
Ruby port is the youngest, most common style of Port — a sweet red fortified wine from Portugal’s Douro Valley.
Any other ruby-style port works one for one. A reserve ruby or a Late Bottled Vintage (LBV) is as sweet and as strong, with deeper fruit. Basic rubies have 96–106 g of sugar per liter at 19–20%, and LBVs about 90–110 g, so the drink barely changes. With no port at all, a sweet red vermouth comes nearest: 15–16.5% and 130–170 g. The drink turns a little weaker, sweeter and more herbal.
Aged in casks with more contact with air, so it turns amber and smells of dried fruit and wood rather than fresh red fruit. It is about as sweet: 95–114 g of sugar per liter for basic and reserve tawnies. One for one, the drink keeps its sweetness and strength but turns brown and loses its berry note.
Ruby is what Port is before wood gets to it. The wine is fortified mid-ferment with grape spirit, which stops the yeast and leaves the unfermented sugar in place. That is why every Port is sweet and strong at once. It is then held in tank or large vats, where the volume-to-surface ratio keeps oxygen away from it. That is the whole difference from tawny, which is aged in small casks precisely so the oxygen can get in.
Keeps for weeks in the fridge once opened. Ruby loses its freshness faster than aged styles.