It’s been a while since I’ve thought about starting a blog to share what I’ve learned on my coffee journey. “While we teach, we learn,” said the Roman philosopher, Seneca. All my posts are based on personal thoughts on what I’ve come to learn and understand. If there are any errors in any of my blog posts, please don’t hesitate to correct me.
What is acidity? Back in elementary school, we were taught that acids tasted sour like lemons, which is why the general public often relates the term “acidity” to things that are sour, such as lemons. In high school, we learnt about how acids have a pH value of less than 7, which is represented by the amount of H+ one would find in a specific solution.
It is important to remember that the pH scale is logarithmic. This means that each whole value below 7 is ten times more acidic. Thus a pH of 4 is 10 times more acidic than a pH of 5, and 100 times more acidic than a pH of 6.
It is important to stress that pH is logarithmic because not many people, including myself, know much about it.
The history of acidity in coffee
Back in the late 1970s, around the time that specialty coffee began as a movement. In order to distinguish specialty coffee from big mainstream institutional roasters, acidity stood out as a main point of difference. At that time, ordinary main stream coffee tasted flat and dull because it was ironically very lightly roasted to maximize yield and profitability. A ‘special’ or specialty coffee was different because it was lively and had vibrant acidity. From this time onwards, acidity was included as a point of difference on specialty cupping sheets to help define specialty coffee. I will go only this point,if you want to read more about it, there is an article about it at the August 2013 issue of BeanScene.
Acidity in Coffee
The history of acidity in coffee. The matter of acidity has always been the subject of hot debate amongst coffee drinkers around the world. In Malaysia, for example, café patrons are often wary of the acidity of their coffee, ironically preferring their coffee to be bitter. The task of deciding which bean to serve has been the constant struggle of baristas and café owners alike. In fact, in places that serve exceptional specialty coffee, more complaints arise than that in places serving poor quality commercial beans. Sadly, there are only a handful of people who actually understand the importance of acidity in a good cup of Joe. The Belco Team have a spot on explanation that I often use when conveying the importance of acidity.
a bright coffee is like a soda which has just been opened (sorry for the heresy), with all of its bubbles that climb into your mouth… if you leave this soda opened for a while, and take it back a couple of hours later, you’re going to feel a drink with no more bubbles and flat. This is what looks like a coffee without acidity: neither bright, nor complex! It is for this reason that acidity is extremely valued in coffee!
II have found this explanation to be of extreme use when educating the public about coffee acidity.
The acidity of coffee has its roots in the production cycle of coffee beans – Growing, Processing and Roasting. This also relates to the terroirs in which coffee is cultivated. The acid present in coffee is called chlorogenic acid, which is developed by the actual plant itself, as a natural form of defence against threats such as insects.The chlorogenic acid breaks down, depending on how much exposure it has to heat. As a result, poorly roasted beans often taste bitter. One must keep in mind that the darker you roast, the more acidity you lose.
On the contrary, lighter-roasted beans tend to give much-needed emphasis on the acidic compounds present and bring more focus towards them. This is why coffee traders prefer to roast their samples lighter, in order to preserve the acidity. In today’s coffee culture, the art of light roasting is a form of appreciation for acidity.
Type of acidity in coffee
The most common acid found in coffee, citric acid plays an important role as a key intermediate compound in the plant’s metabolic cycle. In green coffee, citric acid makes up a significant portion of a coffee’s total acid content.
The taste of citric acid is synonymous with that of lemon or any unripe fruit. However pleasant it may be, this acid diminishes rather quickly during the roasting process. A lightly-roasted bean will contain the highest amount of citric acid.
Acetic acid, often compared to vinegar, is developed post-process, during fermentation. It will often give us a winey month feeling that confused us with the body of the coffee.
Coming close to the taste of an apple, malic acid does not have the explosive tanginess of fruits in the citrus family. The taste of this acid will often linger on the taste palette of a person, and is usually developed during the growth of the coffee itself.
This acid is deemed rather unpleasant by many of those who call themselves coffee drinkers. With the simple mention of the term, any experienced coffee drinker will know that a bitter, harsh and metallic taste will follow suit. Robusta coffee has a much higher concentration of this acid, which explains the extent of its bitterness.
Quinic acid has a bitter, stringent taste. This acid is the end result of the breaking down of chlorogenic acid during the roasting process.
All in all, acidity is probably one of the most important compounds of a good cup of coffee. I would like to reiterate that acidity is what differentiates specialty coffee from commercial coffee.
In my humble opinion, cafés that serve specialty grade coffee should really delve deeper into the understanding and learning of acidity differentiation, in order to blend, roast and brew better coffee. Not to mention, it would definitely help patrons choose their coffee more carefully.