What is and why do we kiln malted barley?
Kilning can be described as the process by which the green malt is dried ready for safe storage, during which time stabilisation of the enzyme complexes take place and flavour compounds required by the distiller are produced.
Those of you who are familiar with Springbank will be aware that we produce three different types of New Make Spirit (NMS) and each of these require a different specifications of malt to produce the desired flavour profiles in the mature whisky. For those who are new to the forum I will explain briefly about the differing production techniques required to produce the malted barley for each product.
Hazelburn NMS is produced from a non peated malt which is dried using hot air produced from a light oil burner alone. There are no phenolic compounds present in the malted barley.
Springbank NMS is produced by smoking the malted barley by burning smouldering peat which produces copious amounts of reek for six hours in the kiln prior to using hot air to dry it down to safe storage moisture. This effect of peating for six hours produces a malted barley with a light phenolic content.
Longrow NMS is smoked for an extensive period of up to 48 hours before final drying with hot air. This produces a malt with a very high phenolic content.
Kilns are basically designed to remove moisture from the germinated barley and methods will vary extensively depending on the technologies employed at sites around the country. There will also be differences within the kiln profiles for certain malts but the basic operation is the same. What follows is a very brief outline of the theory of kilning.
There are three stages to kilning or drying the grain, the free drying stage, where large volumes of heated air is passed through the grain bed. As the term suggests the grain gives up it’s moisture quite easily from the outer surfaces. The forced drying stage as it sounds is when it becomes harder to remove the moisture from the grain. Air volume is reduced and the temperature of the incoming air is increased, this continues until the air temperature above the grain bed begins to increase until such a point as there is dynamic equilibrium of the air on and air off temperatures, i.e. the air temperature below the bed and the air temperature above the bed become constant. At this point kilning is complete but this is not the end of the kiln process. There is a further phase called the curing stage where flavour compounds are developed in the malt and are dependent on the requirement of the distiller. For distilling malts this can last for 2 or 3 hours depending on the specification of the required malt.
Should you want to learn more about the kilning process here at Springbank specifically drop us a line and we will gladly let you have further detail on our production techniques,
Stuart
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Tuesday, 14th April, 2009, 6:22 am, posted by Johannes de Jong
Stuart, Thanks for this fantastic article. I have one question though. You state that there are 3 stages in kilning and from your article it’s quite clear that dry air is used for phases 1 and 2. From your article I get the impression that phase 3 is where the peat is being used but that contradicts with “... this can last 2 or 3 hours depending..” because Springbank needs 6 hours and Longrow 48 hours of “peating”. Johannes
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Monday, 20th April, 2009, 8:42 am, posted by S_B_Distiller
Hi Johannes If you look at the kilning regimes for each of Springbank and Longrow production I explain that the peating takes place at the begining of the kilning process. We use peat at the start of the kilning process to infuse the malted barley with the phenolic odours. Warm air is used to dry the malted barley once the moisture content has fallen below 16%, after which the corn cannot physically take in any further phenolic flavours. Once the moisture content of the corns are below 16% moisture we use the oil burner to produce dry air to complete the kilning process. Only with Hazelburn do we use oil burner for drying throughout the kilning process. Hope this helps. Cheers Stuart
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