Grilled Tenderloin in a Salt Crust

Labor Day traditionally marks the end of summer, and a bittersweet farewell to grilling season. This grilling project is sure to give the season a mighty send-off and delight the family and friends.

A Show-Stopper

Not only is grilling in a salt crust a delicious way to prepare a beef tenderloin, it gives a very impressive presentation to a festive occasion. You get to crack open a charred packet in front of all of your guests to reveal a perfectly cooked tenderloin, and then flambe it right before serving. You will need to sacrifice a dish towel to the effort, but it’s a great showy dish to prepare for holidays or whenever you have company coming over. And you won’t believe how delicious.

Why Cook in a Salt Crust?

Cooking in a salt crust is an ancient method that has been used by many different cultures. But what is it about this salt enclosure that makes it a desirable way to cook meat?

1. Thermodynamic Properties

Grill roasting or oven roasting in a salt crust creates a sort of kiln, or an oven within an oven that roasts your meat. Some traditional recipes call for burying meat or vegetables in dry salt, while others pack the food in a salt paste held together with water or egg whites. Either way, the meat is surrounded by a mineral that affects its thermal properties in unique ways.

➤ Heat Conduction: Salt molecules are made up of sodium ions and chlorine ions and are highly conductive. Packing salt around meat is a very efficient way to transfer  heat energy around the entire surface of the meat and radiate it inward.

➤ Heat Retention: Salt is also excellent at absorbing and retaining heat. Surrounding the meat entirely with salt creates an environment that cooks efficiently and evenly from edge to edge.

➤ Insulator: At the same time, the salt is a barrier around the meat that protects it from the searing heat of direct contact with the coals.

➤ Moisture Retention: Lastly, a salt crust around a cut of meat acts as a barrier to evaporation of water from the muscle fibers. Inside the salt kiln, the meat is steamed with its own juices—very little moisture is lost.

By packing foods such as fish, meats, or potatoes in a mound of salt, you ensure that the outer surface of the coked food doesn’t reach the same surface temperatures as it would if uncovered, leading to a less extreme gradient of doneness. —Cooking for Geeks, Jeff Potter

☼ Temperature Gradients are the differences in temperature from the center to the outer edges of the food.

2. Flavorful and Juicy with a Tender Texture

All of the moisture, volatile flavors, and aromas remain inside the salt crust with this method, creating a finished product that remains remarkably juicy, with very intense, pure flavors. Many salt crusts have fresh herbs and other aromatics mixed into them. The inward direction of the heat transfer infuses the meat with the flavors in the crust.

Less extreme temperature gradients with the even heat transfer of a salt crust means less overcooked meat and fantastic texture as long as your critical temperatures are tracked correctly with accurate thermometry.

3. Quicker Roasting

With powerfully intense heat moving inward from all sides of the salt-encased meat, it cooks faster—about 1/3 the time of regular grill roasting without the salt insulation.

Intense Carryover:

Be warned, however, that the carryover cooking factor (the meat’s internal temperature rise after being removed from the heat source) is exaggerated with this cooking method. After being removed from direct heat, the “salt kiln” can retain and insulate the energy already in the muscle fibers of the meat very well rather than letting it dissipate into the air. We tried a few different methods of salt-crusted cooking with different types of meat in our demo kitchen, and we saw carryover cooking increase the internal temperature of the different cuts of meat as much as 31°F (17°C) while resting! (31°F [17°C] carryover was seen with a pork loin that was oven roasted in an egg white salt crust, and rested in the salt crust for 20 minutes)

➤ But Wait, Won’t It Be Too Salty?

Q: Since the meat is cooked in a thick layer of salt, isn’t it going to taste really salty?

A: Not if done correctly. Keep reading…

Salt as a Tool, Not an Ingredient

With salt crust roasting, the salt’s purpose is to create an exterior shell that conducts, retains, and insulates heat throughout the cook. To ensure that your meat isn’t too salty, don’t salt it ahead of time.

Cook the meat immediately after packing or wrapping in salt. The meat will start cooking over the high heat before the salt has enough time to dissolve and penetrate the surface of the meat. After the meat is cooked and you crack and brush the salt away, the meat will be seasoned, but not salty.

