Q-Grading Coffee: Part 2 of 5. On Acids.

Acidity might be one of the most polarizing things you can talk to coffee drinkers about. When it comes to coffee, we need to reframe our preconceived notions about acids.

The most important thing to remember when you’re tasting for acidity is that it’s not necessarily referring to the pH of a given coffee. Coffee sits around 5 on a pH scale - for reference, a neutral acidity is 7; orange juice sits at around a 3. If you feel sensitive to acid, you can temper the perception of acidity in your coffee by opting for medium or darker roasts, or by adding milk. There’s definitely a solution for everyone.

In the first article in this series, we talked about the organic acids exam for Q-Graders. Learning about the types of acids most commonly found in coffee is a great step towards finding an easier pathway to identifying specific flavors. There are many, many acids found in coffee, but we’re going to focus on the four main types: citric, malic, phosphoric, and acetic acids. Each type has its own distinctive characteristics, and to highlight those characteristics, we’ll be using fruit as a reference to guide us towards adding these different types of acid to your sensory memory. 

A quick note: It’s hard to identify different varieties of fruit by type! But if you look at the small sticker on a fruit, you can usually find an identifier. If you’re unsure, you can actually google the 4- or 5-digit number on that sticker; they are called PLU numbers and are largely universal.

Citrus: Grab yourself an orange and a lemon. Lemon offers that bracing acidity that almost instantly makes your mouth pucker. Oranges have a cleaner acidity; it’s similarly bright but balanced by natural sweetness. Taste the difference here, and consider how sharp or tangy this acidity gets. I recommend using Meyer lemon and Valencia or Navel oranges.

Malic: Get yourself a Granny Smith apple and think of the acidity presentation when you take a big bite. Tart yet clean, malic acidity is often found in apples and pears (malic, from malum, literally means “apple”). I also associate malic acidity with slightly unripe fruits.

Phosphoric: I like to call phosphoric acids “ghost acids” as a joke, because they’re not organic acids (inorganic) and they don’t have a flavor! Still, phosphoric acid deserves its inclusion in this group: it has a pleasant buzzy quality, and it enhances acidity without adding any other tastes or changing the flavor of your coffee. Kenyan coffees are a great example of this: the plants pull phosphorus from the fertilized soil, which electrifies the mouthfeel and raises the perception of acidity. Think about Coca-Cola here too - phosphoric acidity is often added to fizzy drinks and sodas.

Acetic: Okay, we’re gonna veer a little off course with this one. One of these things is not like the others: acetic acid is created through processing and roasting. If you’re familiar with different coffee processing methods, you’ll find that acetic acid flavors are commonly found in naturally processed coffees. So get yourself some wine, cider, or kombucha (booch, y’all!) - all of these are positive examples of acetic acid’s flavors. The best ferment flavors in coffee are berries and tropical fruits. Take it too far, though, and you’ll get unpleasant overly-fermented, boozy, and vinegar-like flavors in your coffee.

Now that we’ve discussed and tasted a bunch of these acids, try each fruit again and really hone in on what you’re tasting. Think about where on the tongue that acid presents itself most prominently. Consider your perception of the flavor of an orange, and attach that memory of citric acidity to it - and so forth! Now you have a toolkit to help you assess what we call the “brightness” of a coffee and guide for talking about acidity and how it relates to flavor.

You also got to eat a lot of awesome fruits in the process -- not a bad deal! Keep an eye out for the next blog post about body and mouthfeel; we’ll tie it into this article’s tasting exercise and keep building our sensory memory. 


You can expand your sensory memory even further by tasting different varieties of fruit. For example, there are several hybrids and varieties of apples found at most grocery stores; Red Delicious, Gala, Golden Delicious, Honeycrisp, Fuji, and Granny Smith apples are just a few of the many options.

*Some fruit resources for folx living in the Triangle Area:

Apples and many different varieties of oranges (like Navel oranges, Valencia oranges, Mandarins, Clementines, and Tangerines) are easy to find at most Harris Teeters, Trader Joe’s, and Whole Foods.

Tropical fruits are a little hit or miss depending on where you live, but I’ve had luck at most Harris Teeter stores, Hispanic markets (like La Superior), and Asian markets (Li Ming’s is a great one here in Durham). I’m also gonna give a BIG shoutout to H-Mart, a huge Korean market in Cary. They’re actually pretty common in most US cities, and you can find a huge variety of fruits and veggies of all kinds at great prices. Go hungry, because H-Mart also has a ton of great food vendors, and I highly suggest the bibimbap at their Cary location.

**Big thanks to Michael Harwood, our Director of Coffee Quality & Innovation and fellow Q-Grader, who contributed to this article. They’re a fantastic educator and offer weekly classes on everything from coffee brewing to decoding the labels on coffee bags. Check out their classes and resources here!