Coffee Acidity

There are over one thousand chemical components that have been identified in coffee and roughly fifty out of those are acids. Acidity’s role in coffee is far from straightforward. Rather, it plays a complex role that affects everything from flavor to smoothness. Acidity is to coffee as carbonation is to soda, take it away and the drink loses its pizazz. If you’ve found your way to this page, it’s likely because you’re wondering 1 of 2 things.

  1. You’ve heard a snooty coffee snob describe the “acidity” in a coffee and found yourself wondering what that meant.
  2. (More likely) you’re one of the many sufferers of heartburn in the world and you’re looking for a way to enjoy your cup of joe, and alleviate that burning all at once.

We’ll do our best in this article to explain all the nuances and complexities of acidity, and the role it plays in one of the world’s most popular drinks.

What Is PH?

To understand what’s going on, we first need to take a little trip back to high school chemistry so we can understand PH values and what they symbolize. Essentially, PH describes how acidic or Alkaline (aka Basic) a water solution is.

The scale goes from 0 – 14 with 0 being the most acidic, and 14 being the most Alkaline. Solutions at either end of the spectrum can be dangerous to unprotected humans. For example, Battery Acid is a 1 on the scale whereas Ammonia is a 12. A value of 7 indicates something that is perfectly neutral; some examples of a 7 include milk and distilled water.

So where does coffee fall on the list? Coffee typically rates about a 5 on the scale which is slightly more acidic than neutral water but well within the range you’d expect to see naturally in surface and rain water.

Here’s a couple more example of PH value for your curiosity:

PH Value Solution
2 Lemon Juice
3 Vinegar
3.8 Apple Juice
4 Adult Fish Begin to die
4.3 Kenyan Coffee
4.6 Sumatran Coffee
6.7 Tap Water
6.9 Milk
7 Distilled Water
9 Baking Soda / Sea Water
11 Milk of Magnesia
14 Lye

 

What Can Affect Acidity

Elevation

One of the biggest contributors to the acid content is the altitudes at which the beans are grown. Coffee cultivated at greater heights or in mineral rich soils is linked with greater acidity, and is valued more compared to coffee cultivated at lower elevations. Coffees from Kenya, Colombia, Papua New Guinea and Ethiopia are farmed at five thousand feet or more and tend to be more acidic. Whereas coffee cultivated in Brazil (Bourbon Santos), or Hawaii (Kona) is farmed at lower heights, less than three thousand feet, hence tends to be less acidic; and unfortunately, sometimes less flavorful as well. But why is coffee grown at elevation more flavourful? The cooler climate at higher elevations slows the growth cycle of the coffee plants. The elongated maturation period allows the bean to develop more slowly, giving it time to imbed the more complex sugars and flavors into the seed. This is why the seed is harder and more dense in an Arabica plant than one from Robusta plant. The enhanced drainage at higher elevations also minimizes the quantity of water in the fruit, which further concentrates the flavors giving the final brewed cup a more intense taste.

Soil

Going hand in hand with altitude is the fertility of the soil. Highly fertile soil which is rich in minerals, like that found around volcanoes, will produce coffee beans which are more flavorful, but higher in acidity. Some of the best coffees in the world are grown in the fertile volcanic soils found around the world.

There are two main species of coffee plants that are used for commercial coffee preparation: the Robusta and Arabica. In nearly every cupping test, coffee brewed with beans from the Arabica plant rated higher than the coffee brewed from beans of the Robusta species. The Arabica plant thrives only at higher altitudes while the Robusta species are better adapted to grow at lower altitudes.

Processing

After picking the fruit from a coffee plant, the next step on the way to producing a great cup of coffee is to extract the coffee bean from its resting place deep inside the fruit. The bean lies buried deep inside the fruit; the outer most layer is the skin, next is the pulpy mucilage and lastly the thin papery parchment before you reach the seed itself. The method used in removing all these layers also impacts the acidity in the final product.

While there are numerous variations and combinations thereof, essentially there are only two methods for removing all the external layers covering the seed; namely the washed method and the natural/dry processing method.  The washed method starts by removing the skin mechanically, then allowing the pulp to ferment so bacteria and fungus can loosen it from the seed making it easier to remove with additional washings.  At this point the green coffee is ready for roasting. Natural processing allows the fruit to dry in the sun over several weeks. The fruit is repeatedly turned and raked to ensure even drying, until there is separation of the seed from the fruit.

The beans processed by dry method impart greater body to the beverage compared to the wet processing method. This is due to the greater quantity of fruit remains that cling to the bean during the drying process. In the wet processing method, the fruit is removed more completely leaving the beans free from any fruit remnants.

Roasting

As a result of the chemical reactions that take place during roasting, concentrations of various acids change. A lot of them degrade in the high temperatures of roasting, but the concentration of others actually increases.  In broad terms, roasting attempts to bring out the best possible combinations of the acids that are naturally present in a given lot of beans, so the resulting roasted beans yields the most desirable characteristics in the brewed cup. Dark roasts tend to be less acidic than lighter roasts. The extra roasting time the beans require for making dark roasts degrades more of the acids, but more importantly, it also allows time for a compound that hinders the production of acid in the stomach to develop.

Acidity As A Flavor

The word acidity has a very bad connotation. When you hear that word you tend to think of highly corrosive substances which may even be dangerous to handle. Unfortunately, for our heartburn sufferers, acidity also tends to be associated with higher quality, more flavorful coffee and is a highly coveted quality among the elite coffee producers in the Middle East and Latin America. It’s also a very good indicator of the freshness of the beans as fresher beans are said to taste “Brighter” (ie: More Acidic). There are many different acids that play a role in your brew, and some have truly marvelous outcomes.

