Sous Vide Rack of Lamb Recipe

Rack of lamb isn't cheap, so it's understandable that cooking it can be even more nerve-wracking than cooking a pricey steak. What's more, lamb tends to be leaner and smaller than a steak, which means that it's even more susceptible to accidental overcooking. All of this makes it an ideal candidate for cooking sous vide, which makes overcooking nearly impossible and perfectly edge-to-edge medium-rare results the norm.

Because rack of lamb is a fast-cooking cut, the good news is that you don't even need a dedicated sous vide immersion circulator, though you can read about our favorites here. A plain old beer cooler will help you achieve better-than-restaurant-quality results.

How to Shop for Lamb Rack

A rack of lamb is a bone-in cut that typically includes around eight rib bones, along with a single small eye of meat. If you're familiar with a prime rib of beef, rack of lamb is the equivalent cut on the lamb. If you're buying your lamb in the U.S., your main choices come down to the origin of the lamb (American versus New Zealand or Australian) and the way it is butchered.

American lamb tends to be larger, fattier, and more strongly flavored than lamb imported from New Zealand or Australia, though that doesn't necessarily mean better or worse. It largely comes down to personal taste. If you typically find lamb to be a little too gamey for your palate, stick to imported lamb. If you like a fuller flavor, pick American. The basic cooking process is identical for both.

Most lamb racks come already frenched, which means that the meat and connective tissue have been pulled away from the ends of the rib bones to expose them. Occasionally you'll find an untrimmed rack of lamb; whether you want your butcher to french it for you or not is, again, entirely personal. Some people like the clean appearance of frenched bones. Others like the bits of crispy fat and connective tissue that you find on untrimmed bones.

How to Select the Right Temperature

The doneness of a lamb rack is by and large determined by the maximum internal temperature it reaches during cooking. For instance, so long as the interior does not rise above 130°F (54°C), it will never cook beyond medium-rare. With traditional cooking methods, there is a very short window of time during which your meat is perfectly cooked. A minute too long will mean overcooked meat. With sous vide cooking, on the other hand, that window of time is stretched into hours, which means your lamb will be hot and ready to go whenever you're ready to sear and serve it.

As with a steak, the muscle structure of a lamb rack resembles a series of long tubes that are filled with juices. The higher the temperature you cook them to, the more juices they squeeze out, and the firmer and drier your lamb will be.

Here's a rough breakdown of how lamb feels at different degrees of doneness.

Rare (115 to 124°F/46 to 51°C)

Your meat is still nearly raw. Muscle proteins have not started to contract much and have a slippery, wet texture. Fat has not yet started to render, so it can be a little tough or waxy. If you enjoy the texture of lamb that's barely been touched by heat, you'll enjoy this.

Medium-Rare (125 to 134°F/52 to 57°C)

Your lamb is still nice and red, but muscle proteins have begun to tighten and firm up. You lose a bit of juice due to this tightening, but what you lose in juice, you gain in tenderness. Medium-rare lamb has a cleaner bite to it: Instead of muscle fibrils mushing and slipping past each other, as they do in very rare lamb, they're cut more easily between your teeth. This is my favorite temperature range for lamb.

Medium (135 to 144°F/57 to 62°C)

Your lamb is a rosy pink throughout and has lost about four times more juices than a very rare lamb rack. If you have a very fatty piece of American lamb, I would recommend the lower end of this temperature range; it will help the fat render more fully, which should keep your lamb nice and juicy.

Medium-Well (145 to 154°F/63 to 68°C)

Your lamb is well on its way to dryness. At this point, it's lost nearly six times as much juice as a rare lamb rack, and the meat has a distinctly cottony, grainy texture that no amount of extra lubricating fat can disguise. If you must have your meat cooked medium-well, make sure to look for a really well-marbled piece of American lamb to ensure juiciness.

Well-Done (155°F/68°C+)

I get it: Some people like their meat well-done. However, there's no real reason to use a sous vide precision technique if you like your lamb cooked this way. Just grill your lamb or pan-roast it until it's as done as you like it.

Does Timing Matter?

I've seen some folks say that with sous vide cooking, once you set your temperature and add your meat, you can let it sit there indefinitely and see no change in quality. I even believed that myself a few years back. Since then, I've come to realize that's not quite the case. Even at low temperatures, things are going on. Enzymes are breaking down proteins. Chemical reactions are slowly taking place.

I cooked identical lamb racks at 130°F (54°C) for intervals ranging from one hour all the way up to 48 hours. As I had experienced with cooking sous vide steak in the past, I found that the most important differences typically appeared between the four- and 24-hour marks.

As you can see, the lamb cooked for four hours stretches and pulls when you tear it. This gives it a pleasant amount of chew even as it's still quite tender. Double that time to eight hours and you have a completely different texture: Rather than pulling and tearing, the meat shreds easily, with a much softer texture that offers little resistance. Increase that time to 24 hours and you have meat that is downright mushy.

For the best results, I strongly suggest cooking for no more than four hours total.

Temperature and Timing Chart for Sous Vide Lamb Rack

Smaller New Zealand or Australian lamb needs only around 45 minutes to cook, at a minimum. Larger American lamb should be cooked for a minimum of one hour. Lamb rack cooked under 130°F (54°C) should not be cooked for longer than two and a half hours at a time, for food-safety reasons.

Frequently Asked Sous Vide Lamb Questions

Q: What are the downsides to cooking lamb sous vide versus using a more traditional method?

