to the acidity present in the wine. Dry wine, for example, has only a small amount of residual sugar. Some wine labels suggest opening the bottle and letting the wine "breathe" for a couple of hours before serving, while others recommend drinking it immediately. Decanting (the act of pouring a wine into a special container just for breathing) is a controversial subject among wine enthusiasts. In addition to aeration, decanting with a filter allows the removal of bitter sediments that may have formed in the wine. Sediment is more common in older bottles, but aeration may benefit younger wines. During aeration, a younger wine's exposure to air often "relaxes" the drink, making it smoother and better integrated in aroma, texture, and flavor. Older wines generally fade (lose their character and flavor intensity) with extended aeration. Despite these general rules, breathing does not necessarily benefit all wines. Wine may be tasted as soon as the bottle is opened to determine how long it should be aerated, if at all. When tasting wine, individual flavors may also be detected, due to the complex mix of organic molecules (e.g. esters and terpenes) that grape juice and wine can contain. Experienced tasters can distinguish between flavors characteristic of a specific grape and flavors that result from other factors in wine-making. Typical intentional flavor elements in wine—chocolate, vanilla, or coffee—are those imparted by aging in oak casks rather than the grape itself. Vertical and horizontal tasting involves a range of vintages within the same grape and vineyard, or the latter in which there is one vintage from multiple vineyards. "Banana" flavors (isoamyl acetate) are the product of yeast metabolism, as are spoilage aromas such as "medicinal" or "Band-Aid" (4-ethylphenol), "spicy" or "smoky" (4-ethylguaiacol), and rotten egg (hydrogen sulfide). Some varieties can also exhibit a mineral flavor due to the presence of water-soluble salts as a result of limestone's presence in the vineyard's soil. Wine aroma comes from volatile compounds released into the air. Vaporization of these compounds can be accelerated by twirling the wine glass or serving at room temperature. Many drinkers prefer to chill red wines that are already highly aromatic, like Chinon and Beaujolais. The ideal temperature for serving a particular wine is a matter of debate by wine enthusiasts and sommeliers, but some broad guidelines have emerged that will generally enhance the experience of tasting certain common wines. White wine should foster