Like many other esteemed spirits, such as Scotch, Tequila and Cognac, there are very strict laws and restrictions governing the production of bourbon whiskey. These legislations have been put in place to guarantee the quality and consistency of the product and to make sure that consumers get the experience they are paying for.
Bourbon must be made from 51% corn (most distillers use between 65% to 75% corn) and a collection of “small grains”. These are usually rye and malted barley, although some producers substitute rye with wheat. The exact combination of grains differs from distillery to distillery and brand to brand. Once quality control has taken place the grains are stored and later ground to a fine flour in a hammer mill.
The grain flour is then placed in a mash cooker with iron-free water and cooked. The different grains (corn, barley and rye) are cooked at different temperatures and for different lengths of time. Once cooked, the mix is transported to a fermentation tank and is then called mash.
It is at this stage that the yeast is added (most distilleries cultivate their own special strain of yeast). The yeast breaks down the sugar in the mash and converts it to alcohol and carbon dioxide. It is a process that takes around three to four days. The product at this stage is a type of beer.
To separate the whiskey from the beer, the mix is pumped into the distillation stills. As alcohol boils at a lower temperature than water – at 78.2º – the beer is heated to this temperature. The vapour rises to the top where it passes through a water-cooled condenser (or worm) where the steam is cooled into a liquid again. At this stage it is pretty rough stuff, so all bourbon has to be distilled at least twice.
Bourbon must be aged for at least two years in new white oak barrels. These barrels are “toasted” over open fire to produce a charcoal layer on the inside of the barrel. These charred barrels significantly influence the taste and colour of the bourbon. The blackened charcoal acts as a charcoal filter which leaches impurities and pockets excess oils, while the red layer of char holds a range of different sugars (around twelve) which give bourbon its colour and confectionery flavours.