This article originally published in The Sturbridge Times, May 2019 By Elvis Dyer, Owner/Roaster, Sturbridge Coffee Roasters
Many of us enjoy a great cup of coffee, however, for some people, coffee may contribute to digestion issues including heartburn, acid reflux or indigestion. It may be possible to enjoy coffee by simply making some switches to your coffee routine.
Acidity Level
Coffee comes in at around a five on the pH scale, which is less acidic than drinks such as beer, orange juice and soda. Some beans are naturally low in acidity. The roasting process and brewing process also have an impact on the overall acidity of coffee. Some people refer to the acidity in coffee not in terms of the pH level but rather in terms of the presence of certain acids that influence the taste of coffee. Acidity is used to describe the flavor note, often called dry, bright, lively, tangy, sharp, fruity and sparkling.
The Region, Variety, Climate and Elevation
The region and climate where coffee beans are grown has a great impact on the level of acid in coffee. Generally, coffee beans grown at higher elevations tend to have higher levels of organic acid and caffeine. An example of this fruity brightness can be found in Ethiopian coffee. In contrast, coffee grown at lower elevations which tend to have a smoother and mellow flavor. Many naturally low acid coffee beans come from medium to low elevation regions such as Brazil, Central America and Indonesia. Certain varieties are more suited to being grown in cooler temperatures than others, which also impacts the flavor. Coffee that is grown at cooler temperatures tends to ripen slower, allowing the development of more complex flavors. When brewed, it tends to be more acidic and aromatic than those coffees grown in warmer climates.
The Processing
The way the beans are processed not only impact the final flavor, it impacts the acidity. Wet/washed coffees are pulped and rinsed in water, removing layers of sucrose and fructose content which makes the acidity shine as it is unfiltered by that sweetness. Dry/natural methods leave the coffee cherry fruit intact while the coffee dries, increasing the overall sweetness and overpowering the perceived acidity. Generally, wet processing methods result in a higher level of acidity. Dry processing methods (more common in hot climates such as Africa) tend to produce much lower acidity.
The Roasting Process
Green coffee contains a lot of different acids and some go away in the roasting process and others don’t, therefore, roasting is all about finding the right balance in terms of acidity, aroma and body. The roasting process also impacts the level of coffee acidity. Coffee bean acidity changes during the roasting process. During roasting, the natural acids in coffee beans are broken down and change. Dark roast beans generally have lower levels of acidity than light and medium roast beans. A longer roasting time may also result in lower levels of chlorogenic acid (which are antioxidants) and caffeine and an increase in the level of N-methylpyridinium (NMP) which may help suppress the release of gastric acids. Manipulating the heat and airflow throughout the roasting process enhances the coffee’s best characteristics.
The Brewing Method
The moment the water contacts coffee, the flavor and aroma compounds begin to diffuse into the water – this is extraction. The degree of extraction will affect the flavors and aromas in the cup, since not all compounds are extracted at the same time. Fruity and acidic notes are extracted first, followed by sweetness and balance, and then bitterness. Under-extracting may lead to a sour taste, as it doesn’t have the sweetness and slight hint of bitterness to balance the acidity. Over-extracting will taste bitter, as the sweetness and acidity will be overwhelmed.
You can control the extraction. The finer the grind size, the more quickly extraction happens. A coarse grind size results in more acidity whereas a fine grind size results in more bitterness. The longer the brew time, the more time extraction will happen. Short brews are more acidic whereas longer ones are more bitter. The hotter the water, the more quickly the extraction will happen. However, if the water is too cool, the acids won’t extract. Generally, a relatively high water temperature with a coarser grind size and shorter brew time will create a more acidic cup. Grind finer and brew longer if it’s coming out sour. Or, try a cold brew method to avoid acids, remembering that extraction takes longer at lower temperatures.
The key to finding the right acidity level in your coffee is about balance. If something doesn’t taste right, change on of these aspects to get the right brew for you. Coffee has so many notes, flavors and aromas for every kind of palate. I encourage you to taste a few different coffees and experiment with how you brew it to find exactly what you like best.