As an aroma or flavor in coffee, ferment is a defect taste, resulting from bad processing or other factors. Ferment is the sour, often vinegar-like, that results from several possible problems. It might be the result of seriously over-ripe coffee cherry. It can come from coffee cherry that was not pulped the same day it was picked, and/or was exposed to high heat between picking and processing. Often it comes from poor practices at the wet mill, when coffee is left too long in the fermentation tank, or old coffee that is over-fermented is mixed with new coffee. Ferment has attributes of vinegar (acetic acid).

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