The Food Lab

Unraveling the mysteries of home cooking through science.

The Food Lab: Foolproofing the Perfect Rack of Lamb

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Clockwise from left: Perfect Slow-Cooked Lamb Rack, the anatomy of well-cooked lamb, the key to success. [Photographs: J. Kenji Lopez-Alt]

I hate badly cooked meat with a passion. Why? Well sure, I admire the hard-working farmers and respect the death of the animal that lived only to provide me with sustenance. And yeah, I'm as cheap as the next guy and am certainly never in the mood to abuse $50 worth of tender, expensive, spring lamb.

But really, the reason is even more selfish. I'm contractually obligated to taste every iteration of every recipe I develop—even the failures. I'd prefer to keep the ratio of delicious to non-delicious bites as high as possible, thank you.

So this week, when I decided to tackle lamb racks—one of the most expensive (try $20+ per pound) and potentially delicious meats out there—I figured my work would be easy. I mean, I'd already tackled Perfect Prime Rib, which is the beefy equivalent. Could the ovine parallel really be all that different?

As it turns out, yes, it can.

Rack Opinions

To roast a lamb rack with the traditional method, you place your seasoned racks in a ripping hot oven (around 450°F), and basically hope that the center reaches the perfect medium rare (around 125 to 130°F), just as the exterior hits that deep-golden-brown-but-not-yet-black sweet spot. This is much easier said than done. Differences in the size of the rack, uneven oven temperatures, strange air circulation patterns, and difficulty finding the exact center of the lamb with your thermometer are just a few of the problems that can affect the outcome.

Worse, even if you manage to pull out the lamb at the exact right moment, the best results you can possibly expect from an oven still aren't that great. It's the age-old "gray zone" problem.

Essentially, it comes down to the fact that meat cooks from the outside in. In a high temperature cooking environment (say, the oven, a hot skillet, or the grill), by the time the very center of the meat has reached a perfect 125°F medium rare, the outer layers are already overcooked. Indeed, slicing open a lamb rack cooked in a 450°F oven reveals a distinct temperature gradient:

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  • The center is 120°F, which is technically rare (apparently, my thermometer probing skills need to be improved—but you get the idea). At this point, the meat is still dark red, barely warmed, and slippery in texture. Not ideal for me.
  • The next 1/2-inch is at 130-140°F, in the medium-rare to medium range. The meat is pink, just barely firm but still juicy, and fat has begun to render and melt, increasing the juiciness and flavor of the meat. This is the ideal target temperature for the entire rack.
  • The outer 1/2-inch ranges from 140°F up to 155°F and above, comfortably in the well-done range. Meat fibers have considerably contracted, juices have been expelled, and the meat is will be tough and dry.
  • The crust is reasonably well developed this time, but can be a crap shoot that depends on several difficult-to-control factors.

With a large prime rib, solving this problem is easy. Simply slow-cook the beef at a very low temperature (say, 200 to 250°F) to minimize the temperature gradient until the center reaches your desired finished temperature. Afterwards, crank the oven up as hot as it goes, and pop the beef back in just to give it a crisp, crackly crust, carve, and serve.

Attempting this exact same technique on a lamb rack proved disappointing. While the initial low-temperature cook was successful, it's the high temperature sear that's the problem. With diminutive lamb racks, even the 15 minutes it takes to achieve a great crust in a hot oven is too long—the racks end up hopelessly overcooked. Time to get back to basics.

The Searing Truth

So how to we get around this problem? Simple: take the lamb racks out of the fire, and into the frying pan. While searing an entire beef prime rib on the stovetop would be impractical, small lamb racks are easy to maneuver.

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I seasoned another batch of chops, placed them in a 200°F, and cooked them until their centers reached 125°F. I then removed them from the oven and seared them in a ripping hot skillet, carefully browning all sides until a deep, flavorful crust had developed. It was a success, revealing the beauties pictured below. As you can see, the temperature gradient has been drastically reduced, showing a mere 1/8th-inch or so of mildly overcooked meat, and the crust is a deeper brown.*

*More astute readers will pick up the batch of bare, pale fat on the bottom part of the chop on the right. This is due to the fact that the crust was so appealing on coming out of the pan that I instinctively picked it off and ate it before remembering I had to shoot a photograph. My sincere apologies.

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"Whoah, nice rack!" I exclaimed, just as my wife happened to walk through the front door, precipitating a disapproving glance.

I was talking to the lamb dear, to the lamb.

Thus far, I was pretty darn happy with my results. I'd proudly serve this to any guest in my home. But there were still a couple of things bothering me. First off, the method wasn't completely, 100% foolproof. As my first batch of lamb indicated, finding the exact center of such a tiny piece of meat with the tip of a thermometer can be a little difficult, meaning that my lamb racks had window of error of about 5°F in either direction.

Moreover, the recipe doesn't give much certainty in terms of timing. Due to the sporadic nature of oven heating, I found that one batch of lamb might come to temperature in 20 minutes, while the next could take over 35, making timing side dishes an exercise in futility.

These were hardly a problems worth losing sleep over perhaps; But for an OCD like myself, they were like glaring, festering, pustulating wounds in the middle of my otherwise blemish-free recipe. I'd have to figure out a better way to do this.

