with diammonium phosphate (DAP) as a nitrogen source to prevent H2S formation. The sensory threshold for hydrogen sulfide is 8-10 μg/L, with levels above this imparting a distinct rotten egg aroma to the wine. Hydrogen sulfide can further react with wine compounds to form mercaptans and disulfides. Mercaptans Mercaptans (thiols) are produced in wine by the reaction of hydrogen sulfide with other wine components such as ethanol. They can be formed if finished wine is allowed prolonged contact with the lees. This can be prevented by racking the wine. Mercaptans have a very low sensory threshold, around 1.5 μg/L, with levels above causing onion, rubber, and skunk type odours. Note that dimethyl disulfide is formed from the oxidation of methyl mercaptan. Dimethyl sulfide Dimethyl sulfide (DMS) is naturally present in most wines, probably from the breakdown of sulfur containing amino acids. Like ethyl acetate, levels of DMS below the sensory threshold can have a positive effect on flavour, contributing to fruityness, fullness, and complexity. Levels above the sensory threshold of >30 μg/L in white wines and >50 μg/L for red wines, give the wine characteristics of cooked cabbage, canned corn, asparagus or truffles. Environmental Cork taint Cork taint is a wine fault mostly attributed to the compound 2,4,6-trichloroanisole (TCA), although other compounds such as guaiacol, geosmin, 2-methylisoborneol, 1-octen-3-ol, 1-octen-3-one, 2,3,4,6-tetrachloroanisole, pentachloroanisole, and 2,4,6-tribromoanisole are also thought to be involved. TCA most likely originates as a metabolite of mould growth on chlorine-bleached wine corks and barrels. It causes earthy, mouldy, and musty aromas in wine that easily mask the natural fruit aromas, making the wine very unappealing. Wines in this state are often described as "corked". As cork taint has gained a wide reputation as a wine fault, other faults are often mistakenly attributed to it. Heat damage Heat damaged wines are often casually referred to as cooked, which suggests how heat can affect a wine. They are also known as maderized wine, from Madeira wine, which is intentionally exposed to heat. The ideal storage temperature for wine is generally accepted to be 13 °C (55 °F). Wines that are stored at temperatures greatly higher than this will experience an increased aging rate. Wines exposed to extreme temperatures will thermally expand, and may even push up between the cork and bottle and leak from the top. When opening a bottle of wine, if a trace of wine is visible along the