Kilning & the Scotch Whisky Production Process

Kilning refers to the method of drying germinated barley using hot air. It is the third and final stage of the malting process (steeping, germination, kilning) and is a crucial step in the Scotch whisky production process.

Steeping sees the barley grains soaked in water which allows germination to occur, activating the enzymes that convert starches into fermentable sugars. After germination, the barley is referred to as “green malt” and at this point, further growth must be halted.

Kilning ensures that germination is stopped. This is achieved by blowing hot air through the bed of green malt. It is at this stage that peat can be burnt to create that smoky flavour that some Scotch whiskies are well known for.

Peat reek (that is, the smoke from burning peat) can be passed through the wet green malt and the phenols adhere easily to their wet surface. It is for this reason that peat tends only to be burnt at the start of kilning.

The green malt is then dried down to about 5% moisture, thus allowing for safe storage prior to use in the distillery. 

The diagram illustrates the kilning process:

1. In a traditional kiln, the green malt sits on the perforated kiln floor.
2. Peat can be burnt for a smoky flavour.
3. Phenols from the peat reek adhere to the surface of the malt.
4. The hot air from the heat source (fire) passes through the grain bed by the natural circulation created by the pagoda roof.
5. As the hot air passes through the bed, the grain is dried, firstly for storage and ahead of use in the distillery.