A.C. Simpson, Gin Manufacture, 1966

I thought this paper was so good and so useful I’d retype it so it could be better indexed by google and more easily found. I have one more bulletin of blockbuster importance to write about before I write my annotated bibliography of gin. Amidst the document, I may input my own comments as quotations via the WordPress formatting.

My aim with all these documents is to raise the quality of gin from new producers. Remember, a high tide lifts all boats.

A.C. Simpson, Gin Manufacture. Process Biotechnology, October 1966.

Gin Manufacture
A.C. Simpson, B.Sc. joined W.&A. Gilbey at Harlow, Essex in 1956 as research assistant. In 1961 he was appointed chief chemist with general responsibilities for quality control and wine and spirit bottling.

The key factors in the manufacture of gin are the spirit used, the botanical formulae and the technique of distillation. Unlike whisky, the spirit used for gin should have no indigenous flavour, the taste of the final beverage deriving entirely from the juniper, and other botanicals. The present article, dealing primarily with the manufacture of London dry gin, also points to the differences between this and gins such as Steinhager and Borovicka.

Most of the gin produced and drunk throughout the world is correctly described as London dry gin: the description relates to the process and not the siting of the distillery. Holland’s gin, centred in the town of Schiedam in the Netherlands, is distinct in flavour and method of production. Plymouth gin comes from a unique distillery in Devon. A large quantity of gin is also made, generally for limited local markets, by various compounding and flavouring techniques. It is the manufacture of London dry gin which is specifically described in this article.

The word ‘gin’ is derived from the French ‘geniève’, meaning juniper: it is from this plant that the principal flavouring agent is drawn. Gin is said to have been invented by the Dutchman, Franciscus de la Boe in the seventeenth century, as a specific based on the diuretic properties of juniper oil [1 Encyclopedia Britannica]. Despite a medicinal origin, gin had acquired a reputation in England a century later which was the contrary in extreme. It had become the principal agent of drunkenness among the lower classes and notorious gin shops of the period displayed such enticements as ‘Drunk for 1d, dead drunk for 2d, straw for nothing’. Improvement came about with the retail licensing system and eventual concentration of distillery practice into the hands of a few large companies which developed individual strictly secret formulae. Lately the production of gin has been subject to scientific control in order to maintain uniformity in an essentially batch process.

By definition London dry gin is made from a relatively pure ethyl alcohol, flavoured by redistillation with various plant materials (botanicals) notable for their richness in essential oils. In a classification of spirits, gin is first cousin to liqueur and only distantly related to whisky and brandy, in which the flavour derives from the source of the alcohol.

Compound gin, made by the direct addition of essential oils to the spirit is inferior in quality to distilled gin. The property of dryness in gin is associated with degree of flavour: a very dry gin is distilled from a low proportion o botanicals.

Gin is classified for Excise purposes as British compounded spirit which can be manufactured from immature spirit and distributed to the public without a statutory age.

All spirits are defined for Excise, general trade purposes and retail in terms of percentage of proof spirit, a scale of alcoholic strength linearly proportional to percent ethyl alcohol by volume in which proof spirit has a specific gravity of 0.92308 at 51°F [2]. On this scale, pure ethyl alcohol equals 175.35% proof; and 70% proof, the normal retail strength of spirits is equivalent to 40% by volume at normal temperature. In the parlance of the trade the former strength is 75 op (over proof) and the latter 30 up (under proof).

Spirit
Gin production demands a supply of rectified fermentation spirit. The spirit much be clean and neutral in taste and odour and contain only traces of aldehydes, esters, fusel oils and other congenerics. The carbohydrate source of the spirit is generally grain (maize) but gin can be made from spirit of any source if it conforms to high analytical standards and is free from contaminant or congeneric odours. Spirit from molasses and, possibly, potato may therefore qualify (in Russia, spirit for vodka comes from these substrates). As the initial production of spirit is not an essential part of gin manufacture many gin distillers are not, themselves, producers of spirit.

This last paragraph is interesting because now there is the emerging idea that you can only be a “craft” distillery if you produce your own neutral spirits even if you probably shouldn’t create the environmental burden.

The basic spirit is made from grain by saccharification of the mash with malted barley and distillation of the fermented mash in a patent still. The methods and materials bear a close relationship with those of the grain whisky industry. A spirit suitable for gin is obtained from Scotch grain whisky by re-rectification.

I wonder what percentage of patent still whiskey production in Scotland is shipped to gin producers. Negligible or greater than 10%?

For the production of alcohol of good organoleptic quality from a fermentation spirit the fusel oils should be removed at the appropriate plate in the rectification column. Neutral alcohol is collected at the highest possible proof.

In North America, grain alcohol of extremely high purity and odour quality is produced in distilleries operating continuous, multi-column stills. Strict attention is paid to the conditions of fermentation, both in temperature control and sterility: the object is to maximize the yield of ethyl alcohol from a given weight of grain. The composition of the mash is regulated to secure good enzymatic conversion without the formation of much fusel oil. The spirit produced is adequate in quality for either gin or vodka manufacture. Some grain spirit made in Britain for gin retains an odour suggestive of its origin, due to incomplete rectification and purification. Many gin distillers who are not spirit manufactures rectify the spirit they buy before distilling it into gin.

It surprised me that they rectified. You’d think as far as energy usage went, it would make more sense to get it done to spec the first time, but maybe the industry was not that organized yet. I think the above paragraph is a shout out to Seagram’s.

Botanicals
The essential botanical of gin is the berry of the European juniper tree, Juniperus communis L; other flavouring agents come from a number of plants including coriander, angelica, orange, cinnamon, nutmeg, cardamom, orris and others. Juniper berries, coriander seeds and angelica root are probably common factors in the composition of all London dry gins but the proportions differ from one distiller to another. The ratio of the three main flavouring agents and the inclusion of other selected botanicals are defined by the distiller’s formula: an original combination which determines the character of gin. Distillers therefore do not disclose their botanical formulae.

