Malt is brilliant. It’s hugely useful to distillers. The enzymes it produces can convert large quantities of starch into simple sugars. Also, It tastes delicious. But what is Malt? And how is it made?
Malt is the name for artificially germinating a grain, and then stopping the process before a plant is grown.
Any grain can be malted. However, barley is the most common malt. This is because malted barley has a very high diastatic power, meaning it contains enough enzymes to convert starch into sugar in several times it weight of grain, whereas most other grain malts have low diastatic power So they only contain enough enzymes to convert itself.
When barley (or any grain) germinates the embryo of the seed needs to access the starch in order to have the energy to grow. The Barley; Forms a root and shoot, releases enzymes to expose the starch, and releases enzymes to break down the starch.
Malting requires a number of processes. Traditionally these would have been done manually on site at the distillery, but now it is more common for distillers to buy in malt from large commercial maltings.
- Steeping. Barley grains are placed in large stainless steel or concrete tanks. They are submerged, drained, rested, and soaked again. This process takes 24-48 hours and should give the barley an optimum water content of 45%. Some maltings will pump in air during the wet phases, to move the grain and ensure an even steeping. The steeping process mimics the natural rain cycle that would stimulate seeds to grow in a field.
- Germination. The grains are transferred into a malting vessel. The grain needs to be kept in motion so that the roots and shoots don’t mat and tangle. Historically, this was done on a germination floor (floor maltings). In a floor maltings the grain is laid out on the ground and turned by hand using shovels, rakes, or specialised devices that look, and function, a little bit like modified lawnmowers. Very few distilleries or commercial maltings still operate a floor maltings, due to the high cost in both space and manpower. These were replaced by Saladin boxes, which are large rectangular boxes, with a gantry holding vertical screws that traverses the box to move the barley and stop the grain matting. These have fallen out of favour in preference of large rotating drums, or static drums with rotating elements, which tend to be more space efficient and stop grain getting caught in corners. Modern malting vessels may also be fitted with the capacity to blow humidified air through the grain to aid in motion, temperature control, and to stop the barley drying out. This process can last up to 6 days.
- Kilning. The malted grain now needs to be dried. This kills the embryo and stops the germination process. It is important to heat gently but consistently in order to preserve the enzymes. In order to be more gentle, kilning is usually done in stages. This process can take up to 48 hours. It is during kilning that peat can be burned in order to give a smoky influence to the produced whiskey.
- De-Culming. Finally, the malt is de-culmed, which removes any roots or shoots that have formed. This is done in a specialised machine that uses rough paddles and a fine mesh grate to knock the roots and shoots off the barley malt without damaging it.
Malt is almost indistinguishable to unmalted barley visually, but is much softer to bite into. Unmalted barley also tastes mealy, whereas malt is slightly sweet and tastes ‘maltier’ so to speak.
