One of the great selling points of single malt whisky is its diversity. From the light fresh flavours of Glenmorangie to the heavy smoky monsters from Laphroaig, the wide spectrum of styles means there is a whisky for almost every single taste preference.
It would surprise some to know then that whisky is made from only three main ingredients: barley, yeast and water. It is the production process – how these ingredients are used and prepared – therefore, that lead to the diversity of flavours in whisky.
The production of whisky starts with the process of activating the sugar content in barley. Barley is steeped in water, allowing it to germinate and produce starch which is the source of the required sugar. To stop the germination process, the barley is then dried over indirect heat. It is here that one key contributor of flavour, peat, is used. Essentially decomposed plant matter, peat creates low heat and plenty of smoke when burnt, and this helps dry out the barley. The smoke sticks to the barley and this gives the distinctive smoky aroma and flavour whiskies like Laphroaig and Ardbeg are famous for. Ardbeg’s distillery manager, Michael Heads, stresses the importance of peat in the production of Ardbeg, “The peat adds rich intense smokiness with medicinal phenols (and) a briney saltiness is also part of the complex aromas (created).” The resultant barley, known as malted barley, is then used to create whisky.
Not all peat around Scotland is the same though, and this leads to sometimes significant differences in the final product. Whilst the peat of Islay’s distilleries lead to a more medicinal smokiness, the peat used in Highland Park’s whisky imparts notes of floral honey, specifically heather honey.
The process of turning malted barley into whisky starts with mashing. The barley is first ground into a mixture of flour and grist, and this is put into gradually warmer batches of water to extract out the sugars. The grinding of the barley makes it easier for the water to extract the sugars from the barley. The resultant liquid, known as wort, is actually very pleasant to drink, and it is this sugary water that would be used to produce the all-important alcohol content for whisky to be made.
After mashing, the wort is then put into large containers known of washbacks, made from either wood or stainless steel, where yeast is added to start the fermentation process. The yeast essentially breaks down the sugars in the liquid into alcohol and carbon dioxide, and this liquid is then sent for distillation. Whilst it is not the most celebrated part of the production process, fermentation times and yeast strains have a big impact on flavours, as many flavour congeners are created during fermentation. Shorter fermentation periods tend to give more cereal, biscuit notes, and longer fermentations produce more fruity notes. It is unsurprising, then, that distilleries adhere strictly to set fermentation times to ensure a consistent flavour is obtained from this part of the process. “Our fermentation is from 52 to 72 hours, never more, and this gives a lot of fruity, floral and crispy flavours to our spirit”, states Martin Marksvardsen, Senior Brand Ambassador for Highland Park Distillery and the Edrington Group. Some smaller distilleries have also experimented in different types of yeast strains, like brewer’s yeast used in beer production, as they believe the yeast itself also creates unique flavours in the eventually spirit.
The resultant liquid from fermentation, known as the wash, is then sent to the stillhouse for the final part of the production process, distilling. The monumental copper stills, an iconic image of the whisky world, produces high alcohol spirit that is eventually matured to become the water of life. Copper, being a very reactive metal, removes impurities, such as Sulphur, during distillation, and this ensures the spirit is not tainted with unwanted flavours. Most distilleries distill the wash twice, once through the wash still which produce a liquid that is between 20 – 25% in alcoholic volume known as the low wines, then through the spirit still where the resultant spirit is then diluted and left to mature in oak casks. Certain Scottish distilleries, like Auchentoshan, choose to distill the spirit a third time by going through the spirit still again, leading to a triple distilled liquid, a practice more commonly seen in other countries like Ireland. These distilleries who practice triple distillation believe it leads to a smoother and cleaner spirit and, eventually, whisky that is lighter on the palate.
The shape and height of the stills, however, play crucial roles in creating a unique-flavoured spirit. The tall, towering stills of Glenmorangie – who have the tallest stills in Scotland – encourage more copper reaction and prevent heavier flavour compounds from reaching the top and condensing, leaving a much lighter, fruitier spirit. By contrast, shorter stills like those at The Macallan Distillery mean the spirit is heavier and oilier. There is no one correct way to distil and a right ‘style’ of spirit, but distillers all keep to a certain ‘cut’ of the spirit run by only taking the spirit from a specific range of alcoholic strength, as the liquid produced before that – known as the foreshots – are cloudy and contain poisonous methanol, and the liquid after that range – known as feints – usually contain unwanted flavour elements.
The resultant spirit from distillation, known as new make spirit, must now spend the bulk of its time resting in oak casks before it can be legally called Scotch whisky. In Scotland, the minimum period it must stay in casks is three years. It is here that whisky picks up most of its flavour in a process known as maturation. The most common oak barrels that are used in the maturation are American Oak casks (Quercus Alba) which previously contained mostly American Bourbon whiskey, and European Oak casks (Quercus Robur) which previously contained Spanish sherry. Maturation accounts for most of a whisky’s flavour, and so it is little wonder that some companies spend most of their money on buying top quality casks. “With up to 60% of [our whiskies’] colour, character and flavour determined by cask quality, the oak cask is the most prominent factor in ensuring and delivering the quality and style of The Macallan,” states The Macallan’s Master of Wood, Stuart Macpherson.
The flavours that maturation gives the spirit are dependent on both the wood type and the previous liquid that was held in the cask prior to maturation. American oak gives coconut and fresh fruity flavours, whereas European oak gives more sweet, woody and spicy notes. Sherry gives more dark fruit and spicy aromas to maturing spirit. In recent years, distilleries have also experimented with maturing in casks that have previously held liquid such as rum and wines. The Balvenie Distillery, for one, has matured their spirit in Port Pipes that have previously held Port Wine and Glenmorangie’s Artein was finished in Tuscan Red Wine casks. Other distilleries like Benromach have even matured spirit in brand new oak casks, all in the name of discovering how different casks add flavours to whisky. These flavours, however, account for what cask maturation adds to whisky, commonly known as the additive component. Maturation also has a subtractive component, removing harsh alcoholic notes with time, allowing a whisky to be less aggressive and biting with time. This process, however, is totally organic and cannot be controlled unlike all previous parts of the production process. This means the spirit in each cask is ultimately unique, adding to the mystique that whisky has.
With so much variation in the production process, it is no wonder three humble ingredients can lead to a whole spectrum of flavours. No matter what your preferences are, there is most probably a whisky (maybe three!) that will appeal to you. Keep exploring, and you will find that the humble whisky has a lot to teach all of us.
Benjamin Chen is Singapore’s only certified Malt Maniac. He runs whisky blog, www.sgwhisky.com