One of the unique things about Vintage Port is that it is made from a blend of grape varieties. There is no fixed recipe for Vintage Port: the exact blend – percentage of each grape variety, percentage drawn from each quinta that goes into a brand’s wines – will vary from one Vintage to the next. It is up to the winemaker, every year, to decide which wines will, together, create an extraordinary Vintage Port, or whether this year we will make a Single Quinta Vintage or simply hold the wines and use them to make other styles of Port.
During harvest, lotes, or batches, of wine are made from the grapes picked that day. Depending on the vineyard and many other variables, the wine may be made from a single variety of grape, or from a blend of grapes. In the case of a blend, it may be either a “field blend” made from grapes harvested from a single vineyard which is planted with a mixture of grape varieties, or the decision may be made to vinify together two small parcels of grapes of specific different varieties.
For greatest flexibility in subsequent blending exercises, the winemaker likes to keep each of these lotes separate after vinification, to watch how they develop after storage in the Douro over the winter, at least. But space constraints may require a tasting of wines mid-harvest in order to identify lotes of similar flavour profile and quality which can be blended immediately, in order to manage available storage space.
At the end of harvest, the winemaker will have probably two to three dozen lotes of wines, from several different quintas, any of which are eligible candidates for Vintage Port.
Over the course of the 12 to 15 months following a harvest, the winemaker will continually taste all those wines. At any time he may decide to blend two or more lotes for further ageing together, and he may rule in or rule out certain lotes as Vintage Port candidates. He may then make trial blends of four or five different lotes, to see if together they make a good wine.
When judging those wines for possible creation of a Vintage Port there are many factors to consider: quality and flavour, of course, but most important of all is structure, whether the wine has the capacity to age well. This is something that only experience can tell – there is no chemical analysis or recipe that can promise a long-lived Port, only the combination of experience and instinct.