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Volatile sulfur compounds of 15 young port wines and 12 old port wines were determined. As there is a great difference in the pool of sulfur compounds between the two groups of wines, an experimental protocol was performed to determine which technological parameter (dissolved O₂, free SO₂ levels, pH, and time/temperature) was related with the formation/consumption of these compounds. Four sulfur compounds were selected for this purpose:  dimethyl sulfide, 2-mercaptoethanol, dimethyl sulfone, and methionol. The synergistic effects of increasing temperature and O₂ at lower pH had the largest impact. Dimethyl sulfide was formed during the experimental period in the presence of O₂. Dimethyl sulfone had the same behavior. Methionol decreased significantly in the presence of O₂, but no methional was formed. 2-Mercaptoethanol, considered to be an important “off-flavor” in dry wines, also decreased …