What Are Fortified Wines?

Fortified wines are wines that have had alcohol, in the form of grape spirit, added at some point in their fermentation process thus making them stronger than light wines. But first off, what is fermentation? This is Nature's wondrous gift, where (in simple terms) yeast consumes sugar and produces alcohol as a by-product of this process, along with a few other things, such as glycerol and carbon dioxide. By and large this is a controlled reaction which results in wines not exceeding 14% or 15% alcohol, though the average is usually closer to 12.5 to 13.5%. Most yeasts cannot tolerate an environment containing greater than 16% alcohol, and will effectively die.

So, when is this grape spirit added? Well, it depends. There are two main methods, loosely called the port method and the sherry method. In the former, the spirit is added before fermentation has naturally finished (i.e. when not all the sugar has been consumed, and when the alcohol strength is at about 8%), and the wine is fortified up to a level of between 16 - 20%. So you are left with a strong wine that still contains a lot of sugar, or sweetness. The character of the wine is then developed by various forms of ageing and maturing. This method is used for Port, most Madeira, Vins Doux Naturels, Australian liqueur Muscat, and other styles. In some cases the spirit is added even before fermentation has begun, leaving you with what is basically alcoholic grape juice (often called Mistelle or Vin de Liqueur).

The sherry method adds fortification after fermentation has completed, either to 15.5% or 17.5% depending on the wine style and ageing process being utilised, which once again determines the final character of the wine. This method is used for most sherries and dry Madeiras (Sercial). It's worth noting that when some intensely sweet grapes are used (such as Pedro Ximenes or PX) there may be sugars left even after fermentation has completed - too much for the yeast to deal with.

These wines will partner an astonishing array of foods both sweet and savoury (sherry is great with tapas), though note that fortified wines are very strong and should be treated with respect. They are also quite different to sweet wines such as Sauternes, which are unfortified.

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