I’ve received a number of questions or claims of late, about this-or-that being the case when it comes to Sherry cask character in a whisky (and not just Smögen, but others as well). It is quite evident that there are a number of misconceptions about what happens in general during maturation and thus the role played by any cask, and what the workings of a Sherry cask are on the maturing whisky.
In a very brief division, any cask will contribute what is termed ”additive maturation”, which is simply congeners (flavour compounds) extracted from the cask, by the spirit/whisky. But the cask will also be important for the ”subtractive maturation” – mainly unwanted congeners being broken down and removed from the whisky – and further plays a part in the ”interactive maturation”, which is a more complex string of chemical reactions in the whisky that are mainly driven by oxygen, but to some extent also by the oak itself.
As the subtractive and interactive maturation phases will occur regardless of what type of cask is involved and are fuelled by the fact that the cask is made out of oak, or even from an external compound such as oxygen, the ”Sherry Cask Character” is in reality an integral part of the additive maturation phase. Thus, what the cask and its historic use and the residues left thereby, will aadd to the maturing whisky.
In turn, the strictly additive maturation can (and do) involve congeners either from the former contents of the cask – such as Sherry – or from the oak itself. It is important to note that there may be no other liquid inside of a cask when it is being filled with new make spirit (or with whisky), other than clean water. Thus, there can be no Sherry left inside the cask. However, if the cask has been used to hold Sherry before, some of that fortified wine will have gone about 10 mm into the oak staves of the cask and will have dried into the cask, with the water and alcohol parts drying off, but the actual flavour congeners being left, locked into the oak staves. The whisky will go slightly farther into the oak staves and will slowly dissolve and leach the winey congeners out into the volume of whisky inside the cask. And while so doing, the whisky will also dissolve some congeners from the oak itself, both water soluble ones and oil/alcohol soluble ones. Thuswise, congeners from both oak and previous Sherry will find its way into the whisky.
Naturally, more extraction will be possible from a ”first fill Sherry” cask than from a second, or third, or fourth fill cask, as there will be successively less compounds to dissolve and bring out to the whisky. In that regard, additive maturation is akin to chewing gum – the longer the chewing gum has been used, the less flavour you will get out of it.
It must also be noted that the toasting (or charring) level of a cask will have a distinctive impact on what and how much flavour congeners can be extracted from the oak, just as different types of Sherry will be able to offer more or – importantly – less different wine-derived flavour congeners. Think Fino/Manzanilla, Amontillado, Palo Cortado, Oloroso, Pedro Ximenez, Cream Sherry and Amoroso Sherry (the latter two being blends of different Sherries); from bone dry wines at 15 % alcohol to stickily sweet and gloopy at above 20 % alcohol. These differences will matter, sometimes a lot.
But anyway…back to the issue of ”Sherry Cask Character”. What is it, really? Strictly speaking, it is any flavour (congener) derived from the former Sherry cask – of whatever specification – rather than from the distilled new make spirit or from the interactive maturation. Some such flavours will then intermingle and interact with spirit derived flavours, but let’s put that aside for the moment.
Many, if not most people, will regard it rather as ”Sherry Character”, omitting the ”Cask” word from the equation. This is very much a misconception. The vast majority of the influence of a Sherry cask will come from the oak itself. This means that it will be in line with or at least quite similar to other types of casks that have a similar history (i.e. has held a wine of some sort, with the same ”fill history” within the whisky industry). Typical oak derived flavours are vanilla notes of various sorts, ginger, peppery notes, woody notes, cherry kernels, apricots, almonds, coffee and chocolate. However, and most significantly if not exclusively from a first fill ex Sherry cask; the Sherry will also make flavour contributions and the typical ones from Oloroso Sherry casks – the most common Sherry casks used – will be walnuts, orange rinds, leather, umami/rancio/mushrooms and to some extent dried fruits.
Fino casks may contribute more ”salty” and umami notes and less opulent fruitiness, while the heavy PX casks will offer straight up raisins, plums, jams, and quite possibly also roasted nuts, coffee and chocolate. From the Sherry itself. In addition, the oak will contribute as well, as mentioned before.
Exactly what percentage of flavour that is derived from the oak itself and from the previous incumbent – the Sherry – cannot be defined and it will also vary depending on a whole host of factors. But as mentioned, the majority of the flavours and their sensations will stem from the oak rather than from the Sherry. Maturation is a complex issue, which is what should be understood first of all, along with the primary role of the oak in the cask in maturing whisky.
But as a final observation, the typical ”Sherry bomb” whisky will be one where it has matured in a first fill cask, often PX or Oloroso, and where the cask derived characters are significantly more overt than the distillate derived ones (sometimes to the point of extinction actually!). And it will be the oak derived flavours that play the dominant role. They can certainly be very good, but they can often be a bit over the top, if there is a lack of balance and a remaining spirit derived character. Balance, to me, is of the utmost importance for a really good whisky; distillate and cask in balance, and offering complexity and good development.
Skål! / Pär