Juniper berries [6] for the purposes of gin distillation are grown in Central Europe; the best berries come from the Chianti district of Tuscany but suitable material is also obtainable from Southern Germany and Yugoslavia. Berries from the Tyrol, Hungery and Czechoslavakia are generally utilised for local production of a juniper liqueur. At maturity the berries are smooth skinned, deep blue in colour and 5-8mm diam. Fruiting is biennial and the ripe berries are removed by harvesters who agitate the branches of the trees causing the berries to fall upon sheets laid on the ground. The berries are winnowed and carefully dried avoiding damage and fermentation, and sorted into culinary and industrial grades. The adulteration of berries with those of other species of Juniperus, e.g. oxycedrus is no longer so widespread because collection of the adulterant is no less arduous.

Gin I imagine demands the culinary grade of juniper?

Juniper berries are classified and selected for gin on the basis of appearance and the physical and organoleptic properties of the extracted essential oil (1.5-3.0%). Several components of the oil have been isolated and identified [6-8], by gas chromatographic analysis, Klein and Farrow [9] found 26.5% ∝-pinene, 9.0% myrcene, 8.8% sabinene and 3.8% limonene. It is to be expected that the components and the flavour of the oil will vary with locality and season: these factors are reflected in the physical properties of the oil on which the criteria of selection are based. For gin the berries should not give an oil with a predominantly terpenic odour [10]; the oxygenated compounds, in particular terpinen-4-ol, possess the aromatic flavour which characterises the best berries.

The criticism here of terpenic odor I think is why non communis Junipers are discouraged.

The second major botanical, the fruit of the herbaceous annual Coriandrum sativum [4], is cultivated in Russia, Roumania and other East European countries, for the supply of gin distilleries and the essential oil industry. The crop is also grown in the US, North Africa and surprisingly, in Essex, whence it is available to the English distiller after a good summer. Harvesting coriander demands judgement, for the fruit ripens sequentially and the farmer risks on the one hand an immature crop, and, on the other, shattered fruit with excessive loss of oil. It has been found that the crop contains the highest proportion of usable seed and quality of oil when the fruit on the central and first order umbels turns a chestnut colour [11]. The dried seeds (fruit) and 2-4 mm diam., number 100-130 to the gram and possess a perfumed but slightly cloying odour. Russian and English coriander seed yield 0.8-1.2% and 0.3-0.8% oil on steam distillation. As in the case of juniper berries, coriander seed is selected for gin on the physical properties of the distilled oil and organoleptic quality in dilute alcoholic solution. The main component of the oil is d-linalool (60-70%); other oxygenated compounds, geraniol, l-borneol and n-decanal are present [4].  Monoterpenic hydrocarbons occur (10-20%), principally as γ-terpinene, d-limonen and ∝-pinene [12].

The dried root of Angelica officinalis (Hoffm) provides a third important gin botanical [4]. The plant is cultivated in the temperate climate of Europe and the distiller’s requirement is met with the produce of an entirely cottage industry in the East German provinces of Thuringa and Saxony. The roots are plaited and hung up to dry: during storage changes occur in the yield and properties of the oil which becomes darker in colour, higher in specific gravity and lower in optical rotation and acquires a musk-like odour due to the predominance of high boiling lactones.

I’ve definitely over looked Angelica, but he’s totally got me with musk-like and high boiling lactones. Does it conform to anyone else’s experiences? A nice thing about Simpson is that he dares use sensory descriptors.

Other ingredients in gin formulae vary with distillery practice and are generally included in lower proportions, often only a few ounces in a charge of several hundred pounds. Common minor ingredients are: sweet orange peel (Citrus sinensis L.); bitter orange peel (Citrus aurantium L.); lemon peel (Citrus limon L.); cinnamon bark (Cinnamomum zeylanicum Nees); cassia bark (Cinnamomum cassia Nees); cardamom seeds (Elettaria cardamomum Maton); nutmeg (Myristica fragrans Houtt); orris root (Iris pallida Lam); and liquorice root (Glycyrrhiza spp.).

A few ounces to several hundred pounds is a big claim. I know a lot of new producers are trying to push supporting botanicals forward in search of distinction and perhaps they shouldn’t. Some of these material are particularly high in oil contents and perhaps have unique thresholds of detection so the addition may be far more than symbolic.

Small quantities of these botanicals may have a considerable effect on the flavour of the gin, being rich in oils of highly odorous composition. Orange oil [3] is 90% d-limonene and cinnamon bark and cassia bark oils [4] contain 60-70% and 70-95% cinnamic aldehyde. Other gin botanicals have been reported; aniseed, caraway seed, fennel seed, calamus root, geranium leaves, grains of paradise, turpentine and cubeb berries [13,14].

Many of the botanical ingredients described lose important quantitative and qualitative fractions of their oil on storage. Juniper berries stored a year for gin suffer a reduction of 20% in oil content and between 15 and 30% in moisture [10]. Coriander seeds lose absolutely 0.18-1.5% oil on prolonged storage at -14°C and 30% total oil in a year when stored in large hermetically sealed containers [15]. Citrus oils undergo autocatalytic oxidation when the peel is exposed to light and moisture [3]. Decorticated cardamom seeds lose 30% oil in eight months [5]. Stored botanicals are liable to insect infestation. Careful storage of botanicals by the distiller is necessary if he is to produce a consistently flavoured gin or avoid the evaporation of his flavouring material into the atmosphere. Ideally the botanicals are stored under temperature and humidity controlled conditions.

Distillation
The botanicals are proportioned according to formula and loaded into the still. A specified quantity of spirit, reduced to a strength of 80-100% proof is added (the exact strength depends on individual practice) and gin is collected as a definite fraction of the distillate. In Britain, gin distilleries and rectifying premises are not bonded but the still are secured by Excise lock and distillation of a set volumetric charge only is permitted. In North America, gin distilleries can be operated under bond.

