Scottish whisky mash bill

Malted barley is the main ingredient in Scotch malt whisky. Barley (Hordeum) is a member of grass family, just like most cereals in the world. There are two main types of barley: two-row and six-row. Both have six rows of seeds, but in the two-row varieties only two are fertile. The two-row varieties have usually plumper grains, less protein and husks and more fermentable sugars than the six-row varieties. The British malting barley varieties are and were almost exclusively of the two-rowed type, and the protein-rich six-row barley is mostly used for cattle feed. Barley can be sowed during the winter or in the spring, depending on the variety and the climate. Most distilling malts are made of spring barley, because they malt better with less dormancy issues. European brewers mostly use two-rowed barley, while Americans utilize mostly 6-rowed. Some varieties are naked, ie they do not have so much husks.

During the 17th and 18th century the main cereals grown in Scotland were barley, oats and rye. It is likely that all of them were used to produce distilled spirits (and whisky), although barley was probably favoured for its better enzyme activity. Additionally oats had too much husk for efficient mashing and rye tended to produce excess yeast growth. Mixed fermentations were probably often used, after all distilling was merely a way to preserve excess crop. Martin Martin in 1702 describes the practice on the Isle of Lewis: "The corn grown here is barley, oats and rye... Natives brew several sorts of liquors; as common Uisquebaugh, another called Trestarig, id est Aqua Vitae, three times distilled, which is strong and hot; a third sort is four times distilled Uisquebaugh-baul; id est Uisquebaugh...The Trestarig and Uisquebaugh-baul are made of oats". The oats were likely to produce a wash lower in alcohol and higher in congeners, so the process of three or four distillations makes sense. Multiple distillations and narrower cuts were most likely used to produce a palatable spirit, not so much to reach high alcohol strengths.

Chevallier barley was recently revived in Norwich by Dr Chris Ridout

During the 18th and 19th century the barley varieties used were local landraces, which were selected by the local farmers. In Scotland local landraces, probably most of the variations of Scotch Common, a two-row, narrow-eared, small-grained, early ripening variety, dominated until the 19th century. In colder climates, especially in the Northern Highlands some bere barley, a six-rowed landrace, was cultivated, but it was mostly used as cattle-feed. Most early 19th century English landrace varieties were probably close to Czech Hanna variety, a two-row, early ripening barley with a quite brittle straw. First generally successful variety in Britain was Cheval(l)ier, discovered in Suffolk, 1819. It spread across the country quite rapidly and most of the barley sown in the 1840's Britain was Chevalier, especially in the South. The other widely spread variety in England was Annat (1830) and in Scotland some of the Hanna varieties were still used in the late 19th century.

The price of maize and grain whisky (Weir 1995)

Malted barley was the main ingredient in both pot-still and column still whiskies in the 1830-40s, although column distillers began adding unmalted barley into the mash. In 1848 adjuncts, such as molasses, treacle and sugar were permitted in whisky production (1847 for beer) and further tax cuts made it possible for especially column distillers to produce whisky from a variety of  raw materials, mainly from cheap American maize. Maize was about 30% cheaper than barley at the time and as the production in the USA increased during late 19th century, it quickly became the major ingredient of column still whisky. By 1877 the average grain whisky mash-bill was: maize 77%, barley 20%,oats 2,5%, wheat 0,4%, rye 0,02%, malted barley 0,14%. The grain for column distillers was bought predominantly from abroad, less than 1% of the total grains and 2-6% of the barley were sourced from UK at the time. Oats, rich in fibers, were in mainly to improve the draining. The role of rye was to propagate yeast, while barley provided the enzymes. The cheap maize, efficient continuous Coffey still and the crisis in wine/cognac industry helped the boom of grain whisky in late 19th century. Brewers turned to foreign barley in the late 19th century mainly because of better quality of the Danish malt, not so much for the price. The  Irish distillers used a mixed grain bill from the late 19th century, usually consisting of barley malt (30-50%), unmalted barley (30-40%), oats (20-30%), rye (3-6%) and wheat (5-10%).

The pot-still malt whisky distillers were more traditional, even superstitious in their grain purchases compared to brewers and grain distillers. They used mostly local barley throughout the 19th century, although during the periods of bad harvests and/or higher whisky demands, as during the 1890's whisky boom, they were forced to use some foreign barley, mostly from Denmark, the Baltic and Morocco. There were other significant reasons for pot distillers to use local barley: They were trying to ban the grain distillers from marketing grain spirits as whisky or Scotch and proposed that only whisky made from Scottish grain could be called Scotch. The local farmers also bought much of the draff (waste product of the first distillation, great cattle feed) from the distilleries, so both benefited from direct sales to each other without any mediators. One likely explanation for the local sourcing of barley is the traditional and frankly sometimes superstitious approach on any improvement or change of the process or the product.

