Ian Wisniewski investigates distillery character versus maturation character
The benefits of oak aging have been appreciated far longer than they’ve been understood, as it’s only since the 1970s-80s that detailed research has enabled science to supplant, or confirm, what experience had indicated. However, while maturation can account for up to 60-70 per cent of a malt’s final character, this is such a complex process that it’s still not fully understood. Maturation can be divided into three elements: subtractive, additive and interactive, which occur simultaneously although at differing rates. Subtractive maturation deals with the loss of immaturity, while additive maturation sees the oak endowing the spirit with colour and character.Interactive maturation refers to the complex reactions occurring between the spirit and the oak (including evaporation and oxidation), which yield an additional range of characteristics that neither possess individually.“Maturation is all about integration, taking components in new make spirit and marrying those flavours with the types of cask you’re using, some will be enhanced, some diminished,” says Gordon & MacPhail’s Ewen Mackintosh.This means the balance between the ‘distillery character’ embodied in new make spirit, and the ‘maturation character’ that develops during aging is continually evolving. Certain aspects of the distillery character remain, others are lost, some are masked by the growing influence of the cask, while others evolve.“Some fruits found in the new make spirit evolve during maturation, some also show differently as there are so many reactions happening inside the cask. As well as evolving, fruits interacting with vanilla become more than just pear and vanilla, becoming sweeter and more luscious, moving to a riper pear,” says Glenmorangie’s Rachel Barrie.Consequently, deconstructing a mature malt’s flavour profile, and attributing certain aspects to the distillery or maturation character, can be difficult.How a cask influences the aging process, and the distillery character, depends on various factors.This includes the ‘fill’ (whether filled with spirit for the first, second or third time – the cask’s influence diminishing and changing with each successive fill); the type of oak, American or European, and the previous incumbent (sherry or bourbon).Additional factors to consider are the location and type of aging warehouse, and an individual cask’s position within it, and of course the nature of the new make spirit.Whatever the character of the new make spirit, whether elegantly fruity or heavily peated, it interacts with the cask in the same way. What differs is how those characteristics subsequently show within the spirit.The process of maturation begins as soon as a cask is filled, as this initiates various reactions, including oxidation and evaporation. However, it takes approximately a year to 18 months for the first indications of oak derived flavours to show, and provide an indication of how the cask is influencing the spirit.Meanwhile, the level of sulphur character, which is variously manifested as struck match, rubbery or meaty notes, reduces as it’s absorbed by the charred surface of the cask. This is essentially an amelioration rather than removal, with sulphur compounds also oxidising into subtler, less flavour-active forms. However, as sulphur character masks other notes, reducing this can significantly alter the spirit’s profile, by allowing ester notes to show. In addition to the type of oak and the cask’s previous incumbent, other vital factors are the fill and cask size. A smaller cask influences the spirit more rapidly and more intensely than a larger cask of the same provenance, though contributes the same range of characteristics.Moreover, each fill of a cask results in a diminishing influence on the spirit. If a first fill cask is said to contribute 100 per cent of its characteristics, a second fill contributes around 60 per cent, which means less oak derived character, and a relatively more prominent distillery character, with the influence of oxidation also showing more clearly.Oxidation is a consequence of casks breathing in ‘fresh’ air, and exhaling ‘saturated’ air. When air enters the headspace, ie. the area above the level of liquid in the cask, it dissolves into the spirit (oxygen being the key element). This sees the spirit continually reaching a new equilibrium. In terms of flavour profile, the spirit tends to become fruitier, more balanced and mature. Consequently, oxidation evolves the distillery character while also creating new characteristics.“I think oxidation creates more perfumed top notes which work hand in hand with the fruit in the new make spirit,” says Glenmorangie’s Dr Bill Lumsden.Alcohol and water evaporating from the cask is an essential enabler of the aging process, which entails loosing certain undesirable elements such as sulphur compounds (although they are mainly absorbed by the layer of char in the cask), while also developing complexity.The evaporation rate is influenced by factors including the type of aging warehouse and a cask’s position within it, the ambient temperature, humidity levels, and the filling strength. Exactly how varying evaporation rates influence maturation is still not fully understood, though higher rates aren’t considered to promote a finer result.Comparing different styles of new make spirit, at various ages, gives a more individual sense of the changing balance between distillery and maturation character.“The Balvenie new make spirit is fruity, with sweetness and richness, while low in cereal and sulphur character. After three years in first fill bourbon casks it’s starting to develop that typical honeyed note, which isn’t there when it’s distilled, and vanilla sweetness from the wood, though it still has an immature note. At five years the honey is coming through, it’s fruity, sweet, more rounded, more mellow. It’s a similar character at eight years, but a bit mellower, rounder and with a bit more oakeyness,” says David Stewart of William Grant & Sons.“The key components in Benromach new make spirit are a nice toasted malt character, with peatyness coming through at the back, and green apple. After five years in a first fill bourbon cask there’s still fresh fruityness, citrus, a wee bit of ripe banana. Sweetness and fruityness come together, while the peaty character becomes more mellow, the maltyness is sweeter, more refined,” says Ewen Mackintosh.Analysing older examples of Glenmorangie provides another insight into the evolutionary process.“In the new make spirit we’re looking for lots of fruity character, mintyness, a hint of ginger, Earl Grey tea and butterscotch. At 10 years old the fruity influence is a result of distillery character, the minty character can come from various sources, partly from the distillation character. Vanilla and coconut are directly wood-derived. Comparing the 10 year old with the 18 year old, the 10 year old is lemons and oranges while the 18 year old is more grapefruit and marmalade fruit, I’m not sure whether this is down to the wood or oxidation,” says Glemorangie’s Dr Bill Lumsden. With a larger range of much older malts being bottled, the balance of characteristics at a more advanced age is the next consideration.“The essential character of citrus notes coming from Dalmore are still there in the 40 year old, though more marmalade. You mustn’t let the wood take over the spirit completely. Balance is so important, and trying to bring all the elements into an equilibrium, that’s the ideal single malt and making sure the distillery character is showing in its true light,” says Whyte & Mackay’s Richard Paterson.Another aspect is the development of a ‘maritime’ character in certain malts.“This is definitely a maturation character as you don’t get saltyness in Old Pulteney new make spirit.“I believe it’s to do with the environment, the warehouses are right on the shore, there is salt in the air which enters the warehouses, and the warehouses have high humidity. I tend to find a wee bit of saltyness in the 17 year old, but not as much as the 12 year old, and even less in the 21 year old, as I think it’s been masked by stronger flavours from the cask,” says Stuart Harvey of Inver House Distillers.Meanwhile, a classic example of the distillery character is smoke and peatyness (which can also be ‘boosted’ by similar compounds from the cask’s toasted/charred layer).A long-running debate is whether the peating level diminishes during maturation, or merely seems to diminish due to the increasing influence of the cask, and the accompanying characteristics becoming more pronounced.“Highland Park’s new make spirit has an even balance between ester and peaty aromas, being a light, sweet, smokey spirit.“The 12 year old has an even balance between heather honey sweetness and peatyness.“The phenols don’t really change that much depending on the age of the product, though they may concentrate slightly, but as the overall flavour profile changes this influences the impact of the phenols,” says Highland Park’s Russell Anderson.
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