2-bromo-4-methylphenol, a compound responsible for iodine off-flavor in wines

This study focuses on an off-flavor in wines treated by an acidification technique involving ion-exchange resins. Applying reversed-phase HPLC on a C18 column to a contaminated wine extract resulted in 25 fractions in dilute alcohol medium, and only one, fraction 19, presented this off-flavor. Its composition was analyzed using gas chromatography coupled to olfactometry (GC-O) and mass spectrometry (GC-MS), leading to the identification of 2-bromo-4-methylphenol for the first time as a compound associated with an "iodine" aroma in white, rosé, and red table wines. Contaminated wines presented a wide range of levels, with maximum concentrations of 28900, 7556, and 48000 ng/L and minimum values of 260, 35, and 63 ng/L in white, rosé, and red wines, respectively. Sensory studies investigating 2-bromo-4-methylphenol gave very interesting results. Individual thresholds ranged from 0.15 to >77.4 ng/L in reverse osmosis water, from 0.4 to >193.5 ng/L in white wine, from 0.5 to >774 ng/L in rosé wine, and from 0.5 to >774 ng/L in red wine. The very wide distribution of individual thresholds suggested the presence of two populations, sensitive and nonsensitive, with a bimodal frequency distribution. The odor descriptions quoted by the more sensitive group characterized 2-bromo-4-methylphenol using terms with "iodine" connotations in both the reverse osmosis water and red wine matrices. The descriptors for commercial wines naturally affected by this defect were seafood, iodine, mud, and fish.