Peat Terroir

Arbroath maltings

In 1800's the peat used in maltings was commonly local and the kilning was done in almost every distillery. During the latter part of 1900's and the invention of industrial malting processes the maltings have been concentrated to bigger facilities, such as Diageo's Roseisle, Glen Ord and Port Ellen, Simpson's Tweed Valley, Baird's Abroath and Inverness, Greencore's Glen Esk and Buckie and Edrington's Tamdhu. Several distillery maltings are still operational, but only a few distilleries malt all of their barley on-site (Springbank, Glen Ord, Tamdhu). The use of peat has diminished as more economical fuels have been introduced, but some peat is still used to create smoky flavoured malts. The peat used in Scotch whisky maltings is sourced mostly from the north-east of Scotland, Islay and Orkney.

Peat is formed in waterlogged lands by partial degradation of organic matter. There are some differences between peat compositions based on different climate, vegetation, bog type and cutting depth.

Peatlands can be divided into bogs, fens, marshes ja swamps.  Bogs are formed by heavy rainfall (therefore called ombotrophic) and usually contain more sphagnum moss and less woody vegetation than the other peatland types, which are formed mostly by waterlogging from the ground water (minerotrophic). Fens (aka basin bogs or valley bogs) contain more sedges and grass. Marshes are treeless intermittently waterlogged areas and usually accumulate peat very slowly. Swamps are very minerotrophic and contain large amounts of wood and nutritients. Average peat contains 90% water and 10% dry matter, of which 92% is organic and 8% inorganic (practically ash). Organic matter consists mainly of residues of lignin and different carbohydrates, but there are considerable variations depending on the vegetation and the bog type. Ombotrophic peats are richer in phenols and aromatics, but due to poorer vegetation they lack carbohydrates, lignin and nitrogen. Western Scotland and the islands are especially abundant with blanket bogs. About 10% of Scotland in covered by blanket bogs and 1% by basin bogs.

Peat bog	Maltings	Location	Bog type
Glenmachrie	Laphroaig	Islay	basin
Gartbreck	Bowmore	Islay	basin
Castlehill	Port Ellen	Islay	blanket
Hobbister Hill	Highland Park	Orkney	blanket
St Fergus	various	Aberdeenshire	basin
Tomintoul	various	Speyside	basin
Machrihanish	Springbank	Campbeltown	blanket

The extraction depth is also important as the surface layers are usually rich in carbohydrates and poor in phenols and the deeper layers might have too much harmful nitrogen- and sulphur compounds due to anaerobic fungal and bacterial metabolism. On the other hand some fungi seem to produce vanillins such as acetovanilline from lignin, for some unknown reason especially so in island peats.

Location of peat bogs used in whisky production

Islay peat bogs (from left: Gartbreck, Glenmachrie, Castlehill)

It seems that the most significant factors in peaty aroma are the bog location and the cutting depth. The bog type and the vegetation play some role, but they are not that important for peaty flavour. The peats from Islay, for example, are very similar with each other as the peat from the basin bogs Glenmachrie (Laphroaig) and Gartbreck (Bowmore) cannot be identified by infrared spectroscopy. 

The Castlehill peat for the Port Ellen Maltings somewhat different from the basin bog peats from Islay, probably due to different microbiology of the blanket bog and a greater amount of woody material are therefore more lignin-derivatives and carbohydrates. 

Surprisingly, Hobbister Hill peat from a blanket bog is chemically more similar to the Islay basin bog peats (Gartbreck/Glenmachrie) than the blanket bog Castlehill peat. The local microbiology of peat bog might therefore have a greater impact on the peat composition, influencing both the nitrogenlevels and phenol-concentrations in the peat. Another explanation is that the bog types are overlapping, for example Hobbister Hill bog might have some basin bog properties (standing water bowls) especially in the deeper layers; this might explain the similarity of peats cut from the deeper layers of Hobbister Hill bog with the Islay basin bog peats. 

Tomintoul peat is different from the Island peats; a basin bog, as expected, contains great amounts of carbohydrates, but there is also lots of sphagnum moss, which for some reason does not result in the same amounts of phenols as in the islands. It could be speculated that this is due to different climate, microbiology or variety of Sphagnum in the western islands and the mainland.

St Fergus peat is rich in woody material and therefore rich in lignin derivatives, especially syringyl. There is however a great amount of phenol-compounds in the St Fergus peat, although it is a basin bog and the sphagnum-content is lower than in for example Tomintoul peat. The location of St Fergus bog is closer to the sea than of Tomintoul bog. Maybe the proximity of sea results in greater amounts of phenols in peat? Explanation might be for example lesser temperature fluctuations or differences in microbiology or drainage.

There are no scientific analyses available on Machrihanish (Springbank) peat, but since it is cut from a blanket bog and located near sea in the western Scotland, it probably is closer to the Islay and Orkney peats than the mainland peat.

Some breweries use artificial smoke flavourings in their malting processes, apparently common raw materials are extracts from burnt deciduous trees, such as beech or birch. These are likely to produce more aromas from syringyl, guaiacol and carbohydrates resulting in softer but not as phenolic aroma as from peats. I don't know whether Scotch whisky industry uses smoke flavourings in their maltings, but it is not prohibited in the Scotch whisky regulations. A black alder smoked malt could be an interesting experiment (a free hint for any progressive distillers reading this).

Anyway, there clearly is a peat terroir and even some local variations in the compositions. Also the cutting depth is important and it will be interesting to see wheter the peat composition will change as the limited amounts of peat for example from Islay are utilised and either the cutting depth or the cutting location changes.

