Chapter 21

The Role of Oak in Winemaking

Oak Alternatives Used in Wine Production

High-quality wines are traditionally stored in oak barrels for periods in the range of months to years to improve their sensorial attributes. Contact between the oak wood and wine allows a number of compounds to diffuse out of the oak into the wine, and these substances are known to improve the intensity and complexity of wine flavor. Additional benefits of oak aging include color stabilization, lower astringency and bitterness, disappearance of reduction taste, and the reduction of excessive vegetative/ herbaceous aromas. However, oak is an expensive raw material, and barrels contribute significantly to production costs in terms of both capital investment (i.e., barrels) and labor associated with cellar management. For these reasons, more and more wineries are using alternative oak products - powder, chips, blocks, staves, barrel inserts.

Dosage Rates

The impact of oak compounds obtained from oak alternatives not only depends on the type of products (e.g., size, grain size, etc.), the origin of wood (e.g., French oak, American oak, etc.), the toasting (e.g., light, medium, etc.), the length of exposure time, but also on the quantity of oak which is put into contact with the wine. Thus, the repeatability of the processes is not always consistent, especially if there is variation in quality between batches.

Micro-Oxygenation

TMicro-oxygenation (MOX) is being used increasingly by cellars. In addition to softening wine tannins, improving the color stability of red wines, integrating wine flavors and reducing reductive flavors, MOX can also be used with alternative oak products as an alternative to barrel maturation. By using MOX in conjunction with oak alternatives, winemakers are able to replicate many of the maturation characters of barrel ageing without the cost or microbial risks of using oak. In addition, by using alternative oak products combined with MOX winemakers have more latitude in manipulating wine styles. As an alternative to using oak adjuncts in tank with MOX, many wineries use in-barrel oak adjuncts.

Oak-Alternative Products

There are a number of oak-alternative products which can add toast, spice and vanilla flavors to wine, stabilize color in reds, reduce green tannins, and improve mouth-feel. All of the oak used in alternative products is derived from the same sources as those used in traditional barrels. Processed oak is generally available in four forms: powder, chips, blocks, or staves. They are available with a light, medium, or dark toast and also available in different wood species.

Oak Powder

Oak powder can be used mainly to stabilize color and reduce and soften unwanted green, vegetal or herbaceous tones of red wines, especially but not exclusively in Cabernet Franc, Cabernet Sauvignon, and Merlot. (Figure 21.10).

Oak Chips

The most common oak alternative used is oak chips (Figure 21.11). Oak chips are added at various stages during the winemaking process. Some wine makers prefer to add oak chips directly to the fermenting wine, while others use permeable bags full of oak chips in wine tanks in a manner similar to steeping tea.

Oak Blocks

Larger and more finished than chips, but smaller than a stave, oak blocks (sometimes called cubes) occupy the middle ground between chips and staves (Figure 21.13).

Tank Staves

The major selling point of staves or slats is that they mimic the oak, air, wine interaction that takes place in a barrel (Figure 21.14). The staves may be new and fire toasted or may have been reconditioned from broken down old barrels.

Barrel Inserts

Oak barrel inserts allow the winemaker to exert far finer control over the amount, type, and toast of oak alternatives used. This procedure significantly reduces aging periods and allows wineries to release their wines into the market sooner.

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