tequila margaritaHave you had 10 bad margaritas for every good one? You could be using inferior tequila that is not 100 percent agave, but a more likely reason is that you are using a distasteful concoction for the other main ingredient.

One of the best articles I’ve ever seen on the perils of bar mixers just came out from cocktail expert Eric Felten. Called Prefab Mixes: Buyer Beware, it bring to light why most of these chemical collections range from bad to undrinkable.

The core problem with cocktail mixes is that they almost all involve lemon or lime juice, which are notoriously difficult to bottle. Sara Risch, a food chemist and member of the Institute of Food Technologists, told me why: “Among the major components of citrus flavor are terpenes,” she explained, compounds that are grievously subject to oxidation, and that break down quickly, especially when cooked (as in the pasteurization process such bottled juices require). The volatile terpenes in the juices and oils of lemons and limes turn inexorably toward the piney taste and smell of turpentine.

Even with preservatives, the off-sour taste of vintage citrus comes through. I suspect that lemon and lime concoctions go as heavy on the sweetening as they do in an attempt to overwhelm the terpene twang. The result is a mix guaranteed to make your teeth ache in anticipation of dental trauma.

In my home city there’s a restaurant that wins the “best margarita in town” award year after year from every local newspaper. “It’s not that hard to make a great margarita,” the bartender told me once. “It’s just that most bars use some kind of premade sour mix.” Since this particular restaurant never does, she explained, even the house ones made with Cuervo Gold are so far above the norm that people immediately notice the difference. Here’s a clue: if your drink looks like the one pictured here (from an article in Epicurean.com) or lighter, then it’s probably drinkable. If it looks neon green and like it would glow in the dark, beware.

If you’re going to mix up a batch of margaritas, of course buy quality tequila and go light on the Contreau or triple sec. It’s the last step that’s most important though: don’t ruin the whole thing by tossing in something made of chemicals and high fructose corn syrup, even if it does come from Williams Sonoma.

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