The aesthetics of lime: contrast enhancement through terpene removal

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If you are a commercial distiller, flavor chemist, or over achieving bartender, you may want to read the prequel to this article, High Fidelity Gin Distilling / Perceptual puzzles / Musings.

Long ago, from Gordon Shepherd, I learned about contrast enhancement in the olfactory sense. In his text, Neurogastronomy, he likened many of the phenomena within olfaction to other senses like vision where contrast enhancement and its mechanisms are better understood. This led to my still leading theory of wine & food interaction: Contrast Enhancement in (Space & Time) for Wine and Food Interaction.

Contrast detection and contrast enhancement are still both poorly understood and little explored in the culinary arts. Neurogastronomy opened my eyes, but it has been slow to launch other ships. Since then I’ve learned more chemistry and even more about aesthetics and have slowly begun to apply some of Shepherd’s ideas to cocktail and distilling problems.

A big problem I came across was how the hell do terpenes work? Do they have any parallels with the esters, which in regards to still operation, are better understood? We can talk about this abstract stuff on paper, but can we ground it easily in an accessible sensory experience that provides an nth degree lesson? Enter clarified lime juice.

I remember the first time I made the FCI’s clarified lime juice. The recipe is brilliant, though I didn’t exactly enjoy the product and I don’t think its creators realized what exactly they clarified from the lime or its implications to understanding other processes, but I did quickly come up with a beautiful cocktail:

.75 oz. mezcal
.75 oz. milagro mandarin (not sure how this made it into the house)
.75 oz. der lachs danzig goldwasser
.75 oz. FCI clarified lime juice

I may have made the comparison of clarified lime juice to “Rose’s lime acid” which sort of compares an idea that is thought to be cutting edge with something plebian and ordinary. It definitely aroused the wino in me and I denounced it as against terroir. It is everything many of us complain about in overly manipulated wines, though few others seem to share that opinion.

Back then, I didn’t know that the big difference, before and after clarification, was with the terpenes, they’re pretty much all gone. Weakly soluble terpenes get bound in the agar which is separated by centrifugation. If you haven’t experienced any clarified lime, in the mind’s eye, it sort of glows neon like Rose’s and though its wholly natural, it seems so artificial. Terpenes are the class of compounds that gives lime (and so many other things) its piny character. They contribute an extraordinary timbre when fairly fresh, but then degrade into something very ordinary and pine-sol like as they oxidize.


Patterns were beginning to emerge between these sensory experiences and all the things I’ve read. Joseph Merory’s very elaborate recipe for orange liqueur is all about terpene removal. The primary explanation (because I said so!) of why its done is pretty much left as to improve stability and reduce cloudiness as terpenes come out of solution because they are so weakly soluble in water (think louching absinthe), It is not widely acknowledged that there are big aesthetic consequences.

Infused orange has all its terpenes intact and that gives it a more irregular shape rendered in the mind’s eye where its roundness is juxtaposed with the abundant angular terpenes. This is especially true as you get away from sweet oranges into the Sevilles and sours. Cointreau, which is distilled, glows like Rose’s and clarified lime juice. It’s aroma has perfect roundness and near no slight angular facets, because when its distilled, the terpenes are carefully cut away. Actually, they might be retained to very selective degrees and that might provide nuance and identity to the different brands (besides the other aromatic adjuncts like coriander and the mints, etc).

So far I’ve just used the term terpene as a catch all, but there are so many types just like the esters. You can get PhD’s in terpene science that will take you far away from here. Some aromatic terpenes are noble and some are less so just like the esters. Some are particularly volatile and some less so. Some are significantly effected by heat and some less so which is why vacuum distilling is popular in terpene territory.

Making, blending, and drinking clarified lime juice might just be that accessible nth degree exercise I was looking for, but how can we wrap more language around contrast enhancement? What we are doing when we clarify lime and blend it back in with plain lime is extracting and blowing out features. Sharper divides are created between the various spatially perceived facets of the experience. What we are creating is a sort of noirish effect. We are going down David Lynch’s Lost Highway. We are also creating a super normal stimuli (remember that forgotten nobel prize idea I’m always talking about?).

All creative linkage in the culinary arts is governed by the principles of the super normal stimuli and so is the joining of terpene free lime juice and normal lime juice. Features lurk under the olfactory shadows cast by those terpenes. To use another metaphor, when the ratios get changed, the ass on that lime, that part that resembles Rose’s, blows up. Where there was a response tendency, there is now an exaggerated response tendency and you’re going to chase it down the street. This is subtle and is governed by our ability to even detect contrast in the first place which is not always the most refined. If we can harness and wield these concepts just articulated, we can create more seductive gins and that is the real prize I’m after.

In truth, these gins have already been created. Terpene management for the sake of contrast enhancement is at the heart of the leading gins on the market, but its never articulated that way. Saying why we enjoy this thing we take for granted becomes a thing in itself. It also opens doors for small producers instead of only the chromatography wielding genius architects of the big gins.

