20th October 2018

Whisky Production: Malting Barley

As mentioned in our previous article, “What is whisky made from?“, whisky is made from grains. Malt whisky more specifically is made from barley. The yeast added during the fermentation stage however are unable to use the starch present in the barley to produce alcohol. The starch must therefore first be converted into fermentable sugars. This is achieved through a process known as malting.

If left out in the field, this conversion of starch to sugar would occur naturally. Cytase and protease enzymes within the grains would begin to degrade the cell walls, making starch available for α-amylase and β-amylase enzymes to turn into sugar. It is this sugar that the barley embryo would then normally use as fuel to grow. Malting takes advantage of this natural process by tricking the barley into thinking it is time to grow. This sets off the chain of events to convert the starches into sugars which is then abruptly stopped before the embryo can consume them, after all, we need them to make alcohol.

The malting process consists of three stages: Steeping, germination, and kilning.

Steeping

The first stage in the malting process sees the grains steeped in water. The purpose of this is to increase the moisture content of the grain from 12% to around 45%. The grains are soaked in water for a period of several hours, during which time air is blown through the grains to ensure enough oxygen is present for the developing embryos. Once hydrated the enzymes begin to degrade the cell walls making the starch available and germination can begin. The water is then drained and the wet barley is allowed to rest in air, helping to control the heat and carbon dioxide levels produced during germination.

This process is repeated 2 to 3 times over a period of 2 to 3 days in order to ensure all the grains are evenly hydrated and germinating.

Germination

Once germination has started, the damp barley – now called green malt – is transferred to a germination vessel to allow further enzyme development. This was traditionally a malting floor where the grain would need to be turned by hand using a shovel – this led to an injury in many maltsters known as monkey shoulder. These days most malting is done in modern, industrial malting towers. However, some distilleries (Laphroaig for example) still produce a fraction of their own malt in the traditional manner and seeing this being done is a real highlight on their distillery tours.

Throughout this stage the green malt has to be turned frequently to ensure an even distribution of temperature and moisture and to prevent the grains from sticking together. Modern facilities have perforated floors where air can be blown through the grain bed to control temperature and moisture. Most also incorporate some kind of mechanical turning arm to mix the grain bed and keep it loose.

The germination stage lasts approximately 5 days, depending on the required malt specifications.

Drying in the Kiln

As mentioned above, the germination process has to be stopped before the embryo consumes the sugars. This is done in the kiln – the chimney of which is the large pagoda roof featured on the majority of distilleries – by blowing hot air through the grains.

It is at this stage that many whiskies pick up their smoky character. Prior to drying with air the green malt is introduced to smoke by lighting a peat fire below the kiln. Back in the day many distilleries would not have had access to other heating materials such as coal or wood and will have used what natural resources were available for drying the malt. In the case of many areas in Scotland, especially Islay, peat was an abundant material. Even after the introduction of better heating sources the practice continued due to the distinctive character it lends to the whisky.

By adjusting the level of air flow and temperature, malts of different flavours and colours can be produced. The moisture content of the dried malt is roughly 3 – 6%. The malt is then put through a deculmer machine to remove the tiny rootlets that emerged during germination before being stored ready for the next step in production: Mashing and Fermentation.

Want to learn more about whisky production?

Take a look at the next step in the production process: Mashing and Fermentation

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Whisky Production: Mashing and Fermentation

