FLAVOUR FOCUS
The world of washbacks
Ever stuck your head in a washback on a distillery tour? The powerful reactions taking place are crucial in transforming the wort into wash, and creating essential flavours along the way. Gavin D Smith has more
MAIN PHOTOS: PETER SANDGROUND AND MIKE WILKINSON
Fermentation is the process that happens when yeast is added to the wort created during mashing in order to convert sugar in the wort into alcohol. Carbon dioxide and heat are generated as the yeast does its work. Up to 80 per cent of the character of new-make spirit comes courtesy of fermentation, and there is an old saying that you can’t make good whisky without good wash. In other words, what happens during mashing and fermentation is crucial to creating quality spirit.
As with every aspect of whisky production, there are many variables regarding fermentation, including the kind of vessels in which the process takes place, the type of yeast used, the prevailing temperature and the length of time for which the process is allowed to progress.
At the start of fermentation, wort is pumped into the washbacks, having been cooled to around 23°C in order not to kill the yeast. The washback will usually be filled to around two-thirds of its capacity, as a significant amount of ‘headspace’ is required when the yeast goes to work.
Yeast itself is an important variable in whisky production, and can have an appreciable effect on spirit character. Today, most distilleries use specific distillers’ yeast, available in liquid cream, pressed semi-dry or dried format. Of these, liquid yeast is the most commonly used, and modern strains offer high levels of efficiency and consistency.
Not all distillers see efficiency and consistency as the holy grail, however, with the likes of the Thompson brothers of Dornoch distillery prizing flavour character over yield. They favour brewers’ yeast, once common in whisky-making, and yeast propagated ‘in-house’. According to Simon Thompson: “Yeast can produce more than 200 flavour by-products, some of which are yield-expensive and some yield-cheap. Modern distillers’ yeasts are all very similar, but there’s vast potential beyond them.
ABOVE: The Thompson brothers at Dornoch distillery favour brewers’ yeast in their quest for complexity and tropical fruit flavours
“We’re looking for high levels of complexity, extreme fruit flavours, and especially extreme tropical fruit flavours – we’re always chasing them down. We’re looking for specific esters that create them.”
While converting the sugars created during mashing into alcohol, after a calm early start, the reactions taking place in the washback may cause the vessel to rattle and shake. To help prevent a potential overspill, some washbacks are fitted with a rotating arm, known as a switcher, which skims off the froth as it rises.
The late Drew Sinclair, latterly manager of Dalmore distillery, recalled his early days in the tun room when interviewed for my book The Whisky Men in 2005. “We would use soap in the washbacks. It was curd soap, obviously not scented. We had switchers in the washbacks, blades, and there were two speeds, a low speed and a high speed. Now even on the high speed you would see these backs shaking, just bouncing away like that at times. Really, really fierce. And they would bounce the lids off. That was when you put the soap in. And the soap just knocked it back.”
ABOVE: A traditional wooden washback under construction, although stainless steel is more common nowadays
ABOVE: John Fordyce at Borders distillery has been experimenting with short and long fermentation times
The length of fermentation is an extremely important factor in determining spirit character, and although fermentation is usually complete in 48 to 50 hours, many distillers allow the process to extend well beyond that timeframe. Additional flavours are created as the amino acids produced during initial fermentation build up during secondary, or malolactic, fermentation, leading in particular to those “extreme fruit flavours” favoured by the Thompsons of Dornoch.
Some of the most significant examples of long fermentations are seen at Dornoch distillery – a minimum of 160 hours in open-topped washbacks – and at Dunphail, where 144 hour-long fermentations are practised.
At The Borders distillery in Hawick, differing fermentation regimes have been employed to produce an intriguing whisky named The Long & Short of It. A batch of wash with a short fermentation time of 55 hours was created, along with a batch with a long fermentation time of 150 hours. Both batches were then distilled twice and matured in first fill ex-bourbon barrels, before being married with single grain.
Received wisdom is that short fermentation times produce crisp citrus flavours and longer fermentation leads to deep flavours of ripe fruit and toffee, and John Fordyce, managing director of The Borders Distillery, says: “What’s interesting about The Long & Short of It is that you can clearly pick out the contrast between the two whiskies; the green gooseberry at the front end and the fig and toffee-type notes from the long fermentation at the back end.”
After fermentation is complete, the result is ‘wash’, with an alcohol content of 7-8% abv, and at one time a popular drink among distillery employees, being known on Speyside as ‘Joe’. The wash is now pumped from the washbacks into the wash still or stills, ready for the first distillation to commence.
Gavin D Smith’s book The Whisky Men, a collection of stories and insights from old distillery workers, was published by Birlinn in 2005, and you might still be able to track down a copy online.