The Chemistry of Whisky

[slkinsey]

My mother is always directing my attention to articles she thinks I will find interesting (and can understand) from Chemical & Engineering News, one of her favorite periodicals. I suppose the fact that I grew up in a family with subscriptions to C&E News, Science and National Geographic instead of Time and Sports Illustrated probably has something to say about how I turned out. But I digress. . .

Anyway, a recent issue included a short article on the chemistry of whisky (mostly Scotch whisky) that makes some interesting points from the perspective of a chemist:

• The peaty taste comes from phenols that are acquired by the malt when it is dried with smoke from peat.
  
• The distillation process involves more than just concentration of alcohol through selective evaporation and recondensation. If the still is made of copper, the copper "acts as a catalyst, esterifying, oxidizing, and reducing compounds" in the wash.
  
• Distillers take the heart of the run and not the head or tail in order to capture fruity and flowery esters while avoiding long-chain alcohols, fusel oils, undesirable esters, nitrogen compounts and sulforous chemicals.
  
• An average Scotch whiskey contains more than 700 different flavoring molecules.
  

This last bit I found especially interesting:

"Maturation is easily the most important part of the whisky production process as regards to flavor," Hills notes. "A malt whisky acquires more than half of its flavor during maturation; some would say as much as 80% of the final flavor of the spirit comes from the cask." These chemical flavorants come from the wood itself and from absorbed compounds left by the cask's previous contents, such as sherry or port.

[culinary bear]

[*]An average Scotch whiskey contains more than 700 different flavoring molecules.

People have been hanged over that 'e'... :)

I'd thoroughly recommend Pip Hills' book; it goes into a great deal of detail about the chemistry of whisky (and indeed, whiskey) production.

[slkinsey]

[*]An average Scotch whiskey contains more than 700 different flavoring molecules.

People have been hanged over that 'e'... :)

Yikes. What the hell was I thinking? I'll have to turn in my kilt.

[culinary bear]

:)

The casks can be hugely influential on the character of a malt whisky. You can get a good idea of the natural variations by comparing some of the single-cask offerings available nowadays.

Distilleries have a wide variety of casks to use at any one time, and the 'brand' is vatted between these casks in much the same way as a tea-blend is formulated, in order to maintain the same profile year upon year. Sometimes a little older whisky is incorporated - for a while, Ardbeg's 10yo contained a large proportion of older whiskies due to the distillery haing been mothballed for a period and thus having insufficient actual ten-year old whisky to meet demand.

Whether the current trend for 'designer' finishes continues is yet to be seen. The Famous Grouse now bottle a blended whisky which has spent some time in old beer barrels, and in a delicious twist, Innis and Gunn have brought out a beer matured in whisky casks! It's particularly fine.

[Ed Hamilton]

"Maturation is easily the most important part of the whisky production process as regards to flavor," Hills notes. "A malt whisky acquires more than half of its flavor during maturation; some would say as much as 80% of the final flavor of the spirit comes from the cask." These chemical flavorants come from the wood itself and from absorbed compounds left by the cask's previous contents, such as sherry or port.

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As the distillation purity of the spirit increases certainly maturation becomes more important, and I would agree that whisky can acquire more than half its flavor during maturation, but even more important than maturation to the final quality of the product is fermentation. You just can't make good spirits from a bad wash, wine, beer or whatever you want to call the fermented sugar that you are going to distill.

At many distilleries a special strain of yeast is used to convert the sugar in the raw material to alcohol and to limit the number of unwanted congeners. Some of these yeasts will produce a high alcohol wash in as little as 18 hours, while others will take as much as 3 or 4 days to complete the fermentation cycle.

[culinary bear]

It's like the Chorleywood process for making bread. You can get the same level of dough maturation as you would in an 18-hour rise simply by beating the living shit out of the dough for a few minutes, but flavour does suffer.

I suppose it comes down to a question of whether you like your spirits (or bread, for that matter) traditionally made, or 'improved'.

Ed, I'm interested in the parallels of rum and whisky production. Are the majority of fine rums distilled in pot (batch) stills as opposed to patent (Coffey) stills?

[Mayhaw Man]

As the distillation purity of the spirit increases certainly maturation becomes more important, and I would agree that whisky can acquire more than half its flavor during maturation, but even more important than maturation to the final quality of the product is fermentation. You just can't make good spirits from a bad wash, wine, beer or whatever you want to call the fermented sugar that you are going to distill.

A

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This could not be more true. A, ummm, close friend of mine, has distilled many, many runs of rum in a pretty scientific and controlled manner. I can tell you, without a doubt, that the stuff that he makes from beer (generic term for liquid that is being distilled-which in the case of many grain based beverages, is in fact, unhopped beer) that has been fermented in a controlled manner is far superior to that which has been basically allowed to ferment wildly. This seems to be true for all manner of spirits that my friend has made. In particular, whiskey made from corn or other grains. The distillate resulting from controlled fermentation (temp. control to keep the sugars from being metabolized by the yeast too quickly) is always much tastier as a young beverage-i.e. straight out of the worm-also, the head of the run seems to be much shorter-meaning that the level of fusels and other volatiles that give home brew some of it's more colorful names-such as "jake leg", "pop skull', etc. -meaning that the yield per gallon of fermented base seems to be a bit higher.

There have been studies on this, but the information, as with much distillation research, is not available on line or even at your local library. This stems from the fact that most research done has been done by private companies and also from the fact that making distilled beverages at home is, if not outright illegal (depending on where you live), usually pretty close to it.