Real Deal on Acid in Coffee

Have you ever heard a non-coffee drinker say they would drink coffee but for the “bitter” taste? In certain professional circles, coffee also takes a lot of heat for stomach maladies by being branded as an “acidic” drink. Facts are it rates a five on the pH scale, bringing it below common drinks such as soda, beer and even orange juice! When we study the chemistry of coffee, we quickly see a complex array of compounds that shed light on what is really meant by words commonly attached to this mistakenly maligned beverage.

Acid vs. Acidity

Just saying the word “acid” invokes mental distress! When paired with the word food or drink, the normal reaction is to keep your distance! However, in the vast scheme of how coffee flavors exist, “acidity” is deeply woven into an intricate tapestry which, in the end, produces a truly beautiful drink completely void of negative backdrop.

Grasping the qualities of the 16 different compounds that attribute to coffee acidity can be a daunting task worthy of a third year chemistry student but suffice it to say, every coffee bean uses certain foundational acids to create the myriad of flavors we take for granted. Coffee aficionados use the term “acidity” in reference to these acids, not on a scale of content but more in terms of how they influence coffee flavor notes. They use terms such as “bright” to describe good flavor acidity. So in the world of coffee lovers, acidity is not such a bad thing!

Included in our discourse should be an awareness of what is called “perceived bitterness.” Some of the acids in coffee present a flavor aspect which can be unpleasant or overwhelming unless balanced by other compounds. Each coffee type unravels perceived bitterness in its own way. Bitterness is influenced by the levels of a particular acid and may actually add to the value of a coffee flavor. So here again, common words can mislead the casual thinker but real coffee lovers experience these nuances of taste in a different way.

Let’s look at some of these acids as they relate to our favorite morning brew.

Which Acids Are in Coffee?

As we dig deeper for the truly curious, we see various types of acid in our daily joe.

Chlorogenic Acids

One of the main group of acids present in coffee are chlorogenic acids, which also happen to be an important group of antioxidants. While the overall effect of antioxidants in coffee is still in the research stage, some people are very excited about the very large concentration of chlorogenic acid in green coffee beans compared to other plants. In its purest state, green coffee contains a lot of different acids – some good and some not so good. Most of the bad ones disappear during the roasting process, or are transformed to a less aggressive state, but it may also reduce the antioxidant levels of the coffee. The green versus roasted coffee debate rages on, but that article must wait for another day.

The chlorogenic acids are a group that contributes to perceived bitterness. They break down however, during the roasting process, which is why coffee expert James Hoffman writes, "the longer and darker that a coffee is roasted, the lower the perceived acidity tends to be when that coffee is brewed and tasted."

An actual graph of different coffee roasting levels show us darker roasts present lower levels of chlorogenic acid. Therefore, the lighter roasted coffees, which are popular today, have a more pronounced acidity in their flavor profile. Keep in mind, Arabica types have a lower concentration than Robusta.

Quinic Acids

As coffee is roasted, the chlorogenic acids degrade to form quinic acids. This acid group plays a very important role in overall coffee taste. They affect the astringency of a beverage (think of sampling a green banana).  Dark roasted coffees are high in quinic acid, but low in some of the other acids responsible for flavor. This why darker roasts can cause that hollow, sour sensation in the tummy. If this is you, a lighter roast may serve you better or savor your dark roast in smaller amounts.

Fresh Coffee Is the Always the Best Coffee

Roasting is not the only action affecting coffee acids. As coffee sits, certain chemical reactions occur and change the level of acidity we taste. Drinking coffee that has been left on a hot plate for several hours can literally be a gut-wrenching experience!

Making a fresh pot of coffee will eliminate that less-than-glorious encounter of the worst coffee kind!

Enjoy!