REFERENCES AND FURTHER READING:

Bozkurt  S et al. Peat as a potential analogue for the long-term evolution in landfills. Earth Sci Rev 2001; 53; 95-147
Bryce JH et al (ed). Distilled spirits, production, technology and innovation. Nottingham Univ Press, 2008
Da Porto C et al. A study on the composition of distillates obtained from smoked marc. Anal Chim Acta 2006; 563; 396-400

Guillén M et al. Carbohydrate and nitrogenated compounds in liquid smoke flavorings. J Agric Food Chem 2001; 49; 2395-2403 

Guillén M, Manzanos M. Study of the components of a solid smoke flavouring preparation. Food Chem 1996; 55; 3; 251-257

Guillén M, Manzanos M. Characterization of the components of a salty smoke falvouring preparation. Food Chem 1996; 58; 1-2; 97-102

Harrison B, Priest F. Composition of peats in the preparation of malt for scotch whisky production. J Agric Food Chem 2009; 57; 2385-2391

Harrison B et al. Differentation of peats used in the preparation of malt for scotch whisky production. J Inst Brew 2006; 112; 4 ; 333-339

Jefford A. Peat, smoke and spirit. Headline 2004

Jounela-Eriksson P. The aroma composition of distilled beverages and preceived aroma of whisky. Academic Press 1978

Kostyra E, Barylko-Pikielna N. Volatiles composition and flavour profile identity of smoke flavourings. Food Qual Pref 2006; 17; 85-95
Lehtonen M. Phenols in whisky.  Chromatographia 1982; 16; 201-203

Russell I (ed). Whisky, technology, production and marketing. Academic Press 2003

Swan JS, Howie D. Sensory and analytical studies of regional influence on the composition of Scotch malt whisky. Institute of brewing, 1983.

Valaer P. Scotch whisky. Industr Engineer Chem 1940; 32; 7; 935-943

Walker GM, Hughes PS. Distilled spirits, new horizons: energy, environment and enlightenment. Nottingham Univ Press, 2010

Peat

Pagoda-roof of a kiln

Heat is needed in kilning to dry the malts. Peat has been traditionally used as fuel for kilning in Scotland, especially in the areas where coal was not easily available, such as the islands, Campbeltown and nothern highlands. During the 20th century more affordable coal, gas and oil became more available and gradually the use of peat in kilning dimished. In 1940 it was common to use 25-50% peat for Lowland malts, 50-75% peat for Highland malts and usually 100% peat for Islay and Campbeltown malts. The rest of the fuel was usually coal or anthracite. Nowadays the Islay, Orkney and Campbeltown distilleries are famous for their peated malts, but also some mainland distilleries have experimented with peated malts.

Sphagnum bog

According to Encyclopedia Britannica peat is spongy material formed by the partial decomposition of organic matter in wetlands. Usually peat consist of decomposed Sphagnum and low growing plants such as heather and different sedges (cotton grass, rushes, grasses). Wetlands can be formed by heavy rainfall or by a water basin filled by ground water. Scottish peatlands are usually formed by heavy rainfall and therefore contain more sphagnum moss and heather and less any woody vegetation. The surface layer of a peat bog is thin and aeriated moss and the deeper layers below 50cm are usually waterlogged. As the moss grows the deeper layers decompose. Because of the waterlogging there is less oxygen available and thus the decomposition of organic matter is slow and incomplete. The growing moss on top creates pressure on the deeper layers, producing thicker peat especially below the waterlevel.

 

Heather (calluna vulgaris)

Peatland plants consist mainly of cellulose, hemicellulose and lignin. The lignin in grasses contains all the monolignols; coniferyl, sinapyl and p-coumaryl-alcohols, as lignin in heather is mostly coniferyl-sinapyl-type (see previous blog). Sphagnum is very different in structure consisting of a sort of polyphenolic network. Sphagnum moss is therefore richer in p-hydroxyl-phenols instead of the usual lignin-derived compounds. Therefore burnt sphagnum releases more simple phenols and burnt wood more syringol and guaiacol-derivatives with slightly different smoky aromas. Wooden stemmed plants with more cellulose and hemicellulose decompose into simpler carbohydrates. Surface layer has proportionally more carbohydrates and less phenols and deeper layers have increased levels of potentially harmful nitrogen compounds and hydrogen sulphide (aroma of rotten eggs). Nitrogen compounds are probably produced by a range of fungi. Hydrogen sulphide is generated by bacteria in anaerobic conditions, usually below the waterlevel, from other sulphur compounds.

Anthracite coal

The smoky flavour of a peat reek is supposedly coming from simple phenols, such as phenol, its alcohol-derivatives and creosols, and to some extent from guaiacols, furans and pyrans. Syringyl-compounds are not thought to be of major significance in producing smoky aromas. Different carbonyl-compounds seem to soften the phenolic aromas. Without the carbonyls and guaiacols the phenols can taste ashy, sharp and hard, whereas together they produce aromas of smoked meat, savory "maggi" and burnt sugar. Large amounts of nitrogenated compounds give higher levels of pyridines and result in astringent, green and rubbery flavours. In addition the nitrosamines produced by the nitrogen oxides in malt are carcinogenic. The formation of nitrosamines can be blocked by sulphur oxides, which can be produced by burning sulphur-containing coal or rock sulphur with peat or by adding gaseous suphur dioxide to non-sulphurous gas. Paradoxally the rubbery, unpleasant "sulphury" odor (from nitrogenated compounds) in a whisky can result from not using enough sulphurous fuel in kilning. Also the right temperature in firing is important as more smoke and lignin-derived aromas are extracted and less nitrogen released if the peat burns without flames in relatively low temperatures.

