by Rishidev Chaudhuri
The Great North American Lime Shortage of 2014 has people panicked. As the heat of the summer looms, the national media is running frenzied articles, families are being ripped apart, bartenders are at each other's throats and lime hoarding is rampant. The causes of this terrible situation read like a list of contemporary American anxieties. Consumption (of limes) has risen dramatically since the 70s, and people have been living beyond their means, delaying the inevitable reckoning with citrus-fueled bacchanalias. Globalization and the destruction of lime farming in the U.S. now means that most limes here come from Mexico. And this production has been severely damaged by a combination of bad weather (probably caused by global warming), bacterial infection (no doubt drug resistant) and, of course, drug cartels, who are supposed to be hijacking supply.
When asked excessively metaphysical questions (“Is the world finite?”), the Buddha would not answer and instead told the story of a man shot with a poisoned arrow, who refused to have a doctor attend to him until he knew who his assailant was, why he had been shot, what kind of bow was used and which animal's feathers were used to make the arrow. Taking a similar pragmatic stance, we will not inquire further into the ultimate causes of the lime shortage and simply discuss coping mechanisms (or, if you prefer, routes to salvation). And to fortify ourselves we will remember that possibility emerges within constraints and it is hard to create anything interesting without them.
To replace the lime we must first know the lime and understand its particular role. At least to a first approximation, this rests on its utility as a source both of acidity and of fragrant citrus oils, and so these are the dimensions we will seek to replace.
Much of what makes citrus fruits distinctive (as opposed to just generically sour-sweet) comes from particular aromatic oils and the oil glands in the peel are especially rich sources of these. The classical citrus aromas result from compounds like limonene which, unsurprisingly, smells like lemons and is extracted for use in both fragrances and cleaning products. But the peels also contain piney and herbaceous oils, in line with the general observation that almost nothing has a simple aroma. A nice way to introduce yourself to these aromatic oils (if you haven't already) is to use a vegetable peeler to cut a swath of lemon rind and twist it, which breaks the glands and releases the oil. This is a deservedly popular garnish for cocktails. Note that by “peel” I just mean the superficial yellow part; the white pith that lies underneath is bitter and should be avoided (though as in marmalade, small amounts of this bitterness can nicely complement added sugar).
If we are looking for a citrus-replacement for limes, the lemon is a natural candidate. Despite not being as acidic and having more sugar, it is biologically quite close (perhaps descending from a lime-citron hybrid) and contains similar aromatic oils. Fortunately, lemons are superior for most rind-related purposes: they're bigger than limes, making them easier to peel; and in general the oils seem to me less bitter. Lemon peel and lemon zest are lovely and quite commonly used, though I'm always excited to see them used in creative ways. But really the one thing that everyone should be doing more of is using lemon peels to make oleo saccharum. Over the last few years oleo saccharum has been spreading across cocktail menus, driven by David Wondrich's wonderful book on punch. It has certainly made my life happier and more citrus-infused, and it's one of those culinary techniques that feels mildly revelatory and that everyone should have in their repertoire, especially for warm weather drinking.
As the name suggests, oleo saccharum is a sugar-oil mixture. The basic idea is to steep lemon peels in sugar, which pulls out water and citrus oils, resulting in a concentrated aromatic sweet-citrus mix, which can then be used as the base for punches and lemonade, to flavor cocktails and so on. You'll be using the lemon peel, so look for clean lemons (preferably organic, though I don't know if this actually makes a difference) and rinse them well. Use a peeler to take off the yellow peel, leaving behind the bitter white pith underneath (as far as possible; you don't need to be neurotic about this and you'll be adding plenty of sugar). This is easiest if your peeler is sharp; if you pull it towards yourself just under the surface you should be able to take off large swathes. Put the peels in a bowl or container or zip bag with sugar (about a cup of sugar for the peels of four lemons, says Wondrich, though that always looks like a lot and I inevitably use less; you should just experiment with quantities and find something you like). Muddle them to mix and slightly bruise the peels and then cover or seal. Leave them this way for a few hours, stopping by occasionally to shake or muddle. The sugar will become damp and partially dissolve in the liquid leaking out.
Now you get to use the lovely citrus syrup that's collected, which isn't hard because it makes everything that it touches taste bright and sunny. One simple option is to put the whole mixture into a punch bowl and use it as the base for a marvelous punch; I recommend trying this at least once (see the template below or acquire David Wondrich's book on punch where all this is much better described). You could also make lemonade by adding lemon juice and water/sparkling water to the mixture and then straining out the lemon peels. Or you could pour/scrape off the sugar and syrup and use that in small quantities in a variety of cocktails and desserts. There'll still be some sugar clinging to the lemon peels, so I like to add some water or alcohol or lemon juice to dissolve that off too. Remember to juice the lemons soon after; they are vulnerable without their yellow coats.
You can apply a somewhat similar technique with salt instead of sugar, which makes for a less fragrant result but yields nice warm citrus salt. You should use less salt, since it's hard to eat a cup of salt. If you add some water and strain out the peels you'll be left with a lemon-salt tincture. A few drops of a salt tincture is wonderful in many cocktails and sweeter drinks; you can't quite tell it's there but it makes everything more flavorful. The lemon-salt tincture could be used in the same way. It could also serve as the base for lemonade when mixed with more water or sparkling water (lime juice and salt is often drunk with water or club soda in India, and is great in the heat). A useful side-effect of steeping lemon peels in salt is that the peels soften and can be used as a shortcut to preserved lemons.
