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

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.

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