The wood must respect the fruit…

A favourite motto of barrel producers (coopers) is that the wood must respect the fruit in wine, something a certain ex-president of ours were not really inclined to do with our constitution… So let’s zoom(a)  into the main differences between new and old oak barrels used for winemaking…

About a decade ago the use of new wood in winemaking were quite popular. Winemakers used to mature a large percentage of their red wines in so called new wood, which is basically when wine comes into contact with mostly oak wood for the first time. Wine in an oak barrel is often removed after around 12 months and replaced with wine from the new vintage. This leaches out the aroma compounds from the barrel, leading to barrels which has been in contact with wine for three times (say around 36 months) with little oak flavour to impart to the wine. Research has shown that certain compounds reach their maximum levels in wine matured in new oak barrels after around 9-12 months, such as furfural, vanillin and lactones. Furfural, although not really potent in wine individually, contributes to the almond, nutty flavours, vanillin obviously yield vanilla and lactones give wood, coconut aromas. Guaiacol and eugenol (smoky and cloves respectively) keep on extracting even after this initial 12 months, but vanillin and lactone levels can decrease after this period. This could be due to reabsorption on the barrel’s internal surface area or microbial activity. In old barrels the levels of these compounds however, are much lower. When wine is matured in barrels which have been used more than three times very little wood aroma and tastes are thus imparted to the wine.

The amount of oxygen going through old barrels is also much lower than when new barrels are used. This could be due to blocking of the pores in the older barrels, and is further reflected in the free sulphur dioxide levels in wines matured in new barrels normally dropping quicker than those in old barrels. In new barrels the higher amounts of oxygen and tannins being leached out from the new wood can react quicker with the sulphur dioxide than is the case with old barrels.

Older barrels in theory can then lead to more fruity wines, as wood derived compounds can possibly mask fruity aromas such as those caused by esters and thiols. However, older barrels also have certain risks associated with their usage. Chances of microbial spoilage starts to get larger when older barrels are used (if not looked after properly). However, if cared for properly older barrels can be re-used a number of times or even rejuvenated by removing the hoops, dissembling the staves and shaving off a few millimetres of the inside of the stave and reassembling the barrel. This can be seen in the following picture, which shows staves before and after shaving.

staves rejuvenated

There will always be a debate with winemakers on how much new wood one should use when making wine. One of the major factors is cost, as a new barrel can easily cost up to R15000, depending on the volatile Rand (barrels are mostly imported).

The wine itself can also play a role in how the wood is reflected in the wine. Certain wines will absorb the oak derived compounds quicker than other. One trail where a Merlot (alcohol level 13.6%) and a Cabernet Sauvignon (alcohol level 12.3%) were compared in terms of their oak wood extraction when placed in the same barrels, led to the Merlot in some cases extracting up to twice the amount of lactones, vanillin and guaiacol after 12 months compared to the Cabernet Sauvignon. One then cannot really compare a Shiraz wine made from vineyard A and matured in an old oak barrel with one matured in a new barrel, but produced from vineyard B. Check out my website (www.collatiowines.co.za) where I offer the same Shiraz wine aged in a new and old barrel. Balance is key when deciding on a wood treatment for wine and in this case the wine matured in the new barrel were not “captured” by its new “state”…

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