Originating from the Douro Valley in Portugal, Port wine is a sweet fortified wine made by adding a clear brandy-like spirit during fermentation to halt the process.

Instead of the grape sugars turning into alcohol, their sweetness is preserved, allowing the winemaker to retain a significant portion of those sugars in the final product.

David Guimaraens, Head Winemaker from Taylor's Port, explained this unique process: "When half of the sugar has been converted to alcohol, we will run off the juice."

Adding a neutral grape spirit kills the yeast, and Guimaraens said the wine alcohol raises the "port to an alcohol level of 20%, where it is stable and has the ability to age."

Port wine must come from the Douro Valley in Portugal, which has a protected designation of origin (PDO) and is subject to regulations that ensure it meets quality standards.