Maintaining barrels for longer use

by Charl Theron | Oct 1, 2023 | Practical in the cellar, Technical

Barrels are an integral part of winemaking due to the extraction of wood flavours and micro-oxygenation during barrel maturation. In addition to increasing new barrel prices, transport and logistics problems are forcing winemakers to be more innovative regarding using barrels.

Oak barrel life cycle

The forest cycle begins with the seeds, resulting in 50 000 trees per hectare of forest. These are thinned out gradually to 100 trees per hectare. A matured oak tree is harvested after 175 years, although each tree can grow until 600 years. The oak log is transported to the stave mill, where less than 20% is used for quality barrels or approximately 150 kg per tree. The oak goes through different processes, such as stave milling, air drying, maturation and toasting, before barrel assembling is initiated. Each tree is converted into three barrels of 225 litres capacity, which can be used for wine barrel maturation. The effective life of a barrel is only three years, and barrels are usually disposed of after four to five years. After 12 months, 60% of the oak flavours are extracted, followed by 25% in the next year and only 15% in the third year. During this time, only 22% of the new wood is utilised.

Oak barrel trends

Oak trends are changing amongst certain consumers, who do not prefer too prominent oak character, which masks the freshness of fruit-driven wines. In addition to trying to obtain a subtle oak character, it is also essential to maintain consistency regarding the oxygen transfer rate (OTR) since it can also affect wine style. This is difficult since the oak extraction and porosity change during the maturation cycle of standard oak barrels, which makes it essential to buy new barrels annually to fit in the maturation cycle.

Consumers are also becoming more aware of environmental sustainability. Unnecessary waste and the importance of carbon footprint are forcing cellars to adjust their maturation protocol accordingly. When alternative wood maturation is considered, the following should be kept in mind:

Larger containers will lead to a more subtle oak character.
Forklift stackable barrels improve safety and save space.
The individuality of barrels should be eliminated.
The elimination of topping can decrease labour costs.
Easier cleaning can save water and be more hygienic.
The potential of all added oak should be utilised thoroughly.

Extending the barrel life cycle

Although the extractable components are removed within three years, barrels can still be in good physical condition after that period. Cool temperature, humidity and proper washing contribute to this. The barrel life can be extended up to 12 years if it is always filled with wine or an acidic sulphur dioxide solution. However, it only becomes a container seeing that potential wood extract has already been extracted and wine precipitates block the porosity. Different ways exist to remove these, but only to a minimal extent. The shaving of barrel insides is also limited before leakages will appear. The loss of potential wood extraction and micro-oxygenation due to changes in porosity can be supplemented by adding alternative wood products like chips or staves and applying micro-oxygenation (MOX).

Alternative “barrels”

A company called Flexcube, developed a product to extend the life of “barrels” and add more flexibility to the use of wood and lower the carbon footprint. Instead of adding wine to wood like with traditional oak barrels, wood is added to the wine. New oak can consequently be added to wine annually.