Cider apple
Cider is made in several countries and can be made from any apples. Historically the flavours preferred and varieties used to produce cider have varied by region. Many of the most traditional apple varieties used for ciders come from or are derived from those from Devon, Somerset and Herefordshire in England, Normandy in France, and Asturias in Spain, and these areas are considered to have their own broad cider styles although the many exceptions make this more of a historic footnote. Normandy cider is usually naturally carbonated and clear: Asturian cider apple varieties are mainly 'sharps' or mild 'bittersweets', producing a mildly acidic cider which is customarily served by being poured from height into the glass to oxygenate it.
Cider
Fermentation of ciders occurs by a very similar mechanism to the fermentation of wine. The process of alcoholic fermentation is characterized by the conversion of simple sugars into ethanol by yeasts, especially "Saccharomyces cerevisiae". This is because, as “Crabtree positive” yeasts, they produce ethanol even during aerobic fermentation; in contrast, Crabtree-negative yeasts produce only biomass and carbon dioxide. This adaptation allows them a competitive edge in the fermentation of ciders due to their high alcohol tolerance, and because of this tolerance, it is common for ciders to be fermented to dryness, although that is not always the case. Fermentations will carry on until the yeasts run out of nutrients and can no longer metabolize, resulting in a "stuck" fermentation, or the fermentation is stopped.