To make alcohol, we need sugar. A nice, warm climate might provide us with a raw material already rich in sugar, like grapes or sugar cane. Our Irish forebears were not so fortunate and had to put their biotech thinking caps on. They solved the problem with the happy discovery that starch can be converted to sugar which may then be fermented to yield the desired alcohol.
In Ireland, therefore, we start with a readily available starchy grain. Converting the starch to sugar requires an enzyme, diastase (also called amylase). Allowing germination of the grain to begin is the trick that supplies us with sufficient amounts of that enzyme to catalyze the starch conversion. During germination, enzyme levels rise, the production of sugar begins and the cell walls of the starchy reserve break down, thus making the starch more soluble in water. In the malted grain, germination has been halted before the sugar is used up by the young shoot.
We can malt any grain but as far as whiskey in Ireland (and Scotland) is concerned the grain is barley.
'Malt', in the whiskey business, usually refers to malted barley. Up until the 19th century, however, Irish distillers also malted oats. E.B McGuire, in his book, Irish Whiskey (1973), reports that oats were said at the time to produce a better flavoured whiskey.
The practice of malting oats died out when a duty was imposed on malt. Since the duty was assessed on a volume basis, and since oats swelled far more during the steeping process than barley, it made economic sense to abandon oats.
An example of a whiskey made from a malted grain other than barley is Old Potrero, a rye whiskey from the US.
We will examine here the traditional malting process, known as floor malting. Although this is not the method in use in Ireland today, it's worth knowing about since it explains several features of the historic distillery buildings still dotted about the country. Also, no matter what technique is employed, the stages the barley must go through are the same.
- Steeping
- The malting process begins with steeping in a stone or cast-iron cistern. The grain is covered with water and light barley (unsuitable for malting) and debris that floats to the top is skimmed off. The grain is left for at least forty hours and perhaps as many as sixty. The water may be drawn off and replaced several times during steeping. When the barley has absorbed enough moisture the cistern is drained and the grain is transferred into a couch frame.
- Couching
- The couch frame is a wooden-sided receptacle in which the grain lies at an even depth of about 16 inches. It is left here for a day or more until the temperature of the grain begins to rise and surface of the grain begins to dry. Germination is beginning.
- Flooring
- The grain is now spread out on a stone or concrete malting floor, initially to a depth of about 12 inches. The temperature continues to rise and it is at this point that rootlets appear. To keep the temperature from rising above 60°F, to ensure even germination, and to stop the rootlets becoming entangled, the grain is regularly turned over. At each turn, the grain is laid a little thinner. The turning is typically done by tossing the grain over the shoulder with a wooden shovel, known as a shiel.
The shoot, or acrospire, has started to grow within the husk. Flooring is deemed complete some time before the acrospire breaches the husk. The flooring stage might take ten days or considerably more, depending on the ambient temperature. Cold weather slows the grain's development. - Kiln-drying
- The final stage is to halt all further growth by heating the grain (now called green malt) in a kiln.
Early kilns consisted of a fire below a floor of fine wire mesh, perforated tile or perforated metal plate. The malt was spread thinly over the floor and the fire's heat allowed to rise through it. Anthracite was burned to minimise the amount of smoke, which would taint the malt. Occasionally peat was used. Peat smoke imparts a very particular flavour to malt and this feature of early kilns is recreated in modern times for the production of many Scotch whiskeys (along with the odd Irish whiskey).
An improved kiln design saw the furnace gases conducted via flues below the kiln floor, these flues heating the air that rose through the drying malt. This eliminated any possibility of smoke taint.
At first, the kiln temperature is not higher than about 90°F but this is slowly increased to about 120°F over a period of two or three days. To prevent charring, the malt is regularly turned.
At the conclusion of kilning, all growth of the grain has ceased. A light raking of the malt is enough to separate the rootlets from the grains and these can be sold separately as animal feed.
The dried malt can now be stored for a considerable time without degradation until ready for use in the next stage of distillation, mashing.
Until 1880, a duty was applied to malt as well as to the finished spirit. Excise laws specified in great detail how malt should be made to ensure that the dutiable volume was as great as possible. For example, since the Excise men gauged the malt in the couch frame after steeping, a minimum steeping time was specified to ensure that the grain was fully saturated. Lest the maltster be tempted to trim the steeping time, subsequent sprinkling with water during flooring to make up any deficiency was strictly limited.
A contemporary description of malting (An historical account of the malt trade and laws, William Ford, 1849) lamented:
Since the Reign of Queen Elizabeth... no trade nor manufacture has laboured under so vast a complication of oppressions from fiscal regulations and other disadvantageous circumstances as the malt trade...The "superabundant restrictions, regulations and penalties" stifled experimentation and innovation in malting for a long time.
Today, a mere handful of Scottish distillers (and no Irish ones) maintain a traditional floor maltings. While the process is still much the same as described above, a greater understanding of the science behind germination, careful selection of barley varieties and some new tricks (like pumping oxygen into the steep) have knocked days off the total malting time. It still takes as many as twelve days to complete a floor malting, however.
We shall look at other malting methods in a later article.