Before the global pandemic ground international travel to a halt, anyone passing through an airport duty-free store would probably have noticed Glenfiddich making quite a lot of noise about its latest high-profile release: the 23-year-old expression called Grand Cru. Named for the influence imparted by partial maturation in ‘French cuvée casks’, the launch of Grand Cru also marked the creation of a new ‘Grand’ collection of venerably aged Glenfiddich expressions, which will include the rum-cask matured Gran Reserva 21 Years Old and a third whisky, also aged for more than two decades, that is expected to appear in late 2020 or early 2021. This new ‘Grand’ range will sit apart from the Core range (12, 15, and 18 Years Old) and is also distinct from the distillery’s Experimental family of spirits, which includes Project XX, IPA Experiment and Winter Storm.
The observant will also have noticed that the practice of borrowing terminology and, by virtue of that, the premium cachet of French wine and Cognac has become an increasingly common feature in the marketing of Scotch whiskies – and it is a trend that doesn’t look to be losing momentum. These brands, it seems, are hoping to become the preferred choice for those ‘occasions’ that are traditionally reserved for other drinks. In truth, this strategy is following a successful historical precedent – it’s no coincidence that sherry was one of the most popular drinks in Britain and Ireland during the same century that maturation in sherry casks was inexorably intertwined with the maturation of both Scotch and Irish whisk(e)y. Sure, there were practical reasons of logistics and cask supply, but there’s also much to be said for introducing familiar flavours to what might be an unfamiliar product. Whether this will successfully flip wine and Cognac drinkers to favour Scotch remains to be seen.
Whatever the motivation, during the past two decades wine-cask finishes of various kinds have gone from being reserved predominantly for special editions or limited one-off releases, to something of an industry staple, with named vineyards and grape varieties seeping in as brands seek to differentiate their new releases from competitors. Though some cynics decry this as a marketing-led fad, the reality is that there’s a long history of using casks that once held wine, both still and fortified, to mature whisky. Thus, it could be argued that we’re simply returning to a ‘traditional’ style of maturation that predominated in whisky production prior to the mid-20th century, when ex-Bourbon casks rose to prominence.
Today, wine casks (meaning still or ‘table’ wine as opposed to fortified wine like sherry, port or Madeira) are sourced directly from vineyards, or sometimes indirectly via independent cooperages. These vessels have been used for usually no more than five years, as after this time the cask will impart less tannin and aromatic influence to wine than might be desired. It really depends on the preference of the winemaker, the style of wine produced, and, ultimately, the distillery purchasing the wood. Though it varies depending on the whisky brand, little emphasis is generally put on the variety and heritage of the oak (which is often French, but may be American or Eastern European and can be Quercus Robur, Quercus Petraea, or Quercus Alba – to name the most common types) and the inherent character imparted to spirit by a particular oak species or regional forest environment. Instead, focus is on the style of wine the cask once held and the impact that wine will have on spirit during maturation.
Will whisky fans soon have to become wine experts to understand the dram in their hand?
For example, finishes in casks that previously held the sweet but crisp dessert wines of the Sauternes region of Southern France will generally impart an element of Sauternes-like character to whisky: honey, citrus zest, melon, and stone fruit. Furthermore, because residual sugars from wine persist in the cask after the wine is disgorged, sweet wine casks such as these measurably impart more diluted sugars than would be found if the same spirit had been matured in an ex-Bourbon barrel or a wine cask of a drier, non-dessert style. These diluted sugars do, of course, have a profound impact on the profile of the resultant whisky and, interestingly, this can also be said of the acidity of the wine. In general, and regardless of sugar content or acidity, distillers report that shorter finishes tend to mostly impart these ‘wine-derived characteristics’ to the spirit, while in instances of longer finishes (sometimes called ‘secondary maturations’) of many years the impact of the wine cask’s oak tends to become far more apparent. What this means is that distillers have a number of different strings they can pull when it comes to using wine casks and are able to decide if they want the wine, the oak variety, or both elements to come into play when developing maturation and blending plans.
