Recently, I was asked the following question:  “What, exactly, is Single Malt Scotch?”  I love these kinds of questions the most.  Not because I know the answer, but because the answer is usually a surprise for the person that asked the question.

Single Malt Scotch is a type of whisky, distilled by a single distillery, usually in a pot still, using malted barley, in Scotland.  All Scotch whisky, including Single Malt Scotch must be distilled in Scotland and matured in oak casks in Scotland for at least three years.  Most Single Malts are matured for much longer.  The word single indicates that all the malts in the bottle come from a single distillery.  The word malt indicates that the whisky is distilled from a single malted grain.  In the case of Single Malt Scotch, barley is always the grain used.

The distillation of whisky has taken place in Scotland for at least 500 years.  The first written record of it dates back to 1494 with an entry on the famous Exchequer Rolls.  The years that followed saw the various governments of Scotland taxing the production of whisky to the point where most of Scotland’s whisky was produced illegally.  By 1823, the Scottish Parliament passed an act making the commercial distillation of  whisky more profitable, while imposing severe punishments on landowners with unlicensed distilleries on their property.  A man by the name of George Smith was the first to receive a license for a distillery under the new law.  This distillery, Glenlivet, was founded in 1824 and still exists today.

All Single Malt Scotch goes through a batch production process.  At the time that it is bottled, various batches are mixed together to achieve consistent flavors from one bottling to the next.  Water is the most important ingredient in the production of single malts and is used in each phase of  the process.  It is first added to the barley to promote germination.  It is mixed with ground barley to create mash.  It is also used to dilute the whisky before it is mature and again before bottling.  Most distilleries use different water sources for the different steps.  Most modern distilleries use distilled water for diluting the whisky before it is put into casks.  They also use distilled water to dilute the whisky to 40-46% alcohol by volume before bottling.  Some distilleries, like Bruichladdich, use local spring water for dilution before casking.

Barley is the other key ingredient in single malts.  Barley is malted by soaking the grain in water for 2-3 days and then allowing it to germinate in order to produce the necessary enzymes required to convert starch into sugar.  Before modern techniques were developed, most distilleries had their own malting floor.  The germinating seeds were regularly turned there.  These days, distilleries use commercial malt companies that make malts for individual distilleries to their exact specifications.  After 3-5 days, the germination process is stopped.  Then the germinated barley is dried using hot air produced by burning oil or coal or by using an electric heating source.  At this point, peat smoke is introduced to add phenols, a smoky aroma and flavor to the whisky.  The best examples of this  type of Single Malt Scotch come from the Isle of Islay.  I’ve tried a couple of them, most notably Lagavulin and Laphroaig.  Lagavulin is very smooth and delicious.  Laphroaig, on the other hand, has a very peaty aroma and taste.  It’s definitely unique among the Single Malts I’ve tasted.

Once the malt is dried, it is milled into a coarse flour, known as grist.  It is then added to hot water to activate the enzymes which will convert the starch to sugar.  The long starch chains are broken down into glucose, maltose, and maltroise.  The sugary liquid that is produced is called wort.  Yeast is added to the wort which is then contained in large vessels, usually thousands of liters in size.  They are either made of stainless steel or Oregon Pine.  The yeast consumes the sugar and produces alcohol and carbon dioxide.  You’ll probably recognize this process.  It’s called fermentation and we’ve seen this in the production of beer.  When this process is complete, we are left with something known as wash.

The wash is pumped into a copper pot still, a wash still, for distillation.  It is heated to boil off the alcohol.  The vapor is captured in a condenser that has been submerged in cool water which causes the vapor to condense back into a liquid.  This liquid has an alcohol content of 20-40%.   From here, the liquid is pumped into a second still, a spirit still, and distilled a second time.  This final spirit, called new-make spirit, has about 60-70% alcohol content. It should be noted that some spirits get a third distillation.

At this point, the new-make spirit is placed in oak casks to mature.  Scottish law requires that all Scotch whisky must be aged a minimum of 3 years in oak casks in Scotland.  You’ve probably noticed that most of the Single Malt Scotches at your favorite bar are aged much longer.  It’s not uncommon for a Single Malt to be aged for 20 years or more.  Like cognac, which I’ve written about recently, the alcohol content decreases during the maturation process in the cask due to evaporation.  And like cognac, this loss is referred to as the angels’ share.

The type of casks used for aging have a profound effect on the finished product.  Single malts are too delicate to be aged in new oak casks because new oak can overpower the whisky with vanillin (the primary component of vanilla bean extract) and tannin.  Instead, used casks are used.  The most common practice is to purchase used casks from American whiskey makers.  You may recall that U. S. law require bourbon and Tennessee whiskey to be aged in new oak casks, so after their first use they are taken out of service.  Another recent trend is the practice of using sherry casks.  They are far more expensive than bourbon casks, so they are rarely used.  One of the benefits of using sherry casks is that it imparts the flavor of the sherry and gives the whisky a heavier body and a deep amber color.  Single Malt Scotch that has been matured in sherry cask are highly sought after.  Macallan Distillery actually builds casks, leases them to sherry cellars in Spain, and then has them shipped back to Scotland to be used to make Scotch.

Finally, after a bit of aging, the whisky is bottled.  The bottle can only contain malted barley produced at a single distillery.  Otherwise, the contents are referred to as a vatted malt or a blended malt.  Single malt whisky mixed with grain whisky is called blended Scotch whisky.  There is no law to dictate who bottles the finished product.  They can either be bottled by the distillery or by an independent bottler.  The age on the bottle refers to the age of the youngest malt in the mix.  Mixing of whiskies from several different years is done in order to maintain consistency.  One recent trend has been to bottle cask strength or undiluted whisky which can have a alcohol content approaching 60%.  There are also Single Cask offerings which is whisky bottled from a single cask rather than blended from multiple casks.

Before I finish, I wanted to add a couple of final notes.  Unlike wine, once bottled, whisky does not continue to mature.  Also, its quality doesn’t diminish once opened.  Lastly, Drambuie, the honey and herb flavored golden Scotch liqueur, also made in Scotland, is made with a Single Malt Scotch called Talisker. Talisker is made on the Isle of Skye and is my personal favorite when Single Malt Scotch is my flavor of the day.