During coffee harvesting, one branch of the coffee plant might contain cherries displaying a range of different degrees of ripeness. As a result, often the red cherries are picked. But do non-fully ripe cherries actually affect the quality?
Stages of Ripening
Coffee cherries start green and end up almost purple when they are overripe. As the cherry ripens, the fresh weight increases until it hits the fully ripe state where it stays stable. As it progresses into the overripe phase, it loses weight rapidly due to various reasons.
Mucilage Changes
The mucilage content varies per stage during ripeness, typically increasing linearly and reaching its peak at full ripeness. However, when the ripeness progresses into the overripe phase, the mucilage content decreases. If slightly overripe cherries are pulped, it can lead to quicker occurrence of cracked or broken beans. While picking and sorting is laboursome for producers, there is merit for it in terms of preventing product loss.
Acidity Through Ripeness
Moreover, organic acids undergo a change when ripeness progresses. Citric acid and malic acid are the main acids in coffee. Quinic acid, which is known to contribute to the acidity and mouthfeel of coffee, increases as ripeness progresses. Chlorogenic acid, which contributes mainly to the bitterness of the coffee despite it being an acid, has been found to be higher in unripe cherries. During roasting, chlorogenic acid is broken down into quinic acid and caffeic acid, however the coffee might need to be roasted until it can be perceived as a “dark roast” to get rid of the “excess” chlorogenic acid. Therefore, for coffees that are designated to be light roasts, picking ripe cherries is of utmost importance.
Sugar Development & Transformation
The main three sugars in coffee cherries are sucrose, glucose and fructose. During ripening, the sugar content increases until full ripeness, after which it plateaus. However, sucrose is broken down by the enzymes present in the coffee cherry, resulting in increased glucose and fructose. This phenomenon is more common in “natural” processed coffees, since the coffee is dried in the whole cherry state and drying occurs gradually, allowing for more time for the sucrose in the pulp to degrade and potentially transfer to the seed.
At HEQA, we utilize a machine sorter that can sort cherries automatically based on color. This sorting machine has a built-in camera, which has the precision of rejecting a single cherry based on the input color. While we utilize handpicking, the machine sorter helps us to reduce human labour tremendously and keep the quality equally consistent.
