Production

The elements of style part 1

Part one: the raw materials What determines the character of a malt whisky? In the first of a three-part series Professor Alan Rutherford looks at the effect water, barley and yeast have on flavour.
By Alan Rutherford
At any one time, over recent decades, there have been between about 80 and 100 malt distilleries operational in Scotland. The fortune and reputation of each of these is dependent on the consistency and distinctive character of its spirit. In this piece I will try to describe from my own experience those aspects of the distiller’s raw materials that have most effect upon malt spirit character. In the next issue I will cover the distillery processes, and finally I will explore the art and science of selecting casks to suit the spirit and the effects of maturation.The process of making Scotch whisky is rigidly defined in UK and EC law, and this legality extends to most overseas markets. In addition to geographical restrictions, the law allows the use of only very few natural and wholesome ingredients, with no processing additives: the permitted ingredients at the distillery are water, cereals and yeast. In the case of Scotch malt whisky, the cereal used is simply 100 per cent malted barley. How important is each of these to the final spirit character?Water
The tale is often told of two neighbouring distilleries, taking their water supplies from different slopes of the same hill, yet making very different whiskies. I have no doubt that this statement is true, but I am equally sure that the reasons for the differing whisky characters have nothing to do with their water. Most Scotch malt distilleries have their own jealously guarded water supplies, and rightly so as water is their life’s blood: without copious supplies both for mashing and for cooling the stills, a distillery will cease production. Most distilleries use surface water, collected in a dam uphill from the distillery, and therefore very soft. A soft, clean and abundant water supply has always been the first requisite when choosing a site on which to build a malt distillery. There are exceptions to any rule, and one or two malt distilleries do have underground supplies which therefore have significant levels of dissolved minerals, but the precise effect of these harder waters on final spirit character is, I believe, unproven. Certainly, in most respects, malt distilleries use very similar high purity water, and seasonal variations of water temperature are likely to have a greater influence on spirit character than switching supplies from adjacent hillside streams.Another myth persists regarding the peatiness of highland burns – supposedly imparting the peaty flavour to distilled spirit. Many distillery burns will deliver a brownish peaty water, especially in summer when seen by the tourist, but much less so when the winter snow melts into a spring spate. While the levels of peat phenols surviving from mashing water through to distilled spirit might be just detectable, they have a very minor effect. The peated flavours adored (or otherwise) in malt whiskies from Islay, Skye and Orkney are totally dependent on the malt kilning process (which I will describe in a future issue) and not on the peat in the water supply.So assuming we have a distillery with a good supply of soft burn water, we will be able to distil a regular output of malt spirit, but we do not yet have a means of differentiating our spirit character.Malted barley
The barley plant Hordeum is of central importance to Scotch whisky production, and there is no doubt that the origins of Scotch malt whisky lie in locally grown Scottish varieties. The first known written record of Scotch in 1494 is in the Exchequer Rolls of Scotland and cites: ‘eight bolls of malt to Friar John Cor wherewith to make aqua vitae’. There is little doubt that this malt would have been made from locally grown barley. However, as Scotch whisky production grew from a cottage craft to industrial scale during the 19th and 20th centuries, Scotch malt distilleries bought their barley from far and wide, particularly from England but also at times Ireland, Finland, Denmark, France and Spain. In the days before the UK’s entry to Europe, and the consequent trade restrictions of the EU’s Common Agricultural Policy, imports of barley for distilling also came from the Commonwealth grain baskets of Australia and Canada – particularly varieties of high enzyme content prized for grain distilling. Fortunately, the legal definition of Scotch, unlike those of Cognac or Champagne, places no geographical restriction on the origin of its raw materials. Thus, demand for Scotch has thankfully never been constrained by a shortage of barley. In recent years, barley breeding programmes have accelerated and improved considerably, and there is now a whole range of malting barley varieties (as opposed to feed barleys) which can meet distillers’ requirements in terms of spirit yield per tonne of malt, and which can be grown successfully by the Scottish farmer at an acceptable yield in terms of tonnes per hectare. This has not always been the case, and when combined with the vagaries of the Scottish climate, plus the fact that our barley each year is the last in Europe to be harvested, then it is not surprising that barley imports to Scotland have been , and still are to some extent, essential to our maltsters and distillers.Agricultural research in the UK was given a boost by the post-war government, and a major breakthrough for Scotland occurred in barley breeding with the development of a variety called Golden Promise. This variety met the distillers’ requirements and could be grown successfully north or south of the border. Golden Promise dominated the malting scene during the late 1960s and 1970s but has since been eclipsed by many new varieties of both spring and winter barleys. Indeed