The comment “the exact strength depends on individual practice” may conform to my idea that percentage alcohol in the still governs time under heat and that too low an alcohol content uses excessive time under heat (heating water you don’t need) while too high risks boiling the still dry.

The shape and design of the gin still and the manner of distillation constitute the third important factor in the manufacture of gin. The dimensions of the still relative to the volume and strength of the charge, the supply of steam to the jacket and cooling water to the head, determine the reflux ratio and hence the composition of the distillate. For a still of given reflux ratio and charge of specific composition the distiller modifies the production by selection of the middle cut of the distillate and also sometimes by a second distillation. Gin stills are built to exacting specifications by experts; and vary in capacity from a few hundred to several thousand gallons, measured to the level of the man-door in the pot of the still. The construction is always in copper and usually in the form of a simple pot still with tapering head which curves at the highest point into the downward sloping lyne arm (Fig. 1). The head may be expanded into a bulbous shape immediately above the pot. In some distilleries still heads are equipped with water jackets through which cold water is circulated during distillation; at another distillery a system of return flow conducts a preliminary condensate of higher boiling volatiles back to the pot of the still. All these features promote reflux in the course of distillation. The distillate is conveyed through a tubular condensor and is piped to inspection chambers for continuous measurement of alcoholic strength by means of in-line hydrometers; thence it passes to collection vessels. Stills are heated with steam generally applied to the jacketed base but some stills function with internal steam coils. Gauges for steam pressure, temperature of the liquid contents of the still, temperature of the distillate vapour and the condenser water are centralised in the modern distillery in a control panel.

The still head jacketed with water is sometimes called a “brandy ball” and is a method of providing optional degrees of reflux.

In operation the still is brought to boiling and the first few gallons of distillate rejected; this fraction is termed heads. Collection point for the middle cut of the distillate may be determined by an arbitrary quantity of heads, by the temperature in the column or by the appearance of the distillate. As the still charge is depleted of alcohol and steam pressure is raised to maintain distillation rate and when strength of the distillate falls to a predetermined value the still is struck and the distillate diverted into the second collection vessel. The still much now be exhausted of alcohol (tails) before the residue may be discharged. Combined heads and tails are called feints. The middle fraction of the distillate is gin, with a mean strength of 30-50 op. Still residues may be discharged to sewer after sedimentation and appropriate treatment. Feints are rectified in a special still with high reflux ration and the recovered spirit is added in constant proportion to the gin still charge. Feints may also be cleaned up by treatment with charcoal or potassium permanganate.

“by appearance” I think implies a demisting test where a sample is quickly taken and diluted to observe the degree of louching. This is correlated to how far has progressed and can probably be performed quickly enough to make a useful decision. The decision is gin product is of elevated importance because fractions are not recycled like other spirits. When the feints are recycled, they are stripped to neutral.

Alternative systems of distillation are sometimes adopted. In one variation the botanicals are place in a mesh tray above the liquid surface in the still. Volatile oils are extracted by heat and by contract with refluxing liquid but the botanicals so not undergo the maceration which occurs in the action of boiling. Some gin stills have been operated under reduced pressure.

What I haven’t figured out yet, is whether only the largest stills used gin baskets (my theory) because their time under heat was so long it compared to botanicals being boiled in a smaller still. Seagram’s early on was experimenting with partial vacuum.

In order to equalise the slight differences which result in the product of successive distillations in spite of the applications of rigorous quality control methods, gin should be blended in large holding tanks before transference to the bottling warehouse. Gin is diluted with distilled or demineralised water to bottling strength which in Britain is generally 70% proof. Water, free of dissolved solids, is used because otherwise the calcium and magnesium salts of hard ware are precipitated, giving sediments and chalky incrustations in the bottles [16]. Gin is colourless liquid and is often marketed in clear glass bottles. In order to attain the clarity demanded, gin is filtered (polished) before bottling, usually with cellulose-asbestos sheets in plate and frame or where throughput is large, with a filter-aid such as kieselguhr. Gin requires no period of laying down or maturation for improvement. The flavour derives entirely from the essential oils of the botanicals which are present in the condensate of the still. With gin the maxim might be ‘the earlier drunk the better’, for essential oils in dilute solutions tend to oxidise slowly with a detrimental effect on the flavour of the gin.

I think filtration and “polishing” are more important than some would think. I used to think polishing was only for dust and dirt but I think freshly distilled gin with always have errant out of solution terpenes that are some how emulsified and prevented from floating to the top. I’ve had big successes polishing very cloudy gins with sand (and there are lots of ins and outs of that), but the kieselguhr (diatomaceous earth) idea was new to me and I still do not exactly understand how it is applied. Stirred to attract particles then collected by the filter?

Analysis and quality control
The difference in flavour between well known brands of gin is distinctive even to the untutored palate. In order to maintain the distinction the distiller seeks to reproduce from one distillation to the next and from one year to another, a gin which is uniform in flavour. This is the aim of all producer of blended and compounded spirits but in the case of gin the process is more amenable to control. The whisky blender chooses from a wide range of finished whiskies, where as the gin distiller selects his raw materials and adapts his process to suit them. In the past, distillery organisation was based exclusively on the distiller’s palate and practical experience: today laboratory analysis and panel tasting play an important part.

I’m wondering if when Simpson says “where as the gin distiller selects his raw materials and adapts his process to suit them” he pretty much refers to scaling the botanical charge and blending stocks of botanicals to average out oil yields and their sensory properties. I suspect that the cut points stay as definite as possible batch to batch and the charges are reconfigured from different lots of botanicals to fit. And what of these master distiller’s? Do decisions at Tanqueray get made by the sole experience of a Tom Nichol or does he crunch numbers on the tasting panel, consult the analysis and paint by numbers? He did say recently that I make things too complicated. How far into the future are the international brands from the techniques laid out in this document?