Peat layers

There are considerable differences between peats from different origins. Islay peat is usually richer in phenols, guaiacol, vanillic compounds and nitrogens but poorer in carbohydrates than the peat from the mainland . This is probably because of the greater amount of Sphagnum and lesser amount of wooden stemmed plants in Islay bogs. Wooden plants, especially decideous plants contain grater amounts of syringol-based aromas compared to phenol-rich Sphagnum and relatively guaiacol-rich bog plants. Orkney peats are of an intermediate type as they contain more carbohydrates than Islay peats and more phenols than mainland peats from Tomintoul. The extraction depth is also important, as especially in Orkney there are great differences in peat composition as surface peat is closer to the mainland peat and deeper layers resemble Islay peat. The best extraction depth seems to be just above the water level near the surface. This is probably because of greater amount of carbohydrates and lesser amount of nitrosamines and hydrogen sulphide in the surface layer. The drying of peats and the controlling of burning temperatures are also easier if the peat is not too thick.

The middle cut (from bruichladdich.com)

Malt adsorbs the smoky flavours best when hand dry (15-30% moisture), therefore peat must be burned in the early stages of kilning. Also the grinding and composition of the malts affects the aroma, as the husks are more prone to absorb the phenols. Usually the malt is specified by measuring the phenol-content with high performance liquid chromatography (HPLC); lightly peated malt has <5 ppm phenols, medium peated 5-15 ppm, heavily peated 15-50 ppm and some experimental peated malts have well over 100 ppm phenols. The taste tresholds for different phenolic compounds vary greatly, for example 3 µg/l for guaiacol, 10-68 µg/l for creosols and 7100 µg/l for phenol. The phenol content and the strength of the smoky aroma in the spirit is usually much lower than in the malts and little lower than in the wort, but it depends heavily on the distillation practice. The foreshots contain barely any smoky flavour, the middle cut is also quite subtle, but the last part of the cut is very smoky, about six-fold compared to the middle cut and about the same intensity as the wort. The tails (feints) has about third of the phenols in the last cut and twice of that in the middle cut. To produce heavily smoked malt it seems important to continue the middle cut as long as possible bearing in mind that too much feints produces unwanted off-flavours. None of the distillers have (yet) used only the last cut to produce very smoky spirit. In the table below are some phenol contents and middle cut alcohol contents. Possibly the more intense smoky flavour of the southern Islay whiskies (Ardbeg, Laphroaig, Lagavulin) is partly due to their longer middle cuts.

Lagavulin 1969 (from Whisky Exchange blog)

Phenols decrease during maturation, but the exact mechanism has not been described. It is estimated that 25 ppm phenol content in a new make becomes 10 ppm after 10 years, 8 ppm after 15 years and 6 ppm after 30years of cask maturation. Altough the synergetic nature of oak derived compounds (guaiacol, vanillin etc) can enhance the peaty flavours, it usually softens and diminishes during aging.

Phenol-levels of malts and new-makes in different distilleries and the ABV of the middle cut. (modified from Misako Udo: The Scottish Whisky Distilleries)

DISTILLERY	MALT PHENOLS (ppm)	NEW MAKE PHENOLS (ppm)	MIDDLE CUT ABV
Ardbeg	54 (42-70)	24-26	73-62.5
Bowmore	20-25	8-10	74-61.5
Bruichladdich	3-4		76-64
Port Charlotte	40	20-25
Octomore	129 (in 2003)	46 (in 2003)
Brora	7-40
Bunnahabhain	1-2 (peated malt 38)		72-64
Caol Ila	30-35	12-13	75-65
Highland Park	35-40 (and unpeated malt used together)	2	70 and then 2h40min
Lagavulin	35-40	16-18	72-59
Laphroaig	40-45	25	72-60.5
Springbank		7-8 (formerly 15-20)	68-63
Longrow	55
Old Ballantruan (Tomintoul)	55

REFERENCES, FURTHER READING:

Bozkurt  S et al. Peat as a potential analogue for the long-term evolution in landfills. Earth Sci Rev 2001; 53; 95-147
Bryce JH et al (ed). Distilled spirits, production, technology and innovation. Nottingham Univ Press, 2008
Da Porto C et al. A study on the composition of distillates obtained from smoked marc. Anal Chim Acta 2006; 563; 396-400

Guillén M et al. Carbohydrate and nitrogenated compounds in liquid smoke flavorings. J Agric Food Chem 2001; 49; 2395-2403 

Guillén M, Manzanos M. Study of the components of a solid smoke flavouring preparation. Food Chem 1996; 55; 3; 251-257

Guillén M, Manzanos M. Characterization of the components of a salty smoke falvouring preparation. Food Chem 1996; 58; 1-2; 97-102

Harrison B, Priest F. Composition of peats in the preparation of malt for scotch whisky production. J Agric Food Chem 2009; 57; 2385-2391

Harrison B et al. Differentation of peats used in the preparation of malt for scotch whisky production. J Inst Brew 2006; 112; 4 ; 333-339

Jefford A. Peat, smoke and spirit. Headline 2004 

Kostyra E, Barylko-Pikielna N. Volatiles composition and flavour profile identity of smoke flavourings. Food Qual Pref 2006; 17; 85-95
Lehtonen M. Phenols in whisky.  Chromatographia 1982; 16; 201-203

Russell I (ed). Whisky, technology, production and marketing. Academic Press 2003
Smith GD, Wallace G. Ardbeg, a peaty provenance. GW Publishing 2008  

Udo M: The Scottish Whisky Distilleries. Black & White 2006

Valaer P. Scotch whisky. Industr Engineer Chem 1940; 32; 7; 935-943

Voigt J et al. New highly aromatic products and distillates from smoked malt. In Distilled Spirits, Nottingham Univ Press 2010

Walker GM, Hughes PS. Distilled spirits, new horizons: energy, environment and enlightenment. Nottingham Univ Press, 2010

Sulphur

Sulphur candle

Sulphury notes are a controversial part of whisky aroma. Individual differences in perceiving the sulphury flavours seem to be great and easily arguable. Sulphur in its natural S8-form is quite stable with an odor of matchsticks. Most organic sulphur compounds however have usually very low perception tresholds and pungent odors. Organic sulphur compounds have been associated with meaty, burnt, rubbery, rotten aromas, but also some unexpected aromas such as grapefruit. Often low levels of sulphur are associated with mature, rancio, complex and meaty notes in whisky.