"I Can't Believe It's Not Sous-Vide"

The answer, of course, lay in breaking out my $450 Sous-Vide Supreme and cooking the lamb in a vacuum-sealed bag in a precisely controlled 125°F water bath, finished by a quick sear on the stove top. Perfect, foolproof results, and the ability to hold the cooked lamb for as long as I want, making timing side dishes a snap.

But wait—what's that you say? You don't have a $450 low-temperature water oven? I don't blame you.

In fact, there's a whole legion of people out there on the interwebs who have figured out ways of cobbling together DIY low-temp water baths (the more accurate term for "sous-vide," which technically refers only to the vacuum element). The problem with those is that most of them fall into two categories:

  • Category 1: The rice cooker, aquarium bubbler, PID controller, which is accurate, but requires a fair amount of DIY know-how, and costs a couple hundred dollars to hack together.
  • Category 2: The pot of water on the stove, fiddle with the heat as necessary method, which is inaccurate, and requires you to hover around the stove for the entire cooking time, which can be up to several hours. I'd rather watch a Jaleel White and Olsen twin marathon that do that.

Convinced that there was a fast, easier, cheaper, and more foolproof way to achieve the same results, I started poking around my kitchen.

Essentially, in order to create a low-temperature water oven, all you need to do is keep a large body of water at the same temperature for a couple of hours. Suddenly, a big red logo caught my eyes:

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Even though a cooler is designed to keep things cool, there's no reason why it shouldn't perform equally well at keeping hot things hot, right? The principles are the same—the interior of the cooler is separated from the outside environment with two layers of plastic with a vacuum in between them. Heat transfer is minimized, thus any volume of hot water inside the cooler should stay hot for a long, long time. That's pretty exciting.

The other part of precision low-temperature cooking is vacuum sealing the food. This is necessary primarily because when placed in the water bath, any air bubbles left in the bag will insulate the food within, causing uneven cooking. That said, the strong vacuum provided by a commercial chamber vac or a food saver are completely unnecessary for most cooking applications. In fact, the only thing you need to do is ensure that your cooking bag has no bubbles in it.

Thanks to a tip I gleaned a couple of weeks ago from Dave Arnold of the French Culinary Institute, achieving this is a snap. It uses the simple property of displacement. All you have to do is place your food in a regular zipper-lock bag, seal the zipper most of the way, then slowly dip it into a large volume of water, keeping the zipper-lock end above the water line.

As you submerge it, air should be steadily squeezed out (sometimes a little coaxing is necessary), and the bag will conform to the shape of its contents. Once you get the the very top, seal the bag, and there you go: food sealed in a perfectly air-free environment.

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Now to put it to the test. I sealed my seasoned lamb racks into gallon-sized zipper lock bags, then filled my picnic cooler up with water at 130°F** (figuring it would lose a few degrees as I place the cool lamb inside), dropped in the lamb, sealed the lid, draped the cooler with a few towels to help retain more heat, crossed my fingers, and waited for an hour.

**Which serendipitously is the exact temperature that hot water comes out of my kitchen tap, sparing me the need to even heat water on the stovetop

Right on! In all that time, the temperature had only dropped 2.6°F, and the lamb was a perfect 125°F in the center. In fact, I found that even after 3 hours, the water was still at a comfortable 124°F! Of course, this all depends on how good your cooler is and how warm your kitchen is, but mine is certainly not top-of-the-line, and my kitchen is not overwhelmingly hot, so it's a good bet that most people can get similar results at home.

All that was left was to take the lamb out, pat it dry with paper towels, and sear it in a hot skillet to give it a nice golden brown crust.
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The verdict? The best lamb I have ever cooked at home. Perfectly evenly cooked from edge to center, beautiful, crackly, crispy, melt-in-your-mouth crust, and on top of that, the ability to hold it in the water bath for up to three hours, meaning that dinner is on the table when I say it is, not the lamb gods.

Moreover, with grilling season right upon us, this method promises an exciting new way to get perfectly grilled food. Fill up my cooler with hot water and bagged chops and steaks, seal it, bring it out next to the grill, then pull the meat out of the bags as needed to finish off on the hot grill just before serving. Simple!

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So there you go: a the world's cheapest DIY sous-vide, low-temperature water oven rig. Does this mean that a more expensive sous-vide machine has no place? Of course not. I'll continue to use mine for it's accuracy and ability to hold temperature indefinitely, but this is certainly the best alternative I've seen for the home cook who only occasionally wishes to cook in this way.

By the way: for those of you who prefer to cook their beautiful lamb racks to well done, here's an idea: stuff yourselves in the cooler and save the lamb for the rest of us!

(I kid. Sort of.)

Continue here for Foolproof Perfect Slow-Cooked Lamb »

Full disclosure: I just know that I've heard of this idea—using a cooler for low-temp cooking—somewhere before, but after doing extensive online searching, looking through my books, and checking old emails, I can't for the life of me figure out where. Perhaps I hadn't heard of it from anywhere else, but... If you at some point told me this idea, please come forward—I don't want to claim credit for someone else's inspiration!

About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.

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