The factors which determine the flavour in a bottle of gin have been described: spirit, botanical formula and technique of distillation. The distillation is a matter of control on the spot, with the still operator making adjustments in steam pressure and water flow from observations of the strength and rate of flow of the distillate. Modern distilleries utilise automatic steam valves, flow meters and other mechanical devices to obtain a precise control and the time of the entirely automated gin distillery approaches.

Did we ever get there? And if so, how small does it scale?

Botanicals and spirit were in the past selected wholly on the organoleptic evidence and while this method remains paramount in importance, it is necessarily supplemented by laboratory analysis. Control by tasting in the food industry has undergone a major rethinking in the last 10-15 years and the new methods are finding their way into traditionalist strongholds. In the US the standardisation of quality in distilleries through the use of taste panels numbering 20-30 persons is a widely employed technique [17]. Panelists are members of the distillery staff selected by test and they examine apparently similar samples daily in difference tests of the triangular or duo-trio type. Differences between the samples examined are expressed in statistical terms. Gin is amenable to this method of organoleptic examination because the accepted standard sample, properly stored, remains in good representative condition for a number of weeks. Panel tasting can be applied to finished gins as a test of uniformity, to spirit to check that it is up to standard and to dilute alcoholic solution of essential oils extracted from botanicals.

I was at a coffee roaster recently, Blue Bottle, and they were setting up panels for their quality control and every staff member knew how to quickly participate. I’ve tried to explain the importance to a few small distilleries and they just weren’t there yet.

Analysis of spirit has been restricted mainly to chemical methods: esters (expressed as ethyl acetate) by direct saponification; aldehydes (as acetaldehyde) using Schiff’s reagent; and fusel oil by the Komarowsky reaction. These methods give acceptable, meaningful results at intermediate and high levels of congenerics but approach the limit of accuracy when applied to the highly rectified spirits required for gin. It has been reported that the ‘fusel oil value’ of rectified spirits measured by the Komarowsky reaction is not necessarily an accurate measure of higher alcohol content but is a useful index of spirit quality [18]. Another widely used empirical measure of spirit quality is the permangranate time test which estimates the content of reducing substances by the rapidity with which a standard solution of potassium permangranite in contact with the spirit is decolorised. Ultra-violet spectrophotometry has been applied with some success to spirit analysis and provides a rapid instrumental assessment of inherent quality [19]. In Table 1 an analysis of an number of spirits used or proposed for use in gin distillation is presented together with a ranking of organoleptic quality by a small taste panel.

This all concerns the neutrality of the base spirit which is less of an issue now because it can be purchased from exacting specifications.

In the examination of gin botanicals for purchase or at intervals in storage, only juniper, coriander and angelica are likely to be subjected to a detailed laboratory analysis. The other botanicals would be distilled on pilot scale both individually and as ingredients in the formula and compared by taste against accepted standard. The essential oil of juniper berries, coriander seeds and angelica root are isolated from the plant material by steam distillation [20] and are measured volumetrically and for refractive index. The range of refractive index of the oil of juniper berries suitable for gin has been reported as 1.4840-1.4870 [10]. Lower values are indicative of a high content of low boiling terpenes which is undesirable in gin. Coriander and angelica oils should show refractive indices between 1.463-1.471 and 1.476-1.488 [4]. Ultra-violet absorption provides a rapid and valuable check of oil composition; juniper oil absorbs strongly in the region 220-240 mμ which is coincident in wavelength with a plateau in the absorption spectrum of terpinen-4-ol, and important constituent. Dilutions of juniper oil in 70° proof alcohol demonstrate an obedience of Beer’s Law at 225 mμ. Coriander oil begins to absorb at wavelengths less than 220 mμ but useful data are obtained if stray light factors are considered. Dilutions of the oil in alcohol are check by taste against standard samples. Moisture content of botanicals is determined by Dean and Starke tube.

New to me was that only the most significant botanicals were analyzed for oil yield and refractive index. I’ve slowly been doing a lot of work on the techniques and just found the block buster document on the subject from the horse’s mouth. Insignificant botanicals still get essayed but in an abbreviated form. I remember years ago tasting single botanical distillates from Citadelle, and each was startlingly beautiful with amazing focus and clarity of aroma. I thought that maybe they were prepared specially for the presentation, but they made have just been routine distillations performed for every batch of new botanicals.

Analysis of gin botanicals enables the distiller to base flavouring formula of his gin upon the definite properties of the batch in current use. Lots of berries or seeds with high and low oil contents may be blended together to give an appropriate intermediate level and a new season’s crop rich in oil can be phased into production with the least disturbance of the flavour characteristics of the gin. Purchase of botanicals each year from a range of samples supplied by the broker is made selectively on the basis of oil and moisture content, and composition and flavour of the oil in comparison with current stocks.

The finished gin is too dilute in oil to allow chemical analysis but control by tasting is supplemented by measurements of ultra-violet absorption. No published work exists on the application of gas chromatography to gin analysis but even with the most sensitive equipment, some preparation and extraction of sample is anticipated.

Other gins
Holland’s gin possesses a heavy, full-bodied flavour which derives not from the botanicals used in the gin distillation but from the original spirit; the gin character comes essentially from juniper berries but is overlaid with whisky-like congenerics. A mash containing up to 30% malt is fermented and distilled in a pot still with low rectification. The distillation may be repeated several times but the final spirit (moutwijn) does not show the neutral characteristics demanded for London dry gin. Originally the botanicals were added to the fermented mash before distillation.

Steinhager (Germany and Austria) or Borovicka (Hungary) is the distilled product of crushed fermented juniper berries [21]. It is twice distilled to a final alcohol strength of 70-85% proof. The stillage is and important source of oil of juniper.

