Many people are interested in the acidity of coffee- how acidic a cup of coffee tastes, the measurable amount of acid within beans, and which brewing methods and growing regions produce more or less acidity.
As a primer, acidity is measured on the pH scale with values less than 7 being acidic and values greater than 7 being basic. The pH of pure water is 7 (neutral), and soapy water has a pH of 12, making it a strong base. The average pH of plain, black coffee hovers between 4.5-6, but varies depending on a number of factors.
As a side note: while some are concerned with the measurable pH of coffee, many are also concerned with the flavor profile resulting from the acids in the coffee. Higher acidity, when it relates to flavor, is generally a desired quality that can really make a cup of coffee pop and stand out. In addition, there are several different acids that can compose coffee, all of which are naturally occurring and produce different flavor profiles: lactic, acetic, citric, malic, phosphoric, quinic, chlorogenic, palmitic, and linoleic acid. These are topics that we won't address in detail here, but plan to address in a future post- so stay tuned!
3 Factors Affecting the Acidity of Coffee
Factor #1: Growing Conditions
The growing conditions of coffee play a major role in the acidity of the eventual brewed coffee. The mineral content in the soil has an outsized impact in this regard- the less acidic the soil is, the less acidity will be transferred into the final product. Coffee from some locales in Brazil and Indonesia will tend to be less acidic than that of other growing regions, but this is far from a hard-and-fast rule. However, in general, coffee that is more acidic tends to come from high elevation areas and/or volcanic soil in countries such as Peru, Ethiopia, and Guatemala.
Once the coffee cherries are picked, they are usually processed in one of three ways: wet (also called washed) processing, dry processing (sometimes referred to as natural processing), and a hybrid of the two. While processing method has a minimal impact on pH among the three, wet processed coffee tends to taste more acidic than dry processed; dry processed coffee tends to have a stronger body that masks the acidic flavor.
Factor #2: Roasting Method
Roasting also has a dramatic impact on acidity. Lighter roasts have high acidity (lower pH) than darker roasts due to the way the roasting process neutralizes or “burns off” much of the acid in the beans. While roasting for a longer duration reduces the acidity, roasting at a higher temperature also reduces the acidity. For example, a dark roast roasted at 410 degrees Fahrenheit (210 C) will be more acidic than the same roast at roasted at 500 degrees Fahrenheit (260 C).
Factor #3: Brewing Method
Brewing methods also affect coffee acidity. Coffee brewed with a method utilizing a fine grind, such as that made with a standard drip brewer or AeroPress, tends to have less acidity. In contrast, coffee prepared with a French press (utilizing a coarser grind) yields fairly acidic coffee; the lack of a paper filter, which would absorb some of the acid, also is a factor. Water temperature also plays a key role in acidity: higher water temperature extracts more acids, whereas a lower temperature extracts less. This is why cold brew is notoriously less acidic than other brewing methods. The room temperature water used helps limit acid extraction, in addition to typically darker roasted coffee being usually used.
How Can I Drink Coffee if I Suffer from Acid Reflux?
If you suffer from acid reflux, you may think coffee is off limits. And while ultimately you should follow your doctor’s recommendations, coffee could shift from a relic of the past back to your morning routine; making coffee that is close to neutral pH isn’t too difficult. We’ll divide this section into two parts: 1) things you can do before/while brewing to reduce the acidity of coffee and 2) things you can do after brewing to reduce the acidity of coffee.
Tips for Reducing Acidity in Coffee Before/During Brewing
Tip #1: Picking a Less Acidic Roast
If you’re looking to add coffee back to your life, the first step is to utilize a less acidic roast. Try finding a darker roast that was grown in a location with lower elevation, such as Sumatra.
Tip #2: Using a Less Acidic Coffee Brewing Method
Brewing your coffee through a method that utilizes a paper filter can also reduce the acidity of your coffee. Keep in mind that using the reusable coffee filter that some drip brewers come with won’t do much to remove acid during brewing. For the reasons we previously outlined, cold brewing is also very advantageous for reducing acidity.
Tip #3: Adding Egg Shells to Your Coffee Grounds to Reduce Acidity
If you are feeling a little adventurous, you can take 1-2 fresh, well-rinsed and crushed eggshells and add them to your coffee grounds before brewing. Eggshells are alkaline and will neutralize some of the acid and the filter will ensure that none of the pieces end up in your brew.
Tips for Reducing Acidity in Coffee After Brewing
So, let’s say you have a cup of dark roasted drip coffee- how can you further reduce the acidity of it? One option is to add milk, which has a pH level of around 6.7, but this results in a relatively minor decrease in acidity.
A more potent option is to add a small amount of baking soda (¼ of a teaspoon), which is a base, to a pot of brewed coffee to neutralize the acidity.
Also, keep in mind that different types of sugar have different pH. For example, raw and unprocessed sugar is slightly basic, but white and brown varieties of sugar tend to be acidic. Thus, if you regularly add sugar to your coffee, you may want to consider switching varieties if acidity is of concern.
Once you’ve mixed up your cup of coffee this way, you’ll notice that it is significantly softer on the stomach. However, if you find that you can’t tolerate anything but plain, black coffee, then you still have an option: coffee acid reducers. These are small packets, or tablets, that are to be dissolved in a cup of coffee to neutralize the acid. Products that are marketed towards coffee drinkers tend to alter the flavor of the cup as little as possible and can reduce the acidity by up to 90%.