Aerating of wine is one the most common practices involving decanting when wines are poured into a decanter or a similar container such as carafe, in order to improve the flavor of the wine. Older red wines are often decanted to remove sediment, while younger reds are decanted to soften their flavor faster, soon after opening. White wines usually have no deposits so decanting is not necessary to remove sediment, but is advisable when a bottle is colder than desired and the temperature needs to be decreased. The container into which the wine is poured is called a decanter.
The process of decanting is generally belived to be a process that allows a wine to breath, so that it softens younger wines such as reds with higher levels of tannins. This is felt to make the wine more supple and pleasing to the taste as it removes some of the hardness of the wine. The flavor of red or white wines may tend to be dry and bitter tasting (higher levels of tannins) or tart and harsh tasting (more acidic) so that the wine may need to be softened, which is thought to occur by decanting. Similarly, it is believed that decanting will improve the bouquet (aroma) of the wine making it more complex as the fruit aroma is emitted and easily detected. There are a number of individuals who feel that decanting will not improve the flavor and will only serve to flatten and reduce the quality of the fresh fruity flavors so often sought in a good wine. It is generally agreed that there is little or no value to decanting lower quality wines, younger white wines, rosé wines, or blush wines.
Decanting is a good method to remove sediment existing primarily in hearty red wines, while not generally present in white wines unless they are more mature. As wines age, the tannins, the acids, and the pigments of color start to separate and collect on the bottom of the bottle. Therefore, when decanting wine, the sediment can settle on the bottom of the decanter allowing it to be kept separated from wine poured into another decanter or a glass and not adversely affect the flavor of the wine being consumed. Older white wines are decanted to remove any sediment which exists in the form of clear crystals. Port wines have a sediment referred to as "crust" which forms and can be removed with a decanter.
When decanting, decanters with a wider base are quite popular for allowing the wine to be dispersed fully in order to effectively aerate and separate sediment in older wines. Some decanters may be made with glass containing lead and since there may be a concern regarding the lead content in the glass affecting the wine to be consumed, it may be wise to check with the supplier or manufacturer to determine the components existing in the glass decanter. On the day the wine is to be served or the night before, place the wine bottles in an upright position to allow the sediment to settle on the bottom. When the wine is opened, slowly pour a continuous stream into the decanter while watching the sediment to keep it contained in the bottom of the bottle. Some use a flashlight or a candle to view and highlight the sediment within the wine as it travels toward the neck. As the sediment begins to arrive at the shoulder of the bottle (where the bottle decreases in size), cease from pouring and discard the remaining wine. If however, the sediment is more fully dispersed throughout the wine or if there is a reasonable amount of wine with sediment as it begins to enter the neck, strain the remaining wine through a decanting funnel that has a stainless steel mesh filter to trap the sediment. A muslin cloth also works well to separate any sediment still existing.