Old Tom is a gin sweetened after distillation of approximately 3% w/v sugar. It is uncommon now in the English market but is still exported. Sloe gins, lemon and orange flavoured gins are made by steeping finished gin in the fruit or peel.

Acknowledgements
Thanks are due to the directors of W.&A. Gilbey Ltd for permission to publish this article; to Mr. M.S. Aldridge, distiller for his co-operation and Messrs M.G. Farey and C.C.H. Macpherson for analytical work.

References
1. Encyclopedia Britannica, 1964
2. Customs and Excise Act, 1952, Section 172(5).
3. Guenther, E. ‘The Essential Oils’, Vol. III (1949), D. Van Nostrand Inc. New York.
4. ——, Ibid., Vol. IV (1950), D. Van Nostrand Inc. New York.
5. ——, Ibid., Vol. V (1952), D. Van Nostrand Inc. New York.
6. ——, Ibid., Vol. VI (1952), D. Van Nostrand Inc. New York.
7. Motl, O., et al. Chem. Listy (1956), 50, 1282.
8. Hirose, Y., et al., Nippon Kagaku Zasshi (Japan) (1960), 81, 1776.
9. Klein, E. and Farrow, H. Dracogo Rept. (1964) 11, (10), 223.
10. Willkie, A.F et al. Ind. Eng. Chem. (1937), 29, 78.
11. Chikalov, P.M. Maslob-Zhir. Prom. (1962), 28 (2), 26.
12. Ibeda, R.M., et al., J. Food Sci. (1962), 27, 455.
13. Levin, H.J., Am Wine Liquor J. (1940), 7, 26, 33.
14. Jacobs, M.B., Am Essent. Oil Rev. (1949), 53, 54.
15. Rabora, N.V., Spiritovaya Prom. (1961), 27 (5), 13.
16. Warwicker, L.A., J. Sci. Food Agric. (1963), 14, 371.
17. Brandt, D.S., Lab. Pract. (1964), 12, 717.
18. Berganger, E., and Babel, W., Nahrung (1964), 8, 192.
19. Merke, R., et al., Branntweinwirtschaft (1960), 100, 479.
20. Clevenger, J.F., J. Amer. Pharm Assoc. (1928) 17, 345.
21. Stucklik, V., Sbornik Ceskoslov. Akad. Zeinedelske (1950), 22, 363.

Process Biochemistry, October 1966

Rare Vantage: Beverage History From The Spirits Chemist

I recently acquired another forgotten gin document, titled The History of Gin, by the chemist, D.W. Clutton, who gave us some of the most important works on gin distillation and chemical analysis. But what would such an important chemist speaking in 1972 have us know about gin? Read it and find out.

Clutton also wrote a wonderful history of rum that is notable and well organized. There are brilliant snippets and descriptions plus a bibliography of forgotten articles not seen elsewhere (that of course I’m already tracking down).

I also just digitized my copy of Herman Willkie’s Beverage Spirits in America —A Brief History (I apologize, but you will have to rotate the view of the PDF once you open it). This was an adaptation of Willkie’s 1947 address to the Newcomb society. It also answers the question: what would the greatest distiller of the 20th century have us know about American beverage history? And he goes on to say a great deal of things that were new to me. Some parts are so wonderful I dare not spoil them for you.

Clutton’s history of gin is really interesting and I’ll highlight what caught my eye. The most interesting parts are centered around Plymouth Gin and Old Tom.

J.B. Priestly described Plymouth gin as the gin ‘with a suggestion of a fresh morning at sea about it’.

The production of Plymouth gin is very localized. Messrs. Coates & Co. (Plymouth) Ltd. are the sole agents for its manufacture (with the exception of New Zealand, Germany, and Italy, where it is produced under license).

This was new to me and surprising as lately they hype their appellation status. More spirits are licensed for production in multiple locations than you’d think.

The secret of the success of Plymouth gin derives from the soft pure water which runs from the river Meavy, through the granite of Dartmoor. Spirit is obtained from grain whisky distilleries in Strathclyde, or occasionally from a London grain spirit supplier.

I began to wonder why he goes into such detail. Either Clutton was an employee or they just hosted him. It seems like Plymouth existed in a world where gin was simply a commodity but as often as possible they tried to elevate it to something fine.

During the war, molasses spirit had to be used, much to the disgust of the manufacturers. Eventually, however, the switch was made back to grain spirit, and this was commemorated by the following telegram sent from Glasgow—

From the land of Scotch and Bonnie Lasses,
We’re glad you’ve given up molasses
and Plymouth gin is once again,
The very best and made from grain.

The grain spirit is pumped into the still and reduced with the famous water to ca. 25° over proof and the spirit is rectified. The spirit is then pumped into a pot still and the botanicals are added. The centre portion of the distillation is reduced in strength, taken into bond and bottled as Plymouth gin. ‘Plym-Gin’, as it is affectionately called, is exported to 80 overseas markets.

The term ‘dry’, as applied to London dry gin, means that the over-all flavour content is low. This arises since the gin is distilled from extremely pure spirit and a low proportion of botanical ingredients.

I interpret “low” here as low enough to be crystal clear. If the gin is cloudy from insoluble terpenes, it either has too much flavour and/or is cut improperly. I’ve been exploring a new technique for post distillation clarification of cloudy gins and I’ve having spectacular success. It will be the defacto practice once I write it up.

Another explanation [of Old Tom gin’s origin] of the term was given by Boord’s (Distillers) Ltd. of London (Est. 1726) They established that Old Tom referred to Old Thomas Chamberlain of Hodges Distillery. He was an experimenter in gin flavourings, and once added sugar syrup to London gin. One of Boord’s ancient labels showed a picture of ‘Old Tom’ Chamberlain.

Old Tom is a gin sweetened, after distillation, to 3 to 6% w/v of sugar (or occasionally glycerine). Occasionally the sugar syrup is flavoured with orange flower water, and is known as capillaire. Old Tom is no longer popular in England, but is still exported.

