Fermentation is the process in which grape sugar is converted by naturally occurring yeast into alcohol and carbon dioxide. Juice begins to ferment as soon as it is released from the grapes. In the lagare, floating skins, stems and seeds form a cap over the juice. This cap has to be stirred in occasionally to make sure the juice has enough colour from the skins.
Workers use wooden paddles called macacos, probably the same macacos that their grandfathers and great grandfathers used in years past. Mechanical systems have pum ps to circulate the juice and skins.
Once the juice is the right colour, any skins, stems and seeds are removed and the juice is pumped into primary fermentation tanks. These tanks are usually stainless steel, and must be properly vented to let carbon dioxide out without allowing outside air in. Outside air contains contaminations such as mould spores that can ruin the wine.
At this point the juice is allowed to ferment undisturbed, although vintners keep a close eye on the process. As soon as the juice contains 7 per cent alcohol, they add brandy. The brandy is 77 per cent alcohol and by adding one part for every five parts of fermented grape juice, the percentage of alcohol in the port rises to about 20 per cent. This process, called fortification, stops the fermentation immediately by killing all the natural yeast. Some natural sugar remains which is why port wine is sweet.
After the brandy, the very young port begins the aging process. It may be stored for a while in tanks of various sizes and shapes at the quinta. Some unusual outdoor storage vessels are called mamas for obvious reasons.
Most young wines are shipped down to the cellars at Vila Nova da Gaia. There was a time when wooden casks of port were loaded onto Barcos Rabelos and sent down the river. Today, they travel along the roads on trucks.
Types of Port