Principal Types of Whisky
- Scotch Malt Whisky: 100% malted barley
- American Single Malt: 51% malted barley, the balance usually wheat or rye
- Irish Pot Still Whiskey: At least 30% malted and 30% unmalted barley plus up to 5% of another grain allowed.
- Bourbon: 51% corn, the balance being either wheat, rye, and about 5% barley
- Rye: 51% rye, the balance being either wheat, corn, and about 5% barley
- Corn: 80% corn, often with malted barley but also rye or wheat
Contribution to Taste
- Malted Barley: imparts a warm, roasted toffee taste to a spirit. Also, nutty, smoky, chocolate or cocoa and often a cereal or toast character.
- Unmalted Barley: Unmalted barley enhances the grain and cereal qualities and introduces light sharp and sour fruity notes like green apple and lemon.
- Corn: Very little flavor comes from the corn, corn’s values lies in its high starch content. But its lower flavor profile allows the taste from the charred oak barrels, i.e. oak sugars and vanillins, to shine through.
- Wheat: fresh honey-baked bready-ness, some slight hints of mint, smooth out a whisky.
- Rye: notes of cinnamon, nutmeg, and other baking spices such as black and green pepper, anise, mint and, also enhances clove and nutmeg flavors from the barrel.
A water’s purity is critical. Water sourced from a clear mountain spring compared to chlorinated water sourced from a municipality will impart a different weight and mouth-feel to a whisky.
Not only is the purity of the water important but its mineral content and pH play a critical role in determining the quality of the whisky. For example, water used to create a Scotch from Islay often has a distinct briny, medicinal taste due to the higher iodine content of the nearby seawater. Compare that to a Kentucky Bourbon sourced from water filtered through limestone thus having a higher concentration of calcium and magnesium.
But it’s the presence of those elements we detect, not the water itself.
However, water forms the solution in which the complex chemical reactions necessary to make whisky occur. Therefore, the quality of the water is important throughout the whiskey-making process: from the moment grist (grain) is added to warm water to the bottling of the finished product.
But it is worth keeping in mind that the water goes through a distillation process. At that point, it’s the alcohol compounds imparting the majority of a new-make spirit’s taste. The water content has dropped considerably.
Regardless of its contribution to taste, it stands to reason that good water is essential for good whisky
Distillers mix ground grain (grist) and warm water to create a mixture referred to as mash. When held at a consistent temperature, the starches within the grains break down into sugars. They then add yeast to the mixture and an anaerobic process begins wherein the yeast multiplies rapidly and consumes all the free oxygen. Once the yeast depletes the oxygen, it sets about ingesting the available sugars and excreting ethanol, an alcohol compound.
There are over 1,500 species of yeast, but
S. cerevisiae is the principal yeast used in fermenting mash for whisky production. That’s not to say all the yeast used in making whisky is the same, far from it. There is a multitude of strains, each with varying characteristics.
Some American, Canadian and Japanese distillers spend a lot of time and money cultivating proprietary yeasts. However, the Scots and the Irish place less emphasis on yeast strains and tend to use a handful of yeasts derived from the common “M” strain, introduced to the Scotch industry in the 1950s.
While many distillers believe the yeast has only a minor impact on taste, many of the new artisan distillers are experimenting with a wide range of yeasts including wild yeasts endemic to the region wherein the whisky is produced.
Only time and experimentation will reveal a yeast’s effect on taste.
Types of Oak Used
- American Oak– American White Oak (Quercus alba) is used in the production of 90% of the world’s whiskey. The Scots and Irish rely on used Bourbon barrels. Whereas Bourbon distillers are required by law to use “new” charred barrels.
- European Oak– European Oak (Quercus robur) commonly used for wine, Sherry and Port. Whisky distillers primarily use European oak casks to finish whiskies after they have been aged in American White Oak.
- Japanese Oak– Japanese Oak (Quercus mongolica), is prone to leaking and damage during storage but is popular with Japanese distillers. Typically, Japanese distillers first age their whisky in sherry (French oak) or bourbon (American oak) barrels, then transfer it to Japanese oak towards the end of the process.
Oak Barrel’s Impact on Flavor
- As the seasons change the whisky expands and contracts. During this process, charred wood removes undesirable compounds (sulfur) and imparts new flavorful chemical compounds.
- Oakwood extractives include two different natural isomers of oak lactones. The cis-oak lactone gives a sweet coconut-vanillin aroma. The trans-oak lactone is spicier (cloves, celery, incense). Wood contributes other lactones described as fruity, peach-like and vanillic.
- Distillers employ used Bourbon barrels to age the majority of whiskies, Scotch, in particular. However, distillers often use other types of barrels to “finish” their whisky. These include wine barrels (contributing flavors = red berry, cherry, and plum), Sherry barrels (contributing flavors = dates, walnut, sultana), Port barrels (contributing flavors = Berry fruits, red currant, sultana), Maderia barrels (contributing flavors = Sweet fruits, figs, spice), and even rum barrels (contributing flavors = molasses, vanilla, tropical fruits) barrels to “finish” (add another taste dimension) a whisky.