Without cask ageing, whisky would be just a common distillate

I don't know if I've told you but, besides wood, I have another passion. I want to know as much secret about how alcoholic beverages are made, how they get their particular flavor. After all, they are all products of distillation. I learned a lot of interesting stories about whisky from my life partner, a true encyclopaedia on the subject. I know a lot of interesting stories about whisky which I promise to tell at some point. But now I want to combine my two passions and tell you about the influence the whisky cask has on the final taste. Experts say that without that barrel aging, whisky would be just a banal distillate.

First of all, the barrel

The whisky cask has a determining influence on taste. It is virtually all the elements that make up the taste we perceive. Scientists have discovered that there are substances in the wood that even very small amounts, such as ppm (parts per million) or even ppb (parts per billion), can alter the taste.

Despite the advent of all sorts of machines that process wood, barrels are still made by hand. The wood used for whisky casks is American white oak or European oak. American oak is faster growing and rich in fine flavors. European oak is slower growing, has harsher flavors and is rich in tannin. The wood must be between 70 and 200 years old. American oak should not be cut under 70 years old, and European oak under 100 years old.

Cutting dock planks can't be done anyway. The pore direction must be upwards and the radial vessels must not cross the plank. If not cut this way the alcohol evaporates easily and the barrel may start to drip. After cutting, the planks are dried to an equilibrium moisture content of 10%. The way drying is done, naturally or in dryers, does not influence the quality of the barrel.

Burning the barrel

Casks made from the wood that has reached the above stage can only be used for storing whisky. For maturation it must be heat treated. The treatment is done in 2 stages. In the first stage the wood is kept in special ovens at 200°C for 30 minutes. During this time the cellulose in the wood partially decomposes into sugars which are caramelized, and the lignin is partly converted into vanillin. This wood is used to make the barrels, which are then put through the second stage of the treatment. They are burned for 3-5 minutes after which the fire is extinguished with water. This activates the wood to release the flavors.

If you cut into a treated barrel, you will see on the inside of the barrel, first the layer of burnt wood, then a ring of reddish wood. That's what they call it - a red ring. This is where the whisky will extract its flavors.

Whisky maturation

New, freshly distilled whisky has a metallic and astringent taste. This taste disappears with barrel maturation for 5-8 years. That's why there are few whiskies aged less than 8 years. From the moment it is put in the cask it begins to extract vanilla, caramel and oak flavors. Over time, these flavors begin to intertwine with the distillate's qualities from the type of malt used.

If whisky is put into American oak casks, the longer it sits, the more refined it becomes. This is not the case with European oak. Kept for more than 8 years, it takes on an unpleasant taste because of the tannins and is virtually undrinkable. In this case a trick is used. After 8 years, it is moved to European oak barrels in which it has been aged and kept for another 1-2 years, during which time takes on new flavors. But such a treatment can only receive first-fill whisky.

In the past barrels were used only once for maturation. Due to increased production and decreasing wood resources, they started to be reused. A barrel can be reused a maximum of 3-4 times, after which it loses its flavors. The best quality whisky is first-fill, which is specified on the label.

Lately, a way has been found to make barrels more usable. The treated layer, that red ring I was talking about earlier, is removed and then the wood undergoes the same treatment again. The process is called rejuvenation and is supposed, because not enough time has passed yet, to extend the life of the barrels by up to 50-60 years.

When you want to buy a special whisky to taste with friends, it's a good idea to look for as much information as possible on the label. This will help you make the right choice and make the tasting a success.