Whiskey refers to a grain brandy obtained from the distillation of fermented musts and resulting from the saccharification* of cereals (barley, rye, oats, corn) using malt.

Since whiskey is not directly linked to a terroir, it can be produced in any region of the world. However, there are protected whiskey appellations such as Bourbon (USA), Tennessee (State of the same name), Scotch (Scotland) and Pot still (Ireland) linked to a specific terroir and manufacturing process. In France, there are two PGIs: one for Breton whiskey and the other for Alsatian whisky.

From a historical point of view, Scottish and Irish still dispute the paternity of whiskey today. The origin of this cereal brandy remains difficult to date or locate geographically. It is nevertheless commonly accepted that the first written mention relating to whiskey is Scottish and dates back to the year 1494: it is an extract from an account book, the Exchequer Rolls of Scotland dated June 1, 1494, allotting to brother John Cor, by order of the king, eight bolls* of malt for the manufacture of brandy. On the Irish side, the distillation process is mentioned a century earlier in Chaucer’s Canterbury Tales (circa 1387-1394).


Three basic ingredients go into making whisky: grain, water, and yeast. Despite this apparent simplicity, whiskey production requires a lot of know-how and several manufacturing steps are necessary before obtaining the final product. Each manufacturing step also plays a key role in the construction of whiskey aromas.


The malting stage consists of immersing the cereals in water for 2 to 3 days (soaking or wetting). Malting is a sprouting process that aims to develop amylase in cereal grains. Amylase allows during subsequent manufacturing steps to transform the inert starch into a sugar called maltose.

All cereals can be malted. The choice of this or that cereal will depend in particular on the aromas that the distiller wishes to develop: barley will bring a great aromatic richness, rye a spicy touch, wheat light and floral notes and oats roundness. Corn, which is notably used in the composition of Bourbon (up to 51% minimum), cannot malt. It therefore undergoes steam cooking which allows the transformation of the starch it contains into fermentable sugars.

The malt obtained is then dried and then cooked during kilning. The kilning stage is traditionally carried out with peat, which gives the characteristic smoky notes. Once kilned, the malt is ground into a coarse flour called grist.


Brewing completes the process of transforming starch into sugar before the fermentation stage.

The grist is first mixed with hot water (between 60 and 65°C) in order to extract the starch from the cereals to transform it into sugars. Above 65°C, the malt enzyme dies and transformation into sugars becomes impossible. The sweet wort obtained after this first brew is called wort. This undergoes a second stirring in water heated between 70 and 75°C to extract the sugars remaining in the malt. A third brewing in water heated between 80 and 85°C is necessary to complete the brewing step.

Water quality is essential for brewing. Although it is generally considered that water only enters 5% of the aromatic palette of a whisky, breweries generally choose to locate strategically near sources of pure water.


The must obtained after brewing is cooled to a temperature of around 20°C and added with yeast. This is the ideal temperature for alcoholic fermentation to take place. The fermentation lasts between 40 and 72 hours, until all the sugar is transformed into alcohol.

The mixture obtained after fermentation, called wash, is a kind of malt beer whose alcohol content is between 6 and 8% vol.


To increase its degree of alcohol, the wash is then distilled, in two stages (sometimes three as for Irish whiskey), in copper stills whose shape and size will affect the aromatic palette. The first distillation takes place in a large still, and the second in a smaller still. At the end of the distillation, only the middle cut, a colorless eau-de-vie measuring around 70% vol., will be put into barrels.


It is important to note that the distillate resulting from the previous stages of production is not yet called whisky. It is only after aging in oak barrels for a minimum of three years that the eau-de-vie becomes whiskey by coloring and developing the majority of its aromas.

Aging can be done in new or used barrels. The main types of kegs used are:

  • Bourbon barrels, with a capacity of 180 to 200 liters, in American oak (quercus alba). The Bourbon appellation requires aging in new barrels. After being used for aging Bourbon, the barrels are resold for aging rum or whiskey (Scotland and Ireland).
  • Sherry butts, with a capacity of around 500 litres, in European or American oak.
  • Hogsheads, with a capacity of 230 to 250 litres, are made from Bourbon barrels to which new staves or staves from sherry butts are added.
  • Wine or brandy barrels of different origins such as the 600-litre Port Pipe (Portugal), the rum puncheon, with a capacity of 480 to 520 litres, the 350 or 400 liters in French oak used for the aging of Cognac…

The aromatic toasting also has an impact on the aromatic palette depending on its intensity but also depending on the number of fillings, it being understood that the cask will only give notes to the whiskey during the first two fillings (first fill and second fill).

Tonnellerie Leroi is able to provide you with specific and personalized advice in terms of oak barrels or large containers for aging your whiskey, but also for the design and layout of your storage cellars.
Contact Thierry Marrot, on +33 (6) 80 37 91 26 or by email t.marrot@tonnellerie-leroi.com

*Process of transformation into fermentable sugars (glucose, sucrose) of starchy or cellulosic substances.

**Old measure of weight worth just over a ton.