Whisky is made by distilling beer. As such, we first need to produce a beer before we can distil it. This article covers the brewing process for whisky. Having converted the starch in the barley to fermentable sugars by malting, we now want to extract the sugar. The yeast can then be added in order to produce the alcoholic liquid that will later become whisky. Brewing is separated into two distinct stages: Once the malt has been milled, it is mixed with hot water to extract the sugars and any remaining starch. This stage is known as mashing. The milled malt is initially mixed with water at a temperature of around 64°C. During mashing the grist absorbs water and the sugars begin to dissolve. The remaining starch gelatinises in the hot water, making it easier for the enzymes to hydrolyse it further into fermentable sugars. The first water is then drained off and a second water is added at a temperature of around 70°C. The higher temperature of the second water dissolves further sugars, increasing the extract efficiency. This water is again drained off and a third water is added at temperatures between 80°C and 90°C. The third water ensures that as much sugar as possible is extracted from the mash. The sugar content in the third water is so low however, that it is not used in fermentation but instead recycled and used as the first water for the next mash. Depending on the distillery, occasionally a fourth water is also used. There are three types of vessels in which mashing can take place: mash, lauter and semi-lauter tuns. Traditional mash tuns use large paddles to mix the grain whereas lauter tuns use a series of revolving rakes. Lauter tuns are thereby able to agitate and apply pressure to the mash to a higher degree, increasing extraction efficiency. All other designs between mash and lauter tuns are categorised as semi-lauter tuns. All three have slots in the floor to filter off the sugary liquid, now called wort. Once mashing is completed, the remaining grain (called spent grains or draff) is removed from the mash tun. It is often sold on to farmers to be used as cattle feed due to its nutritional value. The wort now moves to the fermentation tanks, or washbacks, for the next stage: fermentation. The yeast is added to the wort in a large vessel (up to 30,000 litres) known as a washback. These were traditionally made from Oregon pine, although steel is becoming more popular for its ease of cleaning. Many people within the industry swear that the wooden washbacks lend a flavour to the whisky that steel cannot replicate. Distilleries that use steel claim however that tests on both types of washbacks show no significant difference in flavour. After pitching there is an initial lag phase when the yeast acclimatises to its new environment. During this time the yeast begin absorbing nutrients from the wort and producing the enzymes necessary for growth. The yeast then begin to consume sugar and produce alcohol, growing exponentially. As already mentioned the yeast also produce carbon dioxide. This causes the wort to foam and can lead to the washbacks overflowing. Many washbacks have rotating blades above the wort to cut the foam and prevent this from happening. The process also produces heat, raising the temperature of the wort from about 20°C to roughly 32°C. This heat increase must be kept in check as excessive temperatures can exert stress on the yeast and negatively affect the fermentation. Once the nutrients and sugars in the wort have been exhausted, the yeast activity begins to decline. The length of the fermentation process varies between distilleries but is commonly between 48 and 100 hours. The alcoholic liquid, now called wash and very similar to an un-hopped beer, is transferred to the stillhouse for the next stage in whisky production: Distillation. Take a look at the next step in the production process: Distillation

