There was a scene in the film “A Film About Coffee” where Blue Bottle Founder, James Freeman shares about the first time he tried coffee. After catching a whiff of the coffee his parents were making, he wanted to try it out, and was surprised to find that it tasted bitter.
Many of us who’ve had our first cups of coffee can attest to this experience. Although there are people who have grown to love the bitterness, there definitely is more to the cup than meets the eye. Coffee doesn’t need to be bitter, but yet that descriptor is what sticks most for people.
What makes coffee bitter?
From a scientific perspective, there will always be some element of the coffee that will contain bitterness. To keep things simple, we’ll be identifying the most common of these elements which are: Chlorogenic acid and Caffeine. Chlorogenic acid in its original state is not bitter, but as the coffee undergoes the roasting process and depending on the roast profile, chemical changes occur.
You can probably guess - if the coffee you’re tasting is roasted on the lighter side (light roast), you’re likely to find less bitterness and more balance in that cup of coffee; whereas when roasted on the darker side, you might find that familiar lingering bitterness in your cup.
Caffeine also plays a significant role in bringing forward bitterness, coffee types with more caffeine content will be more bitter than those with less. By that association, it explains how Robusta is a naturally more bitter coffee than Arabica, and why certain instant coffee blends are made with a mix of both to try and find that balance in the flavour.
How do you control bitterness?
All things above considered, extraction then plays the next part in determining a coffee’s bitterness. When brewing coffee, you’re ultimately trying to extract the best of its flavours, and anything more than that will be the unpleasant elements of the coffee. When at a specialty café, you might notice that when pulling the shots of espresso, the barista takes extra care in adjusting the grind size, water temperature and timing of how long the shot is pulled, for good reason - because these variables affect coffee extraction.
These same principles apply to home-brewing:
Grind Size: Decreasing the coffee grind size (smaller) means an increased surface area around the coffee ground. This means an increased area that comes into contact with water, resulting in more flavours, which may include bitterness, being extracted.
Water Temperature: The optimal brewing temperature recommended by the Specialty Coffee Association is between 90°C and 96°C but going slightly further off from that range may not be all bad. Do note that the higher the water temperature, the easier it is to extract flavour and aroma compounds, including bitterness.
Brew Time: Brew time translates to the amount of time that the coffee grounds are spent in contact with water. The longer that time is, the more extraction will occur, releasing more bitter elements into the cup.
There are a multitude of other factors that might determine the taste of your coffee, whether bitter or sour, the list goes on. The key is to find that balance in all of these variables and when you hit that sweet spot, it results in a delightful cup that extracts the intended flavours of your coffee.