This wonderful Difford’s Guide article gives even more background to the origins of Old Tom. I think its references mainly comes from a book titled Slang and its Analogs.

Clutton’s Rum had some spectacular passages I’ve love to quote, but I’m short on time.

Juniper Report: A Blog-Quality Survey of Academic Gin Literature

Feel free to skip to the very end if you get bored.

the first paper I found on Juniper was Controlling Gin Flavor by Herman Willkie and the team at Hiram Walker in 1937. Hiram Walker, I just noticed, was located in Peoria Illinois which is the same city as H. Shufeldt & Co. whom was an American producer of maraschino liqueur that was unearthed in the last post covering benzaldehyde in maraschino liqueurs from 1912.

Willkie explains new methods of standardizing the botanical charge to account for the varying essential oil contents of the botanicals.  He covers numerous testing procedures.  Most interestingly Willkie gives an introduction to the terroir of juniper and how it varies significantly by latitude.  He even gives some opinions.  Juniper expressions that Willkie did not enjoy I really enjoy.  This also led me to wonder if when recreating historic forms of gin such as Old Tom or Genever that we must consider their juniper sourcing.

In the limoncello article roundup where it was revealed that limoncello goes through no terpene separation and that terpenes and their unique distribution are the terroir of the product; what its all about. Terpenes got me thinking about juniper again and I wanted to see if there were any other great papers out there that would help connoisseurs understand gin and maybe even help new producers make the product of their dreams.

Numerous papers exist. Here is a bullet point run down of whats going on:

Characterization of Volatiles in Different Dry Gins from the J. Agric. Food Chem 2005, 53, 10154-10160 written by a Spanish team.

**they look at london dry gins and other “gins with geographic denominations”

**”When the production process takes place within a specific geographical area and fulfills certain  requirements concerning elaboration, composition, and quality, the gins can receive the denomination of geographical indication, as in the case of Plymouth gin (U.K.) and Mahon gin (spain).” I cannot not wait for “west coast” styles gins that match the ethic of west coast style I.P.A.s.

**G1-G4 are the top london dry brands while G5 is plymouth and G6 is Mahon. maybe we can guess the london dry brands by looking at some of their data. I bet they have tanqueray, beafeater, bombay or saphire? and I’m out of touch on what the fourth would likely be.

**they basically spend all there time proving that a method can detect compounds and how you need overlapping methods to get accuracy.

**”The highest contents of juniper characteristic monoterpenes were found in samples with geographic denomination G6, whereas sample with the geographic denomination G5 showed the highest concentrations of limonene and γ-terpinene. This is probably due to the use of citric species during gin aromatization.” so basically the spanish gin is my style and plymouth is boring and too citrusy.

**”In all of the samples, except G6, linalool was the most abundant among these compounds. Linalool is present in traces in juniper berries, whereas it is the major compound in the essential oil of coriander, in which it may represent >60%. Coriander seeds are well-known ingredients in gin aromatization, and linalool concentration may indicate the proportion of coriander employed for this operation.” … “The highest concentration of this compound was present in the London Dry Gin samples of the G4 group.” maybe that hint will elude to which is G4?

** there is a chart that quantifies the amounts of 66 different components in the six samples but I couldn’t get any great sense of the flavor from the numbers.

Comparison of a Novel Distillation Method versus a Traditional Distillation Method in a Model Gin System Using Liquid/Liquid Extraction from the J. Agric. Food Chem. 2008, 56, 9030-9036 by a team from Bacardi-Martini product development in collaboration with Clemson University in South Carolina

[Edited to add: It was explained to me by a well published, well patented mentor of mine that this study is likely a red herring. I wondered what incentive Bacardi had to publish it and it turns out it is likely just to support their patent application which they mention at the end.  The results are manipulated to build false novelty to justify a patent.  Things are presented in a way to throw people off. The model gins are not fractioned and the monoterpene level of the novel gin is never compared to other conventional commercial brands so you never get a true enough sense of the novelty on a chemical level.  They also never analyze what is left in their big ice chunk that represented the non-volatile fraction. The researchers are not naive and likely know all the finer points they should be pursuing.  The research went on to become the Oxley gin brand and I’m not sure if a patent was granted but I hope not. The process is not novel and spirits have been vacuum distilled for decades. Hopefully they cannot do anything to prevent smaller distilleries from experimenting with vacuum distillation. I should probably look into this more.]

**the novel distillation method was high vacuum distillation

**they studies a four botanical model gin composed of juniper, coriander, angelica, and lemon peel.

**”This research demonstrates the benefit of distilling botanical extract (particularly for the manufacture of gin) at temperatures below 0°C, which retains natural flavor of the botanicals better than under the traditional conditions, thereby producing a superior gin.”  this stupid statement sets the tone for the paper. they use two horrible oversimplfications: “better” and “superior”.

**in regards to traditional gin, “Some makers will apply a slight vacuum to get the distillation to take place at or around 60°C.” as opposed to 70-80°C.

**”The technical literature from the past 15-20 years has shown that vacuum distillation effectively circumvents high temperatures and reduces monoterpene formation in the final product” whatever that means.

**”Using a digital balance, 37.2 g of juniper berries, 52.8 g of coriander seeds, 18.0 g of angelica root, 10.8 g of dry lemon peel, 4270 g of 95% ABV GNS, and 687 g of deionized water were weighed and placed into a stainless steel pot and allowed to steep at room temperature (23°C) for 24 h.”

**for the atmospheric distillation: “and distilled until the thermometer reached 95°C. This insured that most of the alcohol had distilled at that temperature point.”

**for the vacuum distillation: “The distillation continued until the contents of the kettle froze, signifying that the majority of ethanol had been distilled.” cool!

