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A Technical Guide for Wine Producers
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WINE in WOOD and WOOD in WINE
The necessity of wood specifications in the vinification process
Charl Theron
General management of a production process implies that efficient control be exercised over people, money, materials and equipment. At an operational level it requires that relevant characteristics of the material, processes and products be identified and measured, and then controlled according to acceptable guidelines, norms or specifications. In vinification, material and process specifications apply to both the vineyard and the cellar. Specifications provide the basis for purchasing and selling, manipulating, producing and evaluating.
In the first article of this column, reference was made to the importance and necessity of specifications for wood, i.e. wood products, in the vinification process. As indicated by the oak import statistics and also in practice, the oak barrel is no longer the only wood product being used in SA, and has not been for a long time.
Inevitably, due to cost and material considerations, other wood-related technologies were developed and are already being applied. Thanks to continued research and development, wood chip, wood powder and wood extract technology will be complementary to the well-known, traditional wooden barrel technology. These new wood-in-wine technologies no longer focus on the function of wood as a physical container in which wine is transported, kept or matured, but only on the role it plays as a chemical substance in the vinification process.
Specifications that are applicable to the use of wood and wood-related products are controlled by industry regulatory legislation. Wood or related substances which may be added to wine in terms of the Liquor Products Act (Nr 60 of 1989) which was published in the Government Gazette of 29 June 1990, were referred to, at the time, as:
Firstly, "Wood deriving from barrels in which the particular liquor product is being matured", and secondly, as "Tannin".
The spirit in which the legislation was formulated may give rise to experimentation, for example whether the wooden barrel was used for one day only or for several years, which type of wood was allowed, how the wooden barrel was produced or to which processes the wood present in the barrels was subjected. Due to the wide variety of possibilities and permutations this would have been simply impossible to regulate. The source of tannin was also not described or qualified. From a wood scientific interpretation the tannin(s) of any kind of wood, for example of Eucalyptus, some pine (Pinus) or Acacia species, and others might be candidates for adding to wine as extracts.
When amendments were published on 7 March 2003, the above two entries were replaced by respectively "Wood" and "Tannin, provided it is not alien to wine".
By so doing the opportunity to experiment was theoretically extended to all wood. Moreover, as long as a tannin or tannins occur naturally in wine or different kinds of oak wood, whether the species was previously used for barrels or not, it would pass as "a tannin not alien to wine". These industry regulatory specifications create an even bigger opportunity for experimentation, while at the same time placing an even bigger onus on the winemaker to exercise caution and good sense when using these wood and wood-related additions. Knowledge, in other words research and development, is essential to develop - at an operational level - specifications for wood and wood-related additions to wine.
These regulations are very much applicable to the addition of solid wooden pieces (staves), chips, powders and liquid extracts. It goes without saying that one has to ask how descriptive, complete, useful, effective, verifiable, etcetera the specifications are that are relevant to wooden barrel technology. Obviously the specifications are directly forthcoming from the characteristics and function of the wooden barrel. The wood of the barrels has to be easily crafted to produce a vessel that does not leak, is strong, durable and permeable by gas. Chemically the barrel is a source of chemical substances that impart a specific, unique flavour/taste/colour to the wine, or facilitate a process such as micro-oxygenation.
When purchasing new wooden barrels, the physical and chemical functions and characteristics mentioned above are specified only in terms of material (physical) parameters that include: species, place of origin and grain (density). Processing parameters which may be largely controlled by the cooper, include which part of the tree is being used, methods of stave production, drying, barrel manufacture and toasting techniques. In the manufacture of wood-in-wine products such as chips, powders and extracts, similar specifications for material and processing parameters are required. The smaller wood products become, the more it will be necessary to verify species and origin, as well as to specify the chemical content (concentration and type of ingredients), geometry and size of wood products.
At this stage specifications are agreed upon wittingly or unwittingly by the winemaker and barrel supplier. From conversations with winemakers and barrel suppliers/producers who would like to exercise control over the repeatability of a unique wooden taste/flavour/colour and the fact that it is difficult for the winemaker to verify characteristics of wood products, it is clear that it is essential to establish a mutual, healthy situation of trust.
Detail and systematic investigations will result in applicable, measurable and controllable specifications for wood and wood-related technologies.
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