Meat allowed to rest for eight hours in a salty crust before cooking loses a ton of its weight through osmosis, as its juices get pulled into the salt and eventually evaporate during cooking. Cut the crust open on a long-salted roast, and there’s a good half inch of space all around it that used to be occupied by meat. It also comes out inedibly salty. Make sure you cook the beef immediately after wrapping it. —Kenji Lopez-Alt, The Food Lab, Serious Eats

The Cook

Lomo al Trapo

Lomo al Trapo is a Colombian method of cooking a beef tenderloin surrounded by salt and rolled in a cotton towel, then cooked directly over hot coals. We followed Kenji’s recipe for Lomo al Trapo, and added a few modifications of our own.

Ingredients

• 1 Beef tenderloin
• 3 pounds kosher salt
• 1 tbsp ground black pepper
• Fresh herbs: rosemary, oregano, and/or thyme
• 3 cloves garlic, minced
• 1/2 cup brandy (flambe is optional)

Equipment

• Kitchen towel (100% cotton)
• Butcher’s twine

Instructions

—Light one chimney full of charcoal. Prepare the salt-crusted tenderloin while coals are heating.

—Trim tenderloin of excess fat and silverskin.

—Tie the tenderloin into a tight roll with butcher’s twine a 1-2″ intervals.

☼ Tip: Salt-crust roasting produces a wonderful even doneness and texture but it does not develop a traditional crust on the outside of the meat. We seared our tenderloin in a cast iron pan over high heat before encasing it in salt to give it a good savory crust in the final presentation.

—Toss the salt with pepper, herbs, and garlic.

☼ Tip: We added a little less than 1 cup of water to our salt mixture to create a salt paste. We found packing a paste around the tenderloin to be easier than trying to roll dry salt around the meat with a towel. Too much water can dampen the towel, however, and slow down the roasting process.

—Place about half of the salt mixture on the towel, 12 inches in from one end, crosswise on the towel in a rectangle shape about the size of the length of the tenderloin.

—Set the tenderloin on the salt mixture. If using a salt paste, pack the salt paste around the tenderloin and roll up.

—If using dry salt, place the tenderloin carefully in the center of the the towel, being sure to cover it in salt as you roll, until it is completely surrounded in salt.

—Secure the wrapped tenderloin again with butcher’s twine tying in 1-2″ intervals, tightly.

—Pour hot coals onto the bottom grate of a kettle grill, smoker, or barrel-style cooker. Do not put the top grate in place.

—Place the tenderloin directly onto the hot coals! Cover grill partially and cook for 10 minutes.

☼ Tip: The bundle may begin to flame, or it may not. No need to be alarmed if it does.

—Flip meat and cook for an additional 10 minutes. Spot-check the roast’s internal temperature with a Thermapen^® (you may need to forcefully puncture the towel with your Thermapen’s probe). Pull the tenderloin from the coals once the lowest internal temperature found reaches 120-125°F (49-52°C) (or 115°F [46°C] if you’re going to flambe the roast).

☼ Tip: The towel may burn through, exposing the meat. It’s ok if that happens! You can brush or rinse off the ash when the meat is done.

—Crack the package open (cut open with kitchen shears if it will not crack open), remove the tenderloin and brush off excess salt (rinsing will more thoroughly remove the excess salt).

—Optional Step: Place the roast into a hot cast iron pan over high heat, pour brandy onto the roast, and allow the roast to catch fire in the pan. Continue to cook until the flame dies.

☼ Tip: The roast will quickly catch fire if you’re cooking on a gas stovetop. Just tip the pan slightly so the high flame ignites the alcohol in the pan. If cooking over an electric stove top, or you can’t get a flame to start, use a lighter to ignite the brandy.

—Transfer roast to a carving board, slice, and serve with salsa fresca or chimichurri sauce. Enjoy!

This method of cooking a beef tenderloin in salt wrapped in a towel directly over coals is a fun project to try, and a Thermapen will ensure perfect results every time.

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Resources:

Lomo al Trapo: The Colombian Technique that will Change the Way You Grill Beef, Kenji Lopez-Alt, Serious Eats

It’s White Magic, Russ Parsons, LA Times

Cooking For Geeks, Jeff Potter