This versatility and the unique characteristics that can be delivered have made still wine cask ageing something of a hallmark of all three malt brands owned by Whyte & Mackay – from The Dalmore’s Quintessence, created using an assemblage of five different wine cask finishes, to Jura 18 Years Old, finished in red wine casks, and Tamnavulin’s Tempranillo cask edition – on account of master blender Richard Paterson’s penchant for this style of maturation. It could be said that Reynier-era Bruichladdich built its reputation on this kind of maturation as he leveraged his connections in the wine industry and, more recently, Speyside’s Glen Moray Distillery has also explored the world of wine casks, with positive results such as the Cabernet and Chardonnay cask finishes. Whether sweet or dry styles of wine once occupied these casks, and regardless of the species of oak they are made from, distillers using these types of cask are actively seeking out distinctive wine-derived characteristics in their whiskies that would otherwise be impossible to replicate through extraction of wood character alone.
Ex wine casks maturing single malt whisky at Tullibardine Distillery.
More recently, another type of wine cask has crept into the world of whisky. The use of ‘shaved, toasted and re-charred’ (STR) red wine casks, often sourced from Portugal, is something of a hallmark of the late Dr Jim Swan, a well-respected distillery consultant. Until the time of his passing in 2017, Dr Swan worked on many new distillery projects worldwide including Lindores Abbey, Kingsbarns and others in Scotland, Milk & Honey in Israel, Kavalan in Taiwan, and Cotswolds and St George’s in England – to name but a few. In theory, distillers use STRs because they aren’t so much seeking influence from the wine that was once held in the cask, but instead are after the character of the oak itself. This oak may be European or American, though the latter (Quercus Alba specifically) is more common; but it really depends on the country and vineyard from which the cask was sourced before undergoing the STR process. In terms of size, many of these are traditional wine cask volumes, such as 225-litre barriques or 228-litre ‘Burgundy’ barrels, but others are 250-litre hogsheads. Some American oak STRs have even been fitted with European oak ends to further alter their maturation influence.
However, it must be said, although these STR casks have lost the layer of wood that once had immediate contact with wine, and the ‘new’ layer below has been toasted and charred, they don’t behave in the same way as similarly ‘re-conditioned’ or ‘rejuvenated’ ex-Bourbon barrels or similarly treated hogsheads. This is almost certainly because STR casks have not previously held high-strength spirit and thus are still packed full of elements which can only be unlocked and transformed through the introduction of liquids with higher concentrations of alcohol.
The depth of wood removed during the shaving or scraping process seems to vary depending on the cooperage and whisky maker commissioning the work. This means a greater or lesser amount of wine may remain ‘soaked’ into the staves, depending on how much has been shaved away – though some distillers argue the process shouldn’t leave behind any evidence of wine at all. This is important to bear in mind as, interestingly, STRs tend to deliver a distinctively dark, ruddy-red colour after a relatively short period of maturation. To see for yourself, look no further than the 100% STR release for Kingsbarns Distillery’s Founders’ Club in 2019, which has a striking colour and character that belies its youth.
However, while this distinctive colour could be chalked up solely to the influence of tannin and other wood derivatives unlocked during the toasting process, some distillers using these casks think that the wine has played a role too. Some speculate that a little wine does remain in the wood after the shaving and that this remnant is transformed during the toasting and charring process, leading to the distinctive colour and aromatic profile derived from the casks. For further reference, other examples of STR-matured whiskies can be found from Cotswolds (Founder’s Choice, released 2018), Kilchoman (STR Cask Matured Ltd Edition, released 2019) and Kavalan (the Vinho Barrique range).
Examples of whiskies matured in traditional wine casks (Arran & Tullibardine) and STR casks (Kingsbarns & Kavalan).
The flavour profile achieved by using red wine STRs is, as one would expect, distinct from that imparted by red wine casks that haven’t undergone the STR treatment – such as Arran’s 2018 Tuscan wine cask matured expression. What’s really fascinating, however, is that some distillers report that the STR cask-derived characteristics appear to integrate more quickly with new spirit than those coming from a conventional wine cask or even a virgin oak cask. This speedy integration of flavours or ‘accelerated maturation’ was, at least according to most of the distilleries that use STRs, Dr Swan’s stated aim. Some believe that this is due to the reduced stave thickness of STRs resulting from the ‘shaving’ or ‘scraping’ process, which it is thought may impact the rate of oxidisation in the spirit – one of the key processes in maturation. In sensory evaluation, spirits matured in these casks also differ greatly in character from those aged in similarly toasted and charred virgin (new) oak casks, despite the fact that on paper the STR process exposes entirely ‘new’ or ‘fresh’ wood. This point of difference highlights the fact that the STR treatment does not fully negate the impact of the wine-ageing process on the oak.
