The Malting Process

Click on the small pictures to see a larger version

Whisky-making is a seemingly simple endeavor, using only four major ingredients - water, barley, peat, and yeast - and some distilleries pride themselves on eliminating peat from the equation (although that is hard to do entirely, given than much of the water in Scotland flows through or over peat at some point in its journey to the sea. However, the differences between the products of different distilleries are readily discernible, even in the raw spirit fresh from the still - and this in spite of only minor variations in the raw materials and basic process. The first step in the process is malting. Malting is the process of taking green barley, partially germinating it (which activates important enzymes within the seed, which in turn begin to reproduce and to turn the more complex starches into simpler starches and sugars), and then drying the resultant malted barley.

First, barley is acquired, then alternately soaked and dried in “steeps” for about three days; once the grain has absorbed enough water and oxygen, it is dumped on the malting floor, and spread out to a depth of 4-6 inches. On the malting floor, the barley starts to warm up and germinate. Over the next week or so, the barley is turned about twice a day, with windows being used to adjust the temperature. The turning serves to both moderate the temperature and disentangle the rootlets as the barley starts growing. During this process, important enzymes within the seed are activated, and begin to reproduce and to turn the more complex starches into simpler starches and sugars. Once the barley root is about is long as the barley seed, the process is halted.

Very few distilleries do any of their own on-site malting these days. Those that do generally do not produce more than 1/4 to 1/3 of their requirements. The rest comes from industrial box or drum maltings (see, for example, the maltings at Port Ellen). The following pictures come from three distilleries which still (as of late 1998) perform at least some floor maltings - Springbank, Laphroaig, and Bowmore. In the few remaining floor maltings, the barley is alternately steeped and then dried (i.e., drained and aerated with a compressor). This sequence of twelve hours steeping followed by twelve hours drying is repeated three times (over three days). Then the green malt is then shoveled out onto floor to a depth of about four inches.

[Freshly laid out germinating barley] Freshly laid out germinating barley

After about 24-36 hours the green malt starts to heat up and germinate (it needs to be in the range 60 - 80 °F, depending on the distillery, barley, etc.) Generally, the maltings have windows which can be used to adjust the temperature. The malt is turned whenever it starts to go over the target temperature. At the start, this is 2-2 1/2 times per day. After seven days, the malt is being turned about once every eight hours, more often in summer. Several different tools (shown below) may be used to turn/separate the barley after it has been laid out on the malting floor.

[Malting tools] Tools of the (malting) trade

Generally, the shiel (or malting) shovel shown above on the right is used for the first few days. Then, as the barley begins to send out shoots (see picture below), the puller (hand rake) is used.

[Two day old germinating barley] Two day old germinating barley

Below is a picture of a puller in use.

[Turning the malt] Turning the malt

Later still a rotary turner may be used. After about seven days, the root is approximately the length of the grain, and the process is ready to be stopped. The green malt is transferred to the kiln, where it is heated to dry it. Originally, peat fires were used to dry the barley; now, oil or coal are often used instead, with some peat thrown on the fire to provide the “traditional” peat (phenol) character to the malted barley when desired. Drying time is a function of method: with peat fire only, it might take 2-3 days; with oil heat only, it can be done in less than half the time. After drying, the malt is dressed, roots are removed, and it is allowed to sit and cool.


For more information on barley and the malting process, see:

American Malting Barley Association Publications List

American Society of Brewing Chemists

The International Centre for Brewing and Distilling

Brewing and Malting at UC Davis (Looks like much of the former content here has transitioned into an off-line book)


Other References

The contributions of the process to flavour in scotch malt whisky, Alistair Paterson and John R. Piggott, in Distilled Beverage Flavour: recent developments, edited by J. R. Piggott and A. Paterson, Cambridge, New York, 1989.


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