Sulphur in the whisky is mostly sourced from the aminoacids of the grains used in fermentation. The barley used in the whisky production are usually spring varieties and typically very low in protein and thus low on sulphury aminoacids (cysteine, methionine), too. However the yeasts metabolise the available aminoacids and in the process produce a variety of organic sulphur compounds. Typical byproduct of anaerobic sulphur metabolism is hydrogen sulphide (H2S), which has a strong unpleasant odor of rotten eggs and can further metabolise into thiols and other organic sulphur compounds. Excess amounts of yeast or the use of brewer's yeast or long fermentation times tend to increase the autolysis of yeasts and therefore add to the sulphur content of the wash. The lactic acid bacteriae can produce sulphury compounds, especially Lactobacillus brevis tends to impart a sulphury aroma.

Some sulphur is used during the kilning process, especially if peat is used to dry the grains. The anaerobic bacteriae in a peat bog produce sulphury compounds and obnoxious nitrosamines and by burning some sulphur with the peat the off-notes (and toxins) can be converted mainly to sulphur oxides, which do not spoil the grain.

The copper used in the distillation stills reduces the sulphury content of the whisky most likely by acting as a catalyst in processes resulting in insoluble copper sulphates. On the other hand copper has been associated with an increase in some sulphur compounds in the spirit, such as dimethylsulphate (DMS). Low copper contact (small/squat stills), fast distillation and high temperatures increase sulphury notes on new make spirit. Direct heating probably increases sulphury notes as there is bound to be some burning of grains at the bottom of the still and temperature variations between different parts of the still.

Cask maturation significantly reduces the amount of most sulphur compounds in the whisky, even so that in a recent study all of the dimethyl sulphide (DMS), 3-methylthiolpropylacetate, dihydro-2-methyl-3(2H)-thiophene and ethyl-3-methylthiol-propanoate had disappered after 3 years of oak maturation. Most organic sulphur compounds such as DMS decrease gradually during aging. This is most likely due to evaporation and to a lesser degree to oxidation or reactions with the carbon layer of the charred cask.

Key sulphur compounds in new-make spirits and single malt whiskies (Masuda & Nishimura 1982)

The individual perception of different sulphury compounds appears to be very different. As experienced tasters rated different sulphur compounds (in a study by Jack FR et al 2008), there was considerable variation between individuals and compound.

Sulphury character of different sulphur compounds, modified from Jack et al 2008

The most perceived MMFDS and 2-thiophene-cis-aldehyde, 4-methyl-thiazole, 4-methyl-5-vinyl-thiazole as sulphury and the mix of all was statistically the most sulphury of them all. At least one taster did rate the sulphury taste less than 1 out of 10 for all but two compounds. Several tasters were non-tasters for some compounds that the others rated highly sulphury. It is to be noted that all but one tasters rated one individual compound more sulphury than the mix of all, so the sulphury taste is not an add-on characteristic but rather a combination. For example 2-pentyl furan distictively suppresses the sulphury character of DMTS, just like salt suppresses a bitter taste (just try a tiny amount of salt in your coffee).

Sulphury character of different sulphur compounds, modified from Jack et al 2008

However, there has been controversy about sulphury casks in the whisky industry. Especially Jim Murray, the author of The Whisky Bible has been worried about sherry cask-derived sulphur-taints. Sulphur is widely used in wine industry to prevent bacterial growth in must and to improve the stability of wine. It is usually used in the form of sulphur dioxide, usually soluted in to a liquid form for ease of use. Sulphur dioxide acts as an antioxidant and antibacterial agent in wines. Excess sulphur dioxide content may intensify some allergic reaction and impart off-notes into wine. Sulphur candles or brimstone sticks have been used to preserve casked wine and to prevent bacterial contamination of casks stored empty.

Fumigation of casks with sulphur has been used probably from the Roman era. The use of sulphur matches and candles for preserving wines and other perishables was common in late 18th century Europe. Wine writer André Jullien describes the fumigation of wine casks in 1825:

"Fumigating wines is impregnating them with sulphurous vapours, obtained by the burning of brimstone matches... aromatics are often mixed with the brimstone... the Strasbourg [violet scented matches] are to be preferred for wine... When old wine runs clear, it is sufficient to burn a bit of match in the cask you are going to fill. To hasten the fermentation of new wine, burn several matches and shake the wine in the vapour... Many vineyards produce wines of a sulphurous taste, which goes off in time" (as cask maturation/storing was common at the time). This practice reduced the oxygen in the cask and prevented lactic bacterial brettanomyces contamination, therefore enhancing the stability and quality of wine.

Sulphur burners are still used
by amateur winemakers.

There are many references from the 1700s and the 1800s describing different cask sulphuring methods. Usually sulphur was introduced into the cask through the bunghole in a wire containing a linen cloth, which had been coated with sulphur. The cloth was burned and the bung closed, resulting in oxygen-deprived cask with some sulphur dioxide and some sulphur trioxide gasses. A fresh cask usually used first for fermentation was considered quite clean, so they were only slightly or not at all sulphured. Sulphur dusting of the vines was used as a cure against oidium (powdery mildew), the first of the fungal diseases from America, in the 1850s.