So, while there’s still room for debate, what can be said for sure is that an STR is certainly nothing like a traditional wine cask, or a conventional ‘rejuvenated’ ex-Bourbon cask or indeed a ‘virgin’ oak cask – it really is something else altogether.
Now we understand the two most common kinds of wine cask seen in the modern era of Scotch whisky production, into which of these categories do we place the ‘French cuvée casks’ used to mature Glenfiddich Grand Cru? In short: neither. What makes Grand Cru particularly intriguing for those with an interest in maturation is that this whisky has been aged in another breed of vessel altogether. After 23 years in a combination of European oak ex sherry casks and American oak casks, the spirit destined to become Grand Cru was vatted and finished for up to six months in a combination of first fill and second fill French oak barriques that were previously used to ferment (not age) wines. In particular, they were used as fermentation vessels for the vinification process of musts (grape juice) pressed from grapes grown in the vineyards of Northeastern France, musts that eventually become, in the words of Glenfiddich, ‘some of
the world’s most extraordinary sparkling wines.’
This description my seem a little convoluted, as the glitzy gold packaging, references to ‘celebration’, and the coupe glasses used in this whisky’s marketing none-too-subtly suggest to us that this spirit has a link to one effervescent wine in particular; a sparkling wine that is the undisputed symbol of status, luxury and festivity the world over. However, on the bottle we are told only that this whisky has been matured in ‘French cuvée casks’ – why the dancing around the C-word? It’s for good reason. When it comes to a product that combines the heritage of two of the world’s most famous alcoholic beverages, both of which are protected by strict definitions and laws of Geographical Indication, one does indeed have to choose their words carefully. What’s more, this famous French sparkling wine that we all know and love may not be called by its true name, Champagne, until it has undergone a secondary fermentation in the bottle.
What’s important for the purposes of understanding Glenfiddich Grand Cru is that it is the lightly toasted, French Limousin-oak barriques used for the initial fermentation of wines (which eventually become Champagne) that have been utilised for the whisky’s finishing. A close reading of the Champagne production process thus shows that there can technically be no such thing as a ‘Champagne cask’ – hence the raising of eyebrows when the term has been used in the past for expressions such as Bunnahabhain’s similarly matured 2019 Feis Ile bottling and historic releases by Arran and The Dalmore. It is for this reason that Glenfiddich settled on the term ‘cuvée cask’, as it points us, with a knowing wink, in the right direction without oversimplifying or falling foul of any regulated terminology. Nevertheless, that technicality doesn’t take away from what makes this wood interesting.
Unlike casks used to age still wines, which tend to be used only for a few years and retain relatively high concentrations of both water-soluble and alcohol-soluble aromatic compounds, casks used for fermentation tend to have had more of their easily accessible, water-soluble elements depleted through repeated use over many vintages. However, this doesn’t mean they’re not packed full of character that can be unlocked by the introduction of spirit. In the case of the casks used to mature Grand Cru, they had actually been used to ferment up to 10 years of grape harvest. In spite of this, according to Glenfiddich global brand ambassador Struan Grant Ralph, the casks were still very ‘active’ when introduced to high-strength whisky for the first time:
“The cuvée cask is not ‘spirit depleted’ in the way a Cognac or Bourbon cask will be, meaning the tannins, lignin and the building blocks of that oak wood are still very accessible and readily available when we fill with high-strength Glenfiddich for a finish,” explains Struan. “The must and wine had a subtle influence in the early stages of whisky maturation, but this impact is far less than that of the innate quality of the wood, and the fact that they are still ‘active’ casks.”
Though subtle, the casks did deliver characteristics that seem to have been derived from the vinification process. Specifically, they have imparted a degree of acidity to the whisky, along with distinctive floral aromas. Regarding this characteristic, Struan says: “The low pH of the previous ferment does add an interesting acidity to the resulting whisky, which we balance out by using the casks again for a ‘second fill.’ This is then vatted with the whiskies finished in the ‘first fill’ casks to achieve the balance we want from every Glenfiddich.
