As far as I knew, whiskey had to be aged in oak barrels/casks/butts. But I recently learned more about this, from the Liquid Irish blog, by David Havelin. He pointed out that in Ireland, the law only states that it needs to be made in wood casks, So what is the law for the countries that have historically made whiskey, and the European Union? Ireland, Canada and the European Union allow any kind of wood (although, in practice, distilleries almost exclusively use oak wood.)
Scotland – “which has been matured in an excise warehouse in Scotland in oak casks of a capacity not exceeding 700 litres, the period of that maturation being not less than three years”
Ireland – “subject to the maturation of the final distillate for at least three years in wooden casks, such as oak, not exceeding 700 litres (185 US gal; 154 imp gal) capacity.”
“Technical file setting out the specifications with which Irish whiskey / Uisce Beatha Eireannach / Irish Whisky must comply.” Food Industry Development Division Department of Agriculture, Food and the Marine October 2014.
The earlier Irish definition is from Irish Whiskey Act, 1980, which stated “the spirits shall have been matured in wooden casks – in warehouse in the State for a period of not less than three years”
Canada – “shall… be aged in small wood for not less than three years”
United States – Straight Whisky ” and stored in charred new oak containers for 2 years or more”
European Union (EU) – “maturation of the final distillate for at least three years in wooden casks not exceeding 700 litres capacity.”
REGULATION (EC) No 110/2008 Of The European Parliament and of the Council of 15 January 2008 on the definition, description, presentation, labelling and the protection of geographical indications of spirit drinks and repealing Council Regulation (EEC) No 1576/89. Annex II Spirit Drinks
From the Liquid Irish blog, by David Havelin
There is a little extra wiggle room in the definition of Irish whiskey compared to Scotch. Whereas Scotch must have been aged in oak casks, Irish whiskey regulations specify simply that the casks must be wooden.
It has only been of theoretical interest up to now, because in practice oak is exclusively used in Ireland. But they are curious folks at Midleton and because they could, they did. Seven chestnut casks were commissioned from a cooperage in Bordeaux. The wood is sometimes used for wine in Europe.
I learned, by the way, from Master of Maturation Kevin O’Gorman, that the sweet chestnut tree involved here bears no relation to the horse chestnut tree we are more familiar with in Ireland. It is, rather, a first cousin of beech and oak, and grows reasonably straight and knot-free, making it suitable for coopering.
The seven toasted virgin chestnut casks were used to finish a medium style pot still whiskey for 12 months. There are 900 cases in this batch but there are more casks being filled so if it’s well received, we’ll see it again.
When Midleton Dair Ghaelach was released, the distillery boffins noted the higher contribution of furfural and vanillin from Irish oak, compared with American or Spanish oaks. These are credited with imparting enhanced vanilla, caramel and chocolate flavours. According to Kevin, the levels of these compounds in sweet chestnut are higher still.