I found this page on Port so useful i use it on my websites Port section.
Port, the Winter Beverage By William H. Edgerton
February 2001
Brooks Newspapers
If it is true that the best wines always seem to overcome difficult growing conditions, then port must be near the top of the list. The mountainous Douro region in northern Portugal, the home of port, is a primitive land with sweltering summers and freezing winters. By Portuguese law port must come from this region and be shipped from the City of Oporto at the mouth of the Douro River. Port is one of the few fortified wines in wide circulation. It is fortified by adding grape alcohol to fermenting port wine which simultaneously stops the fermentation and increases the alcohol content to about 20%, but retains the sweetness since all the sugar has not been changed into alcohol.
Up to 20 different grape varieties are blended to make port. The United States and Australia, as well as other producing regions, make port-like wines, which at their best are fine sweet wines, but due to loose regulations, a consumer doesn't know what is in the bottle. Some of these port clones are worth trying, however, for whatever the techniques and grapes used, a few mimic real port exceedingly well. One Australian wine in this category is Yalumba "Port" which has fine port-like flavors and sweetness at about $10 a bottle. No one, however, has yet been able to beat the port producers themselves who make a sweet, elegant, smooth wine with berry flavors and complexity.
There are several types of port on your retailers' shelves:
Vintage Port is created two or three times each decade when the grapes are exceptional. A vintage date on the bottle indicates that the wine came entirely from that vintage and that the shipper considers it one of its finest efforts. Vintage port is matured in the bottle after a short time in the cask, and although it can be consumed immediately, it should be cellared for 10-15 years before reaching maturity. Vintage port always throws a heavy sediment which often settles on the side of the bottle and sticks, forming a crust. This sediment is normal and these wines must be decanted.
Ruby Port or just "port" is the same wine from lesser years and carries no vintage date. It usually is a blend of grapes or wines from different vineyards and different years and has spent some time maturing in wood casks. Ruby port is at least 3 years old when shipped and can be drunk immediately.
Tawny Port is a blend and spends more years in wood than vintage or ruby port. It is then clarified and filtered, often several times, to remove suspended particles. Tawny ports pick up a brownish cast in their color due to long contact with wood and the filtering which removes some of the coloring matter. Since the wine can come from several different years, no vintage date appears on the bottle. Age dates such as 5, 10, or 20 year-old tawny means that the average age of the wine in the bottle is that number of years. As a tawny port ages, it loses some of its sweetness; 15 years may be an optimum age for Tawny port but most producers only market 10-and 20-year-old tawny port.
Late Bottled Vintage (LBV) Port is a port from a single year which has had extra aging in wood and is not blended. It thus has some of the mellow flavors of a tawny together with the nice fruit of a ruby or vintage port. LBV ports usually represent tremendous values.
Colheita Ports are tawny ports produced in a particular year, aged in the wood for many years, resulting in an acidic, rich, nutty flavor. Colheita ports must carry the vintage date and bottling date. Many consumers find these wines dull and unexciting, as well as being very different in style from shipper to shipper and, therefore, unpredictable.
Single Vineyard Vintage Ports are, as the name implies, made from grapes originating at a specific vineyard site in an exceptional or vintage year. The vineyard name usually appears on the label.
White Port is made exactly like red port but with white grapes. It usually is dry and smooth with a bigger alcoholic "kick" than one expects from a white wine.
Port should be served at room temperature. All vintage ports must be decanted and some of the others may need decanting to remove the sediment. Check the bottom of the bottle by looking at it sideways with a bright light on the opposite side to see if there is any sediment. Once opened, port can be consumed over days or weeks, or even months in the case of a younger vintage port. The fortified nature of the wine will slow but not stop deterioration or oxidation. Ruby and tawny ports will survive longer after being opened. Port should not be served in the traditional small glass for this does not allow the aroma to develop. A regular wineglass can be used, but small amounts should be poured since the wine is more alcoholic than most other wines. Since it is a sweet wine, port is usually served with or after dessert.
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