The Science Behind The Perfect Cup of Coffee

chantel Carnes

Uncategorized

How do you like your coffee?

It’s an age-old question, one that you will ask every single one of the customers coming through your doors.

Regardless of whether you’re an espresso expert, a cappuccino connoisseur or an americano aficionado, when it comes to the chemical composition of your perfect cuppa, most of us are in the dark.

Sure, without the trimmings, they’re all the same thing – good old coffee. But not all coffee is created equally and no two cups are ever the same. And that’s thanks to the fancy-shmancy chemistry involved in specialty coffee.

An incredible cup requires excellence in three parts: the bean, the processing and the roast. Without further ado, welcome to Conical’s Coffee Chemistry 101.

—

THE BEAN

Coffee beans are actually the seeds of the coffee fruit, which – curiously enough – resemble a cherry.

Each ‘cherry’ fruit has two seeds. Each is individually enclosed by a thin parchment membrane, then enveloped by a sweet and fleshy layer known as mucilage and, finally, coated with a protective husk.

Most specialty coffee belongs to the coffea Arabica species. Within this broad umbrella, one can find different types – examples include catuai, gesha, bourbon and catimor – which impart characteristic flavours into their seeds.

Additionally, the climate, altitude, soil and terrain of a coffee crop can have significant effects on taste. For example, low-altitude have fruits that grow rapidly and produce deep, earthy coffees; the slower-growing, high-altitude coffees are more acidic, with floral and fruity notes.

In the beginning, coffee fruit has a distinct green colour but upon maturation, the cherries turn yellow to deep red, depending on the variety.

The cream of the crop is chosen by coffee professionals called Q graders and awarded the title of ‘specialty’.

THE PROCESSING

The real treasure – the seed – lies within the fruit and, thus, the coffee cherries need to be processed. Effectively, processing is the removal of the outer husk and the mucilage; how this is done has a profound effect on the final taste.

Washed-processed coffee comprises the majority of specialty coffee; the result is a clean cup of joe. Once the fruit is picked, just the outer husk is removed by a de-pulping machine and the seeds are left to ferment in water for upwards of a day.

This serves two purposes: to facilitate the removal of the mucilage and begin fermentation. Fermentation – when done correctly – produces sweetness in the final taste profile.

To achieve a desirable 10 – 13% moisture content, seeds are left to dry for approximately a week. They are then sent off to a dry mill, where thorough removal of the mucilage and parchment membrane occurs prior to packaging.

Since washed coffees require high volumes of water, drier areas such as Africa specialize in naturally-processed coffee. Here, the husk and mucilage are not removed from the cherries until after the drying stage (which can be up to a month!). The result is a considerably sweet bean, thanks to extended contact between the porous fruit and the sugary mucilage.

It’s no wonder they’re often called ‘fruit bombs in a cup’. The quick fermentation that occurs lead to strong and funky blueberry/strawberry notes.

Honey-processed coffee is a compromise between the latter two methods; although less common, it is rapidly gaining popularity. Within this method, the cherry’s outer husk is stripped after picking and the mucilage-enveloped seeds are dried in the sun.

Honey-processing can be divided further, depending on the amount of mucilage that is left on. For example, in black honey processing, a significant amount of mucilage is left on but in white honey processing, it is minimal.

It’s an excellent middle ground, allowing for more sugars to be absorbed than the washing process but not as much as the natural process.

THE ROAST

Just as impacting to the final taste and quality profile is the roasting process. Essentially, the roaster’s heat triggers a series of chemical reactions within the processed seeds; in turn, these produce the characteristic tastes and aromas of the coffee.

The heat forces the water within beans out in the form of steams; the seeds consequently degrade, becoming a pale cream colour.

As more heat is absorbed, all-important flavour compounds (such as vanillin) begin to develop, alongside the Maillard reaction.

The branching Maillard reaction involves the reaction of amino acids and sugars to produce hundreds of new tastes and aromas. The longer it continues, the more complex the final flavour profile is.

However, the Maillard reaction can lead to a rapid drop in pressure which triggers the decomposition of critical acids.

The roasters’ skill now comes into play, as pleasant-tasting acids must be kept whilst undesirable acids need to be removed. For example, fruity notes can be achieved by preventing the decomposition of citric and malic acids.

The chemical reactions continue even after the roasting and packaging stage. Ever noticed those valves in a packet of coffee? They’re not there for a sneaky sniff; rather, they allow carbon dioxide produced by the beans to exit the bag and prevent an explosion.

Caffeine levels stay quite constant throughout the roasting process so, unfortunately, a dark-roasted coffee won’t give you more of a hit than a light-roasted one. Myth, consider yourself debunked.

—

The bean selection, the processing method and the roasting choices are just the tip of the iceberg. Everything and anything that happens before the pour can make or break a cup of joe.

Next time you’re sipping your ride-or-die, you’ll know exactly what’s contributed to the flavors you love so much and the jargon to describe it.

That’s class over for Conical’s Coffee Chemistry 101.

Want to know more? Conical’s got you covered. Contact us today, here.