“Without the spirit matured in the second-fill casks, the final whisky would manifest with dryness.”
Though very uncommon today, fermentation casks were in fact regularly used to mature Scotch whisky in the past. However, these barrels were not from France but from Spain and instead had been used to ferment the young wines that become sherry. Fermentation was seen as a key step in preparing export casks before they were filled with mature product and shipped to Scotland for sale. Historic sources suggest the prevailing wisdom of the time was that repeated use for fermentation ensured that there would be little to no cask influence imparted to the sherries, which are fortified but rarely stronger than 22% ABV, during shipping. Upon receipt, the sherry would be disgorged and the cask either returned to Spain for further export use or sent to a Scotch whisky distillery to start a new life as a maturation vessel, where plenty of character derived from both the sherry and wood could be extracted through the introduction of high strength new-make spirit.
Indeed, up until the late 1970s, when the practice of fermentation in tanks became more common in sherry production and the shipping of product in cask less so, the symbiosis between sherry bodegas and the Scotch whisky industry was such that, upon taking a stroll through the fermentation warehouses of almost any Jerez winemaker, one would see row upon row of casks emblazoned with the names of Scotch whisky distillers that had bought and paid for the casks long before taking delivery of them. Today, sherry fermentation casks are almost unheard of and, instead, most ‘sherry casks’ used to mature whiskies are made to order (without a fermentation step) by Spanish cooperages using fresh oak, which can be American or European, before being ‘seasoned’ for a minimum of one year with sherry – often young, dry oloroso.
Though they are few and far between in the whisky world, Glenfiddich’s malt master Brian Kinsman is no stranger to fermentation casks, as he used comparable vessels for the Experimental Series IPA Finish. “The fermentation there helped to impart the hop derivatives into the wood,” says Struan. “During cask finishing we were able to extract them, as they are only really extractable from wood at higher strengths.”
Boasting aromas of apple blossom, freshly baked bread and candied lemon, with sweet brioche, sandalwood, pear sorbet and white grape on the palate, those wishing to experience for themselves the flavours that a French oak, white wine fermentation cask can impart to Glenfiddich spirit will find Grand Cru domestically bottled at 40% ABV, while travellers visiting duty-free are able to pick up an exclusive version bottled at a special strength of 43% ABV. With Grand Cru, Glenfiddich’s malt master Brian Kinsman has achieved two things: a new style of Glenfiddich, and another type of wine cask being brought to the table for whisky lovers to learn about and enjoy – something that’s surely worthy of celebration.
The observant will also have noticed that the practice of borrowing terminology and, by virtue of that, the premium cachet of French wine and Cognac has become an increasingly common feature in the marketing of Scotch whiskies – and it is a trend that doesn’t look to be losing momentum. These brands, it seems, are hoping to become the preferred choice for those ‘occasions’ that are traditionally reserved for other drinks. In truth, this strategy is following a successful historical precedent – it’s no coincidence that sherry was one of the most popular drinks in Britain and Ireland during the same century that maturation in sherry casks was inexorably intertwined with the maturation of both Scotch and Irish whisk(e)y. Sure, there were practical reasons of logistics and cask supply, but there’s also much to be said for introducing familiar flavours to what might be an unfamiliar product. Whether this will successfully flip wine and Cognac drinkers to favour Scotch remains to be seen.
Whatever the motivation, during the past two decades wine-cask finishes of various kinds have gone from being reserved predominantly for special editions or limited one-off releases, to something of an industry staple, with named vineyards and grape varieties seeping in as brands seek to differentiate their new releases from competitors. Though some cynics decry this as a marketing-led fad, the reality is that there’s a long history of using casks that once held wine, both still and fortified, to mature whisky. Thus, it could be argued that we’re simply returning to a ‘traditional’ style of maturation that predominated in whisky production prior to the mid-20th century, when ex-Bourbon casks rose to prominence.
Today, wine casks (meaning still or ‘table’ wine as opposed to fortified wine like sherry, port or Madeira) are sourced directly from vineyards, or sometimes indirectly via independent cooperages. These vessels have been used for usually no more than five years, as after this time the cask will impart less tannin and aromatic influence to wine than might be desired. It really depends on the preference of the winemaker, the style of wine produced, and, ultimately, the distillery purchasing the wood. Though it varies depending on the whisky brand, little emphasis is generally put on the variety and heritage of the oak (which is often French, but may be American or Eastern European and can be Quercus Robur, Quercus Petraea, or Quercus Alba – to name the most common types) and the inherent character imparted to spirit by a particular oak species or regional forest environment. Instead, focus is on the style of wine the cask once held and the impact that wine will have on spirit during maturation.
