Sugar and coffee: old friends
Along with milk, sugar is the most common thing that people like to add to their coffee. It seems normal to see bowls of the stuff on café tables, or sachets ornamenting your espresso’s saucer. But why do we actually add sugar to coffee?
It stems from the fundamentals of flavour in coffee. Coffee is inherently bitter tasting. Because of the original function of taste – alerting us to things that might be dangerous to consume – we perceive certain compounds as bitter. Caffeine, as a potentially toxic substance in high enough quantities, tastes bitter to steer us away from it. Luckily, it's perfectly safe to consume in the quantities found in a cup of coffee, but that doesn't change the fact that we perceive it as bitter.
But caffeine isn’t the only source of bitterness in coffee. Roasting is effectively the controlled burning of green coffee to increase its solubility, allowing us to extract more flavours and make a stronger brew. Like burning anything, this imparts bitterness, especially the darker you roast.
How can sugar help mitigate this bitterness? Taste is ultimately relative, meaning that while you can’t “remove” the bitterness from the cup, you can make it seem less prevalent by balancing it out with the other primary tastes: sweet, sour, and salty. A good balance of these is the key to making anything tasty, as it means that all the different taste receptors on your palate are being stimulated. This state of balance is sometimes referred to as “the fifth taste”: umami.
No one wants to drink a salty coffee, and acidic coffees are a relatively new trend, and something that can only be achieved at lighter roast levels that aren’t that bitter to begin with. Sugar, therefore, is the most popular way of balancing out the bitterness in coffee.
Even a little bit of sugar can be enough to change the bitterness from the dominating component to a complementary one. If a coffee tastes only of bitterness, it is of course an overwhelming, face-changing hit of unpleasantness. But if that is balanced out with a sugary note, the bitterness becomes one of several flavours, adding to the complexity of the cup.
White, brown, raw, cubes, sticks - there are lots of different forms that your sugar can take. While white sugar is probably the cleanest form of sugar, thanks to its thorough processing, many people prefer to use raw or brown sugar. These suagers have had less refinement, and so generally have a more complex flavour, which can make the cup just that little bit more interesting.
At the end of the day, we all have different palates, with different sensitivities to different flavours. Some people have a big sweet tooth, others love bitterness. So it’s up to you if you add sugar to your coffee: if it tastes good, do it!