There are simple ignoble terpenes that are the equivalent of ethyl acetate or acetaldehyde which are congeners that distillers are typically more familiar with. When concentrations are too high they can come out of solution and that is a big negative because most styles of gin should be brilliantly clear. They also bridge aromas like simple esters often can. The perceptual bridges reduce those defined lines where things really pop which is our contrast enhancement phenomenon.

Aromatic bridges are features or flaws depending on the context. Concentrations of compounds also change when above the various thresholds I’ve discussed before. There are absolute thresholds and recognition thresholds and the rules of thumb governing esters likely also apply to the noble and ignoble aromatic terpenes.

Gin producers tune their stills to get the results they want. Most of the time they don’t actually know how to wrap language around what they are getting or where they want to go. They just tuck in a cut, reduce the heat with partial vacuum, vary reflux, modify time under heat by applying more or less energy to the boil, use a gin basket, and pretty much systematically try everything. Basically its all more cow bell and then gets sent to a tasting panel for consensus.

The parameters get varied and the product is examined to be relatively more extraordinary. Chemical compounds are also counted up and correlations are found between what is ordinary and what is extraordinary.

We find ourselves squarely in the territory of the ordinary and the extraordinary and its all about the frequency of occurrence of the aromas sets and their relationships. This was modern for a while and most certainly was in the 1990’s when the big gins went turbo via their semi-secret in house research programs.

What happens when we go post modern? When everybody learns the trick and we are saturated with high contrast experiences? Can the whole world go noir? Of course not. We eventually attach symbolism to sensory experiences and that helps resist initially seductive aesthetic experiences. I pronounced the clarified lime juice as artificial right away which is purely symbolic. Humans have a more complicated relationship with supernormal stimuli than do animals (for animals, it always leads to their doom). The Australian beetle tries to mate with the bigger, more orange, more dimpled beer bottle and it dies out (or they famously change the design of the beer bottle).

For gins these days, the most extraordinary to me, have been ones that have juniper from far flung latitudes and close proximity to the coasts. This is funny because pretty much no one talks about juniper sourcing. Classically these are not desirable sources, but they are so uncommon, and you just know they are from the nether regions, so the symbolism of terroir creeps in and they get prized by me, a wino.

Some new classes of gins I’m finding extraordinary are partially infused. I don’t completely understand their chemistry, but I think this gives them acidity which makes them sippable even at room temperature. It is a genre more people should explore.

So now we have grounded this terpene business in all sorts of things people can relate to and hopefully we have a useful framework for contemplating the experience. I propose every one drinks several daiquiris arranged in an epic flight just like some of the varied contrast photos above. Make sure to make full sized drinks because the lesson really needs to sink in. To vary the contrast, mix different ratios of untreated lime and clarified lime. Your drinks should look like this:

.75 oz  lime (1:0, 2:1, 1:1, 1:2, 0:1 clarified lime juice to unclarified lime juice)
8 grams non-aromatic white sugar
1.5 oz. unaged Cape Verdean rum
stir in the sugar to dissolve then shake with four cubic inches of ice

Watch a waxing and waning moon unfold within your mind’s eye. To help create the lime juice ratios, use the kitchen scale to measure juice by weight instead of volume. Alternatively or in conjunction, a pipette is helpful.

Now that you’ve experienced it, lets back up for a minute, reference the prequel, and touch upon those olfactory shadows cast by the terpenes. The terpene literature leaves a lot to be desired and the lessons all just end in because I said so. Lets quote Gary Reineccius again:

Terpeneless and concentrated citrus oils from which only a part of the terpenes have been removed are widely used as flavoring materials as they have improved stability and a longer shelf life, a lower usage rate, and improved solubility making them of particular value in the flavoring of soft drinks and liqueurs. -Flavor Chemistry And Technology, Second Edition by Gary Reineccius.

Hopefully the curious language that is popping out is lower usage rate. That is the language Reineccius came up with to describe the contrast enhancement phenomenon. Something perceptual happens but he couldn’t encircle it with language. He was not confident enough to say something like there was a change in threshold of perception, but he recognized the usage rate in formulations went down. When there is less to overshadow the the glowing lime, it pops and you need less. Hopefully my metaphors do the topic justice, but I’d love to hear some feedback.

I’m not really sure how this will be received. There will be aha’s! and epiphonies, there will be confusion, disbelief, and denouncements. There will be those that got to the end and never figured out what I’m talking about. If you are in the direction of the later, I urge you to drink more, make a pilgrimage to view a Caravaggio, or re-watch Sin City while drinking the above daiquiris.

You can also sign up for my aesthetics workshop at the sMFA this fall.

[Yes, there was that time I was supposed to teach an aesthetics workshop at the Museum school. It was cancelled when the college merged with Tufts University.]

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