Identification of Ethyl 2-Sulfanylacetate as an Important Off-Odor Compound in White Wines

A number of Sauvignon blanc wines made from hard pressed juices in an inert atmosphere (nitrogen) or in contact with oxygen were identified as having heavy off-flavors to varying degrees. Samples were extracted and subjected to time-based HPLC fractionation. The fractions were assessed by a sensory panel and those with unpleasant, irritating, off-odors were re-extracted. The extracts evaluated by gas chromatography coupled with olfactometry revealed a number of odoriferous zones, including one with an off-odor similar to the one perceived in two HPLC fractions. The odor was less intense in fractions previously supplemented with copper sulfate, suggesting that the compound(s) responsible were possibly thiol-related. A selective thiols extraction protocol and the analysis of the extract by gas chromatography coupled with mass spectrometry identified a new potent thiol in these wines. The compound responsible for the odoriferous zone, ethyl 2-sulfanylacetate (1), had an odor reminiscent of baked beans and Fritillaria meleagris bulbs. Its perception threshold was determined and sensory studies using graduated supplementation in dry white wines demonstrated its contribution to the off-odor observed in dry white wines.