The effects of sulphur in casks were not completely understood and in 1873 there was a scandal in Britain, as Dr Thudicum wrote that the sulphuring, plastering (adding calciumcarbonite into must) and fortification of sherry was to be considered as adulteration and that the sherry wines were inferior to the French wines and probably dangerous to health. The fact that also the French were sulphuring their casks was not discussed and there were probably some trade-oriented motives behind the argument.

Different types of sulphur used in winemaking

Adding sulphur dioxide into wine has been common from at least the 1890s. It prevents bacterial and wild yeast growth and acts as an antioxidant preventing overoxidation and browning. During early 1900s some wineries used (hugely) excess sulphur dioxide in order to use bigger tanks and less strict oxygen control, but it resulted in sulphur tainted wines with overly "reduced" aromas. Sulphur dioxide content is limited by EU under 160mg/l in red wines, 210mg/l in whites and 400mg/l in sweet wines. Most wineries use concentrations below 100mg/l, but non-sulphured commercial wines are rare as they easily become oxidized. Sulphur dioxide was obtained by burning sulphur candles in the late 19th century, but since the early 1900s it has been mostly used in liquid form or as potassium metabisulphite; Californian wine expert Maynard Amerine stated already in 1970 that no burned sulphur is commonly used in wine making anymore, and there is no evidence that the major sherry cask suppliers or whisky distillers had used sulphur candles for several decades. Theoretically excess sulphur dropped from a candle might be reduced to H2S or mercaptans by yeasts producing sulphury off-notes.

Since 1986 Spain has been a member of EEC and the shipment of sherry has been made very hard by the Denominacion de Origen to encourage bottling in Spain. Bottling of sherry is done almost exclusively in Spain and full sherry casks are no longer imported. The sherry shippers had already started their own bottling plants in Spain in the early 20th century. Pedro Domecq started their bottling operations in Jerez in 1920 and Gonzalez Byass was to follow gradually during the interwar period. Sandeman bottled some of their sherries and ports in location as early as 1880, but the bottling of sherry in England by Sandeman ceased in 1969. Harvey's were the last big shipper to bottle their sherries in England, as they bought a winery in Jerez from MacKenzie in 1970 and since then have been bottling practically all of their sherries in Spain. Therefore since early 1970s many distillers have been maturing whisky in sherry casks made to order in Spain. Both American and Spanish oak casks are coopered and usually the sherry used in seasoning is oloroso, but sometimes lower quality blending sherry called raya, which resembles oloroso. Some bodegas, for example Gonzalez Byass and Pedro Romero trade their old empty solera casks, which are made exclusively of American oak and usually 80-100 years old and probably very different from a typical sherry shipping cask or a seasoned cask. Another quite popular way of producing sherry casks was to rejuvenate old exhausted cask by scraping the inner surface, toasting it again and seasoning it with sherry. Aeriation of whisky, during bottle maturation or in greater extent after the bottle has been opened, usually decreases the highly volatile sulphury notes.

In conclusion, there is good and bad sulphur in whisky. To simply pin one or two sulphur compounds responsible of the good or the bad aromas would be an oversimplification. Similarily the origins of sulphury notes seem to be impossible to track to just one source, such as sulphury cask and there is no evidence of excess use of sulphur candles in the sherry industry during the last decades, in fact quite the opposite. More likely is that there are some bad batches distilled too fast or in too warm climate that are over-sulphury, or maybe a cask has not been properly sulphured and has been contaminated with brettanomyces.

REFERENCES AND FURTHER READING
Harrison, B et al. Impact of copper in different parts of malt whisky pot stills on new make spirit composition and aroma. J Inst Brew, 2001;117(1);106-112
Jack, FR et al. Sensory implications of modifying distillation practice in Scotch malt whisky production. In Distilled Spirits, ed Bryce JH, Piggott JR, Stewart GG. Nottingham Univ Press 2008.
Jack, FR. Understanding Scotch whisky flavour. Food Sci Tech 2003;14;28-30
Jullien, A. Wine merchant's companion and butler's manual. 1825
Labuza, T et al. Maillard reactions in chemistry, food and health. RSC 1994.
Masuda, M and Nishimura, K. Changes in volatile sulfur compounds of whisky during aging. J Food Sci 1982; 47(1); 101-5
Reaich, D. Influence of copper on malt whisky character. In Proceedings of 5th Aviemore Conference on malting, brewing & distilling. 1998
www.practicalwinery.com/janfeb09/page1.htm

http://www.smws.co.uk/your-society-adventure/article-archive/A_matter_of_taste.html

Bengt Thorbjörnson in Scotland, 1929

Bengt Thorbjörnson (1891-1975) was a Swedish chemical engineer. After graduating from Kungliga Tekniska Högskolan of Stockholm he worked in sulphite factory in Bergvik (1916-1917), which manufactured sulphite spirits as a side product from 1911 at least until 1917. In 1917 he moved to Kramfors to work in a cellulose factory (1917-24) also producing industrial spirits as a side product. After a short spell at a margarin factory in Kalmar (1924-26) and a visit to Nashwalk Pulp & Paper Co in USA (1924-1925) he was appointed as the chief chemical engineer for Vin & Sprit AB (Wine & Spirit). He continued to work for the biggest Swedish alcohol producer for 30 years until 1957.

