During roasting, citric acid reaches a maximum at light to medium roasts then quickly diminishes as roasting levels progress. A typical medium roast will lose about 50% of its initial citric acid concentration and with progressive destruction in latter stages of roasting progresses.
From a taste perspective, citric exhibits strong sour characteristics similar to what we would taste in unripe fruits. Although pure citric acid is commonly used as a food additive to impart sour/tart notes, excessive citric acid is a sign of poor processing at origin.
Since a high concentration of citric acid is found in unripe coffee cherries, it is important for producers to only select the ripest cherries especially when selling to the specialty coffee industry.
Unripe/Ripe Coffee Cherries
However, as maturation continues citric acid levels continue to decrease with a parallel increase in sugar production. Generally, Kenyan coffee tend to have lower levels of citric acid than those of Central America, suggesting a less advanced form of plant metabolism.
Citric acid is one of the four acids used for the Matching Pairs exam on the Q-grader examination. If you are preparing for the Q-grader certification we highly suggest you practice using our organic acids kit before the exam.