**they acknowledge the significance of terroir on juniper berries when making comparison to other studies.

**vacuum distillation had a lower recovery rate than atmospheric distillation due to quite a few variables.

**they acknowledge “‘blow-by’, or vaporized alcohol that failed to be recondensed by the coldfinger and was passed out of the system through the vacuum pump.”

**”Coriander seeds (which are actually fruits) are normally the largest ingredient by weight in most gins.” is this really correct? their model gin had more coriander than juniper.

**linalool concentration decreased in the vacuum distilled gin post distillation relative to their un-distilled infusion of botanicals.

**vacuum distilled gin is a product with “less nasal pungency, more floral, less spicy aroma” So basically it is less of an acquired taste. Monoterpenes probably represent the most angular of junipers aroma components. To me, gin is supposed to be an acquired taste.

**they mention a patent application and that “proof of concept testing on a commercial scale is ongoing.” Bacardi who co-authored this paper owns Oxley Gin so this is apparently their feasibility study and Oxley is the product that emerged from the work. Why they would need to make this research public or team up with a university is beyond me. You would think they would have the capability and resources to do all of this privately.

Clutton, D.W. The Flavour Constituents of Gin, journal of chromatography, 167 (1978) 409-419

**”Dutch gin resembles the original gin produced in the 17th century, in that its flavour, reminiscent of almonds, is derived from the botanical ingredients and the source of the spirit used to make it.” I’m not sure how he comes up with “almonds” but Clutton is a big name in distillation research.

**”‘London’ relates to the method of production and not to the geographical location of the distillery; ‘Dry’ means that the flavour level is low.”

**their five samples varied and they only seemed to like one. others seemed to have flaws. who knows if they used famous brands.

**”UV analysis provides information on botanical flavour levels since juniper oil absorbs between 200 and 240 nm and coriander oil between 200 and 225 nm.” I’ve never seen UV analysis used and I’m wondering if there is anything low enough involvement about it that small distilleries could use it. An ultraviolet-visible spectrophotometer is only $1500 on ebay but knows how much time the testing takes to administer. They provide a chart which is pretty cool:

sample                   dilution       ppm juniper      ppm coriander     ppm cassia
1 london dry gin         1:1              45.8                   18.1                       —
2 london dry gin         1:1              27.7                     6.7                      0.5
3 london dry gin         1:1              37.5                   19.6                       —
4 plymouth gin           1:1              37.5                   24.6                       —
5 geneva gin              5:1              87.6                   26.2                       —

“The results show that the concentration of juniper oil in commercial gin samples varies from 25 to 50 ppm and for coriander oil from 5 to 25 ppm. The results obtained for Geneva gin (sample 5) must be regarded with caution since this product contains other species such as aldehydes, esters, etc. formed during fermentation.” …. “UV cannot differentiate between gin containing orange oil and those not containing this botanical, since limonene, the principal component, absorbs at 200 nm coincident with the absorption of coriander oil.”

“UV analysis only provides an indication of ‘total flavour level’ as ‘Juniper’ or ‘Coriander’. This is because the oils used for standardisation are steam distilled products, whereas gin is distilled in ethanol and part of the botanical flavour components are rejected as
‘feints’.”

So the technique has limitations. Here he acknowledges that steam distilled oils are un-fractioned unlike essential oils distilled with ethanol. In my distillation text I raised the same point in differentiating between distilled gins and compounded gins. One is fractioned and one is not. But from the above vacuum distillation study we also know that they may also differ significantly in degradation products (mono-terpenes) from time under heat. A steam distilled oil likely sees more time under head and higher heat than co-distillation with ethanol.

**There was some interesting stuff about odor thresholds and what constituents likely define the aromas but I’ll spare you. What is interesting is a chart they give that shows all the compounds then acknowledges what is at or above the threshold limit. This sort of proposes an active ingredient. I suspect though there are some flaws to the idea and there are all sort of synergies and interactions that change the threshold of perception. If compounds weren’t perceivable below the threshold they wouldn’t matter and it would be easy to compound things from only the “active ingredients” and I think that idea floated around in the artificial flavor business decades ago but the situation turned out to be more complex than that.

**A lot of their effort isn’t so much getting somewhere with the gin but getting somewhere with their analysis techniques. This was probably a pioneering a paper that opened up new analysis techniques to studying spirits.

**They spent a little time looking at how compounds like mono-terpenes accumulate in the heads and gradually decline. These compounds were the flaws of the vacuum distilled gin study. That study might have been biased if they never fractioned them in their model gin. So yes they are created but maybe you can remove them… The fractioning and selective
separation of this class of aroma component might be why big London Dry distillers expend so much effort tuning their stills.

**”GLC analysis shows that the early fraction of gin distillates are principally composed of juniper components. Coriander components distill over after a strength of approximately 75% ethanol is reached. Indeed a large quantity of flavouring components are run to waste in many typical distillations.” what I think he means is that fractioning is a big part of the gin distillation process but he is cheap and throwing away things annoys the engineer in him.

I wonder if before this era of analysis that even the big London Dry’s had a fair degree of inconsistency. This kind of research might have created an era of precision sculpted products that could meet global demand.

Sensory Characterization of Dry Gins with Different Volatile Profiles by a Spanish Team from Barcelona

**This study looks at 6 gins, four of which are London Dry and two geographic gins which are Plymouth and Mahon from Spain.

**They try and develop a sensory vocabulary and see if it can successfully be matched to chemical composition.

**The descriptors they narrow gin down to are juniper, citric, aniseed, spice, and licorice. These are all object comparisons and it would be interesting to see if the study could be done again with cross modal descriptors like looking at all the volatile components in terms of the gustatory division they converge with.

**They reference Clutton’s definition of gin from 1978.

**They mention other geographic indications I’ve never heard of: Ostfriesischer Korngenever, Genievre Flandres Artois, Hasseltse Jenever, Balegemse Jenever, Peket de Wallonie, Steinhager, plus the usual Plymouth Gin, and Gin de Mahon.

