Coffee 101 - Acidity
ACID: Now what about acidity? There is a lot to say about acid in coffee hence it receives its very own singular position as Part 3 in Coffee 101.
Coffee beans have been found to have about 30 types of acids, many familiar such as those found in citric fruit, malic acid found in apples, and acetic acid found in vinegar. The primary acids in coffee are part of a group called chlorogenic acids and are largely responsible for flavor. These are actually antioxidants and beneficial.
Often identified as an acidic drink coffee comes in at around a 5 on the pH scale. Drinks like beer, orange juice, and even soda have a higher pH and therefore higher acidity. So, coffee generally is viewed in error when it comes to acidity. However, keep in mind that acidity in coffee is directly responsible for flavor.
Given there is a direct correlation between the pH in a coffee and its level of acid the trick is to select coffee that has the right acidity for you. In other words, if coffee affects your stomach adversely pick a coffee with lower acid content.
The type of bean, the roast method, the grind of the roasted beans and the type of brewing all contribute to the acid balance of the coffee. Arabica beans are more acidic than Robusta beans. Low altitude grown beans are less acidic than those grown at a high altitude. Coarse ground beans are less acidic than finely ground beans.
The naturally occurring acid in a coffee is primarily the result of the coffee bean’s growing conditions. The higher elevation coffees tend to have a higher acid content. These are typically the higher quality coffees.
The longer roasting method for Dark Roast causes the chlorogenic acids to degrade forming quinic acids. It is the quinic acids that affect the astringency of a drink and can cause a sour sensation in the stomach. However, the longer roasting method also creates a chemical compound that counteracts acid production in the stomach. So, everyone will be affected differently. This degradation of chlorogenic acids, responsible for origin flavor, in Dark Roast coffee, affects the natural flavor of the beans and the roasted flavor becomes predominate.
Cold brewing uses cold water which in turn extracts less of the coffee's natural acids. As a result, cold brewed coffee is less acidic than a typical cup of hot-brewed coffee, perhaps by as much as 70 percent.
Extra-finely ground coffee will produce three times more chlorogenic acid. As brewing times increase the levels of most acids go up when brewing time increases.
Arabica beans contain double the sugar, half the caffeine and about 2 percent less chlorogenic acid than Robusta beans. In spite of having less acid, the sugar in Arabica beans decomposes during roasting, creating a flavor that may seem more acidic.
Decaffeinated coffee has been found to have 3 to 9 percent less chlorogenic acid than regular coffee.