Bengt Thorbjörnson on the left

 Thorbjörnson toured Scottish whisky retailers and distillers in 1929-1930. The main object was to investigate whether it was profitable to start whisky production in Sweden. After the tour the Finnish alcohol monopoly consulted Thorbjörnson on the same subject and the record of the Scottish tour is still available in Swedish from the Kansallisarkisto (The National Archive) of Helsinki. Thorbjörnson visited the warehouses of W.H. Chaplin, John Walker & Son and The Distillers Company, as  well as the distilleries in Caledonian, Mortlach, Cardow (Cardhu), Glen-Mhor, Glen Albyn and Adelphi.

He preferred the Highland malts and considered the Campbeltown malts were "lacking midtaste". The factors most affecting the flavour of whisky according to his studies were: 1) Water, which should be low in calcium. The water of River Spey was good as it ran through soil rich in granite and sand. 2) Climate, which should be quite cold but even to allow long stable distilling times. 3) Amount of peat used in drying the malt. 4) Bacteriae flora, as the local bacteriae influenced the quality of the brew. 5) Experience of staff. 

The first place to visit was the wine and spirit retailer W.H.Chaplin & Co in London, who were at the time the sole representatives of the popular Long John brand. Their warehouse at Tower Hill consisted of 10 floors, of which 3 were underground. Huge glazed concrete cisterns (136 000 l) were used to vat and cold-chill-filter port wine. The whisky was vatted on demand in smaller concrete vats of size about 22 000 litres from different casks and different distilleries. According to other sources, Ben Nevis was the leading malt for Long John.

At John Walker & Son Thorbjörnson was hosted by the manager Sir Alexander Walker. At the time their Johnnie Walker blend was the most sold whisky brand in the world. Only sherry casks were used at the time. About 20% of them were new casks seasoned with sherry and the rest were refill casks rejuvenated with a small amount (about 35 litres) of sweet dark sherry for six weeks during which they were turned regularly. After the sherry-seasoning they are treated with pressure to impregnate more sherry into the wood. The sherry in the cask was then poured off and used several times for other casks. The pressure treatment had been developed by WP Lowrie in late 19th century and at the time of Thorbjörnson's visit it was used by many other blenders and distilleries as well. The Walkers had recently shifted to mainly hogshead size casks to ensure even quality. At the present time the Johnnie Walker recipe consisted of 10 parts Highland malt (Mortlach, Benrinnes, Ord, Cardow, Glenlossie, Dailuaine, Aultmore, Coleburn or Clynelish), 2 parts of Islay malt (Talisker (classified as Islay!), Caol Ila or Lagavulin) and 2 parts of Lowland malt (Rosebank or Glenkinchie). The blended malt was then again blended with grain whisky (mostly Caledonian) and the malt content varied between 40-60%. Long John blend consisted of 65% grain, 15% Lowland malt, 15% Highland malt and 5% Islay malts.

Caledonian distillery in 1966 (scotlandsplaces.gov.uk)

Caledonian grain distillery produced 40 000 gallons per week, which equalled 9 000 000 litres 50% abv- spirit per year. Maize was the most common cereal, but wheat and barley were sometimes used, too. About 30% of the mash came from barley malt dried over coal fire to gain diastase power. The maize flour was pressure cooked to prevent bacterial contamination. Brewers' yeast from Edinburgh was used to ferment in covered washbacks of 225 000 litres capacity (Cardow used pressed yeast). Carbon dioxide was collected and sold to mineral water producers. Column distillation with 20 plates in the analyser and 40 plates in the rectifier was used to produce new make spirit of 67 degrees over proof (95,3% ABV). The spirit was cut with water to 11 over proof (63,4% abv) for maturation. Draff was given for free to farmers. At the Adelphi grain distillery weekly production was 36 000 gallons/week and the only significant differences were the cooking of maize (not pressurised in Adelphi) and the fermentation time (72h in Adelphi, 96h in Caledonian). About 125 men were employed in each.

Mortlach produced high quality Highland malt with "quite old-fashioned means". A total of 24 men were employed to produce 8 000 gallons per week. Production was bigger than at the Invergordon distilleries, as Glen-Mhor and Glen Albyn managed only 2 500-3 000 gallons per week each. Distillation was carried out from September to end of May and the spring production was considered to be of the best quality. Mostly foreign barley was used and floor malted on site. Two kilns were used to dry malt for 50 hours in up to 77C after 9 days of germination. About 18 kg peat for every 120 kg of coal was used in kilning. Fermentation time in seven 60 000 gallon washbacks varied between 46-56 hours. After each fermentation the washbacks were washed with lime and peat was burned on the bottom of the washback to avoid bacterial contamination. The spirit was double distilled (no mention of the Wee Witchie or even partial triple distillation) to a very high proof of 45 over proof (82,8% abv) and reduced to standard 63,4% before maturation. Rummagers for wash still and direct firing with coal for both stills were used. 

Thorbjörnson calculated that the blending and maturation was cheaper in big English warehouses compared to the Swedish Reymersholm or Slottet warehouses. He also thought that the flavours came mostly from the malt whiskies and therefore the malt content of the Swedish blends (Crown Blend and Black Label) should be increased. On the other hand Scotch grain whisky could be replaced with cheaper domestic neutral potato spirit to cut costs. He also made a a costs-analysis for building a Swedish malt distillery with a 500 000 litres capacity per 6 months, which apparently never came to be.

References and further reading:
Kansallisarkisto, Helsinki. http://www.arkisto.fi/en/the-national-archives-service/arkistolaitoksen-vaiheet-2

Koch B. Från idé till produkt. Svenska Uppfinnarföreningen, 1963.

Morrice, P. Schweppes guide to Scotch. Alphabooks 1983
Spiller, B. Cardhu. John Walker & Sons, 1985.

History of the column still

Coffey still

Whisky can be distilled in column or pot stills. Grain whiskies are usually distilled in the faster and more economical column stills, which produce light or almost neutral spirit opposed to the heavier malt whiskies produced usually in pot stills. 

