Wine Words: Flor

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Flor is a wine word that you may have heard mentioned in conversations about Fino or Manzanilla Sherry. Do you know what it is? And what it does to a wine?

Flor – A Collection of Yeasts 
Flor is actually a collection of yeasts – and good’ yeasts at that! While flor yeasts can carry out the regular ‘fermentation’ activities (i.e. converting sugars into alcohol) of other wine yeasts, they are best known for their role in the development of Fino style Sherry.

In the Sherry region, the flor yeasts collectively form a veil or film on the surface of certain young Sherry wines. These wines are stored in wooden casks known as butts (i.e. 600 liter American Oak barrels), which are not filled to the top, leaving enough room and air for the flor to develop.

Flor will not survive on wines above 16% alcohol.
Flor does not form on all Sherry wines. Sherry is a fortified wine. Wines destined for Fino style are only fortified to 15.5% whereas those destined for Oloroso style are fortified to 16%. Above 15.5% flor yeasts cannot survive. An environment 15% to 15.5% alcohol is considered ideal for flor to thrive.

Biological Aging – Maturation under a Veil of Flor
Wine that is matured under a film or veil of flor undergoes what is called is called biological aging. Flor provides a protective layer on the wine, preventing any oxygen from influencing the style. This is the opposite to Oloroso style Sherries, which have no flor protection and age oxidatively.

The Magic of Flor
As well as preventing oxidation, flor yeasts do all sorts of other things that result in creating the characteristic Fino or Manzanilla style. The flor yeasts interact with the wine. They metabolize or consume the glycerol and nutrients in the wine, as well as some of the alcohol. As they do this they also significantly increase the amount of acetaldehyde, which gives Fino Sherry its characteristic sharp aroma and taste.

The result of all this is a pale colored, extremely dry wine, with a noticeable acetaldehyde, green olive, nutty aroma and flavor.

How Flor Survives – The Solera System
When all the nutrients and glycerol have been consumed the flor yeasts die off. However, thanks to the traditional Solera maturation system of fractional blending, there is a regular addition of a newer/younger wine into each cask. The younger wine brings nutrients to enable the flor yeasts to continue to grow.

Fractional blending is a dynamic maturation system, by which wines from different stages of the maturation process are blended together. Some liken it to keeping the young wines in touch with their ancestors!

Flor – Not just a Sherry Phenomenon
While Sherry is the most celebrated flor influenced wine, there are a number of other wines around the world that are also flor influenced. The most important of these are the Vin Jaune wines from the Jura area of France, and certain styles of Tokaji from Hungary. 

(Image: Underlying image by Sadovnikova Olga/Shutterstock)

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Mary Gorman-McAdams, MW (Master of Wine), is a New York based wine educator, freelance writer and consultant. In 2012 she was honored as a Dame Chevalier de L'Ordre des Coteaux de Champagne.