Will whisky fans soon have to become wine experts to understand the dram in their hand?For example, finishes in casks that previously held the sweet but crisp dessert wines of the Sauternes region of Southern France will generally impart an element of Sauternes-like character to whisky: honey, citrus zest, melon, and stone fruit. Furthermore, because residual sugars from wine persist in the cask after the wine is disgorged, sweet wine casks such as these measurably impart more diluted sugars than would be found if the same spirit had been matured in an ex-Bourbon barrel or a wine cask of a drier, non-dessert style. These diluted sugars do, of course, have a profound impact on the profile of the resultant whisky and, interestingly, this can also be said of the acidity of the wine. In general, and regardless of sugar content or acidity, distillers report that shorter finishes tend to mostly impart these ‘wine-derived characteristics’ to the spirit, while in instances of longer finishes (sometimes called ‘secondary maturations’) of many years the impact of the wine cask’s oak tends to become far more apparent. What this means is that distillers have a number of different strings they can pull when it comes to using wine casks and are able to decide if they want the wine, the oak variety, or both elements to come into play when developing maturation and blending plans.
This versatility and the unique characteristics that can be delivered have made still wine cask ageing something of a hallmark of all three malt brands owned by Whyte & Mackay – from The Dalmore’s Quintessence, created using an assemblage of five different wine cask finishes, to Jura 18 Years Old, finished in red wine casks, and Tamnavulin’s Tempranillo cask edition – on account of master blender Richard Paterson’s penchant for this style of maturation. It could be said that Reynier-era Bruichladdich built its reputation on this kind of maturation as he leveraged his connections in the wine industry and, more recently, Speyside’s Glen Moray Distillery has also explored the world of wine casks, with positive results such as the Cabernet and Chardonnay cask finishes. Whether sweet or dry styles of wine once occupied these casks, and regardless of the species of oak they are made from, distillers using these types of cask are actively seeking out distinctive wine-derived characteristics in their whiskies that would otherwise be impossible to replicate through extraction of wood character alone.
Ex wine casks maturing single malt whisky at Tullibardine Distillery.More recently, another type of wine cask has crept into the world of whisky. The use of ‘shaved, toasted and re-charred’ (STR) red wine casks, often sourced from Portugal, is something of a hallmark of the late Dr Jim Swan, a well-respected distillery consultant. Until the time of his passing in 2017, Dr Swan worked on many new distillery projects worldwide including Lindores Abbey, Kingsbarns and others in Scotland, Milk & Honey in Israel, Kavalan in Taiwan, and Cotswolds and St George’s in England – to name but a few. In theory, distillers use STRs because they aren’t so much seeking influence from the wine that was once held in the cask, but instead are after the character of the oak itself. This oak may be European or American, though the latter (Quercus Alba specifically) is more common; but it really depends on the country and vineyard from which the cask was sourced before undergoing the STR process. In terms of size, many of these are traditional wine cask volumes, such as 225-litre barriques or 228-litre ‘Burgundy’ barrels, but others are 250-litre hogsheads. Some American oak STRs have even been fitted with European oak ends to further alter their maturation influence.
Distillers have a number of different strings they can pull when it comes to wine casks
However, it must be said, although these STR casks have lost the layer of wood that once had immediate contact with wine, and the ‘new’ layer below has been toasted and charred, they don’t behave in the same way as similarly ‘re-conditioned’ or ‘rejuvenated’ ex-Bourbon barrels or similarly treated hogsheads. This is almost certainly because STR casks have not previously held high-strength spirit and thus are still packed full of elements which can only be unlocked and transformed through the introduction of liquids with higher concentrations of alcohol.
