Wine Production : Vine to Bottle - Vinum Vine

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Wines are transferred into barrels known as ‘butts’. The butts are
not completely filled, leaving a small air gap over the top of the wine.
A feature of Sherry production is a naturally occurring yeast
(Saccharomyces beticus) which may grow on the surface of wines in
some barrels or vats, creating a yeasty crust known as ‘flor’. Flor
tends to grow thickest in cooler coastal areas. After fermentation,
wines destined for the Fino style are lightly fortified to 15%, which
is the ideal alcoholic degree at which flor develops. Flor also requires
oxygen and nutrients (which are naturally present in the wine) to live.
The crust of flor protects the wines from oxidation – the ageing of
the wines is microbiological. If flor dies back, microbiological ageing
will cease and chemical changes will take place. Oxidation will occur
and the wines will naturally darken. These wines may be designated
as ‘Amontillados’.
Wines of the heavier Oloroso styles will have been fortified up to
17% or 18% after fermentation. Flor will not grow at these alcoholic
degrees and thus the wines will age in an oxidative manner. They may
ultimately be sweetened, as for ‘cream sherries’. Sherry wines will
then mature in a ‘solera system’, which is a means of blending young
wines with old to ensure consistency of style and quality. In order to
be legally sold as sherry, the wines have to be aged for at least
three years in the solera system.
CHAPTER 14
14.3.2 Port production
The Upper Douro River in Northern Portugal is home to the vineyards
producing grapes for Port wine. A most important feature of Port
making is the extraction of colour and tannin from the grape skins.
Traditionally, this was done by treading the grapes by foot, still
considered by some to be the gentlest way. More mechanised
methods are now generally used. During the early stages of fermentation,
it is critical that the skins are kept in contact with the
juice to continue the extraction of colour and tannins. The fermentation
process is then interrupted, when there is somewhere
between 6% and 9% alcohol, according to the house style. The
juice is drained off and fortified to between 18% and 20% ABV.
Yeasts will not work at this level of alcohol and so fermentation
is stopped. There are various styles of Port, including Ruby, Tawny,
Late Bottled Vintage and Vintage. Each of these styles has its
own particular length and style of maturation. Some styles involve