Vinification of port wine

The sweetness of port wine results from stopping the fermentation, at a time when still not all glucose has been converted to alcohol. The time of stopping is usually reached after two to three days of fermentation, depending on the desired sweetness, when the must has already been separated from the grape skins. The fermentation is stopped by adding 77% brandy to the must, in a ratio of 1: 4, resulting in an alcohol content of 19% -20%. peel at this time.

It is very easy preserving the sugars of the must and producing the alcohol, but it is very difficult to extract aromas and polyphenols such as color and tannin out of the skins of the grapes during the short fermentation time. The classic, mainly applied method was until well into the middle of the 20th century, the pounding of grapes in about 60 cm high stone troughs with large volume (5,000 -15,000 l). In these troughs called Lagares men and women stomp the berries with their feet, squeezing grapes and peelings, and thus contribute significantly to the extraction of the important polyphenols. Since this pounding leaves the grape seeds intact, no bitter phenols are released. The resulting from the onset of fermentation alcohol helps further to extract color and aromas. That’s why one pays attention to submerge the floating grape skins again and again.

This classic way of manufacturing is nowadays only used for the best qualities. For medium qualities one uses mechanical stamping machines such as the robotic lagares. Lower grades of port wines are subjected to autovinification, in which the carbon dioxide produced during the fermentation of the grapes drives a process that repeatedly pumps the wine via the surface of the grape skins, which increases the speed of extraction of the polyphenolic components.

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