The depth of wood removed during the shaving or scraping process seems to vary depending on the cooperage and whisky maker commissioning the work. This means a greater or lesser amount of wine may remain ‘soaked’ into the staves, depending on how much has been shaved away – though some distillers argue the process shouldn’t leave behind any evidence of wine at all. This is important to bear in mind as, interestingly, STRs tend to deliver a distinctively dark, ruddy-red colour after a relatively short period of maturation. To see for yourself, look no further than the 100% STR release for Kingsbarns Distillery’s Founders’ Club in 2019, which has a striking colour and character that belies its youth.
However, while this distinctive colour could be chalked up solely to the influence of tannin and other wood derivatives unlocked during the toasting process, some distillers using these casks think that the wine has played a role too. Some speculate that a little wine does remain in the wood after the shaving and that this remnant is transformed during the toasting and charring process, leading to the distinctive colour and aromatic profile derived from the casks. For further reference, other examples of STR-matured whiskies can be found from Cotswolds (Founder’s Choice, released 2018), Kilchoman (STR Cask Matured Ltd Edition, released 2019) and Kavalan (the Vinho Barrique range).
Examples of whiskies matured in traditional wine casks (Arran & Tullibardine) and STR casks (Kingsbarns & Kavalan).
The flavour profile achieved by using red wine STRs is, as one would expect, distinct from that imparted by red wine casks that haven’t undergone the STR treatment – such as Arran’s 2018 Tuscan wine cask matured expression. What’s really fascinating, however, is that some distillers report that the STR cask-derived characteristics appear to integrate more quickly with new spirit than those coming from a conventional wine cask or even a virgin oak cask. This speedy integration of flavours or ‘accelerated maturation’ was, at least according to most of the distilleries that use STRs, Dr Swan’s stated aim. Some believe that this is due to the reduced stave thickness of STRs resulting from the ‘shaving’ or ‘scraping’ process, which it is thought may impact the rate of oxidisation in the spirit – one of the key processes in maturation. In sensory evaluation, spirits matured in these casks also differ greatly in character from those aged in similarly toasted and charred virgin (new) oak casks, despite the fact that on paper the STR process exposes entirely ‘new’ or ‘fresh’ wood. This point of difference highlights the fact that the STR treatment does not fully negate the impact of the wine-ageing process on the oak.
So, while there’s still room for debate, what can be said for sure is that an STR is certainly nothing like a traditional wine cask, or a conventional ‘rejuvenated’ ex-Bourbon cask or indeed a ‘virgin’ oak cask – it really is something else altogether.
Now we understand the two most common kinds of wine cask seen in the modern era of Scotch whisky production, into which of these categories do we place the ‘French cuvée casks’ used to mature Glenfiddich Grand Cru? In short: neither. What makes Grand Cru particularly intriguing for those with an interest in maturation is that this whisky has been aged in another breed of vessel altogether. After 23 years in a combination of European oak ex sherry casks and American oak casks, the spirit destined to become Grand Cru was vatted and finished for up to six months in a combination of first fill and second fill French oak barriques that were previously used to ferment (not age) wines. In particular, they were used as fermentation vessels for the vinification process of musts (grape juice) pressed from grapes grown in the vineyards of Northeastern France, musts that eventually become, in the words of Glenfiddich, ‘some of
the world’s most extraordinary sparkling wines.’
This description my seem a little convoluted, as the glitzy gold packaging, references to ‘celebration’, and the coupe glasses used in this whisky’s marketing none-too-subtly suggest to us that this spirit has a link to one effervescent wine in particular; a sparkling wine that is the undisputed symbol of status, luxury and festivity the world over. However, on the bottle we are told only that this whisky has been matured in ‘French cuvée casks’ – why the dancing around the C-word? It’s for good reason. When it comes to a product that combines the heritage of two of the world’s most famous alcoholic beverages, both of which are protected by strict definitions and laws of Geographical Indication, one does indeed have to choose their words carefully. What’s more, this famous French sparkling wine that we all know and love may not be called by its true name, Champagne, until it has undergone a secondary fermentation in the bottle.
What’s important for the purposes of understanding Glenfiddich Grand Cru is that it is the lightly toasted, French Limousin-oak barriques used for the initial fermentation of wines (which eventually become Champagne) that have been utilised for the whisky’s finishing. A close reading of the Champagne production process thus shows that there can technically be no such thing as a ‘Champagne cask’ – hence the raising of eyebrows when the term has been used in the past for expressions such as Bunnahabhain’s similarly matured 2019 Feis Ile bottling and historic releases by Arran and The Dalmore. It is for this reason that Glenfiddich settled on the term ‘cuvée cask’, as it points us, with a knowing wink, in the right direction without oversimplifying or falling foul of any regulated terminology. Nevertheless, that technicality doesn’t take away from what makes this wood interesting.
