Burning a barrel’s interior primes the wood and makes it easier for the spirit to interact with different components:
– Hemicellulose breaks down into toasty caramel notes, colour and aromas
– Lactones add woody, coconut-like notes
– Tannins become less astringent when exposed to heat
– Lignin breaks down into flavour molecules, like eugenol (spiced/cloves) and more famously, vanillin (vanilla).
But toasting and charring are two different burning procedures.
Toasting is a slower process. It involves gently heating the barrel’s interior over an open flame so that the heat penetrates deep into the wood, which takes on a dark brown colour as it mellows.
Charring gives your barrel a burnt interior, like a campfire log after the fire. The carbon in the ash is the filter that takes the edge off your liquor. Charring also imparts darker colours and sweeter flavours since the intense heat caramelizes the wood sugars and releases more compounds that will leach into your spirit
A barrel’s char level can range from No. 1 (medium char), which gives you a mix of complex flavours and aromas, to the greater char depth of a No. 4, which yields a bold and intensely smoky spirit.
Our American oak aging barrels have a medium char. Check out this blog post about the difference between toasting and charring an oak barrel to learn more!