What is a phenolic defect in coffee?

Phenolic is a cupping descriptor used to identify a specific type of off-flavour in green or roasted coffee - a medicinal, chemical, or antiseptic taste reminiscent of iodine, plasters, carbolic soap, or disinfectant. It's considered a primary defect and significantly impacts both the clean cup score and defect deductions on the SCA cupping form.

Phenolic character in coffee is typically caused by chlorophenols - compounds formed when chlorine or other halogenated substances come into contact with naturally occurring phenolic compounds in the coffee during processing or storage. The most common causes are: contaminated water used in wet processing (particularly water containing chlorine or disinfectants), contact with pesticides or herbicides that are phenolic in nature, contaminated storage containers or jute bags that have previously held other substances, or smoke contact during drying.

Because phenolic is caused by environmental contamination rather than intrinsic quality, it can appear unpredictably in otherwise well-produced lots. A cupper identifying phenolic notes should flag it clearly - it's distinct from ferment, mustiness, or earthiness, and diagnosing the exact character matters for understanding the cause. A single phenolic cup in a set of five significantly reduces the clean cup and uniformity scores, and a lot with widespread phenolic character is typically rejected or reclassified as below-specialty grade.