Beaven 1947

In the beginning of 20th century the predominant varieties were Annat, Goldthorpe, Archer, Spratt and Chevallier. After the World War I hybrid selections began to be made. Spratt-Archer and Plumage-Archer were popular and together comprised of 80% of malting barley until the World War II. The selections were made mostly based on the yield per acreage and the carbohydrate yield of the malt, flavour was rarely discussed. The foreign barley entered the distilling malt markets in 1920s, sourced mainly from Denmark and Chile (probably 6-rowed), and to some extent from Romania, Tunisia, Canada and Australia. Danish and Australian were preferred of for their quality, but for trade protectionist reasons the distillers (lead by DCL) agreed to by preferentially Scottish and English barley.

In the 1920s the prices of cereals varied widely and grain whisky was made from various ingredients based on the world market. Barley from California and Canada (small 6-row), maize from US and Argentina, oats from Scotland and Canada, even Brazilian manioc were used. The column grain distillers used the cheapest available raw materials, for example the maize bought from USA was usually grade 3, while the US domestic distillers used grade 1-2 maize.

During the WW II, Danish Kenia was grown widely for its better yields, however it was not good for malting and after WW II Pioneer (Kenia x Austrian Tshermarks) and Proctor (Plumage-Archer x Kenia) dominated until 1960 with a acreage up to 70%, although DCL seems to have preferred Zephyr. Due to rapid growth in whisky production in the 1950s, more English and foreign barley was used. If six-row barley was used, the smaller grains were sold to the distillers (more enzymes) and the plumper grain (more yield) to the brewers. Golden Promise and Maris Otter were introduced in 1965. Golden Promise became the barley of choice for distillers for its yield and enzyme activity until 1980s and Maris Otter was the brewers' malt, allegedly for its flavour. In the 1980s German Triumph and its many hybrids (Corgi, Natasha, Optic, Prisma, Camarge) surpassed the Golden Promise for their better yield and some winter varieties were introduced in Southern Scotland (Melanie, Halcyon, Regina). After that many different varieties have been developed and the suitable varieties for distilling and brewing are declared annually by Institute of Brewing and Distilling.

Improvement of spirit yield (Russell, 2003)

Brookes 2005

During the 20th century the acreage yield of barley has increased rapidly. Archer gave less than 3 tonnes per hectare as modern barleys for distilling malt give up to over 8 tonnes per hectare. Also the alcohol yield has improved drastically, from 300 litres of pure alcohol per tonne of dry malt to about 460 lpa/t.

Recently old varieties have been revived, mostly due to growing craft beer movement, but also by some malt distilleries. Bere barley was used in whisky production in Highland Park until 1926 and has since been used mainly for bere bannocks, but also for malt whisky. Bere was 6-row barley variety originating probably from northern Scandinavia with long stem and rapid growth (therefore also called 90-day-barley). Michel Couvreur revived the bere whisky in 1985 when he used bere from Orkney to distill whisky at Edradour. Since then at least Arran, Springbank and Bruichladdich have released bere whisky.

Sadly, there are no scientific comparisons between the flavour of different barley varieties. The early malting varieties were proportionally higher in protein and fat but lower in carbohydrates. Steeping times were much longer, probably because lack of knowledge and to some extent because of dormancy-prone barley varieties. The germination times were longer and the temperatures in floor maltings were more uneven than in modern maltings. These differences most likely made the wort more prone to infections of wild yeast and lactobacilli, along with mostly longer fermentations and lower starting gravity. The consistency was probably more viscous due to greater proportion of betaglucans to alpha-amylases. So the wort was likely to have more husks, dead yeast, autolysis products, lactobacilli, oils, diacetyl, esters (from acids and alcohols) and thicker in consistency causing easier burning in the wash still. The result was likely to be oilier, more sulphury and fruity spirit with more higher alcohols (fusels) and more furfural (from the husks, providing nutty aroma), assuming that the other factors were kept constant. It is unlikely that there are considerable differences within the modern barley varieties in terms of distilling, since the specifications for malting barley are quite strict. However, there is proof that the change of barley variety also changes the lactobacilli flora in the distillery, which might have at least some effect to the spirit if long fermentation times are used. The practice of malting (floor malting/industrial malting) has probably greater effect on flavour than the barley variety.

