Feb 15, 2021 - min read
Caffeine (C8H10N4O2) is the world’s most popular and most widely used psychoactive drug, occurring naturally in some plants, including the cocoa tree (Theobroma cacao), Cola trees (notably Cola nitida and Cola acuminata), the tea plant (Camellia sinensis), and some species of coffee tree, (especially Coffea arabica and Coffea canephora).
This stimulant compound is an effective pesticide, and it seems that the higher the caffeine content in a plant’s fruits and seeds, the better protected it is from predator insects.
Of the 120 species in the Coffea genus – a plant indigenous to Africa and parts of Asia – only three are commercially cultivated crops.
Coffea liberica, the main source of coffee in the Philippines and Malaysia, has the lowest caffeine content of the three. Producing large seeds but low yields, C liberica accounts for just 1% of the world’s coffee.
Coffea canephora is a remarkably robust species that produces a bitter, high-caffeine coffee. The two varieties of C canephora are C c robusta and C c nganda. The canephore species is more commonly known as robusta.
A hybrid of C canephore and C eugenioides, Coffea arabica is an autogamous plant, which means it’s able to fertilise itself. Arabica is more susceptible to disease than robusta, and in the past has been at serious risk of extinction. Arabica coffee beans contain more sugar and less caffeine than robusta.
The fruits (cherries) of coffee trees usually contain two seeds (coffee beans), with flattened sides pressed against one another. Around 5% of cherries contain only one seed – a peaberry. On account of having incubated alone, these single coffee beans are more rounded than twin beans and are sorted from the bulk of the crop for separate roasting.
Roasted coffee beans are ground before being infused in very hot water.
Drip-brew coffee is brewed by gentle infusion, and some of its oily solids are lost to the filter. Espresso, on the other hand, is made by forcing a small amount of near-boiling water, at high pressure, through finely ground, tightly pressed coffee. The resulting drink is more full-bodied and flavoursome. But does it contain more caffeine?
There are several factors involved: 1. temperature; 2. grind; 3. time.
Both drip-brews and espressos could be under par due to a coarse grind or low water temperature. But where time’s concerned, the vulnerability is with the espresso, which takes only 30 seconds to brew. If the temperature and grind are not spot on, the espresso runs out of time.
However, if all conditions are right, there’s no significant difference in caffeine content between espresso and drip-brewed coffee.
Freeze-dried (instant) coffee is another way altogether of enjoying coffee.
A highly concentrated coffee brew is spread out thinly, quickly frozen to a temperature of -40°C, and then broken up into small pieces. These granules are dried through the process of sublimation – i.e. the frozen water in the coffee solution is forced into a gaseous state without passing through the liquid state.
When mixed with hot water, the coffee granules will dissolve again – instantly.
As for caffeine content, a spoonful of instant coffee contains, on average, the same amount of caffeine as a shot of espresso or a mug of normal-strength filter coffee.
Decaffeinated coffee – or rather, reduced caffeine coffee – can contain up to 10% of its original caffeine.
Coffee beans are soaked in water, a process that removes many of the coffee’s properties – not just the caffeine. Then the water is passed through activated charcoal (more porous than regular charcoal), which absorbs the caffeine. The water, still containing extracts from the beans, but without the caffeine, is put back with the coffee beans and then evaporated. The coffee has its full flavour, but most of the caffeine has been extracted.
The harvested caffeine is sold on as an ingredient in other products.
Caffeine content in a cup of coffee – whether espresso, drip-brew, or instant – ranges from around 60mg to 150mg.
A cup of arabica coffee won’t contain as much caffeine as a cup of robusta of equal strength. But a filtered arabica will contain roughly the same amount of caffeine as an arabica espresso portion. That is, if the grind and temperature are spot on in both cases.
Instant coffee retains all the caffeine it started out with.
So, to sum up, basic brewing methods make no difference to the caffeine content in coffee.
There’s one more factor, however, in a really good cup of coffee. It’s always that bit nicer when it’s made with pure water.