How Does Charring and Toasting Affect Our Whisky?
Crafting the best spirit needs patient control over the toast and char of the wood used in maturation vessels. At Spirit Thief Distilling Co, we trial different char, and toast levels in our casks for each one of our releases, allowing for different personalities to be imparted into the whisky, tailoring to each unique flavour profile. The simple art of charring and toasting, accentuating the nature of the wood itself to create the perfect union between wood and whisky.
The method for charring and toasting barrels differ in the amount of heat that is applied, and how. Charring occurs at a much higher temperature compared to toasting, and both accomplish different things. We apply both methods to our casks, and at different levels, find the personality and flavour profiles we require for each of our distinct offerings.
Toasting in Oak Barrels and Casks
Toasted oak barrels and casks are heated much more gently, resulting in a dark brown toast character rather than a much darker char. Toasted barrels add notes of vanilla flavour to the whisky, as well as spicy accents.
Charring in Barrels and Casks
The process of charring barrels and casks is different from toasted barrels primarily due to the fact that the wood staves of the cask are changed more, building a deeper flavour profile. The inside of the barrels are charred, imparting a much darker colour.
Charred casks can impart sweeter flavours like caramel and honey. Ageing whisky in charred barrels results in a smoother, mellower flavour, but why does the level of char affect the characteristics of a whisky?
The Effects of Charring
Charring, and toasting oak barrels and casks, is an important process in whisky making, as it allows the liquid to interact better with the wood. It introduces subtle openings in the oak staves, increasing the surface area, allowing more flavour to be drawn out and infused into the whisky.
There is a small group of compounds that influence the whisky’s characteristics that we are interested in through this process. There’s cellulose, hemicellulose, lignin, tannins, and oak lactones. The extent to which you char a barrel will have an impact on the concentration of the last four and how they affect the flavour profiles.
Hemicellulose is one of the most important components of American oak, while having a smaller influence on French oak. Air drying, or “seasoning” starts hemicellulose’s breakdown into simple sugars. During the heating phase at 150°C, more simple sugars form, then at 300°C the hemicellulose will break down and start caramelising on the wood’s surface. If you’ve ever enjoyed a whisky with notes of brown sugar, caramel, or toffee, hemicellulose is the compound you can attribute that to.
Lignin is also very important, when heated it breaks down into its constituent parts: vanillin (aka vanilla flavour) and spice. The same thing happens with the concentration of lignin, the more a barrel is charred, the more the lignin yields vanillin and spicy flavours, adding warmth and cinnamon notes to the liquid. Lignin and vanillin have a larger presence in French oak compared to American oak.
Oak lactones, these compounds are present in many species of oak tree, but in higher volume in American oak. These lactone compounds are responsible for the woody/coconut flavours you’ll find in many whiskies. The higher the char, the less the impact of the oak lactones.
Tannins are the dark horse of red wine and whisky pairing, influencing bitterness and mouthfeel. Well before the oak barrel is charred, the oak itself is “seasoned,” allowed to dry out to get rid of the harsher tannins. Those left over are essential for successful long-term maturation. In Spirit Thief casks, the different red wine varieties impart different tannin levels in the oak, contributing to the different textures and mouthfeel in the whisky.
The Future
We plan to continue collaborating with winemakers across the country, and to continue trialling different cask toast and charring levels, even the strength at which our spirit enters our casks. We feel we’ve only just begun to scratch the surface of possibility when it comes to marrying the characteristics of wine and whisky.