The other dimension to lime is acidity or sourness, which is caused by protons (or hydrogen ions). We seem to directly detect the presence of protons, a fact which is pleasantly reassuring and suggests that at least some subatomic particles have a higher purpose (perhaps they also swerve into our taste buds and create free will). Of course, acidity can be provided in several non-citrus ways, and most cooks know that small dashes of vinegar can brighten food and enhance other flavors much as a lime or lemon will. But vinegar is severely under-rated as a component of drinks, perhaps due to its unfortunate connection to spoilt wine.
Balsamic vinegar, in particular, is often too sweet when used for salad dressings but is lovely when drunk with ice and sparkling water (play around till you find the quantities you like). You could sweeten it with honey or sugar, if you like; we certainly do the same with lemonade. If you're feeling fancier you could reduce it over moderate heat until it thickens. Reduced by about half it's great both as a drink (again cut with, say, sparkling water) and in cocktails (you can make a complex whisky sour, for example). On further reduction it gets very syrupy, and is great drizzled on ice-cream and fruit or when used to draw pretty patterns on food and lovers.
Shrubs (compare sherbet) or drinking vinegars are slightly more involved preparations. They involve a mixture of fruit, vinegar and simple syrup (simple syrup is equal parts sugar and water heated together till the sugar dissolves: sugar doesn't dissolve well in cold alcohol, so simple syrup is often used in cocktails). For example, you could make a simple berry shrub by macerating berries in vinegar for a few days, straining and mixing the liquid with simple syrup. Alternately, simmer the berries, sugar and water together for a while until the berries break down and mix into the syrup, then take off the heat, add vinegar and let it cool before straining. These preparations are relatively stable and will sit in your fridge for a while, and the flavors will soften as they do (though smell and taste to check).
Shrubs are great on ice, topped up with sparkling water. They also allow for a number of interesting sour variations (a sour is a combination of alcohol, something sweet, like simple syrup, and something sour, like lemon juice). Once you've made a shrub, try shaking it up with various alcohols to see what goes with what. For example, a berry shrub goes quite well with gin, and a ginger shrub is lovely with rum (sort of a dark and stormy variant). If you're missing the limes from your margarita, make up a berry and chili shrub and shake it with tequila and a decent triple sec. Go easy on the chilies though; vinegar pulls out the heat beautifully and you can easily make it too hot.
Here are a couple of templates to end. They're just suggestions and you should play around. And if you're looking for inspiration, search for “oleo saccharum punch” or “shrubs vinegar” or something like that, and the Internet will be sure to oblige. I realize that all of this has been about replacing limes in drinks rather than in food, but you already know that lemons and vinegar make good culinary substitutes for limes, and dehydration will kill you before starvation does.
Make the oleo saccharum as described previously, using about four lemons and a cup of sugar, and scrape it all out into a bowl (including the lemon peels). Juice about six lemons (including the four you just peeled) and strain the juice into the bowl. Add a regular-sized bottle of alcohol (brandy or rum are great) and dilute it with water or sparkling water until it's refreshing and not too alcoholic, and then chill by putting it in the freezer or adding ice (you can also make a giant ice-block by freezing water in a metal bowl and then running hot water around the outside to release the ice). Punches on this template are simple to make, can be quite cheap and are delicious and refreshing. As always, tweak proportions until you find what you like. This is a dangerously easy way to unwittingly drink a lot of alcohol; personal experience suggests that it's prudent to warn your guests so that they can titrate.
Simmer equal parts of sugar and water together with berries until they all mix together well. Add vinegar just before the end and strain it out, pressing on the berries to squeeze all the juice out. Proportions depend on how sweet your fruit is and how you want to use the result, but you could start with a cup each of sugar, water and vinegar for about 2 cups of fruit and scale from there.
Another way to make a shrub is to leave the fruit to macerate in vinegar for a few days and then strain out the vinegar and mix it into a simple syrup (again, this is equal parts sugar and water heated to dissolve). This is a little more time-consuming, but the flavors are often cleaner.
 If the war in Iraq did not guarantee cheap oil, and the drug war in Mexico does not guarantee cheap limes, then what is war good for? Also, at least according to the New York Times, drug cartels are taking over the avocado business too, so we should all be concerned. Maybe United Fruit will step in to save us all.
 Of course you can't completely separate them, and anyhow the acidity in citrus fruits comes from citric acid, which deserves to be called characteristic of the family too. But the basic equation lime (or lemon)=sourness+citrus aromas seems useful.
 Lemons preserved in salt are very versatile flavoring ingredients. If you aren't making them and would like to, search for “Moroccan preserved lemons” and you'll find plenty of recipes with pictures.
 Olfaction is a strange sense, seemingly organized on principles very different from the others. In particular, it seems hard to break smells up into base components (both phenomenologically and neurally) in the way that one might break a sound in frequencies or a color into red, green and blue. It's a side project of mine to come up with culinarily-useful olfactory groupings that I can use to organize flavors in my head. At least from a culinary and perfumery point of view, citrus seems like a useful primordial category. Another one could be located in the complex of flavors around vanilla and wood, which are certainly found in well-aged balsamic vinegar. And so drinking balsamic vinegar appeals to me for structural reasons, as a sour-olfactory combination that is an interesting counterpoint to the sour-citrus oil drinks we're used to.