Wood work

how distillers changed their barrel policy

Improved wood management among distillers has had a big impact on quality in recent years. Dave Broom takes us into the mysterious world of charring, first-fill and Quercus alba to tell us how they’ve done it

He’s got good wood’. On the face of it, it’s not a phrase that you’d normally expect to hear at a distillery – and until relatively recently you probably wouldn’t have. The fact is, with a few notable exceptions, most producers of aged spirits paid precious little attention to the quality of the wood they were using for the maturation process. ‘If it’s frae a tree we’ll use it’ was too often the default setting for the scotch industry.

These days, however, the picture has changed utterly. A distillery tour these days will often spend more time in the warehouses discussing wood policy and wood management than it will do looking at the stills.

Why the change? There are numerous, interlinked, factors: the growth of premium, the demand for extra-aged spirits, all of which are underpinned by a realisation that if a spirit gets up to 70% of its final flavour from the interaction between the liquid and the oak in which it is aged, then you had better pay attention to the quality of the latter part of that relationship.

WOOD MATTERS

To be fair, much of the research into this was done in the 1970s, but things move slowly in aged spirits: there are new casks to buy, accountants to persuade, techniques to try and recipes to perfect, and it has really only been in the past decade that we have begun to see the results of this greater attention. The changes in weight and aromatic complexity in Glenmorangie, Glenfiddich, Glenlivet and Jameson are a clear manifestation of better wood management, and while spirits are still playing catch-up with the wine industry, the gap is closing.

The improvements go right back to the start of the process and distillers now must ask themselves a number of key questions. First, pick your tree. What species of oak are you wanting to use (see box below), and where is it growing?

Then, how are you going to season the wood? Kiln drying is quicker, but can give acrid aromas, so there is a shift towards the slower air-drying process. Now make your cask, but ask yourself: what levels of toasting are you wanting?

The wine guys have known about toasting levels creating different aromas for many years, and now that knowledge is slowly filtering into the spirits industry. Are the heads going to be toasted as well? If you are a bourbon producer, what level of char are you then going to apply to the barrel? Again, this will have an effect.

What toasting does is prepare the barrel for use, as the heat caramelises sugars and creates other flavour components: all of that vanilla, pine, spice, chocolate, wood smoke, dried fruit, clove and resin which will be leached out of the wood during the long ageing process. You now have a reservoir of flavours available to you.

Now you can put your spirit into the cask. Three things are going to happen to it as it matures. Firstly the cask will help to remove any aggressive elements from the baby spirit, like sulphury notes, for instance. The charcoal layer on the inside of the cask mostly does this. At the same time the spirit, moving slowly in and out of the wood, begins to leach flavours from it: vanilla for example. Then, after a period of time, those flavours begin to meld together creating new and more complex aromas, until it is hard to say where spirit ends and wood begins. It is this magical interactive process that premium aged spirit producers want.

This process happens within any cask, but the rate at which it happens will vary. Why? Because the first time the cask is filled the flavour reservoir is full – there are masses of flavours for the spirit to absorb; the second time it’s filled that reservoir is a little lower and so on through each subsequent fill until the cask is no more than a neutral vessel with nothing to give (at this point the cask can be re-charred).

IT'S ALL IN THE CASK

This understanding of how active a cask is at various points is crucial to the character of your final spirit. A cask filled for the first time will mature more quickly (in actuality become more woody) than one that has been filled once before. That big hit of flavour might be handy if you want to release your spirit at five years, but not so great if you want to keep it there for 20 and for it to show individuality.

Equally, you might have aged in a knackered cask for 20 years and have ended up with a spirit that is, effectively, immature. This is why an age statement is not a determinant of quality – it simply shows how long the spirit has spent in cask. It’s the cask’s personality that matters.

Cognac (and rhum agricole) producers have a clever way of getting round this. They mature in new barrels for a short period, to absorb the wood-derived flavours, then they decant into older casks for a slower maturation. Scotch producers have to create a recipe of barrels: ‘first-fill’ (because scotch producers use second-hand barrels, ‘first-fill’ means the first time its been filled with scotch) and ‘second fill’, to achieve their balance. Bourbon producers are in a trickier position as they can only use brand new barrels, so balancing wood and spirit is done here by positioning in warehouses: the hotter the spot the ‘faster’ the maturation, the cooler the ‘slower.’

It’s an understanding of all of these possibilities that is improving the quality of aged spirits. The better your wood, the more pleasurable the result will be. Now there’s a maxim for life.

Note: A barrel is a specific size of cask measuring 200 litres. All barrels are casks but not all casks are barrels.

WHICH WOOD?

Firstly, why oak? Quite simple. It works. It is strong, it is easy to cooper, it allows in air, yet is water- (or for our purposes alcohol-) tight and, most importantly, it gives flavours to the spirit. Yes, other types of wood are used in maturation: ash gives a discreet, shadowy effect to grappa, but evaporation rates are very high; chestnut was used by the scotch trade up until the 1960s (though now oak is the only type of wood legally permitted) while there have been experiments with cherry, but its bitterness quickly overpowers spirits and cannot be used for long-term ageing. So… oak it is. That, however, still allows a distiller many flavour-led options as each of the main sub-species use in coopering gives a very different effect.

