This article will focus on the final element of the production process: Maturation.
The first four stages of the whisky production process sets the stage for the fifth and possibly most important stage, which involves the filling of the new make spirit or distillate which was obtained from the distillation process into barrels which are then left to mature for a number of years before the contents are decanted and bottled.
Once the distiller has obtained their desired new make spirit and has made the necessary checks to ensure that the spirit exhibits the characteristics that they desire, they will then transfer the spirit to the barrel filling station, where the new make spirit is filled into a variety of casks which have previously contained different spirits.
The barrel filling station at Bunnahabhain
The vast majority of casks used in the Scotch whisky industry are ex-bourbon barrels from the US and as they are relatively inexpensive to obtain, this has contributed to its proliferation and popularity within the industry.
While some elements argue that the casks impart up to 75% of the colour and flavour of the final product, there are others which argue that the figure is actually closer to 50% and that the other production processes also play an important role in determining the character of the final product.
Distilleries also fill their new make spirit into casks which have previously held a number of spirits such as sherry, port, cognac, rum and wine and there has recently been the trend of maturing or finishing whiskies within barrels fashioned from virgin oak in order to provide an interesting character to the final product.
Wine casks galore at Bruichalddich, with some of the barriques having been sourced from great houses such as Chateau Mouton Rothschild!
Sherry casks used to be rather prevalent within the industry, but the decline in sherry consumption has contributed to a sharp increase in the price of these casks and they are therefore not as easy to obtain as their bourbon counterparts, which also makes them rather prized.
Distilleries are also known to reuse casks for maturation purposes and these casks are known as refill barrels as they are refilled with new make spirit in order to mature it into whiskies as needed by the distilleries. Certain distilleries have been known to mature the vast majority of their whiskies in refill barrels as it provides the desired character that is necessary for their range of products.
Several distilleries are well-known for their use of ex-sherry casks (Glendronach, Glenfarclas and Macallan come to mind) and these casks have contributed heavily towards their signature style. These distilleries are also known for having well-established links with some of the bodegas in Spain which supply their sherry casks and these partnerships go back decades and even more than a century.
Certain distilleries such as The Dalmore mature their whiskies initially in ex-bourbon casks before transferring the whiskies to ex-sherry casks for an extended period of secondary maturation in order to obtain the character that they are looking for with regard to the final product and this has become a well-established practice within the industry where a number of distilleries have either "finished" or double matured their whiskies in different casks.
Due to whisky's popularity, a number of distilleries are owned by larger corporations and are known for being workhorses which produce whiskies primarily for blending purposes. Some of these distilleries may have their own warehouses in which the whiskies are matured, but most of the other distilleries within the corporation's portfolio tend to have their new make spirit tankered away to a central location where it is filled into barrels and matured in warehouses on the mainland.
Other distilleries such as Glenfiddich, Balvenie, Bruichladdich and Springbank are known for maturing all of their whiskies on site and this allows for them to have greater control of their inventory while also ensuring that the vast majority is designated for bottling as single malts.
Over time, the amount of spirit within the barrels will decrease due to a process known as evaporative maturation (which is also known as The Angel's Share) and casks in Scotland are known to lose approximately 1-2% in volume on an annual basis.
An experimental barrel with plexiglass heads which is used at Bruichladdich to showcase the effects of evaporative maturation
Different distilleries also have different processes with regard to the bottling of whiskies and while some will bottle them at cask strength, others will water the whiskies down to a desired alcohol strength (40%, 43% and 46% abv are rather common alcohol strengths these days) in order to maximise the spirit volumes.
Distilleries may also choose to chill-filter their whiskies by passing the spirit through a cold sieve which extracts the precipitates and lipids from the whisky. This is a cosmetic process which prevents the whisky from going cloudy in colder temperatures and it has also sparked a rather robust debate in the whisky community regarding whether this process affects the aroma and flavour of whiskies.
Another process which certain distilleries adhere to would be the addition of caramel colouring, or e150, to their whiskies in order to standardise the colour of the whiskies from one batch to another. While this is another cosmetic process, it doesn't affect the flavour profile of the whisky as e150 is odourless and tasteless.
This is another process which has sparked debate within the whisky industry as some elements feel that the addition of colouring to whisky is a somewhat deceptive process which masks the inferiority of the casks being used for the maturation process, while others see it as a necessary process which is geared towards ensuring a consistent final product from one batch to another.
The final product may be bottled at a variety of alcohol strengths and ages by the distilleries based on what they are looking to provide to consumers and one of the relatively recent trends within the industry has been the proliferation of Non Age Statement (or NAS) whiskies which do not display an explicit age statement and are traditionally said to contain a vatting of young and older whiskies.
Ardbeg's Uigeadail expression is one of the most popular NAS whiskies ever released
These NAS whiskies are becoming increasingly common as distilleries are finding it difficult to maintain present age statements on their products due to demand far outstripping supply. As such, they are forced to seek more innovative solutions in order to provide consumers with new and interesting expressions.
Whatever the case, maturation is the final stage of the whisky production process and marks the end of the long journey where the barley is final converted into whisky which can then be purchased and enjoyed by consumers.
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