Fajita Marinade

 "I wish they made fajita cologne, because that stuff smells good. What's that you're wearing? That's sizzlin'!"- Mitch Hedberg

When you just want a good southwest Texan-style cookout, it don't get no better than fajitas. Often you can't even hear yourself talk over the sound of all that sizzle. In Texas, everybody puts beer in their fajitas marinade. But why? Many say beer helps to tenderize. However, this seems to be a matter of debate. Nobody wants to argue with a bunch of Texans. Yet when you do a little research into the science of marinades, you may start to think some of these beer-drenching folks are talking through their hats. 

The truth seems to be that marinades do more to impart flavor than to tenderize. That's because it turns out that a marinade is a mere surface treatment. Booze, aromatics, herbs, spices, acid, oil: none of these typical marinade elements penetrates deep into the muscle fibers of the meat. The only ingredient that truly penetrates, it seems, is salt. Meat is mostly water, and salt reacts chemically and electrically with water in the meat, helping the proteins to retain more juices during cooking and thus seem more tender and juicy to the bite.

Though every cook loves concocting secret marinades, the other truth about fajitas is that the cut of beef you use has a much bigger influence on the feel and flavor of the final dish. Fajitas are most often made with skirt steak, a very flavorful cut from the plate primal, but you can also use flank steak, hanger, flat iron, and sirloin flap. All these cuts are relatively thin, so they cook quickly (and are more quickly penetrated by the salt), but they are not the most tender parts of the steer. That's where slicing technique comes in. When you slice meat thin, across the grain - that is, perpendicular to the long strands of muscle fiber - you get a much more tender bite. If you use skirt steak, try to get so-called outside skirt steak, which is more tender and marbled than inside skirt steak.

Now, at last, we turn to the marinade. This marinade has a bit of soy sauce for umami; lime for acidity; sugar for caramelization; black pepper, garlic, cumin and smoked paprika for that southwest feeling; and a splash of beer...to appease the Texans. Since you just need to hit the surface, you don't need much. So drink the rest of the beer while you're prepping the fajita veggies, pardner.