QUERCUS ALBA (aka American white oak).

Grown across America with the main managed forests being in Missouri, this is the most widely used oak-type used in scotch, rum, tequila... and bourbon. Growing tall and straight, Quercus alba is high in vanillin, oak lactone and is relatively low in mouth-drying tannin. Spirits aged in Quercus alba therefore tend to be softer with vanilla characteristics (the vanillin), as well as coconut (those lactones) but also notes of pine sap, chocolate, and sweet spices such as cinnamon.

QUERCUS ROBUR (aka European oak)

This was used by the sherry industry for

shipping casks, which ended up being used for scotch – hence its more common name ‘sherry wood’. Also used in armagnac. A more porous wood, Quercus robur has higher levels of tannin (giving greater grip) and colour extractives (a darker reddish/mahogany hue), lower perceptible vanillin but higher levels of other compounds, which are reminiscent of clove, resin and dried fruit.

QUERCUS PETREA (aka Sessile oak/French oak)

The oak type preferred by the cognac industry, in flavour terms, Quercus petraea occupies a mid-point between the first two; having the vanillin hit of Quercus alba, some of the grip of Quercus robur, but also a more intense almost bitter spiciness that takes it into cardamom territory.

QUERCUS MONGOLICA (aka Japanese oak/mizunara)

Unseen out of, well, Japan until relatively recently, Quercus mongolica wasn’t even particularly liked by Japanese distillers because it was hard to cooper and prone to leaking, but was pressed into service because they couldn’t get access to casks during and immediately after WWII. Now, however, there is real interest as Quercus mongolica gives an extraordinarily intense aroma akin to Japanese incense (made of aloeswood/agarwood and sandalwood) as well as coconut. Rare.

SIX OF THE BEST

GLENMORANGIE

Along with Edrington (see below) this scotch distiller was at the forefront of both research into and adoption of a tightly controlled wood policy. Under its distilleries director Dr Bill Lumsden, it has concentrated its work into Quercus alba (as well as other sub species such as Swamp and Post Oak) and now has bespoke barrels made specifically for its own requirements. It was also a pioneer in terms of ‘cask finishing’ and the use of new (ie not second-hand) barrels. The entire range was reformulated in 2008 and is the best place to explore the flavours derived from quality American white oak.

EDRINGTON GROUP

What Glenmorangie is to Quercus alba, Edrington is to Quercus robur. Its master of wood is ‘Don’ George Espie who has overseen a policy which has concentrated on improving the quality of ex-sherry casks, to the extent that the firm now has a close relationship with a cooperage in Jerez (with access to forests in Galicia) which makes bespoke casks for Macallan and Highland Park. Espie’s research into Quercus robur is now bearing fruit at Ron Brugal in the Dominican Republic, in which Edrington has a majority stake.

(We cannot leave scotch without mentioning consultant Dr Jim Swan whose research into wood in areas such as toasting continues to create new levels of understanding into maturation and flavour development).

IRISH DISTILLERS LTD (IDL)

In many ways IDL is the unsung hero of the wood revolution. It could be argued that under its master of wood Brendan Monks, IDL was ahead of its colleagues in Scotland in imposing a quality-oriented wood strategy. Like Glenmorangie and Edrington, rather than buying on the open market, IDL prefers to use bespoke casks made to Monks’ specifics – as well as ex-bourbon and ex-sherry casks (and new wood) this also includes port pipes and Madeira casks. The whole IDL range has benefited from this – go no further than the Jameson range.

SUNTORY

New wood, ex-bourbon casks, ex-sherry casks... Japan’s largest distiller has them all, but it is its research into Quercus mongolica that elevates it into my Top 6. The discovery of some old Japanese oak casks from the early 1960s at the Yamazaki distillery has opened up a new world of flavour opportunities for the firm – just at the time when Japanese single malt was beginning to be recognised globally. Now, mizunara is used as a component in many of the firm’s single malts and blends and it has established a plantation in Hokkaido. In addition, the firm’s Yoshi Noguchi is currently researching mizunara’s properties at Heriot-Watt University.

FOURSQUARE

Though this may be a wild generalisation, it’s widely agreed that rum has, until recently, still conformed to the old Scotch attitude of ‘anything goes’ when it comes to barrels. The lack of an aged category and the concentration on bulk shipments has resulted in the wood being pressed into service in many distilleries failing to be of the best quality. That has now changed. At the forefront of this new scientific, quality-oriented approach to wood and maturation policy is Richard Seale at Foursquare in Barbados. He is currently experimenting with ex-sherry, madeira and French oak as well as tightening up his policy of American oak casks. The results are remarkable.

REMY-MARTIN

The cognac house has a head start when it comes to wood policy as it has a controlling stake in the prestigious cooperage Seguin-Moreau, which has been instrumental in gaining a greater understanding of oak. Its research, both in-house and with the oenology department of the University of Bordeaux, has benefited both the wine and spirits industries in numerous ways, though it’s worth highlighting its discoveries in flavour creation from specific toasting regimes and the development of the U-Stave™ process, where grooved staves increase the surface area of wood in contact with the liquid (be it wine or spirit).

Editorial feature from Imbibe Magazine – March/April 2010