It is not uncommon to hear that they are ”Vanilla”, devoid of interesting character (and colour!), and generally make for uninspiring whisky. And ”Vanilla” in this regard takes the colloquial meaning of ”ordinary”, ”unexciting” and ”beige”. We’re talking about ex Bourbon barrels, visibly represented by their golden brown to outright pale straw colour it lends the malt whisky, and with the typical signature notes of – that’s right – vanilla in various guises, along with light spicy notes such as ginger, almonds, cream and typically promoting lighter fruity notes.
But what are Bourbon barrels – and are they ”just Vanilla”? For starters, Bourbon barrels represent the most common new cask type to arrive with the malt whisky industry, for the simple reason that they are produced at 53-55 US gallons of volume, from American white oak that has been charred inside – and they have held the maize-based American whiskey called Bourbon once, and once only. Bourbon can only be laid down in new casks of charred virgin oak, while the same restriction does not apply to malt whisky. Thus, once used by a Bourbon distiller, the barrel is sold off to other spirits industries and mainly to the whisky industries across the world.
Are these second-hand barrels ”just Vanilla” then, adding meagre levels of congeners (flavour compounds) as the Bourbon has surely taken much of what they had to offer, including most of the colouring effect from tannins that break down during maturation, leaving a pale yellowy hue for the malt whisky to follow? Yes, but also: No. First impressions can be deceptive. As they are in this case. Malt whisky of a yellowy, often pale, colour is not inferior to a voluptuous dark reddish-brown whisky, since as with most things whisky, reality is far more complex than that. Colour CAN be indicative of certain character treats, but it does not have to be thus and nor does it offer an indication as regards quality. So what does a ”first fill ex Bourbon barrel” do to and with malt whisky, then?
The malt new make spirit that is laid down in cask – in this case the aforementioned Bourbon barrel – will mature in three distinct, parallell manners: additive maturation, subtractive maturation and interactive maturation. Additive means the addition of flavours from the oak to the maturing spirit, subtractive indicates what the oak helps with breaking down from the sometimes somewhat harsh new make, and finally interactive is the slow process of oxidation and reaction among various flavour congeners within the spirit as well as those coming from the oak. To start with the subtractive maturation, this is enhanced by the fact that Bourbon barrels are charred – not ”merely” toasted – on the inside, creating great caramelisation and a charcoal layer inside the cask, which offers an efficient capacity in performing the subtraction in question. Naturally, an entirely new/virgin barrel would be even more efficient in this regard, but that would also have a huge impact on the balance of the whisky, as…
…while the interactive maturation is likely less influenced by the type of cask – the main driver being oxygen from the air that gets inside the cask – the additive maturation is the main signifying difference when chosing to use an ex Bourbon barrel. The American white oak when caramelised will indeed offer loads of vanillin to the whisky; just consider how much a Bourbon noses of vanilla and general old style sweetie shop and you get the picture, although the malt whisky gets a much milder hit of the same notes than the Bourbon did. But there is certainly more. Notes of ginger, cedar wood, almonds, marzipan, coconut, lighter fruits such as green or yellow apples and pears when young-ish and even mangoes and banana when older and let’s not forget the texture which can often become outspokenly creamy. Plenty of different flavour congeners will thus be offered from an ex Bourbon barrel. But dialled down a bit in intensity, which gives the often desirable side effect of allowing more room for the distillery’s spirit character to shine through in the final bottled whisky. A very active cask can even end up completely smothering the spirit character, offering merely a dim backdrop of general ”whisky” character to what is really oak juice. Oak is characterful and can be overpowering unless used with due care!
In relation to a virgin oak cask and also the typical ex wine or Sherry cask, the ex Bourbon barrel will give less additive maturation, yes, but that can be a very good thing as regards quality and also forms a choice when it comes to character, allowing more distillery spirit to shine. What is often done is to allow barrels to mature for a bit longer before bottling, or to use their relative freshness to lighten up a vatting of whisky that is made up of whisky from different cask types. Most useful – and for the better.
And please also do take into consideration that when a whisky professional is offered a choice between different bottlings from a distillery, that professional will almost invariably ask for a sample that has been matured in ex Bourbon casks. Simply due to the fact that they allow more of the distillery character and qualitative ability to shine through. So in conclusion of this rant, it is our firm belief that offering the ex Bourbon cask matured malt whisky at least the benefit of the doubt and thus try it, that is an enlightened choice, not a ”Vanilla” one.