The video given here provides you with an outline production process of the scotch whisky industry. However across whisky/ whiskey industries the steps vary with the intervention of factors that provide each of them a characteristic nuance of their own. I have made an attempt to highlight a few of these in the section below, to appreciate whiskies better and for an interesting read as well !
It all starts with a Grain
The four most popular grains used in the making of whiskies are barley, corn, rye and wheat. Each grain variant contributes to a whisk(e)y’s flavour and characteristic individuality of its own. It is from the grain that we extract the starch source essential for the making of the alcoholic spirit.
We need to malt that barley to extract fermentable sugars from it. Malting is an act of deception played on the innocent barley which is wallowing in its world of germination. This is when the cruel kiln cuts it short to dry it into a crisp seed to stop the growth further. Thats the time when the enzymes start breaking the protein walls and also convert the starches into sugars. Yes we are then, quite ready for the next process.
Growing in abundance in America, this had to be their preferred choice as a grain for whiskey making. Lends a great deal of sweetness to the palate in comparison with the other grains and over the years the aromas of corn whiskies turn out to be mellow in the wood, making the resultant whisky, balanced & sweet.
Whiskies made with this grain has a bounty of spices such as cloves, pepper and impart a signature fruity flavour as well.
This grain is more like a balancing factor to the other grain and is hence defined more with attributes like floral, being delicate and rounded.
The malted barley is ground to a fine powder called ‘Grist’, this ground up malt is then mixed during the process of mashing with hot water towards the extraction of soluble sugars. Most of the water taken is from a source close to the distillery. The resultant liquid that we get is called ‘Wort’. The residue from this process is called 'Draff' and is used largely for cattle feed.
Cooled ‘Wash’ is passed into large tanks called wash backs for the process of fermentation. It is at this stage that the yeast converts the sugar into alcohol. Most of the esters which impart the fruity & floral aroma get developed at this stage. Distillers are very particular on selecting the nature of the strain of yeast used, since it can have an effect on the final spirit. This process normally takes 48 hours, however some distilleries may alter this duration towards the higher side to create a further distinction in their spirit. Fermentation leads to the creation of a liquid called ‘Wash’ which is low in alcoholic strength, ranging between 5% - 10% ABV.
Post fermentation the ‘Wash’ is transferred to the holding tanks and then to copper pot stills for distillation. The size, shape and number of stills plays a big role on the characteristic nature of the spirit. Copper has been used traditionally for two reasons, it acts like a catalyst towards removing impurities and is a great conductor of heat. Coming back to the shape of the still, the taller the still, lighter and finer is the spirit, while shorter stills tend to produce richer and fuller spirit.
Stills work in pairs, first the ‘Wash’ enters the ‘wash still’ and produces a liquid called ‘Low Wines’. This is then transferred to ‘Spirit Still’ and the residual alcohol is split into three cuts, the head, heart (also called the middle cut) and the tail. The heart at an alcoholic strength of 65% - 70% ABV is taken for maturation.
While this is the distillation process of most scotches, Irish whiskies are distilled a third time as well and are hence triple distilled, producing an even purer spirit.
This is the magical process that turns the raw, new make spirit into that golden or amber hued sunshine, with varying complexity, a liquid that we finally identify as the matured whisky. The time of maturity depends on the storage conditions, climate, norms set by the industry, size/ nature of cask and most importantly the balance of all of these along with what the master blender is looking for in his resultant whisky.
For a whisky to be classified as a scotch it needs to be matured for a minimum of three years in oak barrels. A Bourbon whisky on the other hand needs a year lesser at two years of maturation in new, charred, white-oak barrels. Maturation rules are similar to scotch for Irish whiskies.
Influence of Wood
The skill and expertise of making casks is an age old practise called coopering. Its an art which makes new and refurbishes' the old casks, both. The job of a cooper is very fine, since much of the flavour of a whisky gets picked up at the stage of maturation, perhaps thats why it takes years of training to acquire this expertise.
There are three main kinds of wood used today in the making of an oak:-
Somewhere in the 1860s UK started to import sherry from Spain. The casks used for transportation and maturation of sherry were made of Spanish oak and turned out to have similar properties as Russian oak which was used earlier in the UK whisky industry for maturation. It was also a more economical substitute then. Sherry industry however, declined post 1970s, but spanish oak is still quite preferred, despite it being nearly ten times the price of a bourbon cask !
Key Flavour attributes - rich dried fruits, spices, caramel, christmas cake, sherry, wood
Post 1920s the world especially, Scotland and Ireland got a profusion of bourbon casks with the law which required American whiskies to be matured only in new oak barrels. This was largely done to boost the coopering industry which had crumbled under the pressure of the prohibition era. These oaks are perfect for cask making since trees are fast growing, trunks are straight with high levels of vanillin’s. The size of the barrel is also sound for the whiskey maturation, for the surface area of the barrel and the liquid within it is of the optimum ratio. Today bulk of the world uses American oak bourbon barrels!
Key Flavour attributes - Vanilla, honey, hint of spice, butterscotch, hazelnuts, almonds, fudge
An introduction by the Japanese whisky industry, this one’s fairly recent and was started being used in 1930s. Being extremely soft and porus, the oak is quite prone to leakage, hence its now used for finishing post having been matured in bourbon or sherry casks to achieve the flavour facets.
Key Flavour attributes - vanilla, floral, spice, wood, fresh fruit - apples
While lending its flavour to the final whisky every cask breathes while it’s maturing as it rests peacefully. Contracting during the cold of the winter and expanding during the summers, in this entire process it loose a share, somewhere close to 2% of its liquid as evaporation annually while it matures.
We call it angel’s share, thirsty happy angel’s of the whisky maturing regions of the world !