Distilling wine was invented in northern Italy during the 11th century, although the Arabs and the Alexandrians had probably used distillation before that to produce infusions and concotions, perhaps even as early as in the 1st century AD. The early stills were simple pot stills with a collection pot. The apparatus was often made of clay and/or copper, sometimes partly of wood, even of leather. The shape of still was usually onion-like; wide bottom to enable efficient and fast heating and narrower head to enable condensation and collection. Some kind of worm was used from the beginning, but efficient water cooling was probably invented as late as in the 18th century. The knowledge of distillation spread through Europe and Russia during the 14th and 15th centuries and malt spirits were probably distilled in Britain and Ireland at least from the late 15th century. The design of the stills remained quite constant from the 11th to the 19th century, although there were numerous experiments with different shapes. The onion pot still however remained the still of choice until the early 19th century. Heating was provided by a naked flame, often by wood fire in southern Europe, but more often by peat in the north and after the 17th century by coal.

Water-jacketed still was invented in 1526 by Paracelsus (alias Theophrastus Philippus Aureolus Bombastus von Hohenheim the Swiss) and it became known as the Baine Marie or balneum Mariae among the alchemists. The water bath allowed the still to be indirectly heated, thus preventing the wash from burning on the bottom of the still and allowing the distillation of pomace and other thicker washes. The risk of cracking stills, especially made of clay, was also diminished by indirect heating. The fractionating system was invented as early as 1553 by German chemist Philip Ulstadius, but it did not possess any significant advantages for spirit distillers and was used primarily by (al)chemists.

The condenser was improved by a German chemist Christian Ehrenfried Weigel in 1771. He placed the worm into a tube, which was cooled by circulating cold water. The invention was named Liebig condenser. Later an englishman William Grimble invented the tube condenser 1825 and it was later improved and distirbuted widely by the Dutch still-manufacturer Armand Savalle.


The Woulfe bottle

The evolution of the still gained pace during the early years of 19th century, especially in France. An illiterate French workman Edouard Adam from Rouen attended chemistry lectures given by professor Laurent Solimani. Adam understood that the principles of the Woulfe bottle, invented by Angelo Saluzzo and used in chemistry, might also work for alcohol distilling and in 1801 invented and patented the first still to produce alcohol in one operation. In principle, that was the first working column still, although the "column" was placed horizontally and consisted of several chambers or pots. It allowed single distillation for high alcohol spirit, more effective heat exchange and relatively simple fractioning of the spirit. Mr Adam was however not successful in commercializing his invention and several distillers, including Solimani, Bérard, Barré, Brugniére, Pistorius and Carbonel, built either direct copies or similar stills with just minor modifications. The three distilleries built by Adam were not successful and he died poor in 1807.


Nääsi distillery, late 19th century Finland.
Pistorius still on the right, Savalle still at the back

Pistorius improved the Woulfe bottle principle and patented his still in 1817. It had many properties of a modern column still; the wort was fed into the rectifying part of the system and divided by the steam rising from the lower pots into alcohols, feints and the rest was piped to be redistilled in the lower pots. The rectifying plates are unique, but quite efficient allowing good reflux but also thick worts. The Pistorius still was used in central Europe and Scandinavia throughout the 19th century.

Armagnac still

The first truly continuous still was made by Fournier, who used two columns, which were heated alternately and fitted with valves for removing the residues. Professor Solimani introduced indirect steam heating for an modified Adam still in 1814 in his own distillery. French Jean Baptiste Cellier Blumenthal invented the first practical continuous still in 1808 and patented it in 1813. Basically he combined Adam's principle of multiple distilling/rectifying chambers, the early ideas of fractionation by Ulstadius, preheating and the vertical columns and the residue removal of Fournier. The apparatus still had a pot still, but the wine was feeded straight from the top of the column while vapours rose from the pot to the vertical distilling column, which had 9 perforated rectifying plates. Thus the distilling column was cooled with wine, which was simultaneously preheated for the distillation. The first stills were built by Cellier and a Dutch sugar-trader Armand Savalle, later to become a global still-manufacturer. The patent was improved with fractionating plates and draff/residue outlets and sold to Parisian apothecary Louis-Charles Derosne in 1818, who succeeded in commercializing the product. Savalle and his family continued with the original apparatus and sold them to various distilleries around the world. Some of their stills are still in use at rum, brandy and neutral spirit distilleries. Many eau-de-vie, armagnac and bourbon distillers adopted a cross-over between column and pot stills. The wort is boiled in the pot and rectified in single column with a lot of reflux.



Savalle still in Demerara Distillery, Guyana
(www.cocktailsoldfashioned.de)

In England a version of the Cellier Blumenthal still was patented in 1815 by relatively unknown Mr. Dihl, but it did not gain commercial success at the time. In the same year James Miller patented a system for preheating the wash in the worm cooler and in 1818 Joseph Corty described a still with double pots and a Pistorius-like condesenser-reflux-system. So basically all the pieces for working continuous still were available in Britain in the late 1810s. In Ireland the big pot stills ruled, although there were some experiments made with continuous distilling. John Stein at Clonmel distillery developed a triple still, basically just three stills attached to each other and Joseph Shee of Cork had a quadruple pot still, in which the first pot acted as a steam source. In 1822 Irish Andrew Perrier patented his vertical continuous still, which strongly resembled the Fournier and Cellier Blumenthal stills and by 1823 a French immigrant, a veterinary surgeon Jean-Jacques Saintmarc build a variation of the Adam still. The Saintmarc's potato spirit was not a success in England and he advanced into Ireland in 1825 and marketed grain whisky distilled with a continuous column still, but that was considered "too pure". It was until 1828 that the first commercially successful column still was built on the British Isles as Robert Stein, a member of the Stein-Haig distilling family, patented his column still. It had three preheaters and steam boiled in a separate vessel was used to heat the wash, which was intermittently sprayed by pistons into a series of chambers. The chambers were divided by crude cloths (probably haircloths). The cloth permeated ethanol well, but less so water and solubles, therefore acting both as a rectifier and a filter. It enabled large amounts of distillate to be produced in a single run and improved the heat economy compared to the pot stills. The process had to be stopped for discarding the excess oily residue, so it was not exactly continuous operation. Surprisingly the Steins used only malted barley in their Kirkliston distillery for several decades, despite the fact that most of the output was sold for gin manufacturers.

