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Issue 79 - Spirit of the times

Whisky Extras

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Whisky Magazine Issue 79
April 2009

 

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Spirit of the times

In the first of a two part series looking at new make spirit, Ian Wisniewski considers the range of characteristics that appear in new make spirit,and how they are created.

It’s a fragrant experience that can be enjoyed with, or without,any further analysis.

Nosing Glenmorangie shows a range of citrus notes, including orange, lemon and mandarin, with fresh fruity notes of green apples and pears, a heart of floral rose and geranium notes, while butterscotch and vanilla appear in the middle and base notes, with some underlying shortbread.

Similarly, The Balvenie’s richness reveals sweet, fruity and vanilla aromas; The Glenlivet’s fruity, banana aroma evolves into toffee and banana; Glenburgie is distinguished by red apple aromas, while Aberlour’s fragrant profile includes blackcurrants.

But I’m not talking about mature specimens, as these aromas are all characteristics of the new make spirit. The obvious question is when, and how, are they created ?

Malted barley is typically assigned a minor role within the big picture, as though merely a pragmatic starting point for distillation. The only credit malt usually gets is contributing ‘cereal notes,’ although it actually has far more to offer.

“The new make spirit vanillin is derived from the traces of cereal husks that have passed to the wash still,”says John Ross of William Grant & Sons.

Glemorangie’s Rachel Barrie continues:“Vanilla, butterscotch and shortbread notes come directly from the malt, and vanilla is often intricately woven with butterscotch. During distillation in Glenmorangie’s tall stills,many of the harsher, heavier cereal notes are left behind in the body of the still, and this unmasks and reveals more of the lighter,sweeterassociated flavours like vanilla, orange and lemon. Of all the fruit flavours created in Scotch whisky, citrus is probably the least understood, with the estery compounds responsible for the perception of apples and pears the most understood.” When assessing each stage of production it’s tempting to establish a hierarchy, ranging from what seem to be the most practical stages at one end of the scale, compared to the more creative stages at the other. But how realistic, or useful, is this type of appraisal,when each stage of production is inter-dependent. And if any stage is less than successful it can compromise everything that follows.

The purpose of milling, for example, is to ensure maximum efficiency during mashing, with a typical milling specification being 20 per cent husk, 70 per cent grits (or ‘middles’) which are mediumground, and 10 per cent flour (or ‘fines’). This provides an optimum surface area, enabling the maximum amount of sugar to be extracted in the minimum amount of time during mashing. But then milling and mashing also influence the range of flavours subsequently created during fermentation.

“Grinding finer can mean smaller grist particles in the worts, which often equates to a higher conversion rate as it’s more accessible to water. But a lot of solids in your wort can result in more foaming up in the wash still, which can give you a nuttier spirit.

We’re looking for as clear a wort as we can get, in order to produce new make spirit with a fruity, green apple character,”says Robbie Hughes of Glengoyne.

Rachel Barrie adds:“During mashing, the distiller will endeavour to make the conversion of starch to sugar as efficient as possible, but at the same time it is important to minimise the number of cloudy, long chain lipids in the wort,because these will inhibit the yeast from creating the delicious fruity esters. It is crucial to get the right environment for the yeast to do the best job.

“If yeast behaves differently it’s quite surprising how different the profile of the wash can be, and the balance of the different flavour congeners will change.” By converting sugars into alcohol, fermentation is in one sense a practical process, but it’s also a transitional stage during which flavours are created.

A successful, and consistent, fermentation depends on a number of factors, including the type of yeast used, the pitching temperature (ie. temperature of the wort when adding the yeast), the length of the fermentation period, and whether this takes place in wooden or stainless steel washbacks.

“In the main, it’s the yeast metabolism and the influence of the length of the fermentation period that creates the profile of the wash (over and above the influence of any peatiness from the malt of course). Apples and pears, for example, are created during fermentation, it’s the chemistry, as the yeast converts many of the amino acids extracted from the barley into higher alcohols and esters. However, the esters also need to be captured within the spirit cut, otherwise you can loose them to the foreshots, or they can be masked by heavier compounds and aromas from the feints,”says Rachel Barrie.

In addition to the choice of yeast, including ‘fast acting’and ‘slow acting’ strains of distiller’s yeast, which behave as their names suggest, the quantity of yeast added is also vital. This can be calculated according to the total litres of wort, or the original tonnage of malt.

“The amount of yeast added has a huge bearing on how the yeast will grow and also on the congener spectrum produced in fermentation. The yeast will double about every six to eight hours, if you add extra yeast on pitching the fermenter you get far fewer doublings in the fermentation. The temperature at which you start the fermentation also has a huge influence on how quickly the yeast will double, at a lower temperature for example the doubling rate will be slower,”says John Ross.

As the temperature rises during fermentation, the pitching temperature (which may be around 20 degrees centigrade, for example) ensures that all the fermentable sugars are converted into alcohol before reaching 34 degrees centigrade, a critical point as yeast expires at around that temperature.

“At the start of fermentation the yeast gets all the nutrients enabling it to grow, with the maximum cell count and peak temperature reached at around the 30 hour mark. The peak temperature has a huge influence on fruit flavours, for example if it’s too hot you produce more offflavours, like butteryness, you need to very carefully control the rate and fermentation temperature,” adds John Ross.

In addition to the yeast, another influence is the bacteria which evolves at a later stage of the fermentation process.

“Alcohol fermentation usually finishes at around 50-55 hours, but if you want complexity you leave it for 60-70 hours, which gives you bacterial growth and acid production. Every distillery has its own individual,natural population of bacteria, lactic acid bacteria. This is present on the malt, and in the washbacks, with wooden washbacks having a higher level, and different range of bacteria compared to stainless steel washbacks, although some will be the same. Bacteria can’t grow until the yeast dies and releases some nutrients. The bacterial population takes hours to grow, and bacteria produces lactic acid and acetic acid, which provides a rich soup when distilling the wash,and impacts on the characteristics of the low wines,”says John Ross.

With so much happening during fermentation, is it possible to quantify the influence it has on production?

“Given an efficient mashing process, I’d say 55 per cent of the character of the new make spirit is down to fermentation, and 45 per cent distillation,”says David Boyd of Chivas Brothers.

Beyond the character of the wash, the influence of distillation depends on various factors. The spirit cut is typically collected at an average of around 70% ABV, which means starting to collect spirit fromaround 75% ABV down to around 65% ABV, though this obviously varies among distilleries.

Fruitier notes including apples and pears, are far more evident at a relatively higher strength, with an increase in heavier notes as the strength decreases.

Additionally, the size and shape of the stills, together with accessories such as boil bowls, determine the degree of reflux and the resulting profile of the new make spirit.

This is because heavier flavour compounds have a higher boiling point than lighter flavour compounds, and as they ascend a taller still the temperature becomes relatively cooler, causing them to condense and return to the boil pot.

Meanwhile, lighter flavour compounds have a lower boiling point, which promotes their progress to the condenser.

Conversely, vapours ascending a shorter still are subjected to less temperature change, and so less reflux, with a correspondingly higher level of richer, heavier compounds eventually reaching the condenser.

The rate of distillation has a similar influence, with a relatively faster rate helping to promote the progress of heavier, richer compounds into the condenser.

How the characteristics of the new make spirit develop during aging, and how the profile changes under the influence of the cask, evaporation and oxidation, will be covered in the next issue.
 

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