Ian Wisniewski reveals the secrets behind this rather complex stage of whisky-making: malting
It’s easy to romanticise floor maltings, but anyone who has turned the malt and pulled a plough (as I did at Bowmore) knows this is a demanding, not to mention expensive, practise.Commercial maltsters, who provide for the vast majority of the industry’s requirements, have been around since the 19th century, though it wasn’t until the 1960s to ‘70s that business began to boom. That’s when various distilleries added new mashtuns, washbacks and stills to increase production capacity, though malting floors were not increased accordingly. It simply wasn’t financially viable, and many malting floors were closed, as commercial maltsters equipped with modern technology offered more consistent quality at a more competitive price. Among the few distilleries retaining malting floors are Bowmore, The Balvenie, Highland Park, Laphroaig and Springbank.Malting comprises three essential stages: steeping, germination and kilning, which provides the distiller with direct access to the grain’s starch content. Starch is present within the endosperm (the main interior section) and serves as a food source, enabling the grain to produce the energy required to develop roots and an acrospire (shoot). The starch is initially enclosed within protein-lined cell walls, which the embryo begins to break down as it grows, in order to utilise the starch. Once the starch has been liberated, further growth is arrested by kilning (applying heat), otherwise a lower starch level would reduce the yield of alcohol.Steeping effectively ‘awakens’ the barley by hydrating the grains in steeps (vessels), with up to three separate batches of water raising the moisture level from around 12 per cent to 40 to 45 per cent. Simultaneously, ‘pressure aeration’ can be applied, which means blowing compressed air from the base of the vessel. This aeration is assertive enough to move barley from different levels of a steeping vessel, but gentle enough not to cause any damage; some movement promotes more consistent growth. Otherwise, barley remaining at the bottom of a steep would receive less oxygen during what is termed an ‘air rest’, diminishing the growth rate.Draining the steeps in between each batch of water gives the grain an air rest of several hours, or longer. During this period ‘suction aeration’ can also be used to introduce fresh air into the steep, while carbon dioxide is removed to ensure even growth.Air rests may seem to extend the timetable, though grain left continually underwater can actually take around twice as long to process. Air rests provide more oxygen which raises energy levels, and makes it easier for the grain to absorb water. This explains why the uptake of water is far more rapid after the first air rest, once the grain is ‘energised’. Moreover, the micropyle (opening) at the tip of the grain is the most efficient conduit for taking in water, whereas the outer layers of the grain are relatively waterproof (and water uptake through these outer layers is slow).The water used for steeping at Port Ellen Maltings on Islay is piped direct from Leorin Loch in the nearby hills. A seasonal adjustment involves heating the water to between 13.5 and 14.5°C from mid-September to late May. Otherwise, adding colder water would simply prolong the time required to initiate germination, and enforce longer air rests. Moreover, as grain generates heat during steeping, adding a subsequent batch of water at a cold temperature would instigate thermal shock (grains loathe abrupt temperature changes).Visible confirmation that the grain is responding to its wake up call is the appearance of a ‘chit’, a small white root tip at one end of the grain. Diastase also begins to form, and continues to develop during germination (this combination of enzymes subsequently starts to break down proteins and starch in the barley, making them soluble, which is essential for the conversion of starch into sugar during mashing).Barley can be germinated either spread evenly across stone or concrete malting floors, or in germination vessels such as drums. On a malting floor this may take five days in summer, seven in winter, reflecting the ambient temperature. The barley is aerated by ‘turning’ (redistributing) it every few hours using a ‘malt shiel’ (spade), which helps control the temperature and rate of germination. Alternative options are a ‘plough’ (a three-pronged rake) or a type of rotivator, supplemented by another basic form of temperature control, either opening or closing windows.The germination drums at Port Ellen Maltings are not only the UK’s largest, but also have the ultimate pedigree of being manufactured by the firm of Robert Boby. Each of seven steel drums holds the contents of two steeps (i.e. 