Winegrowers Supplies  -  the use of barrels (Barriques) and the types of oak

Oak has been used in winemaking since time immemorial. It can be used with great effect, developing the flavour, the tannins, the colour and the texture of a wine.

Oak contact with wine can be through a barrel, during the fermentation or more often during the ageing period.
It can be from oak chips or staves, put into a wine in a stainless steel fermentation vessel.

The use of oak barrels can impart special qualities to a wine through the processes of evaporation and low level exposure to oxygen.
Ageing wine in an oak barrel speeds up the maturation process very considerably.

The porous nature of an oak barrel allows some evaporation and oxygenation to occur in a wine, but not at levels that would cause oxidation or spoilage of the wine.
The small amounts of oxygen passing into the barrel, 'soften' the tannins in a wine.

In a year, a typical 225 litre barrique can lose anywhere between 5 and 10 litres of wine through the course of evaporation, even much more for a new barrique.
This evaporation (of water and some alcohol) concentrates the flavour and aroma of the wine.

The chemical properties of different types of oak can have very different effects on the wine. Phenols within the wood interact with the wine to produce 'vanillin' and other flavours.
The hydrolysable tannins present in oak, known as ellagitannins, are derived from lignin structures in the wood. They help protect the wine from oxidation and reduction.

The amount of 'toast' given to the inside of a barrel, by fire inside, will affect the tannin levels of the wine and the intensity of the 'wood' flavours.

New barrels can be left empty, in a cool cellar, as the staves are close together.

Preparing a new barrel before use:-

First, it is adviseable to rinse the inside of the barrel by filling and emptying to remove any debris that may be inside.

With red wine, a good new barrique can then be filled immediately.

With white wine, a new barrique, is usually 'conditioned' before first use, so it imparts less oak character.

Advice is: first fill it with water and leave for about 3 to 5 days. This will allow the oak to expand and retain liquid; the barrel may leak initially. Top up the barrel during this time. When the barrel stops leaking, empty the water out and rinse again.

After this, place the barrel horizontally on a rack/stand, or on a concrete floor with four wood 'wedges' under, to hold it in place, with the hole at the top !

It is now ready to fill. Fill it completely, so all air is removed; when almost full, hammer the side of the barrel to dislodge oxygen bubbles attaching to the inside.
Place a silicone-rubber bung in the hole and tap it so it seals tightly.

After a barrique has been used it has always to be kept 'green', which means being full of wine (or water containing 300 to 500 mgm/litre SO2) for almost all its life; a month or so empty is ok but if left empty it 'dries out' and the staves shrink so that they are no longer water-tight (or wine-tight), after this they cannot be used as the wood does not expand sufficiently quickly again.

There are various types of oak used in winemaking, each of which may be used at a different stage in a wines development.
Some winemakers put their wines into American oak for a short initial period and then move it to a French oak for a second period of ageing.

American Oak:-

Tennessee White Oak): has comparatively large pores and a high vanillin content, so it tends to be used for big, powerful wines and where the winemaker wants results early.

Missouri Oak: for white wines the characteristics are coconut in the nose with a sweet vanilla cream in the palate.
For red wines, the fruit is highlighted in the nose and a 'juicy' fruit quality in the palate.

Appalachian Oak: has great spices in the nose and a lemon cream in the palate.
A less sweet oak character which retains the perception of acidity. This is a good choice for Syrah, it also works well with Chardonnay.

French Oak:-

Limousin Oak: has small pores and less vanillin, and so offers a slower, gentler ageing process.
Finer wines approaching their bottling date will often spend some time in Limousin casks in order to 'polish' them.

Alliers Oak: has the smallest pores of all, and is the oak used for barrel-fermented wines.
The tumult of fermentation takes a lot out of the oak, and this could result in oaky flavours that are too strong if the other types of oak are used.

Oak from smaller regions of France (Nevers, Troncais, Vosges) are also available. Barrels from eastern Europe (Slavonic oak) are increasingly used, mainly because of the lower prices.

The basic principle is that oak which has grown in a warmer climate will have larger pores, and oak which has grown in a cooler climate will have smaller pores, with different effects on the wine.
Another way of describing this is the 'tightness' of the grain:-

Medium Grain: for ageing wines for 12 months or less, with wines like Pinot Noir and Chardonnay.

Tight Grain: the oak extraction is much slower than the Medium Grain. It is recommended for ageing in barrels for 12 to 24 months.

Extra Tight Grain: the highest quality, carefully selected. The oak extraction is very slow. It is recommended for wines (particularly red Bordeaux and other longer aged varietals) to be aged in barrels for 24 months or longer.

Personally I find that French oak imparts vanilla flavours but very little 'oaky' taste/aroma.