More on the Chemical Reactions of the Sherry Flor

If a butt of wine with a healthy velo of flor is accidentally tight-bunged and a reasonably free circulation of air is prevented, the chemical action of the flor is radically altered and vinegar can be formed. This can also occur if there is a heavy growth of flor on a shallow vessel of wine, but such a mishap is unlikely save in the laboratory. Flor has grown in a sample bottle of must and looked very unpleasant, though the must was perfectly good under­neath when it was shaken off.

There are reports of the same thing happening to a bottle of delicate fino in England, and it is partly to prevent this that fino sherry exported to foreign countries is almost invariably fortified. All the butts used for maturing sherry are made of oak. Other kinds of wood that are more readily available have been tried, especially chestnut, but none has proved satisfactory. Raya sherry that has been matured for nine months in chestnut and compared it with the same wine matured in oak shows that the former was much darker, an altogether different and un­attractive.

The wine was not attractive either. It tasted immature while that matured in oak was rounder and had an attractive slightly woody taste. Chestnut gives no character. The size of the cask is important, too. The smaller the cask the quicker the wine matures, but there is also a difference in the way in which it matures. There are many possible explanations: the surface area in contact with the air, in proportion to the volume and depth, is just right when a butt is used, but tends to be too small in a vat.

A butt puts exactly the right area of oak in contact with the wine, which becomes \"woody\" if a smaller cask is used, and develops less \"character\" in a larger cask. It also acts as a very slow selective filter, allowing some constituents of the wine to seep out and evaporate, while air can get in and help with the oxidation. Trillat has demonstrated that when alcohol is stored in wooden casks, the wood tends to influence the oxidation, producing small quantities of acetaldehyde. Maturation is a natural process and it is an example of the rule that nature cannot be hurried.

There are reports of the same thing happening to a bottle of delicate fino in England, and it is partly to prevent this that fino sherry exported to foreign countries is almost invariably fortified. The butts used for maturing sherry are made of oak.