You may want to look elsewhere if your stomach aches.
Most people that have opinions about coffee also have some sort of opinion on the acidity of the coffee beans they use. Some of us coffee lovers enjoy the way it tastes and some of us don't; some of us worry it's making us feel bad, while others are unbothered. Let's explore the different ways that acidity can impact our favorite beverage.
The most common general measure of acidity level is the pH scale, on which seven is neutral, anything higher than seven is basic (aka not acidic), and anything lower than seven is acidic. So the lower number on the pH scale, the higher the acid level of concentration. Coffee is generally rated around a five on the scale, so yes, in general terms, coffee is indeed acidic. However, for some context, apples and sweet peaches fall between three and four and grapes are even lower. Coffee falls right around bananas, hardly a fruit we tend to think of as an acid bomb.
As cold brew has risen in popularity in the last decade, a not insignificant selling point for it has been its low acidity level. A 2018 study, however, suggests that selling point might be, if not downright incorrect, slightly misunderstood. Brewing five coffees both as cold brew and hot, the study found the two brewing methods resulted in very similar pH ratings. But you’ve tasted cold brew coffee and hot brewed coffee and you know that hot coffee is more acidic, right? How can that be?
There is another way to measure acid called Titratable Acidity, which better measures how much of the perceived acidity we can actually taste. The Titratable Acidity in hot brew coffee was indeed higher than in cold brew, which given the brighter, more complex acidity we taste in hot coffee, makes a lot of sense.
The Scientific Report's study does point to two others that might change your view on coffee acidity even further. The first, published in Gastroenterology in 1980 did find a link between coffee bean and increased symptoms of acid reflux, but it found the risk in coffees ranging from four and a half to seven on the PH scale. The second set of studies, published in Alimentary Pharmacology & Therapeutics in the '90s, found the relationship between coffee consumption and your gastrointestinal health might have more to do with caffeine than acid level. That paper also links to many more recent studies that failed to find a link between coffee and gastrointestinal discomfort, as well as others that showed coffee's many other health benefits. So, even for experts, it's hard to answer the question of whether coffee and its acids are bad for your gastrointestinal tract with anything more than a qualified ¯_(ツ)_/¯.
So if you're a coffee drinker, our best advice comes, you guessed it, from the 16th century Swiss scientist Paracelsus, who famously wrote "All things are poison, and nothing is without poison, the dosage alone makes it so a thing is not a poison." If you're sure drinking coffee's got your tummy acting up, the safest bet is to drink just a little less of it. And when comparing acid content in different coffees, remember that the amount you're drinking matters. Even if you're sure that cold brew treats you better than hot brew coffee, a 32 ounce big gulp of cold brew will impact you more than a 12 oz cup of hot coffee in every way.
Acidity when it comes to regular coffee is, of course, not just a health-related concept. And many people’s preferences for colder brews and darker roasts are based on avoiding what is perceived as sourness. Coffee professionals do use the term acidity mostly with a positive connotation and sourness with a negative connotation, but the concepts are absolutely related. While occasionally there are coffees that either because of a defect or a roasting choice can have out-of-balance sour flavors, a pleasant, in-balance tartness can make drinking coffee truly delicious.
Acidity is so important that when evaluating coffee for purchase on specialty coffee’s official scoring form, the quality of the acidity is worth as many points as aroma, body, and even “flavor” in general. If you want to dive into the deep end, coffees from Kenya are most identified with big acidity, and are because of that, a coffee pro favorite. Most high-quality coffees though, especially a medium or lighter roast, will have some trace of perceived acidity to them. Next time you shop coffee and leisurely enjoy a cup, look for that trace of tartness and how it enhances the other flavors in your cup. You'll start noticing the different types of acidic flavors, such as malic acid (found, amongst other things, in apples), tartaric acid(found in grapes), and citric acid (yup).
Another group of acids found in coffee is chlorogenic acid, which brings us to a brewing (or really post-brewing) tip. Chlorogenic acid breaks down to quinic acid (which you might know from tonic water) and caffeic acids. Those two can result in bitter flavors that we don’t love in coffee and that breakdown happens more at higher temperatures. The actionable info: if your coffee machine comes with a hot plate, you might want to take your coffee pot off of it after brewing. Hot coffee is wonderful for sure, but if you let it cool naturally (or just brew a small enough amount to finish sooner rather than later) it will probably taste better!