Whisky Production: Maturation and Bottling

After distillation the spirit is not yet whisky. It must first be matured in oak casks for at least 3 years before bottling. Whisky was originally consumed straight after distillation, without the mandatory wood maturation. Nobody knows for sure how this practice of oak maturation began. It has been suggested that because whisky was traditionally a seasonal product, it would be stored in containers for consumption throughout the year. What these early whisky drinkers will have noticed is that after some time in contact with wood the spirit became much mellower. This is attributable to the reaction of the spirit with the wood and is one of the major contributing factors to today’s mandatory maturation period. Compounds within the wood, such as lactone, eugenol, and vanillin (responsible for the typical vanilla flavours), are pulled into the maturing spirit, contributing a variety of flavours and aromas. Additionally, the sharp aromas within the new make spirit are lost over time, resulting in a smoother whisky. It is not only flavour that the wood contributes. The new make spirit, as it comes off the stills, is almost completely clear in colour. Whisky’s typical, golden colour is a direct result of the tannins from the wooden casks. What the cask was previously filled with can also have a large impact on the final product. Due to laws governing its production, new barrels must be used for aging bourbon whiskey. This leaves an abundance of barrels that can’t be reused for bourbon maturation. Since there is no such law demanding Scotch whisky be matured in new barrels, many of the bourbon casks end up in Scotland. These casks then lend flavours of vanilla and caramel to the maturing Scotch whisky, typical characteristics of bourbon whiskey. Ex-sherry butts are also a popular choice, although the decline in the sherry industry over the past years makes them rarer and therefore more expensive. Sherry casks generally lend sweet, fruity flavours to the whisky. Temperature changes in the warehouse cause the pores in the wood to expand and contract, allowing the spirit to flow in and out of the staves. This leads to the extraction of flavour compounds as mentioned above. Additionally, many of the casks are charred on the inside, providing a layer of carbon that acts as a filter, cleansing the spirit of unwanted compounds. As oak is porous, the whisky is also able to breath. Over time, some of the alcohol will evaporate from the cask, known as the angels’ share, leading to a change in flavours as the concentrations of alcohol, water and other compounds changes. Once the spirit has spent at least three years maturing, it is legally allowed to be called whisky and can be bottled. The flavour development doesn’t stop after only 3 years however, and the majority of whiskies will be matured for much longer, with periods of 10 or 20 years not being uncommon. As mentioned at the beginning of this series about whisky production (“What is Whisky Made From?”), a single malt does not have to come from a single barrel. The bottled whisky is commonly a mix of several casks from the distillery, allowing the manufacturers to achieve a higher level of consistency in their product despite small variations between batches and casks. It is the role of the blender to design these recipes and manage the inventories in such a way to ensure brand consistency in the future. Of course, distilleries also release single cask expressions, which as the name suggests do come from a single cask and therefore do not require blending. Prior to filtration it is also common that the whisky is reduced in strength. Depending on how long the whisky has been maturing, the strength could be anywhere between 40% and 70%, as a result the whisky is mixed with water to bring it down to a reasonable drinking strength, a minimum of 40% but commonly also 43% or 46%. Of course, it is also possible to purchase cask strength whiskies, which are not diluted at all. Additionally, it is common for the producer to add caramel colouring prior to filtration in order to ensure that the colour is consistent over multiple batches. After filtration the whisky is stored in a whisky vat ready for bottling. Due to the difference in size between individual distilleries, there is no one size fits all approach when it comes to bottling. In the industry everything is observable from hand-filling of bottles, through semi-automatic bottling lines where the bottles are hand fed onto the line at one end and retrieved at the other, all the way to fully-automatic systems where even this step is processed by machines. It is important to note that whisky maturation is dependent on the wooden casks. Once the whisky has been bottled, maturation no longer occurs and the whisky will not improve in flavour over time (in fact, once opened oxidation can quickly degrade the quality of the whisky). That is to say that a 20 year old single malt kept on a shelf for 10 years (unopened or otherwise) is not a 30 year old whisky but a 20 year old whisky that has been kept on a shelf for 10 years.

What is Whisky Made From?

Beer. At least that’s the short answer. Much like brandy is made by distilling wine, whisky is made by distilling beer, or at least something very close to beer – I wouldn’t recommend drinking a pint of it. The longer answer, which is still fairly short is that whisky is made from cereals (grains such as barley, corn and rye – not Cornflakes). These grains are combined with water to produce a sugary mixture known as wort, which is then fermented to produce an alcoholic liquid (similar to beer) called wash. The wash is distilled to increase the alcohol content, while reducing unwanted and concentrating desired aromas before being aged, or matured, in wooden casks. A single malt whisky is a malt whisky produced by a single distillery, i.e. not a blend of several distilleries’ malts. A single malt however does not have to come from a single barrel (which would be a single cask malt whisky) but is commonly a mix of several casks from the distillery, allowing the manufacturers to achieve a higher level of consistency in their product despite small variations between batches and casks. Not quite. Each whisky style or whisky producing region has their own set of regulations dictating when the distilled spirit is allowed to be labelled as whisky. For example, the Scotch Whisky Regulations 2009 set forth that “Scotch Whisky” means a whisky:

produced entirely in Scotland;
that has been distilled at an alcoholic strength by volume of less than 94.8 per cent so that the distillate has an aroma and taste derived from the raw materials used in its production;
that has been matured entirely in an excise warehouse or a permitted place in Scotland in oak casks of a capacity not exceeding 700 litres for a period of not less than three years;
to which no substance has been added except water and/or plain caramel colouring; and
that is bottled at a minimum alcoholic strength by volume of 40%.

We will cover the regulations of each style/region (Bourbon Whiskey, Rye Whisky, Japanese Whisky) when we look at each of these whiskies in more detail in future articles. Take a look at the first step in the production process: Malting barley