Aeneas Coffey (1780-1852)

The French-born Irishman Aeneas Coffey had retired from excise officers duty in 1824 and bought into Dodder Bank distillery in Dublin. He also managed the South King Street distillery (1828) and the Dock distillery (1834) in Dublin. The first Coffey stills were made of wood and iron and consisted of a single column, but copper plates and metallic columns quickly became the norm, most likely because of the better malleability and spirit quality. By the time Coffey patented his still design in 1830, he had introduced perforated copper plates for rectifying and pipes to remove the residual oils during distillation. During the 1830s the system was divided into two columns as it was easier to manufacture, it had better rectifying qualities as well as better heat economy. Numerous designs for rectifying plates were later introduced, although the most common was the bubble cap design. The Irish distillers trusted their big pot stills and only some Northern Irish distillers experimented with the Coffey stills, first in Derry by Andrew Alexander Watt's Abbey Street Distillery in 1833 and later in Belfast at Avoniel distillery (1882) , The Irish distillery, The Royal Irish distillery (the 1890s) and and at Dundalk (the 1880s?) distillery just south of the present border. As his stills were not selling in Ireland, Coffey moved his business to London. The first Scottish whisky distillery to install Coffey still was Grange in 1834 and during the next few years Inverkeithing, Bonnington and Cambus followed. Aeneas Coffey Jr tried his hand at Lewisham distillery, London in 1840, but was not successful and the Coffeys established themselves as still makers. At first the columns stills were used by rectifiers and gin distillers, but during the mid-1840s the Scottish distillers really started building Coffey stills.

Distillery	Still	Year
Kirkliston	Stein	1828
Cameron Bridge	Stein	1830
Grange	Coffey	1834
Inverkeithing	Coffey	1835
Bonnington	Coffey	1835
Cambus	Coffey	1836
Yoker	Stein	1845
Kilbagie	Coffey	1845
Port Dundas	Coffey	1845
Seggie	Coffey	1845
Glenochil	Stein	1846
Haddington	Coffey	1846
Croftanrigh	Coffey	1846
Kennyhill	Coffey	1847
Sunbury	Coffey	1849
Carsebridge	Coffey	1852
Saucel	Coffey	1855
Glenmavis	Coffey	1855
Caledonian	Coffey	1855
Bo'ness	Coffey	1876
North British	Coffey	1885

The Scottish patent still whisky distilleries founded in 19th century

The column still was much more efficient compared to the traditional pot still, producing higher proof (usually 86-95% ABV) spirit about ten times more in volume compared to medium sized pot still distillery. Since the malting, heating and maintenance costs were a fraction of those of a malt distillery, the column still grain spirit cost about 50-70% less compared to pot still malt whisky, even if the set-up costs were included. The northern Britons were not used to the light column still whisky and at the beginning large quantities were sold to rectifiers and gin distillers, who spiced the spirit and sold it as gin or imitation brandy or cognac. As shown in the figure below, the English rectifiers and distillers quickly adopted the Coffey still, but the more traditionalist Irish and Scots remained loyal to the pot still at least to some extent.

(Weir 1995)

During the latter part of the 19th century several factors caused the rise of the column still whisky. Branding and advertising became important at about the middle of the 19th century Britain. Several traders begun blending the products of different distilleries and sold them under their own labels. Blending enabled the inclusion of raw grain column still spirits into the mix and on the other hand blended whisky was easier to sell in the big English markets used to lighter non-smoky spirits. The column distillers began to control their pricing, the first price cartel was formed in 1856 and by the 1890's the century the DCL controlled all but most column distilleries and had a virtual monopoly during the 20th century. The tax reform in 1860 raised the taxation of foreign spirits and fortified wines and allowed commercial yeast manufacturing in the distilleries, which became a substantial source of revenue for the grain distillers towards the turn of the century.

REFERENCES AND FURTHER READING:
Barnard A. The whisky distilleries of the United Kingdom. Birlin ltd 1887
Forbes, RJ. Short history of the art of distillation. Brill 1948
House, J. Pride of Perth, Bell's 1976
Kaukoranta, A. Sulfiittispriiteollisuus Suomessa. Polar 1981
Kauppila, O. Rajamäen tehtaat. Painokaari 1988
Laver, J. The house of Haig, Haig 1958
Morewood S. A philosophical and statistical history of the inventions and customs of ancient and modern nations in the manufacture and use of inebriating liquors. Longman 1838.
Nettleton, W. The manufacture of spirits. London 1893

Townsend B. Scotch missed. Angel's share 2000.
Townsend B. The lost distilleries of Ireland, Neil Wilson 1997

Udo M. The Scottish whisky distilleries. Black&White Publishing 2006.

Weir, RB. The history of the Distillers Company 1877-1939, Oxford Univ Press 1995
http://www.cocktailsoldfashioned.de/2011/02/demerara-distillers-limited-guyana-rum/

A modern Coffey still in North British distillery