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International Coffee Day is October 1st, not that many of us need a day to celebrate the drink we enjoy all year round. What makes a high quality cup of coffee? There are several factors at hand from the origin of the beans and the climate they grow in, to how the beans are processed, roasted, and packaged, and finally how the roasted beans are ground and brewed. In this blog post, I will discuss a bit of the history of coffee, how it is processed, and how to accurately determine the quality parameters in order to brew the most flavorful cup.

Origins of our favorite brew

The word «coffee» was introduced in 1582, derived from the Dutch «koffie». This traces back even further to the Arabic word for coffee, «qahwah», which has been speculated to come from «quwwa» (defined as power or energy), or even from Kaffa (also spelled as Kefa) which was a medieval Ethiopian kingdom that exported coffee plants to Arabia. It is believed that coffee was first discovered by a goat herder in Ethiopia who noticed the energy of his goats increase after consuming the coffee fruit (known as «cherries»). From Ethiopia, coffee consumption spread through the Arabian Peninsula and Middle East during the 15th and 16th centuries.

Coffee cherries ripening.
Coffee is now the most consumed beverage, other than water, around the globe. From the thickest espressos all the way to transparent drip coffee, the world is truly hooked! This beverage is so deeply ingrained in all cultures that the top places for annual World Barista Championships (2019) were taken by contestants from South Korea, Greece, and Canada!

Good coffee: not as straightforward as you might think

Coffee comes in many forms, with niche roasters looking to discover new flavors daily. Since the gourmet coffee market is growing more, specialty coffee is also in high demand. Global Brands Magazine reported the price of Black Ivory Coffee at $500 per pound in 2020.

Why so expensive — is the taste that good? In order to make Black Ivory Coffee, the coffee cherries are fed to and digested by elephants, in a similar manner to Kopi Luwak (or civet coffee), another expensive coffee type created by fermentation of coffee cherries in the gut of civet cats. The resulting coffee beans are then cleaned, dried, and roasted.

Civet cats can digest coffee beans to create a unique coffee experience with a heavy price tag.
Aside from these high-priced small batches, other types of coffee beans are roasted in large quantities for mainstream consumption (arabica, robusta, and liberica). Arabica beans make up 60% of the global market with 2.5 million tons exported per year from Brazil alone. Robusta beans account for a bit less than 40% of the market and are mostly produced in Vietnam. Robusta beans exhibit more bitter flavors, contain more caffeine, and are used more often to create instant coffee. Liberica beans have high levels of sugars but low concentrations of caffeine compared to the other two major species. Very low yields (between two and four times lower than the others) and larger plant size make this type more difficult to mass produce and therefore it only accounts for approximately 2% of the global coffee market. From these major coffee species, several varieties have been produced with a large range of different flavor characteristics and caffeine content.

Typically, coffee is grown in (sub)tropical areas, but the ideal climate differs depending on the species. Some prefer higher altitudes and are more suitable for mountainous regions. Others need hot and dry conditions to produce the best quality beans. Now there are over 70 countries that produce coffee. That’s a good thing, because global coffee consumption in 2020/2021 is estimated to be 167.23 million 60 kg bags, which is more than 10 million tons of coffee!

Map showing the different coffee-producing countries around the world.

Changes in coffee consumption practices

The adoption of the pod coffee machine (e.g., Keurig, Nespresso) over the past decade has pushed the consumption of coffee from something generally enjoyed in a café, restaurant, or on the go, to a much higher rate of consumption at home. With this significant shift to pod coffee, the ability to adjust grind size, water temperature, or extraction time used by the best baristas to counter changes in flavor and strength is no longer a possibility. In fact, the ease of pressing a single button and receiving hot, fresh coffee within seconds is exactly why pod coffee is so popular. This puts new pressures on coffee roasters to maintain the flavor and caffeine strength expected of their brand and varieties.

Though many people may think that the largest contribution to a good cup of coffee is due to the coffee brewing process, many other quality parameters such as acidity, roast temperature, and water quality contribute even more. Two of the main factors in an optimal cup of coffee, the acidity (taste) and the amount of caffeine, are mainly affected by the bean type, region of origin, and roasting temperature.
Progression of the coffee bean roasting process.

Science—brewing up your perfect cup

Not all coffee beans are created equal, but luckily science allows us to define many of the key quality parameters that result in the taste and caffeine strength we expect from our favorite brand of coffee. Coffee is generally acidic with a pH of around five. Highly acidic coffee displays a sour, harsh flavor. While there are ways to counteract this on the consumer side, for manufacturers it is even more important to identify that there is an issue to begin with. A simple identifier is the titratable acidity of the coffee, and this has a direct correlation with the taste you associate with your favorite brew.

Of equal importance is the «kick» you may get from your preferred caffeine fix. Whether you drink one cup per day, or four, the recommended daily limit for adults is suggested at 400 mg caffeine. Of course, decaffeinated coffee is also an option for those who are sensitive to its effects or are looking for ways to reduce their intake (but can’t stay away from coffee).

Traditionally, caffeine has been analyzed by titration, liquid chromatography (LC), or spectrophotometry after a long sample preparation procedure. Now, the analysis of key coffee quality parameters like caffeine content can be done simply and effectively using a single titration system.

Example titration curve for caffeine analysis with OMNIS (click to enlarge).
The pH and acidity of coffee samples are analyzed using a robust pH electrode during titration against standardized sodium hydroxide. Caffeine is determined through a redox back titration after a known excess of iodine is added to the sample and left to react. After the reaction period the sample is filtered and titrated with sodium thiosulfate.

Find out more about this analysis in our free Application Note!

Metrohm has the solution for your analysis needs

The OMNIS platform from Metrohm provides laboratory analysts the automation they need to make each sample determination significantly simpler, faster, and more reproducible thanks to minimal manual sample preparation steps. Key steps in the analysis process that have required manual interactions, reagent addition, filtration, and accurate volume transfers are now completed accurately and automatically. Learn more about the OMNIS titration platform on our website.
Hopefully this article has given you some insight into coffee’s long journey from the farm to your cup, and that you have learned about the chemistry behind the way your coffee tastes! Enjoy International Coffee Day, whether you celebrate on October 1st or every other day of the year.

Download our free Application Note:

Analysis of caffeine, pH, and acidity in coffee – Fully automated determination including filtering, reagent addition, and sample pipetting using OMNIS
Post written by Isaac Rogers (Titration Product Manager at Metrohm Australia & New Zealand) and Dr. Alyson Lanciki (Scientific Editor at Metrohm International Headquarters).
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