barley breeding has moved on so fast that new varieties now last only three or four seasons before being eclipsed by improved versions. The maltster’s vocabulary is constantly changing, with names such as Triumph, Derkado, Chariot, Optic, Prisma and Camargue representing only a few successful varieties of recent years.My purpose in covering this subject in some detail is to illustrate the fact that barley variety, whilst important to the farmer and the maltster, cannot be a significant factor in determining malt whisky character. The great single malt whiskies have constantly changed their barley varieties, and the majority of distillers do not even include this factor in their malt specification. If, for example, a distiller were to claim that his spirit character is dependent upon using a certain barley variety, then he would run the risk of having to support the planting of an outdated variety long after the farming industry had abandoned it. Fortunately, while the characters of fine wines are very dependent upon their individual grape varieties, no evidence exists to my knowledge for any significant relationship between malt whisky character and barley variety.There is however one particular aspect of malting which is of immense importance to malt whisky character, and that is malt kilning. The process of malting, put very simply, consists of subjecting live barley grains to successive regimes of water steeping and aeration to encourage the grains to begin to grow. The onset of growth, or germination, releases natural enzymes into the starchy food reserves of the grain, converting these to digestible sugars. To arrest plant growth, while preserving the sugars, germination is arrested by the traditional process of carefully drying the grain in a kiln, after which the dried product is termed ‘malt’ or, more precisely, ‘malted barley’. The pagoda tops of malt distilleries are visible reminders of the traditionally designed chimneys of the late 19th century malt kilns. The design of the malt kiln is not important to malt whisky character, but its method of heating and the fuel used to provide the heat certainly are. Traditionally, the Western and Northern Isles have depended upon peat as a fuel, and the whiskies from Islay, Skye and Orkney continue this tradition. On the mainland, the norm is for light peating or in some cases no peat at all, the kilns being heated wholly by gas or oil burners. Even with these lightly peated or unpeated malts, opinion is divided regarding whether the kilns should be directly fired using a high sulphur residual fuel oil or indirectly fired using hot water radiators to heat the air for malt drying. There is little doubt that these two extremes, with or without some peat, do produce different malts, with those from directly fired kilns, not surprisingly, producing the heavier characters.Apart from peating levels and the option of direct firing, Scotch malt distillers have very similar malt specifications, with the emphasis primarily (but hopefully not exclusively) on spirit yield per tonne.Yeast
The third permitted raw material is yeast, a living organism called Saccharomyces cerevisiae, as used by bakers and brewers throughout the ages. The work of the yeast is fermentation, which is the process of converting soluble malt sugars into alcohol, not unlike the brewery process (although without wort boiling or the use of hops). The conversion of malt sugars to alcohol must, by the legal definition of Scotch, be achieved only by the indigenous enzymes of yeast, the addition of commercial enzymes being strictly prohibited. This is not the case in most countries for the production of beer and other spirits.In breweries, the yeast grows prolifically and the surplus is ‘cropped’ for sale to, among others, Scotch malt whisky distillers. Traditionally this was the main source for malt distillers, but since 1945, brewers’ yeast has been progressively replaced by ‘pure’ or ‘single culture’ yeasts, specially produced for distillers. There is no doubt that these latter strains are more reliable and more efficient, and some malt distilleries now use them exclusively. Others stick to a mixed formula of speciality distillers’ yeast and some brewers’ yeast in the belief (probably demonstrable) that their spirit character is dependent upon this mixture of yeast strains.From a scientific point of view – given that alcohol is an excretion of yeast, and that each strain excretes a whole range of other flavour compounds specific to the strain – there is no doubt that different yeast strains will have the potential to affect spirit character. The question to be asked is whether this is a significant effect which will survive through the subsequent stages of distillation and maturation. From my own experience, having experimented with some very unusual yeast strains, I know that noticeable flavour effects can result. No brewer of beer would argue with this – his own yeast strain is sacrosanct to his brewery. However, the commercial yeasts generally available to malt distillers permit of little variation, other than perhaps a chosen percentage of brewers’ yeast. My own view is that yeast strains do have an effect, albeit subtle, on spirit character, and may offer a useful means of distinction in the future, particularly for light spirits whose distillery character is not masked by heavy peating or by the use of sherry or bourbon casks in maturation (this will be covered in part three of this series).This piece has been a rapid and somewhat personal summary of the raw materials of malt distilling as they affect spirit character, but the views expressed are underpinned by both scientific evidence and many years of experience. Others may disagree with me: if all aspects of spirit character were capable of explanation and precise control, then Scotch malt whisky would be a much less interesting drink.