Fermentation is an integral part of the distillation process. It takes place after ‘mashing’, where we’ve harvested barley, malted it, milled it and filled it into our mashtun. Here we add hot water to activate enzymes, converting starch to sugar. The sugar-y water is taken from the mashtun, where the fermentation process allows yeast to consume that sugar, in turn releasing alcohol as a by-product and more importantly, flavour! The next stage is distillation.
Our approach to fermentation at Bruichladdich is characteristic of how we work. It’s traditional, taking place in all wooden vessels (washbacks), which are constructed onsite by a team led by time-served coopers and no other technologies. It’s given time, a minimum of 65 hours, and up to double that long, if necessary. It has people as its lynchpin; the fermentation is judged by human beings taking manual measurements and giving the liquid their attention, using all their senses. They monitor its transformation from wort, sugar-y water, to wash, a cloudy 7% alcohol jam-packed with organic chemical compounds and esters. It’s a chemical process, with correct temperatures and volumes that optimise the reactions taking place, the management of which is preserved exactly by one generation of mashmen teaching the next. Their tools are a hydrometer, a “dip stick” (10 foot ruler which gives them the liquid depth and therefore its volume), flasks, and our 6 60,000 litre washbacks with slide-over lids.
If you look at the way we deal with fermentation as a contributor to the flavours in whisky, however, the approach is not like us at all! No continual enquiry like we have over barley variety, how it is farmed, when it is harvested, where precisely it was grown, nor pushing the boundaries like we do with our bold maturation decisions or the types of casks we obtain. Why? Continuity, for now…
There are many types of yeast – brewers (held up for more flavour) or distillers (for more alcohol), dried or fresh, fast or slow, cultivated or wild – and we have been through several options in the past. We’ve conducted controlled experiments with two different strains of dried yeasts over the past few years, but our mainstay is a combination of two live, wet yeasts, to which we always return. Why?
The two yeasts are described on our tours of the distillery as “a sprinter” which starts off the reaction, and “marathon runner” that keeps it going. We always use the same quantity of yeast, same types, from the same supplier, to ferment the same volume of wort in the same 6 washbacks.
Allan Logan, Production Director, explains, “We’re trying to get the flavour from the malted barley through the wash that we can carry through into the distillation process. There are flavours from the spent yeast as well, these added flavours are important to us, you know, we’re not chill-filtering our whisky. But the barley is the main raw ingredient, and one that we’re really really interested in and committed too. If people are buying an Islay barley from us, we want them to be able to taste the difference that that barley makes, or that those farms make. So the yeast strains have become our one constant.”
This is Bruichladdich, though; don’t rule anything out. “Our exploration is not done,” says Allan. “We may have the ability to continue to controlled experiments with different yeasts in the future.”