In the Beginning
Without the marriage of charred wood with Poitín, there would be no whiskey as we know it. Back in the depths of time, the raw material distilled from alembic or pot stills, was most likely stored in whatever barrel happened to be available. Back then, there were not a lot of storage options. One had clay pots, metal (which was expensive) and wooden barrels. In Ireland, one of the earliest distillers of Poitín, barrels would have been made from Irish Oak. Unlike today, with its vibrant green fields, Ireland was covered in native oak forest and many a ships hull and coopers barrel would have been made from that wood. The other options, generally available to Convents and Monasteries, would have been old wine, brandy and sherry casks shipped over to appease the nuns and brothers. What to do with those empty barrels that once held Spanish Sherry or French Brandy? Why reuse them to store that Poitín Brother Willibald insists on making. Store some raw Poitínin a sherry cask, and suddenly that raw alcohol takes on a delightful colour and flavour. Viola! Whiskey.This is an important point, Whiskey comes out as a clear liquid and is called Poitín(pronounced pooch een, it’s Irish, don’t ask) Moonshine, Mountain Dew, the Devils Spittle and a variety of other quaint names. What provides that distinctive colour and flavour is the wood of the barrel and whatever was previously inside that barrel before Poitínwas added. I know, there are many distilleries that use Caramel Colouring (or E150a) as a way to deepen the colour of their product but we won’t go into that right now. If you are interested read Emily Bell’s informative article on the subject.
First, heat the wood until charred
American Bourbon is traditionally stored in in virgin American Oak casks (Quercus alba) and those casks may only be used once. Sherry and Brandy are traditionally aged in European oak (Quercus robur). Originally, early vintners and distillers used whatever barrels were available, whether it be made of chestnut, pine or oak but the tight grain and durability of oak became the coopers wood of choice. Now in order to construct a barrel, the staves of wood must be heated to be bent. Traditionally staves were heated over a fire and when that happened wood became ‘toasted’. This toasting allows multiple different chemical reactions to occur. Oak contains cellulose, hemicellulose, and lignin. The first gives oak its strength, the second two, when heated, begin to break down and create flavour compounds which are soluble in ethanol that slowly leach out adding delicious flavours to the spirits.The Hemicellulose in oak wood contains sugars which caramelise during toasting, giving flavours of nuts (walnut, almond, hazelnut, marzipan) as well as sweet notes of caramel, liquorice and on occasion butter.Lignin is transformed into a wide range of flavours which are slowly released into the spirit throughout maturation, adding in floral elements, spice (cinnamon and clove especially), vanilla, chocolate, fruity elements, and green notes.The oak also contains tannin which helps to carry colour and two types of lactone (commonly known as ‘whisky lactones’). Cis-methylloctalactone provides sweet ‘oaky’ flavours, while Trans-methylotalactone gives a spicier quality and helps to boost the coconut flavour. In order to pull different flavour profiles from wood, barrels are usually burnt or Charred, to 4 different levels, each level of char imparts a slightly different flavour. The deeper the char, the more the wood is accessible to ethanol.
Level 1 char is usually used by home distillers and quick ageing bourbons. Since charring makes it easier for ethanol to leach flavonoids from the wood, a level 1 char is normally not used by most distillers.Level 2 char brings out a level of sweetness and light caramel flavour as well as colour. A few distilleries, like Deerhammer, use a level 2 char for lighter notes of caramel and vanilla.Levels 3 and 4 char are the most common for American bourbons and whiskeys. As the spirits are aged in these higher-level chars, the alcohol develops a more earthy and spicy flavour. Level 3 often has more of a natural wood taste and scent, while the longer chars introduce a deeper colour, vanilla tones, and caramelization. Level 4 char, also known as the Alligator char, because the inside of the barrel is cracked, allows deep penetration of the alcohol into the wood. The higher charcoal also reduces some of the tannin flavours. The spirits pick up more vanilla notes but also a smoky tinge that balances the sweet notes.
In the past, old barrels that previously were used to hold pickles, meat or fish were charred to clean out the insides so they could be reused – waste not want not! In todays world, barrels are still reused and are in such high demand, there is a world wide trade in previously used barrels. Luckily for whiskey drinkers, the barrels used today have been previously used for ageing other spirits and not something like herring. I have already touched on American oak being used for bourbon maturation. Since American bourbon needs to be aged in new American oak casks, those cast off bourbon casks are in high demand around the world as the first step for other whiskies. Sherry and port casks fetch high prices from distillers looking to add sweet notes to their whisky. Whiskey will pick up the flavour profile of whatever was previously stored in that cask along with the flavour of the wood. So red wine, champagne, sherry, rum each alcohol can add subtle (and not so subtle) notes to a whiskey as whiskey is aged in first one cask, then transferred to another. Alternately whiskeys will be stored in different casks then blended together to form a completely new flavour profile.
