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CURRENT VINEYARD AND CELLAR EVENTS
The evaluation of barrels for purchase
Charl Theron
The purchase of barrels represents an enormous financial outlay in the production of wine. It is therefore of the utmost importance for cellars to engage in comprehensive evaluation of different types of barrels and suppliers before finalising barrel purchases. The purpose of barrel maturation, moreover, is not only to impart wood character to the wine, but to complement the quality of the wine by so doing. The evaluation should therefore take place over a period of time so that the actual influence on the quality of the wine can be controlled. The evaluation should also be dynamic, in view of the fact that vinification methods and wine styles or marketing methods are constantly changing.
There is a considerable variety of different oak flavours and their interaction with wine components causes even more complexity. The flavours occurring in the wood are influenced by various factors. The growing conditions of the tree, the age and genetic variation of individual trees influence the structure of the wood and these natural conditions will consequently also influence the extent of flavour extraction from the wood. The original position of a stave in the tree will therefore also play a role. Furthermore the natural drying and toasting of the wood will be the production processes that impact on the flavour components of the barrel.
The various oak flavour compounds cause specifically noticeable flavours:
- Eugenols are responsible for clove and spice flavours.
- Guaiacols are responsible for smokey or tar flavours.
- Furfurals are responsible for sweet and butter caramel flavours.
- Vanillin is responsible for vanilla flavours.
The Nadalie cooperage in the USA launched a project which evaluated the use of various alternative sources of wood such as shavings, cubuses, dominoes, blocks, chips and staves with regard to their respective influence on different sensorial parameters - such as fruit, oak, vanilla, spice, smokiness and other flavours. To this end red wine was exposed to the different treatments for varying amounts of time and the tasting results of the project were processed using standard statistical methods of analysis.
The most important results of the project may be summarised as follows:
- The use of wooden cubuses correlated positively with the smoke, general oak and toasting characters, but negatively with bitterness and fruity characteristics.
- Medium and heavily toasted shavings correlated positively with general fruit character, but negatively with smokiness, general oak and toasting flavours (1).
The procedure according to which barrels are evaluated for purchase, should comply with certain guidelines, however:
- At least 2 barrels of a specific type must be evaluated.
- Before the evaluation, the barrel suppliers must make recommendations regarding the most suitable application of barrels for specific wines. This should put paid to arguments that barrels were not applied correctly.
- The barrel sizes should be the same to enable a comparative evaluation.
- The evaluation should take place over at least 24 months and over this period the wines should be evaluated at regular intervals.
- Certain types of wood or wood treatments react better to specific wines and it is important to bear this relationship in mind when starting the evaluation.
- Apart from different barrel types, the different processes at cooperages, such as drying and toasting, should also be evaluated.
- The evaluation process only makes sense if the barrels are subjected to the necessary quality control upon receipt. Barrels should firstly be inspected for any physical damage such as cracks. Thereafter they should be evaluated for any off-odours and the inside should be inspected with a light for physical deviations such as cracks or excessive toasting. This should be followed by a density test by filling the barrel with water and applying a pressure test. The water that is used for this purpose can also be evaluated sensorially to identify any off-characters in the barrel. Each barrel should be identifiable to enable sensible ongoing evaluation (2).
References:
- Anonymous, 2005. The alchemy of oak add ins. Wine Industry Journal 20(1): 39 - 42 (The full report is available via jcd@nadalieaustralia.co.au).
- Anonymous, 2005. Oak trials give insight into barrel selection. Wine Industry Journal 20(1): 34 - 36.
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