BLENDED scotch whiskies will soon taste as rich as some single malts. With a
pinch of salt and a large toaster, researchers in Scotland have learnt to tease
more flavour from oak barrels so that the whisky can mature faster.
Scotch gets much of its taste from the oak casks in which it ages. Lignin and
hemicellulose in the wood break down and impart the sherry-like character and
tawny colour to the clear distillate. Tannins and other volatiles seep in from
the wood as well.
鈥淭hese compounds have to get into the spirit by diffusion,鈥� says Gordon
Steele, director of the Scotch Whisky Research Institute in Edinburgh. 鈥淚t takes
a long time.鈥�
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Once a cask has been used for scotch maturation, most of these essences have
disappeared from the surface of the wood. To recondition the cask, a cooper must
scrape away the surface layer of wood and then flame the barrel to break down
lignin and hemicellulose, as well as to create a thin layer of char that filters
out unwanted flavours.
The problem, says Steele, is that the flaming is imprecise. The optimum
degree of chemical conversion within the wood can often lie too far from the
surface, thus delaying maturation of the scotch. Furthermore, flame treatment is
frequently uneven.
To get around this problem, Steele and his colleagues press a blend of
salts鈥攎ainly sodium chloride鈥攊nto the individual pieces, or stays,
of a barrel. Then they heat the wood evenly under a specially designed electric
burner. The salt catalyses the breakdown of the wood so that lower temperatures
achieve the same result.
As the oak stays pass under the element on a conveyer belt, the radiant heat
converts the lignin into flavourful aldehydes and toasts the hemicellulose into
caramelised sugars. How the salt works is not yet fully understood, Steele says,
but the improved flavour is proof that it does. 鈥淲e aren鈥檛 creating new
flavours,鈥� he says, 鈥渏ust enhancing the traditional ones.鈥�
Steele emphasises that the new technology does not change the process of
whisky maturation鈥攊t merely optimises the quality of the casks and gives
the producer more control over the final product. He says the technology will be
used mainly for maturing blended scotches, which make up about 95 per cent of
the market. Connoisseurs of single malts need not worry about changes to
traditional cask preparation.
Steele says the first blended scotches made by the technique will be
available in three years鈥攖he minimum time that distilled spirit must
remain in a cask if it is to be sold as scotch. 鈥淲e are making full-sized casks
now,鈥� he says.