Maize mill at Dumbarton (I.Hume)

Because the use of enzyme additions is prohibited in Scottish whisky, the grain distilleries continue to use about 10% of malted barley in their mashes to guarantee sufficient enzyme content for starch degradation. Maize from the USA dominated the Scotch grain whisky mash bill from 1860s until early 1980s, excluding the war years. Since then, wheat has surpassed it, mainly because the trade regulations and taxes, not so much because of the actual cost of raw materials. Actually the price of unmalted barley has been quite competitive against maize and wheat in recent decades, but the processing problems have steered most grain distillers to wheat, mainly from France in the 1980s, but lately predominantly from the UK, with a fraction imported from Germany and France. North British is the last Scottish distillery to use predominantly maize, as the other "maize distillery" Dumbarton was closed in 2002. Some maize is still used at least occasionally in most grain distilleries, most likely to minimize viscosity problems. Maize has lower viscosity of mash compared to wheat and malted barley, because of lower amounts of betaglucan and pentoses. Since 1990s the Scottish distillers' maize has been bought exclusively from southern France due to trade barriers of EU. Bakers and farmers prefer high nitrogen wheat, so there is not a serious competition over low-nitrogen grains and distillers' wheat does not carry a price premium.

Biernacka&Wardencki 2013

The differences between wheat and maize spirits are surprisingly clear, there are less differences between wheat, triticale and rye spirits. Maize spirits contain about ten times less higher alcohols than the other grain whiskies, but have proportionally higher levels of esters (fruity). The higher amount of pentoses in maize also contribute to the higher furfural (nutty) content. The greater variety and amount of higher alcohols in wheat spirit account to more harsh, spirity and solventy notes in young spirit, but a likely to develop to a variety of acetals and esters, with more fruity aromas. The popcorn aroma sometimes present in blended whisky is likely to come from too much feints from the malt whisky involved, not from the grain component. The mouthfeel of wheat whisky can be oilier or waxier due to more arabinoxylans, while corn whisky is usually described cleaner and shorter.

Biernacka&Wardencki 2013

REFERENCES
Agu RC et al. Production of grain whisky and ethanol from wheat, maize and other cereals. J Inst Brew 2006;112;4;314-323
Beal, AD & Mottram DS. Compounds contributing to the characteristic aroma of malted barley. J Agric Food Chem 1994;42;2880-4
Biernacka P & Wardencki W. Volatiole composition of raw spirits of different botanical origin. J Inst Brew 2012;118;393-400
Beaven, ES. Barley. Duckworth 1947
Briggs, D. Malts and Malting, Blackie 1998
Bringhurst TA. Barley research in realtion to Scotch whisky production. J Inst Brew 2015;1;1-18
Brookes, P. Barley Breeding and development in the UK, an historical perspective. Brew Hist 2005;121;25-39
Bryce JH et al (ed). Distilled spirits: Production, technology and innovation. Nottingham Univ Press 2008
Campbell I (ed). Proceedings of the Third Aviemore Conference on Malting, Brewing and Distilling. Intitute of brewing, 1990.
Collins TS et al. Profiling of nonvolatiles in whiskeys. Food Chem 2014;163;186-196
Cramer ACJ et al. Analysis of volatile compounds from various types of barley cultivars. J Agric Food Chem 2005;53;7526-31
Dong L et al. Characterization of volatile aroma compounds in different brewing barley cultivars. Sci Food Agr 2014
Hoff S et al. Influence of barley varieties on wort quality and performance. J Agric Food Chem 2013;61;1968-76
Hornsey, IS. A History of Beer and Brewing. Royal Society of Chemistry 2003
Lloyd, WJW. Adjuncts. Centenary review. J Inst Brew 1986;92;336-345
Mallett, J. Malt. Brewer's Publications 2014.
Martin, M. A description of the Western Isles. 1702
Martin, P & Chang, X. Bere whisky- rediscovering the spirit of an old barley. Brew Dist Int 2008/4;6;41-43
Mather, RT & Willkie, RT. Distillers' grain manual. Seagram, 1942
Piggott JR et al (ed). The science and technology of whiskies. Longman 1989
Priest, FG & Campbell I (ed). Current developments in brewing and distilling. Aviemore conference 1982.
Robson, F. Cameronbridge, a distilling giant. Brewer Int 2001;1;4;16-19
Russell I (ed). Whisky, technology, production and marketing. Academic Press 2003
Weir, RB. History of the Distillers Company 1877-1939. Oxford 1995.