“Wastin’ away again in Margaritaville,
Searchin’ for my lost shaker of salt.
Some people claim that there’s a woman to blame,
But I know it’s my own damn fault.”
– Jimmy Buffett, “Margaritaville”
Poor Jimmy Buffett. He really needs to locate some salt for his margarita. Without it, that frozen concoction won’t taste quite right.
But wait- what is it about salt that makes a margarita taste so good?
Your tongue is covered by taste buds, sites of receptor cells that are sensitive to the five different possible tastes: sweetness, sourness, saltiness, bitterness, and umami (savory). Each taste is the result of some chemical process that occurs when the substances we eat react with the receptor cells. Hydrogen ions in acidic solutions such as lemon juice create sourness. Sweetness typically comes from sugar, but may also be caused by some proteins in amino acids. Salt crystals produce saltiness (obviously). Bitterness is produced from a variety of substances that trigger the proteins in sensory cells. The last taste, umami, comes from glutamic or aspartic acid, common in meat and fermented products.
From an evolutionary standpoint, humans typically enjoy sweet substances, as we associate the taste with carbohydrates, an important energy source. Meanwhile, bitterness is often associated with poisonous plants. (Of course, some people enjoy bitter food such as coffee and unsweetened chocolate, so an aversion to bitterness isn’t a hard and fast rule.)
Your basic margarita contains tequila, triple sec, and lime juice. All three of these ingredients typically have some degree of bitterness associated with them, which can make the combination slightly unpleasant.
Salt reduces bitterness by selectively filtering out flavors. When salt is added, bitterness is more suppressed than sweetness. If you add salt to something that is bitter and sweet, the bitterness becomes far less pronounced while the sweetness is allowed to shine through. Not all types of salt have the same effect- the key is the presence of sodium, such as what’s found in typical table salt (sodium chloride). Potassium chloride, an alternate salt sometimes used in food, does not reduce bitterness. The jury is still out on just how the sodium in salt suppresses bitterness. It could be that the sodium disrupts bitter receptors on the tongue.
Some people actually sprinkle salt on fruit such as grapefruit, cantaloupe, and pineapple to squash bitterness and enhance other flavors. (At first I thought it was weird, but it turns out my grandma’s habit of adding salt to watermelon is pretty common!) People even add salt to their coffee.
Adding salt to your margarita has the same effect- it suppresses the bitterness in the ingredients as you sip them over the salted rim.
So what sodium-based salt should be used for the perfect margarita? Common table salt is readily available and cheap, but its fine texture can end up being overpowering if you add too much. Sea salt can be coarser and more subtle, but it’s rather expensive. Kosher salt combines the best of both worlds as a coarse but relatively inexpensive option. Of course, it’s all a matter of personal preference.
Now excuse me, it’s five o’clock somewhere, and I’ve got to find my shaker of salt.
Keep calm and science on.