None! Just kidding. Sous vide–style precision cooking is a technique, another tool in your arsenal, and just as with all techniques, there's a tradeoff. Here are a few of the most immediate:

• It takes longer. A traditionally cooked rack of lamb goes from fridge to plate in about 30 minutes. A sous vide rack of lamb will take an hour or more, though, with sous vide cooking, this time is almost 100% hands-off.
• You will not achieve the exact same sear. Flag-waving sous vide zealots may claim otherwise, but the rapid sear you achieve after cooking sous vide will not be as thick or crusty as the sear you get from a traditional cooking method. Some folks prefer a heavier sear; others prefer the thin sear achieved after sous vide cooking.
• It requires more equipment. Cooking lamb sous vide requires a precision cooker or beer cooler and a plastic bag or vacuum sealer, in addition to all the tools required for more traditional methods. Chances are, if you're reading this article, you already have those extra tools.

Remember this: Sous vide is not a silver bullet or a panacea meant to solve all of your cooking problems, or to replace more traditional methods. It's a tool meant to expand your options.

Q: When should I season my lamb?

Seasoning a rack of lamb prior to vacuum-sealing it and then letting it rest in the bag can result in meat with a firm texture, similar to that of a mildly cured ham. Some folks find this texture off-putting, though I personally don't mind it. To avoid this texture, it's best to season and bag lamb immediately before cooking, or season after cooking sous vide and before searing.

In either case, only the exterior of the lamb will be seasoned, so it's always a good idea to serve it with some coarse sea salt, such as Maldon, for sprinkling at the table.

Q: What happens if I leave a rack of lamb cooking sous vide for longer than the maximum time recommended? Is it dangerous?

So long as you're cooking at above 130°F, there are no real health risks associated with prolonged sous vide cooking. You will, however, eventually notice a difference in texture. For best results, I don't advise cooking any longer than the maximum recommended time for each cut and temperature range. See the section on timing above for more details.

Q: Should I put olive oil or butter in the bag?

I've seen recipes that recommend adding fat to the bag, though none that offer plausible reasons for doing so. Intuitively, you may think that adding a flavorful fat like butter or olive oil will in turn lead to a more flavorful cook. In fact, it achieves the opposite result: It dilutes flavor. Fat-soluble flavor compounds dissolve in the melted butter or oil and end up going down the drain later. Flavors extracted from aromatics end up diluted, too. For best results, place your seasoned lamb rack in a bag with no added fats.

Q: Can I add aromatics, like herbs or alliums, to the sous vide bag?

Yes, you can. I like to add thyme or rosemary sprigs, along with sliced shallots or garlic cloves, to the bags with my lamb during cooking. Adding the same aromatics to the pan as you sear will bolster that flavor.

Q: Can I add a spice rub to my lamb?

Yes, you can, but spice rubs behave quite differently under sous vide conditions compared to standard cooking conditions. Normally, aromatic compounds will dissipate into the air in the kitchen or over your grill as a spice-rubbed cut of meat cooks. At the same time, moisture dissipates, which means that what's left of your spices sticks firmly to your meat. With sous vide cooking, there's no way for that flavor to escape the bag. Meanwhile, spices rubbed on the surface of the meat have a tendency to get rinsed off by any juices that are expressed.

The short answer is that it's very tough to predict exactly how spices are going to react in a sous vide bag. I've found that for foods with a cook time of under four hours, like lamb, if I want spice flavor, it's better to rub the spices onto the meat after the sous vide cooking phase and before the final searing phase.

Q: Should I pre-sear my lamb?

Through repeated testing and blind taste tests, I've found that pre-searing meat—that is, browning it before it goes into the sous vide bag, in addition to browning it just before serving—plays at most a very minimal role in improving flavor or texture. In most cases, the difference is imperceptible. On the other hand, with a small rack of lamb, there's a very real risk of overcooking the meat by searing it twice. I do not recommend pre-searing.

Q: Can I chill and reheat my lamb after cooking it sous vide if I haven't opened the bag?

It's true that given a high enough temperature (130°F or higher) and a long enough time period (several hours), the contents of a sealed sous vide bag should be close to sterile, which means that rapid chilling via an ice bath, followed by rapid reheating, should pose no health risks. But bags are not perfectly airtight, and chilling is never quite as fast as you'd like it to be, so I still strongly recommend against it whenever avoidable. Repeatedly chilling and reheating also doesn't do any favors for the quality of your meat.

Word of warning: Never chill and reheat any food that has been cooked or held at a temperature lower than 130°F. These temperatures are not hot enough to destroy dangerous bacteria.

Q: Can I cook a rack of lamb straight from the freezer?

Yes! Sealed, seasoned, ready-to-cook lamb racks in sous vide bags in the freezer make for a great easy meal. Allow an extra hour for cooking if starting from frozen lamb.

Q: Does sous vide lamb need to rest?

Traditionally cooked meat needs to rest; that is, it needs to be placed aside for five to 10 minutes before it's cut and served. This resting period allows time for the temperature gradient within the meat to even out. The cooler center is gently heated by the hotter outer edges, while those edges, in turn, lose some of their heat to the outside world. Even temperature is important: It's what prevents meat from leaking its juices everywhere the moment it's sliced open.

Because sous vide techniques cook from edge to edge with more or less perfect evenness, there is no temperature gradient inside. A medium-rare rack of lamb should be 130°F from the very center to the outer edge, with only the outer surfaces hotter after searing. Thus, sous vide lamb can be served immediately after searing. The very minimal resting it needs will happen on the way from the kitchen to the table.

That said, sometimes you want a little bit of breathing room between cooking and serving, in which case it won't harm your lamb to let it rest for a few minutes while you set the table. To re-crisp the exterior, reheat the pan drippings until smoking-hot, then pour them over the resting lamb racks just before carving and serving.