This week in the Dry Bones Blog, we’ll be expanding on the topic of coffee acidity that we touched on in the last post. Just how acidic is coffee? What are some of the acids present in coffee? What makes a particular brew more or less acidic? All of this coming at ya hot, steaming, and delicious!
Acidity is measured on the ph scale, a numbering system that rates a substance’s acidity 0-12. Pure water is considered neutral at 7, with any lower numbers on the scale being acidic and any higher numbers being basic. Some examples would be things like soap and antacids having higher ph values, and things like lemon juice and soda having lower ph values. Though it can vary, coffee on average has a ph value of 4.5 to 5 meaning that it is more acidic than saliva or milk, and less acidic than tomato juice or beer. Personally, I was surprised that it was so mild. It seems to me that some toothpaste commercials would have you believe that coffee is just shy of battery acid.
The ph value alone, however, is not enough to wrap your head around just what all those acids are doing. For that, we need to look at some of the major types of acids at play in coffee. First there are the chlorogenic acids. These acids are known to be antioxidants and are most present in coffee before it is ever roasted. As the beans are roasted, the chlorogenic acids break down, meaning that the darker the roast, the fewer chlorogenic acids. Though the chlorogenic acids degrade during roasting, the chemical components they’re made of reform into the other major type of acid prevalent in coffee: quinic acids. Dark roasts are higher in quinic acids which are closely associated with the astringency of coffee as well as a “sour” feeling in the stomach after drinking coffee.
But all these acids have to come from somewhere in the first place, and even when beans are roasted identically some coffees are naturally more acidic than others. Why is that? As with any facet of coffee, there are dozens of variables that factor in acidity, but the most succinct explanation is: location, location, location. Things like soil content and just good ole’ genetics play major roles in a certain coffee’s acidity. A more universal factor, however, seems to be the elevation at which the coffee is grown. Coffee grown at higher elevations is usually found to be more acidic, and also to have more complex and desirable flavor notes. This is because the climate tends to be cooler at higher elevations which causes the coffee cherries to ripen more slowly. This slower ripening process is how coffee is able to develop more complex flavor profiles.
It may surprise you that acidity is actually a descriptor of positive tasting attributes. Outside of the aforementioned acids; quinic and chlorogenic, there are a few other acids present in coffee that create positive tasting notes in various coffees. Citric, malic, phosphoric, acetic, and tartaric acids can all be found in different foods so naturally when present in coffee they produce those similar tasting notes. These acids produce flavors ranging from citrusy to sweet to grapeish like wine to tropical fruit tastes like mango. Overall, acidity is essential to various positive flavor notes present in coffee.