Coffee is complicated. Finding it isn’t, making it isn’t (provided you have the right office coffee machine), and certainly drinking it isn’t, but a simple cup of coffee is a chemistry lesson unto itself.
You may be familiar with some of the chemicals found in coffee, such as cafestol and kahweol. They’re special oils known as diterpenes and according to Harvard Medical School, they may have anti-cancer properties and provide a benefit to the liver.
You’re probably also aware that coffee is rich in antioxidants and of course, coffee that isn’t decaf contains plenty of caffeine, one of, if not the most famous stimulant in existence and officially the world’s most widely consumed psychoactive drug.
This isn’t to mention the more than 1,000 other individual chemicals found in every single cup of coffee. So, it should follow that the right balance of these chemicals will produce the perfect cup of coffee, right? But what is that balance, scientifically speaking?
Before we begin, it’s important to note that good coffee begins way before the brew hits your cup. Everything from the type of bean used and the way the beans are roasted, to how the roasted beans are ground and the way they are brewed makes a difference to the flavour of your coffee. Even the water matters.
Ultimately, a perfect cup of coffee comes down to four equally important variables.
You know coffee is made from beans. The beans themselves are the seeds of coffea berries. Fresh, they’re not particularly appetising, but once roasted, your perfect brew begins to take shape. The two most popular types of beans are Arabica and robusta, but there are actually more than 70 types of coffea plants.
Arabica beans are generally regarded as superior to robusta beans, which are often described as carrying a burnt or bitter flavour. Robusta plants are more easily grown compared to the far more delicate Arabica plant and robusta berries contain more caffeine than their Arabica counterparts, which contributes to their sometimes bitter flavour.
According to the blog Coffee Chemistry, Arabica beans also contain almost twice the concentration of sugar than robusta beans, which explains further why Arabica beans are more popular among coffee lovers and generally produce coffee that is more pleasant and flavourful.
So, we’ve got our beans, now it’s time to turn them into coffee. The beans start off green and the roasting process, which varies (it can take anywhere from two to 25 minutes and at temperatures between 180 to 250 degrees Celsius), turns them into the darkened brown beans we all know and love the smell of.
Obviously, cooking something has a massive impact on its chemical makeup and in the case of coffee, the roasting process creates an array of chemical reactions involving the sugars, fats, and amino acids found in coffea beans. New compounds are also formed, such as ketones, which makes coffee the perfect paleo drink.
In terms of flavour profile, the darker the roast, the fuller the flavour. Darker roasted coffees are what we generally think of as ‘strong’ coffee, such as espresso, which is typically made from medium-dark and dark roasted beans.
Intense roasting rids coffee beans of their acidity and the coffee is characterised by a distinctly bitter flavour. Conversely, lighter roasted beans, which are oil-free, unlike their oily, dark-roasted counterparts, have a milder flavour, as well as a milder, paler colour.