Courtesy of Wynboer www.wynboer.co.za
Written by Charl Theron
Ever since the introduction of oak alternatives for vinification in several wine industries about three decades ago, manufacturers have been exceptionally creative in the development of various new types.
These range in size and geometric shape, but what they all have in common is being less expensive than oak barrels and rapidly imparting an oak character to wine because the surface/volume ratio is much bigger than in the case of barrels. Winemakers should consider various factors, however, before deciding which alternative oak product to use for a specific wine.In view of the traditionally positive image of oak barrels, winemakers do not necessarily acknowledge the use of oak alternatives. It is nevertheless common knowledge that the use of oak alternatives per se will not have the same impact on wines as oak barrels, but the difference is considerably reduced by using oak alternatives in conjunction with micro-oxygenation (MOX). The price difference between oak barrels and oak alternatives is such a decisive factor that the price at which wine is sold also impacts on the decision about the kind of oak to be used. From a financial point of view, new barrels should only be used for premium wines. In the case of cheaper wines, large cellars prefer to use oak alternatives only, while smaller cellars will use these in conjunction with old barrels.Three basic rules apply to oak alternatives. Firstly, oak extraction usually takes place more rapidly than expected. If the requirement is merely an oak aroma, a few weeks will be required for chips, two months for cubes and six to nine months for staves in tanks. In view of the fact that the extraction of the oak character takes place rapidly, it is preferable to use more oak rather than extend the contact period with the oak. Smaller oak alternatives usually have a bigger surface/volume ratio which will impart more oak character. Secondly, it is better to use smaller oak particles earlier in the vinification process, while bigger products should be used at a later stage. For example, oak powder and small chips can be added before or during fermentation, because they are small enough to pass through cellar equipment such as pumps. Thirdly, it is better to use small particles to obtain aromatic effects and bigger products for a greater impact on wine taste.Oak powder must be used mainly to stabilise colour and reduce the green character of red wines. Although it will also enhance the oak flavour in wine, this should not be the primary motivation for using it. Untoasted oak powder and chips obviously do not add any toasted or vanilla flavours to the wine, but they do stabilise red wine colour, reduce the vegetal or green flavours in wine and balance the wine’s taste. They are consequently used mainly during alcoholic fermentation or within a month thereafter. Small chips are small enough to pass through a pump with a bore width of approximately 6 mm or bigger positive displacement pumps. These are mostly used for the same reason as oak powder, i.e. colour stabilisation in red wines, and also to impart oak character to cheaper Chardonnay during alcoholic fermentation. In the latter instance they are usually used in bags, so that they may be easily removed from the wine if lees contact is a potential option. Large chips are added to wine in bags, not individually, after alcoholic fermentation. If these are used without MOX, the oak extraction is slower than in the case of small chips. Oak cubes are bigger and more refined than chips, but smaller than staves. They may range from 12 mm cubes to mini-staves measuring 200 mm in length. Compared to chips, the oak character of cubes integrates more rapidly with the wine. After nine months or a year of oak contact, however, there is little difference between the use of chips or cubes. Oak staves in tanks, like most oak alternatives, function best when used in conjunction with MOX. The staves can be used in different configurations in tanks and are usually left for six to nine months. They are especially well suited to imparting oak character to a wine that is subsequently matured in old barrels. Barrel inserts refer to any kind of oak alternative placed inside barrels. These may occur in fixed structures, chain form, spirals or chips or cubes, and the form that is selected can impact significantly on the manual labour that is involved. If many barrels have to be handled, the extra labour cost may cancel out the cost benefit of the oak alternatives. For smaller cellars this method of alternative oak application is nevertheless effective, because it does not necessarily entail MOX. Oak tannins may be used at any stage of vinification, but are best used as a technique to balance wines that have already been blended.
FIGURE 1. Various oak alternatives.
The following scenarios may apply if the above-mentioned recommendations are implemented:
A red wine that has to be marketed young, benefits most from oak powder which is added during alcoholic fermentation at a dosage of 2 to 4 kg per ton of grapes.
For practical reasons smaller cellars have to use their old barrels again by inserting barrel staves. The correct maintenance of such barrels is crucial, however, for the oak strategy to succeed. Where possible barrels should always be kept filled and possible contamination with Brettanomyces or flor yeast should be monitored regularly.
A cheaper Chardonnay may be made by fermenting the wine with chips in bags or barrel staves at a dosage of approximately 200 g per 1 000 litres. This may be done in conjunction with micro-oxygenation during alcoholic fermentation.
REFERENCEPhillips, Curtis. 2011. Winemaking. Product Review: Oak Alternatives. The operational pros and cons of using oak alternatives. Wine Business Monthly 18(4): 18 – 26.