In this first Distiller’s Dispatch Jacob, our Distillery Manager, is going to take us back to basics, firstly looking at the process for distilling Scottish Whisky in general, and then into some of the choices we have made here at North Uist Distillery that will make our final spirit as unique as the island we call home.
The Basics of Scottish Whisky Production
We use 100% malted barley, milled into a grist before being mixed with hot water in a mash tun. The mash facilitates the enzymatic breakdown of complex carbohydrates in the malt into simple sugars, more easily utilised by yeast. The next part of the process involves the sugary liquid produced, called worts. This liquid is filtered off the mash, cooled, and filled into washbacks along with yeast to begin fermentation.
During this stage the yeast converts sugar into alcohol, creating a sour beer called wash at 7-8% ABV. Once mature the wash is filled into a wash still, and distilled to separate the alcohol producing a liquid called low wines at around 23% ABV. Finally, the low wines are distilled a second time in a spirit still. The spirit distillation is where the distiller will intervene in the process to “cut” out the undesired flavours while retaining the best portion of the spirit, known as the hearts. These cuts will determine the character of the spirit. The heart of the distillation is diluted to approximately 63.5% ABV before being filled into oak casks and stored in a warehouse for a minimum of 3 years.
What makes us different?
We are a very small scale distillery with a capacity to produce only 60,000 Litres of Pure Alcohol (LPA)/yr. Due to our production style we only achieve about 70% of this capacity. The distillery is sized such that each day of production and each distillation will produce only a single cask of whisky. The manual nature of our production means that the distiller's decisions on the day, the weather, the seasonal variations and many other factors will work together to make each cask a unique snapshot in time.
Barley
We use heritage barley for all our production; these older varieties contribute much more complex flavours and texture to our spirit, although this does come at a cost. The grain we use costs up to three times that of standard distillers malt and yields only 80% of the spirit. We carefully construct our mash bill using different barley varieties for the unique flavours they contribute to our spirit. The back bone of our mash bill is bere barley malt. Crofters have been growing bere in Uist for hundreds of years, it is one of the oldest known barley varieties, specifically adapted to growing in the harsh island conditions. Bere barley provides a very distinctive set of characteristics to our spirit while also intrinsically linking us to the island, its community and its heritage.
Long Fermentations in Wooden Washbacks
Similar to a sour dough starter, our wooden washbacks contain a stable population of micro-flora - a mix of bacteria, fungi and wild yeasts unique to our island home. After around 48 hrs the yeast has completed its work, converting the simple sugars into alcohol, and this is where the microflora will take over. Bacteria and wild yeasts will begin to break down the sugars and other compounds which the commercial yeast is unable to utilise, producing a variety of complex flavours which provide our spirit with more depth. Due to our long fermentations, typically 168 hrs, this secondary fermentation will contribute much more to the character of our spirit than our commercial yeast, creating more of an expression of our environment.
Stills
Our stills have been designed with versatility at the fore: both our wash and spirit stills are oversized and our spirit still has been fitted with a purifier line. Having oversized stills gives the distiller more control over the speed at which the still is run and hence the amount of copper contact or reflux during distillation, while the purifier on our spirit still allows the distiller to return some of the condensed spirit to the pot, allowing further control of the spirit style. The degree of copper contact during distillation has various effects, most significantly influencing the heaviness or robustness of the resulting spirit. We can adapt our production to produce multiple styles of spirit to best showcase the different flavours produced from our malted barley and long fermentations.
Maturation
We have dedicated time to sourcing the highest quality casks which will best showcase the spirit we have worked so hard to create. We use a selection of refill and first fill ex-bourbon casks along with a small proportion of high quality ex-sherry casks. We store all our casks on the island in order to keep a close eye on our whisky throughout maturation. Humidity, salt, and air temperature all have an effect on the ageing spirit, and in the same way that the island environment shapes the community we live in, it will shape our whisky as it matures in our warehouse.
- Jacob
Distillery Manager
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