Aging gives wine time to soften, develop flavours, balance and mellow

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Source: Barrel Associates

I grew up on a vineyard just North of Melbourne, Australia. It was just a small hobby farm with five acres of grapes, but still a lot for a young family of four to tend to. I was handed my first pair of secateurs when I was three and I still remember my brother and myself squashing the grapes with our feet (just for fun) during harvest season. My family producing poor quality wine for eight years. Then in the ninth year we produced a very respectable drop that we were all very proud of. My father went out and bought a brand new oak cask imported from America. I wasn’t until the wine had been in the cask for about three weeks that we realised it had a hole in it. All the wine had oxidised by that time and had to be thrown away. My father was fed up. Two weeks later our house was up for sale and we moved to the city. It is now my aim to find out everything I can about wine barrels so ten years down the track, when I own my own vineyard, I will not share the same misfortune.

Introduction

Aging gives wine time to develop flavours, bouquet and odour. It is one of the most complex and necessary processes of winemaking, yet requires little more than a suitably chosen container and time. Wines may be aged in wood, aluminium, stainless steel or plastic containers, depending on the winemaker’s idea of the style he wishes to make and economic considerations (Maynard, 1981). For younger fruity wines, which are formed by short fermentation, impervious containers are often preferred however the richer, full bodied flavours connected with quality, prestige and value are best achieved by aging in wood.

There are three reactions that occur in wood cooperage aging that make it preferable to impermeable containers for many wines; ethanol and water evaporate through the side of the container, oxygen is admitted and wood substances such as tannins, vanillin and syringaldehyde are extracted into the wine. A further advantage of wood cooperage is barrels can be recycled. For some examples of what can be done with old barrels see When a barrel goes to Heaven. The primary disadvantages of wooden containers are, due to their relative permeability, they are subject to leakage and contamination unless very carefully made and maintained. (Dinsmoor, 1974)

Wood Used

Wood used for cooperage must have strength, resilience, workability and be readily available. The grain must be straight for the length of the staves so the tree must be large, the wood must be free of defects to avoid leaks and excessive oxidisation and the wood chosen must not contribute any objectionable flavours to the wine. Wood of the latter characteristic, such as Eucalypts, may be used at a large surface to volume ratio so as not to extract too may flavours, or for poor quality wine, short storage periods or after heavy leaching. A wood may also be too porous for wine cooperage (Amerin, 1972). Red oaks, Ashes and Chestnut trees tend to have then to be too porous, however the problem may be overcome by coating the inside of the barrel with paraffin. Other examples of unsuitable wood are Redwoods, due to a high content of aqueous alcoholic extract, conifers as they contain too many resins and acacias as they exude a yellow pigment which stains the wine. Some Cypress species are considered suitable, however costs are excessive due to scarcity. (Dinsmoor, 1974)

Why is Oak Best?

After eliminating all those woods less suitable, not readily available, poorly tested and only useful in large sizes, Oak remains. Oaks have large compound rays (higher along the grain than the uniseriate rays and taper to a point at the top and bottom). The size adds dimensional stability and, when quartersawn, wood is relatively impermeable. The pores of some oaks are plugged in the heartwood by the growth of tylosis. If the pores are not blocked the wood tends to be too porous. For this reason, only the heartwood is used for wine cooperage. Other features that make oak attractive for cooperage are a high tannin content, which reduces the attack and decay of wood, and extractants move readily into wine contributing desirable flavours and odours.(Dinsmoor, 1974)

Which Oak is Best?

The preferred oak is dependent on species characteristics, conditions of growth, individual variation, and variations in seasoning practices of different coopers. The three species generally used are the American oak ,Quercus alba, and two European species, Q. rober and Q. sessilis. The American oak provides a stronger intensity than the European species but is generally used only for reds. Q. rober, originating in Limousin, France, tends to be a lighter, less dense, wider-grain oak that grows best in deep heavy soils while Q. sessilis, originating in Nerver, Allier and Troncais and characterised by a dense, tight grain, is most often used in plantation forests. (Marynard, 1981) Other oaks generally do not grow large enough to produce a straight grain the size of the staves. (Dinsmoor, 1974) For further information see How is American Oak Doing in the Oak Choice Race?

How to Make A wine Barrel

First the log is cut into stave-size lengths and quartersawn. Quartersawing minimises the dimensional change of the width of the stave as it shrinks on drying or swelling with wetting and minimises the amount of liquid that can diffuse through the staves. Rough staves are then cut and stacked for drying. Outdoor drying is often preferred as rain washes out most of the tannins. Once dry, the staves will be sorted by length, thickness, quality and grain. The staves are then dresses and shaped and roughly joined by a number of hoops. At this stage the barrel is placed over an open fire to transform the lignin into vanillin and to ensure that the staves keep their shape achieved by bringing down the hoops in the required positions (see adjacent photo, source: The wood and the wine). The hoops are then removed and the barrel planed before permanent steel bands are placed into position. (Bolsmann, 1984)

Oak Chips

The wood of approximately two and a half trees is required to produce one barrel. Much of this is waste. The trees must be between the ages of 80 to 150 years to contain the appropriate lengths of straight grained heartwood to produce the staves. (Bolsmann, 1984) For this reason, Oak barrels are expensive, thus wine matured in oak barrels is expensive. An alternative to maturation in Oak barrels is adding oak chips to an impervious barrels. Oak chips provide many of the benefits of barrel maturation without the cost though is not a well reputed practice in the age old industry of wine making. More information on Oak chips can be found on

I hope you have learned something from this page. I know I have. For more information check out the hyperlinks throughout the document or try this site Benefits of Oak on wine composition

References

Books

Amerin, M.A. & V.L. Singleton (1972), Wine: an Introduction for Americans, University of California Press, Berkeley

Bolsmann, E. (1984), South African wine dictionary, AA Balkema, Cape Town

Dinsmoor, A (1974), Chemistry of winemaking, American Chemistry Society, Washington

Maynard, A (1981), Wine Production Technology in the United States, American Chemistry Society, Washington

Web References

When a barrel goes to heaven

http://www2.wines.com/vwm-online/archive/23-2/oak-6.html

How is American Oak Doing in the Oak Choice Race?

http://www2.wines.com/vwm-online/archive/23-2/oak-1.html

Benefits of oak on wine composition