The Mighty Oak
American Oak is hugely popular in the wine and whiskey industry. Quercus alba matures relatively quickly, has a tight grain structure and has high levels of vanillin and oak lactones. The tight grain structure releases tannins more slowly, hence whiskey can be stored for longer without picking up overly woody flavours. Many whiskies start their maturation process in American oak ex-bourbon casks. The American Oak industry has a forestry plan for the next several decades so is a renewable resource as well.European and Japanese oak have recently gained renewed popularity as they impart subtle but different flavours not found in Quercus alba. Quercus petraea and Quercus robur both called a variety of common names but native to Europe, contain higher levels of tannin and darker, spicier notes including chocolate. Midleton has come out with their Dair Ghaelach, finished in charred oak barrels made from native Irish oaks (Quercus robur). Irish oak contains higher levels of some lignin derivative compounds, such as vanillin, vanillic acid, and furfural which further enhance the whiskey with vanilla, caramel, and chocolate flavours. I can attest, the flavour profile of Dair Gaelach has deep and complex notes of chocolate, spice and a pleasant richness. Swedish distiller, Mackmyra, has come out with Svensk Ek, finished in Swedish oak casks. Svensk Ek is the brain child of Master Blender Angela D’Orazio. “Generally, if you describe them, they are like a cigar box,” D’Orazio says. “They are like an oriental perfume. So you have a lot of exotic wood notes, sandalwood, cedar wood, peppery notes. You have tobacco leaf notes. You have ginger notes, cardamom, cinnamon. This oak has less sweet, vanilla tones and more rougher spices than the American oak.” (source Vine Pair, Whiskey Makers Explore the Weird World of Alt Oak Species by Evan Rail). Glenmoragie has used various oaks including Garry, Bur and an unspecified oak from the Black Sea region.Japanese oak, especially the Mizunara oak (Quercus mongolica), are in such high demand, barrels regularly sell for over $6000 per barrel. The flavours this wood imparts are said to be banana, coconut, sandalwood and incense. Suntory has had excellent success with its Yamazaki aged in Mizunara. The Yamazaki Single Malt does include a complex and delicious flavour profile and is one of my favourite whiskeys.Bainbridge Organic Distillers in Washington, uses smaller mizunara casks 10 – 15 gallon, very different to the much larger puncheons (70–100 gallons) used in Japan. The smaller size means that the whiskey comes into greater contact with the wood, so notes are imparted faster. The inclusion of Japanese oak and the longer ageing time help provide their Yama whiskey with notes of coconut, grain and spice. Chichibu distillery in Japan has gone further, using wash back barrels (where wort is fermented) made of Japanese oak. However whiskey needs time in any cask in order to be infused with the subtle flavours inherent in the wood. So whiskies aged for only a matter of months in special casks may not hold the promised notes of flavour.Some distillers have started using Garry oak, Quercus garryana, an oak native to the Pacific Northwest of America. Westland distillers is at the forefront of this movement with their release of Garryana whiskey. Garry oak has a distinctive profile, “incredibly charismatic, you know it immediately when you taste it. The key indicators are molasses, dark toffee, coffee grounds, blackberry jam, wood smoke, and clove. It’s all very dark, spicy, rich, and complex,” Westland distiller Mathew Hofmann says (source Whiskey Advocate Dec 1 2016). Garry oak contains an unusual amount of phenolics, a compound responsible for smoky flavours normally obtained by using peat fires. But think savoury smoky like a good southern BBQ.Coopers and distillers have been talking about Oak Tree Terroir. As if there is not enough complexity in the industry. The Quercus robur grown in Ireland and used by Midleton is different then the Quercus robur grown in Spain. “Irish oak shows lower density and higher porosity compared to Spanish and American oak, which leads to a more open structure and allows more compounds to be extracted into the spirit and at a faster rate,” says Midleton’s O’Gorman. (source Whisky advocate Why and How Oak Matters in Whisky by Jake Emen Aug 29, 2017).You will notice I have spent a fair bit of time on oak casks. This is because in order for a product to be granted the label Scotch Whisky, that product must be aged in oak casks. America has similar laws dictating American Bourbon must be aged in virgin American Oak casks. However Canadian, Irish and Japanese whiskey have no such restrictions. They only require the barrels to be made of wood. Therefore, in this age of expanded experimentation it is exciting to see whiskey maturing or finishing in different wood barrels. That being said, Belfour Spirits in Texas has taken a giant step and used Texas Pecan wood barrels to finish their Bourbon whiskey after the normal American oak maturation. The pecan wood added notes of brown sugar and roasted pecan nuts. Definitely one to watch.
