Part 1: Identifying acids
As a way to deepen our experience – and enjoyment – of coffee, we’re doing a short series on how to identify the various flavours within each cup. Acids make up a huge component of coffee, so for our first exercise (and video), we’re starting with citric fruits.
At the end of this article you can watch the latest What Would Dom Do video, which is a very simple exercise you can do at home to develop your senses and deepen your experience of tasting coffee.
Why do we harp on about acid in coffee?
There are well over 30 different types of acid within each cup of coffee, of which, we list the main contributors below. But the story of how these acidities marry together, how they respond when the coffee is being roasted, how they mature through resting and how the acidic flavours linger over time is so complex that even red wine is dwarfed in a battle of acidities.
Here are the main contributors to the flavour of White Horse Coffee
Quinic acid plays a large role in the perceived amount of acidity in coffee. While being a quiet achiever in terms of taste, quinic seems to amplify acid on our palate.
Quinic is developed during roasting. It develops counter to chlorogenic acid. So as chlorogenic acid decreases, quinic acid increases. It is widely understood that the darker coffee is roasted, the more quinic acid decreases. This occurs around a french roast, and as far as I am aware, specialty coffee roasters do not roast coffee that dark. So largely this is an untested realm.
Malic acid is tart, as you would experience when eating apples. The name actually comes from the Latin word for apple, mālum. Malic acid lingers, and it seems that roasting coffee does not affect it negatively or positively.
Chlorogenic acid leaves a bitter taste in your mouth. This may sound bad, but the international World Barista Championship (WBC) and the Specialty Coffee Association (SCA) guidelines for espresso, state a harmonious balance of sweet and bitter acidity is important and desirable.
Despite the the name, chlorogenic acid does not contain chlorine. The name comes from the Greek word chloros, which means light green. Chlorogenic slowly decomposes to form caffeic and quinic acid over the roasting process with about 50% of the original Chlorogenic acid being destroyed in a medium roast.
The taste of citric acids exhibits strong sour characteristics similar to what we taste in unripe fruits. Most of us are very familiar with citric acidity, with lemon acidity being the quintessential taste of citric acid. Reaching maximum at light to medium roasts then it quickly fades as the roast darkens.
Phosphoric acid originates from phytic acid in soil, which is why it tastes like a mineral. Phosphoric acid makes up only 1% of coffee’s matter, yet it is 100 times more potent than any other acid. There is much mystery about this acid and not much research has been completed since the 1999 study conducted by J. Rivera of the Coffee Quality Institute.
Lactic acid is hard to perceive and is noticed more in the texture, mouthfeel, weight and body of a coffee. While it is not easily identifiable, lactic acid forms much of what we discern to be a great cup of coffee. It was first identified in milk, hence the name comes from the Latin word lact, meaning milk. In 1808, Jöns Jacob Berzelius discovered that lactic acid is also produced in muscles during exertion.
You are very familiar with this acid through vinegar. Acetic acid gives vinegar its sour taste and strong aroma. While adding vinegar to coffee sounds crazy, natural acetic acid has a unique ability to give clarity and complexity to coffee.
Microbes within coffee skin and the mucilage around the green bean form acetic acid during washing and wet processing. The amount developed is hard to track and is dependant on temperature and length of fermentation. Acetic acid increases during roasting, and is incredibly fragile. It is associated with the myriad of aromas in coffee.
Develop your senses at home
That’s just the start of understanding acid in coffee. The following video will walk you through a simple exercise you can do at home, which will help develop your senses and deepen your experience of tasting coffee.
Watch the video
Thanks for reading and watching