Chlorogenic Acid

One such acid is a substance known as Chlorogenic acid. In addition to being a known antioxidant, the health conscious among you might be happy to learn that chlorogenic acid has been shown to slow the release of glucose following a big meal; giving us a newfound appreciation for our post meal coffee! It also happens to be one of the most prominent acids found in coffee and generally contributes what we would describe as a “brightness” or “sparkle” to the coffee. This should not be confused with citric acid which will give you hints of orange or lemon. Because it is very susceptible to the roasting process, the amount of chlorogenic acid will decrease rapidly as you move along the spectrum into the darker roasts. While the name seems ominous, chlorogenic acid does not in fact contain any chlorine; rather, it derives its name from Greek and owes its name to it’s tendency for turning green following oxidization.

Citric Acid

This is one of the easiest to recognize. Similar to the taste of freshly squeezed lemons or oragnes, some experienced professionals will actually shy away from these beans. Usually it is more common in freshly harvested crop, or if there are too many beans from immature cherries in the lot. This acid cannot be roasted out.

Phosphoric Acid

Phosphoric acid is among the sweetest of the acids and is most notably associated to really sweet tropical fruits like Pineapples and Mangos. This will really give you an extra kick of flavour, particularly if you like your coffee black.

Acetic acid

Acetic acid typically indicates there’s been a problem with the brewing process. This acid is produced if the pulped beans are left in the fermentation tank for too long or the temperature is too high. While some brewers have been known to leave a touch of it in to provide a sharp, biting flavor; it is generally thought of as undesirable. A coffee which is high in acetic acid may present a flavour reminiscent of household vinegar.

Malic Acid

The amount of this acid is on the rise due to higher acreage of sun grown coffee. The vast difference in day/night temperatures produces more of this acid in the beans. Malic Acid is yet another contributor that can often resemble non citrus fruits we traditionally think of as growing on trees. A coffee high in malic acid may have notes of apple, plum, pear, or peach depending on the concentrations.

Tartaric Acid

Tartaric acid is found in grapes; in high quantities it will make your coffee exceptionally sour. If, however, you manage to get it down to the right proportions, you’ll be left with a coffee that has beautiful hints of wine.

Quinic Acid

Finally comes Quinic acid. Quinic acid is actually produced as other acids break down. This is common in coffee which has been sitting on a heat source (like a hot plate) for a while, or coffee brewed with stale beans. Quinic acid will eventually contribute to a cup whose taste you might call “stale”. Unfortunately, this is also one of the main contributors to heart burn so it would be best you drink your coffee as fresh as possible!

Low Acid Coffee

I already feel your pain. As someone who regularly experiences heart burn I can appreciate how desperate you can be to just have the burning stop. If you’re among the gastro intestinally challenged, the good news is there is hope for you yet! Stomach friendly options do exist.

Firstly, there are specially prepared, low acid options of coffee. Some of the most popular brands include Puroast, Simpatico, Hevla, and Healthwise; each of which have their own claim to fame for reducing acid by varying degrees. Hevla for example steams their beans before roasting, while Puroast uses an ancient Venezuelan roasting technique. Not to be topped, HealthWise developed and patented its own proprietary roasting method dubbed “TechnoRoasting”.

In addition to the speciality coffees there are some types of coffee that will naturally contain less acidity than others as we discussed earlier.

How to Reduce Acidity in Coffee

If the acidity in coffee is creating stomach problems, then several precautions can be taken to make the brew more bearable. The first step is to select beans cultivated at lower altitudes as opposed to higher ones. When possible select darker roasts over light. Dark brews are almost always lower in acid as the roasting process has more time to cook out many of those acids which are susceptible to heat. As such, those with sensitive stomachs should start to ween themselves off of medium and light roasts in favor of darker roasts like French Roast or Espresso. Finally, opt for brewing methods that require more coarse grounds as opposed to fine grounds as these deliver less acid in the cup.

Another thing to keep in mind if you’re among those suffering Acid Reflux; start using milk! Adding milk to your coffee will help with your stomach problems in two ways. Firstly, it is a practically neutral solution which will bring down the acidity simply through the process dilution. But it’s also packing a secret weapon, calcium. Calcium is especially good at neutralizing acid and ultimately makes the milk more effective than plain old water at neutralizing those nasty acids (we’re looking at you Quinic Acid!) Antacids are known to defuse stomach acid and calcium is their main component. By adding milk or cream to your cup of Joe, you give your stomach a buffer as you enjoy the drink.

Cold brewing is also becoming more popular, especially during the summer months. Other names for this style of brewing include Kyoto style, cold-drip coffee or Toddy style. This type of beverage can be made by allowing the coffee grounds to steep in cold water for a minimum of two hours. Granted that cold water will extract less of all the flavourful components from the coffee; this also includes roughly seventy per cent less acid. Many people enjoy the mellow, smooth taste of this beverage.

Hopefully we were able to send you on your way with a little more knowledge. Acidity is an essential component of coffee, without it the cup of Joy will be a very bland drink. A sensitive stomach is however no reason to give up this exceptional beverage. The effects of acidity on the stomach can be minimized by carefully selecting the appropriate beans and employing brewing methods that minimize acidity.

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