I have been particularly interested in the distillers that use different woods such as Acacia, Sweet Chestnut and Cherry. Oak wood contains a fair amount of tannin, which adds a definite flavour to whiskey. Other woods lack the strong tannin profile but add other interesting notes based on their chemical compositions. The tight grain of Acacia tends to restrict the transfer of flavour chemicals to alcohol so char and longer maturation would be needed to get those profiles. A delightful study came out comparing the different polyphenols that can be extracted from oak, cherry, acacia, chestnut and mulberry. The main wood species used for making barrels is oak, but in particular cases also acacia, chestnut, cherry and mulberry. In this work, polyphenols contained in the extracts of these wood species obtained by solutions of 50% hydroalcohol as well as a model wine were studied and compared with the extracts from oak. The hydroalcoholic extracts of chestnut and mulberry had higher total polyphenols, followed by cherry, acacia and oak, respectively. The oak model wine extract had the highest percentage of polyphenols extractable by the wine, followed by chestnut, acacia, cherry and mulberry, respectively. Chestnut extracts had the highest percentage of oxidizable compounds, followed by acacia, oak, mulberry and cherry. The GC/MS–EI profile of 50% hydroalcoholic extracts revealed as principal volatiles several benzene compounds containing a guaiacol residue, and high contents of C6–C18 fatty acids. To our knowledge, this is the first study reporting on polyphenolic and complete volatile compounds characterisation of these woods for oenological purposes. (source Rosso, Mirko & Cancian, Davide & Panighel, Annarita & Vedova, Antonio & Flamini, Riccardo. (2009)Meant for the wine industry (oenological is science for vintners), the use of 50% hydroalcohol means these can correlate to a degree for use in the distillation industry. Of course just because one can extract a lot of flavours from any particular wood, doesn’t mean those flavours will be pleasing. More is not necessarily better. However I am choosing to hold this research up to justify my love of the Method and Madness chestnut casks single malt due to it’s complex and rich taste. Bushmills took Acacia, normally used for white wine in France, Italy, Spain and America, and matured their single malt in acacia barrels. The result is an oily, complex and pleasant whiskey. Tasting notes include lemon and orange peels, incense, white pepper, baking spices and a mix of richness with a sharper, astringent side from the acacia (source Bushmills exclusive acacia wood by Jake Emen). I enjoyed this offering from Bushmills and found there was a lighter tone of resin incense like Frankincense or Copal with a unique green leaf astringent flavour that cut the usual caramel and vanilla. Midletons Method and Madness range went farther. Their line used a variety of different woods to finish off a medley of unique offerings. There is an Acacia wood and a limited bottling used Wild Cherry Wood. Limited because the distillers found the cherry wood to be so absorbent the barrels ended up soaking up too much of the whiskey stored inside. Talk about an Angles Share! In addition to unique woods there are Method and Madness whiskey finished in Hungarian oak, French Limousin oak and Spanish Oak from Galicia. Now of course all of these whiskies are first placed in American Bourbon barrels for maturation, then in other casks such as sherry so the finishing in these different wood casks simply adds a layer of complexity to an already complex product. When tasted side by side, I did notice there were substantial differences in taste between some of the whiskies (the Chestnut and Cherry stood out, the cherry not necessarily in the best way). Between the oaks, I found the differences were more subtle.Japan, specifically the Ariake cooperage, is actively encouraging their distillers to use unique woods including native chestnut, native Japanese cherry and native Cedar. Nukada, a growing distillery started by the Kiuchi brothers, has been experimenting with some wild combinations, definitely a distillery to watch. Tsunuki distillery is using cherry sealed with fermented persimmon pulp. While Nagahama distillery is currently using cedar, cherry and chestnut barrels.At some point I will need to write about the use of ex-Sochu and ex-umeshu casks in whisky finishing in Japan. Those different flavour profiles go a long way to creating the unique flavours found in many Japanese Whiskies.With all the experimentation going on, I’m sure I have missed something. But that is the fun of continuing whiskey tasting and education. Let me know if you know of any distilleries doing fun experiments with different wood barrels. It will be interesting to see what happens in the next few years.