculture-related study

The Science of Decaffeinated Coffee: J A Kemp

Member News
The views expressed in this Member News article are the author's own and do not necessarily represent those of Agri-TechE.

Caffeine provides many benefits—improved concentration, decreased fatigue, even lowering the risk of certain diseases. But research reveals a darker side to the drug. It can interfere with our sleep, cause dependence, and heighten anxiety. This has led to a widely felt demand for decaffeinated beverages. Coffee is a prime example, with 12% of coffee in Europe being decaf.

History of Decaffeination
Like many of us, the great German writer Goethe has spent much of his life struggling to reduce his dependence on coffee and so, in 1820, he presents the young German chemist Friedlieb Ferdinand Runge with a bag of coffee beans, hoping he will discover the cause of coffee’s stimulating effects. Within a few months, Runge has become the first person to isolate the caffeine from coffee.

But it isn’t until the 1900s that decaffeination is commercialised. As with many great inventions, it is discovered by accident when a German shipment of coffee gets soaked in seawater. The merchant, Ludwig Roselius, realises that the caffeine has been removed while the flavour is largely intact. Inspired, he goes on to develop a process for decaffeination and obtains a patent in 1908.

This solvent-based process can significantly affect the flavour of the coffee and historically used benzene (now a known carcinogen). Perhaps this explains why many people are still suspicious of decaf?

Then, in 1970, a patent application is made for a revolutionary process: a one-step method that ditches the organic solvent and retains more coffee aroma. While working at the Max Planck Institute, Kurt Zosel swaps the organic solvent for moist supercritical carbon dioxide (CO2). Supercritical refers to the combination of liquid and gas phase properties at high temperature and pressure, which helps the CO2 to penetrate the raw beans. Unexpectedly, the moist supercritical CO2 easily and selectively extracts the caffeine. Much of the world’s decaf coffee is still produced this way.

Future of Decaf
The Covid-19 lockdowns saw a boom in decaf coffee as many people increased their coffee intake but found themselves consuming excessive amounts of caffeine. This trend seems here to stay in the long term, with the decaf coffee market expected to grow to 29 billion USD by 2030 (up from 19.5 billion in 2022). Therefore, technical innovation is likely to continue in this area. Focus is on producing a coffee plant yielding inherently decaf beans. Growing (rather than making) decaf would make production cheaper plus retain as much aroma as possible.

For example, low-caffeine varieties of arabica coffee (the most popular species) are known to exist. The difficulty is then transferring this characteristic into a commercial variety. It doesn’t help that caffeine acts as a natural pest repellent making the cultivation of low-caffeine plants challenging. A highly promising arabica cultivar (“AC1”) was identified by researchers in Brazil and published in 2004. AC1 contains high levels of theobromine (found in chocolate) which is the immediate precursor to caffeine. Carbon-14 labelling confirmed that the final step in the caffeine synthesis pathway is suppressed in AC1. Field trials began in 2023 and could hold the key to commercially viable, naturally decaffeinated coffee. Whilst such plant varieties are often non-patentable per se, there are separate protections available such as the Convention for the Protection of New Plant Varieties.

Genetic modification (GM) provides an alternative way to produce decaf coffee plants. For example, the genes coding for enzymes in the caffeine synthesis pathway can be “silenced”. This is achieved by introducing a sequence into the plant’s genome that is complementary to the targeted gene. The inserted DNA gets transcribed to RNA which binds to the complementary RNA sequence that codes for the targeted enzyme. This stops the plant from reading that sequence, preventing caffeine synthesis. A patent application for this process was made in 1996, although many further GM methods have been suggested since. Interestingly, genetically modified plants are patentable (at least in Europe) because they are produced by a technical process. Although GM is controversial and often tightly regulated, it is a promising source of full-flavour decaf. Furthermore, unlike cross-breeding programmes, GM can be used on already high-quality coffee varieties, reducing the time needed to commercialise.

The pursuit of flavoursome coffee without the caffeine has inspired many exciting inventions historically—only a handful have been mentioned here. With decaffeination set to grow in popularity, many more innovations will emerge in this fascinating area, generating intellectual property across a broad range of disciplines.

J A Kemp has wide-ranging expertise in the technologies mentioned in this article. See our Specialisms section to find out more.