ANALYTICAL INVESTIGATION OF RIO OFF-FLAVOR IN GREEN COFFEE

About 20% of Brazil coffee production presents the so-called Rio defect characterized by a strong off-flavor, often described as medicinal, phenolic, or iodine-like. Occasionally, this defect also occurs in coffees from other origins. An extensive investigation was carried out to identify the compound(s) responsible for the coffee samples. Volatiles were isolated from green beans by simultaneous distillation-extraction and analyzed by capillary GC, GC-sniffing, and GC-MS. 2, 4, 6-Trichloroanisole (TCA) was identified as the most likely key compound for the Rio off-flavor. TCA was found in all Rio samples in concentrations ranging from 1 to 100 ppb. Less than 50% of TCA present in green beans was lost during roasting. 2, 4, 6-Trichlorophenol (TCP), the probable precursor of TCA, was also found in most of these samples. Adding TCA to freshly brewed coffee imparted to it the same off-flavor notes as described in actual Rio coffee. The perception threshold of TCA in coffee brew was found to be 8 ppt for direct odor perception and 1–2 ppt for flavor by mouth. © 1990, American Chemical Society. All rights reserved.