pH of saliva they can become very apparent on the palate, especially at the back of the mouth, as mouse cage or mouse urine. Refermentation Refermentation, sometimes called secondary fermentation, is caused by yeasts refermenting the residual sugar present within bottled wine. It occurs when sweet wines are bottled in non-sterile conditions, allowing the presence of microorganisms. The most common yeast to referment wine is the standard wine fermentation yeast Saccharomyces cerevisiae, but has also been attributed to Schizosaccharomyces pombe and Zygosaccharomyces bailii. The main issues associated with the fault include turbidity (from yeast biomass production), excess ethanol production (may violate labelling laws), slight carbonation, and some coarse odours. Refermentation can be prevented by bottling wines dry (with residual sugar levels <1.0g/L), sterile filtering wine prior to bottling, or adding preservative chemicals such as dimethyl dicarbonate. The Portuguese wine style known as "vinhos verdes" used to rely on this secondary fermentation in bottle to impart a slight spritziness to the wine, but now usually uses artificial carbonation. Bunch rots Organisms responsible for bunch rot of grape berries are filamentous fungi, the most common of these being Botrytis cinerea (gray mold) However, there are a range of other fungi responsible for the rotting of grapes such as Aspergillus spp., Penicillium spp., and fungi found in subtropical climates (e.g., Colletotrichum spp. (ripe rot) and Greeneria uvicola (bitter rot)). A further group more commonly associated with diseases of the vegetative tissues of the vine can also infect grape berries (e.g., Botryosphaeriaceae, Phomopsis viticola). Compounds found in bunch rot affected grapes and wine are typically described as having mushroom, earthy odors and include geosmin, 2-methylisoborneol, 1-octen-3-ol, 2-octen-1-ol, fenchol and fenchone. See also Oenology Acids in wine Browning in red wine Storage of wine References External links Organoleptic defects in wine (PDF document) Link Not Working How to Spot Faulty Wine, from The Wine Doctor Link Not Working in Enobytes Wine Online'' Oenology Wine chemistry Wine tasting Product expiration