50 tons of barley at original weight, 65 tonnes after steeping). Loading the grain into drums inevitably results in two separate piles of grain. As this would foster uneven growth rates in different sections of each pile, the drum is rotated twice. This procedure is assisted by angled fins bearing a corkscrew pattern set within the drum ensuring the grain spreads evenly across the floor.A perforated steel floor enables carefully controlled volumes of air, generated by large fans, to be blown through the grain. This maintains the appropriate temperature, and as the air is humidified with fresh water it also promotes the right humidity for growth (ordinary air would simply dry the barley too soon).The air flow, humidity and temperature are adjustable in order to control the growth rate, with the temperature not exceeding 25 to 26°C. Too high a temperature entails a risk of the embryo dying and damaging the enzymes. Another factor promoting consistent growth rates is that the circulating air also removes heat and carbon dioxide from the drum (exiting through vents).Continued growth sees the grain beginning to break down the cell walls and protein lining to access the starch. Meanwhile, developing rootlets also consume protein, which is another advantage. Protein must be carefully managed in order to avoid problems at subsequent stages in the production process. Higher levels of protein diminish the effect of hot water on the starch during mashing, for example, which
compromises the rate of conversion into sugar. Protein can also burn onto the surface of the wash still, contributing undesirable caramelised flavours to the new make spirit.However, if rootlets were left alone to do what comes naturally, they would intertwine and create a dreadful tangle. This is countered by rotating the germination drums every eight hours, a leisurely turn lasting five minutes at Port Ellen Maltings, with the fins gently teasing the roots apart.After about five days the grain reaches an optimum stage of growth when most of the protein has been utilised for root growth, and the cell walls have been broken down, providing direct access to the starch. The acrospire (shoot) also extends under the skin (husk), along around three-quarters of the grain’s spine. Any longer would indicate excessive growth. Any shorter, and it’s not quite ready.A traditional method of checking growth was for the Maltman to inscribe his initials on a spade using a grain. If legible, the malt was ready. Another low-tech option is the ‘rub test’. By splitting a grain open with a fingernail, a small amount of the endosperm can be rubbed between the thumb and forefinger. If this leaves a fine white powder mark, it confirms that the starch (in the form of barley flour) is ready for kilning. A lack of white powder indicates the starch is still enclosed by cell walls and protein.The aim of kilning is to arrest growth by drying the malt as quickly and uniformly as possible, with the moisture level typically 40 to 50 per cent at the beginning of the process. Taking care not to damage the heat-sensitive enzymes, the initial temperature is around 40 to 50°C. Once the grain reaches the ‘break point’, when the surface moisture has been driven off, the temperature is gradually increased to around 75°C.For malt that is being peated, an important factor is that moisture promotes the absorption of smoke, essentially by the husk. As the surface begins to dry, it becomes harder for the grain to absorb smoke, until reaching the ‘break point’.Once the peating has been concluded, kilning dries the malt further (essentially the interior of the grains) to a moisture level of about 4.5 to 5 per cent. This can take from 25 to 40 hours, using either hot air or firing the kiln with gas or fuel oil. In addition to peaty, smoky flavours created by peating, kilning also develops the malt’s flavour profile with a range of sweeter, biscuity notes.After the rootlets have been removed, malt is subsequently rested in sealed bins for several weeks. As the heat of kilning concentrates residual moisture in the centre of the grain, the resting period allows this moisture gradually to extend back and be evenly distributed throughout the grain. This ensures milling is more even, promoting fermentability and consistency.The rootlets aren’t wasted either, serving farmers rather than distillers. Mixed with dust from incoming barley to form ‘malt residuals,’ then dampened with water and shaped into pellets, this is used as cattle feed. Islay cows are used to the peaty flavour that their local ‘take-away’ serves up, whereas mainland cows are not. However, Port Ellen Maltings also caters for them by adding a small amount of molasses to the recipe, which sweetens the flavour.
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