Unlike casks used to age still wines, which tend to be used only for a few years and retain relatively high concentrations of both water-soluble and alcohol-soluble aromatic compounds, casks used for fermentation tend to have had more of their easily accessible, water-soluble elements depleted through repeated use over many vintages. However, this doesn’t mean they’re not packed full of character that can be unlocked by the introduction of spirit. In the case of the casks used to mature Grand Cru, they had actually been used to ferment up to 10 years of grape harvest. In spite of this, according to Glenfiddich global brand ambassador Struan Grant Ralph, the casks were still very ‘active’ when introduced to high-strength whisky for the first time:
“The cuvée cask is not ‘spirit depleted’ in the way a Cognac or Bourbon cask will be, meaning the tannins, lignin and the building blocks of that oak wood are still very accessible and readily available when we fill with high-strength Glenfiddich for a finish,” explains Struan. “The must and wine had a subtle influence in the early stages of whisky maturation, but this impact is far less than that of the innate quality of the wood, and the fact that they are still ‘active’ casks.”
Though subtle, the casks did deliver characteristics that seem to have been derived from the vinification process. Specifically, they have imparted a degree of acidity to the whisky, along with distinctive floral aromas. Regarding this characteristic, Struan says: “The low pH of the previous ferment does add an interesting acidity to the resulting whisky, which we balance out by using the casks again for a ‘second fill.’ This is then vatted with the whiskies finished in the ‘first fill’ casks to achieve the balance we want from every Glenfiddich.
“Without the spirit matured in the second-fill casks, the final whisky would manifest with dryness.”
Though very uncommon today, fermentation casks were in fact regularly used to mature Scotch whisky in the past. However, these barrels were not from France but from Spain and instead had been used to ferment the young wines that become sherry. Fermentation was seen as a key step in preparing export casks before they were filled with mature product and shipped to Scotland for sale. Historic sources suggest the prevailing wisdom of the time was that repeated use for fermentation ensured that there would be little to no cask influence imparted to the sherries, which are fortified but rarely stronger than 22% ABV, during shipping. Upon receipt, the sherry would be disgorged and the cask either returned to Spain for further export use or sent to a Scotch whisky distillery to start a new life as a maturation vessel, where plenty of character derived from both the sherry and wood could be extracted through the introduction of high strength new-make spirit.
Indeed, up until the late 1970s, when the practice of fermentation in tanks became more common in sherry production and the shipping of product in cask less so, the symbiosis between sherry bodegas and the Scotch whisky industry was such that, upon taking a stroll through the fermentation warehouses of almost any Jerez winemaker, one would see row upon row of casks emblazoned with the names of Scotch whisky distillers that had bought and paid for the casks long before taking delivery of them. Today, sherry fermentation casks are almost unheard of and, instead, most ‘sherry casks’ used to mature whiskies are made to order (without a fermentation step) by Spanish cooperages using fresh oak, which can be American or European, before being ‘seasoned’ for a minimum of one year with sherry – often young, dry oloroso.
Though they are few and far between in the whisky world, Glenfiddich’s malt master Brian Kinsman is no stranger to fermentation casks, as he used comparable vessels for the Experimental Series IPA Finish. “The fermentation there helped to impart the hop derivatives into the wood,” says Struan. “During cask finishing we were able to extract them, as they are only really extractable from wood at higher strengths.”
Boasting aromas of apple blossom, freshly baked bread and candied lemon, with sweet brioche, sandalwood, pear sorbet and white grape on the palate, those wishing to experience for themselves the flavours that a French oak, white wine fermentation cask can impart to Glenfiddich spirit will find Grand Cru domestically bottled at 40% ABV, while travellers visiting duty-free are able to pick up an exclusive version bottled at a special strength of 43% ABV. With Grand Cru, Glenfiddich’s malt master Brian Kinsman has achieved two things: a new style of Glenfiddich, and another type of wine cask being brought to the table for whisky lovers to learn about and enjoy – something that’s surely worthy of celebration.