**They identify the sales of the brands which would help anyone positively identify them if they really wanted to.

**They make reference standard solutions of very specific volatile components that I would love to check out some time.

**They make other reference standards of things like paprika powder by simple infusion. Their choices were all things alleged to be in gin formulas.

**The initial list of descriptive terms identified by the panel in 3 gins during the session of vocabulary development. In bolt letters are the 10 preliminary selected attributes.

angelica root, aniseed, aniseed/fennel, aromatic plant, cane, cardamom, chili, citric peel, clean, coriander, cumin, detergent, eucalyptus, fennel, fertile, floral, fresh, fresh spice, freshener, fruity, herb louisa, juniper, lemon, lemon balm, lime, licorice, licorice root, orange, oregano, painting, polish, resin, rose grapefruit, rosemary, seaweed, seed, soil, solvent, spice, tangerine, thyme, varnish, vegetable spice, wood.

I see angelica root as converging with the same gustatory division as juniper which is olfactory-acid hence all those fresh and clean descriptors. the two combine with the intention of forming an overtone that is extraordinary as opposed to ordinary. citrus peel, fruity, aniseed/fennel, and licorice all contribute olfactory sweetness, but not with overtones so much as intervals when the citrus peels meet the anise. if rendered on an imaginary spatial scale, citrus and anise would be at opposite ends which is why experiencing the two together gives a sensation of depth and enlarged space. coriander is unique because it has qualities in common with the olfactory-sweet and the olfactory-acid so it influences overtones in both directions. spice can often be olfactory-bitter or olfactory-piquant. eucalyptus and licorice can also be olfactory-camphorous which is similar to piquancy and probably operates via the trigeminal nerve.

**descriptors were reduced to the five by a combination of examining frequency quotation and relative intensity. relative importance was then considered and then redundancy.

**”The results of the triangle test (Table 2) showed that the panelists could easily distinguish the gins with geographic indications (G5 and G6) and the London Dry Gin G1 (P<0.05). Gins G3 and G4, however, could not always be differentiated from the other samples.”

**they start to use some awesome spider graphs that I think should really be applied to cocktails. they give an intuitive look at how the gins different with some limitations. I should probably copy in the charts. the basically make it look like juniper does not dominate. the panel ends up searching for the other components and somehow makes them have out-sized intensity.

**”The geographic indication G5 [Plymouth] showed the highest intensity of citric attribute (Figure 3 and 4, Table 4). The intensity of the citric note in this brand was justified by its high levels of limonene and g-terpinene, together with linalool, which could contribute to the citric note (Table 5). On the other hand, G5 presented concentrations of juniper monoterpenes similar to those of G6 [Mahon] but showed the lowest intensity of juniper note by orthonasal perception. The high intensity of citric note in this gin brand could have masked the other attributes. The flavor perception did not depend only on 1 or 2 compounds on a complete volatile composition. Some interactions could take place between some compounds and also some compound could inhibit another, providing a different note.” I wish I remembered these gins better but I gave up on them years ago and now only drink and sell the local stuff.

**”The London Dry Gin G1 obtained the lowest punctuation for the juniper attribute by retronasal perception and was characterized by spices and aniseed notes. This gin contained the lowest levels of juniper characteristics compounds, while it presented significantly higher amounts of d-3-carene (P < 0.05). Also, the multiple regression analysis was performed. The spice note could be explained by a model with sabinene, d-3-carene, and p-cymene + ….; these compounds presented pepper and resinous notes, respectively (Table 5).

A paper I read won’t won’t quote is:

Effect of Latitude and Altitude on the Terpenoid and Soluble Phenolic Composition of Juniper (Juniperus communis) Needles and Evaluation of Their Antibacterial Activity in the Boreal Zone, J. Agric. Food Chem. 2009, 57, 9575-9584 by a Finnish team

The paper looks at the diversity of composition of juniper needles which are harvested for their essential oil which has a gin-like fragrance but also antibacterial properties.  The subject is not juniper berries but I suspect their properties parallel the needles.

As is mentioned by Willkie in the first paper, the character of the berries differs significantly with latitude. This paper adds altitude to the equation but find latitude is more significant.  Other papers I’ve seen add coastal proximity to the equation but I haven’t read them.  The most interesting gin I’ve ever made was with juniper from Cape Cod.

This paper and papers like it can add to gin connoisseurship.  We can now ask where the juniper has been sourced from and we can now ask to have gins made to reflect certain terroirs such as the northern most most juniper example.  Beer brewers already give us this with hops.  We also now know from the vacuum distilled gin paper that juniper Distillation involves the creation of many new aroma compounds through the degradation of precursor compounds.  Attention to detail with the cuts can refine the juniper expression.  Their paper might have been biased because they didn’t make heads cuts on their model gin distilled at atmospheric pressure.

A vacuum distilled gin isn’t without appeal, but I don’t think it should be touted as superior unless they are trying to give us a glimpse of a particular named juniper source.  Really interesting is the acknowledgement of partial vacuum gins which perhaps keep the temperature under a threshold. no brand was acknowledge. If I guessed I’d say Hendricks because they are the newest to the market and possible use new equipment that could handle such technology.  Bombay states the use of Tuscan juniper which is awesome but that isn’t going to mean much unless it is relative to other expressions that we know about.    Cascade Mountain Gin (the name might have changed), which sources their juniper from the world’s largest juniper forest gives us a three-fold unique expression. First its a wild foraged juniper from a distinct location. Second it is infused rather than distilled (or only partially?) so it was never degraded by heat making some of its aroma purity comparable to a vacuum distilled gin. And thirdly it was never fractioned so the outward lying juniper components that often get cut are in tact.  Other things like gustatory-acidity as still in tact which is why I think it is so enjoyable to drink neat. We end up with the pleasure of pondering; is its wild character due to being un-fractioned or due to unique sourcing? Lately it is my favorite gin.