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Yeast species/strain, temperature, pH, wort composition, and open/closed fermentation vessels contribute to how much DMSO gets converted into DMS. For example, ''S. uvarum'' (potentially reclassified to ''S. bayanus'') produces less DMS than ''S. cerevisiae'', as does ''S. pastorianus'' <ref name="bamforth"></ref>. DMSO is converted to DMS by yeast more readily at lower temperatures than warmer temperatures with five times as much at 8°C than at 25°C. Higher gravity worts (1.033 vs 1.060 in the linked reference) also produce more DMS from DMSO during fermentation. A higher pH of wort also leads to more DMS production; for example, lager wort pH is typically 5.4-5.7, while ale wort pH is typically ~5.1. This might explain why DMS is present more in lager beers <ref name="Anness"></ref>.
DMSO that is not converted into DMS during fermentation is left in the beer, and this DMSO can be converted into DMS over time by certain antioxidants during beer storage. Sulfite, in particular, can convert significant levels of DMSO into DMS during beer storage. Thiols have also been reported to convert DMSO to DMS over time during beer storage, although to a lesser extant extent than sulfite. Other antioxidants, such as gallic acid and ascorbic acid, have no effect <ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.531 Baldus, M., and Methner, F.-J. (2019) Effect of antioxidants on dimethyl sulphoxide reduction and impact on dimethyl sulphide formation during beer storage. J. Inst. Brew., 125: 69–74. https://doi.org/10.1002/jib.531.]</ref>.
====Spoilage Organisms and Spontaneous Fermentation====