A Hamburger Today
The Food Lab: The Best Way to Make Carnitas (Without a Bucket of Lard!)
Carnitas. The undisputed king of the taco cart. The Mexican answer to American pulled pork, at their best they should be moist, juicy, and ultra-porky with the rich, tender texture of a French confit, and riddled with plenty of well-browned crisp edges. The most famous version of the dish comes from Michoacán, in central Mexico. Delicately flavored with a hint of orange, onion, and occasionally some warm herbs or spices like cinnamon, cloves, bay leaf, or oregano, all it needs is a squeeze of lime, some chopped onion and cilantro, and simple hot salsa to form a snack of unrivaled deliciousness.
The best part is that they couldn't be easier to make. All you have to do is take whole pork shoulders, chop them up and season them, then dump them into your five-gallon vat of hot lard in order to slowly break down the collagen and connective tissue. Then all that's left to do is shred it, crisp it, and toss it into tacos and you've got some comidas fit for el rey. The more batches of carnitas you make, the tastier they become, as the fat picks up flavor from every previous batch.
But what's that you say? You don't have a five-gallon vat of lard kept at a steady 200°F in your kitchen? Oddly enough, neither do I.
Of course, there are ways to work around it. The best is to buy just as much lard as you need—say a quart or two—and do a small-scale version of the real deal by placing the seasoned pork chunks in a Dutch oven, covering with the hot fat, and cooking it slowly on the stove top. The texture comes out perfectly, though the flavor suffers a bit. Rather than adding flavor to the pork, the brand new lard actually dilutes it. Without the benefit of cooking multiple batches to build up flavor in the cooking fat the way a real taqueria can, your carnitas will never be as good as the real deal.
Not to mention that you end up with an extra quart or two of flavored lard to store until the next time you make carnitas. Maybe that's not a problem for people like Chichi, who seem to have an unlimited capacity to find novel uses for lard, but what are the rest of us to do?
Shedding the Fat
There are pretty much two things that happen when you cook a fatty, connective tissue-laden cut of meat like a pork shoulder in low temperature fat (which I define as under 250°F):
- Connective tissue breaks down. Beginning at around 176°F*, the proteins that make up the connective tissue (mostly collagen) will slowly break down and convert to gelatin. Unlike collagen, which forms tough, fibrous strands, gelatin will not coagulate at serving temperature, instead acting to thicken liquids, allowing them to lubricate muscle fibers, and giving food a luscious mouthfeel. But the breakdown process takes time. At 176°, it can take upwards of 8 to 12 hours, whereas at 200° or so, this time can be reduced to closer to 2 hours.
- Muscle proteins contract, expelling moisture. Muscle fibers begin to contract at around 120°, squeezing liquid out of their ends. They contract tighter and tighter as the temperature gets higher, until eventually the liquid is almost completely expelled. Unlike collagen breakdown—which is time dependent—the amount of liquid expelled from muscle fibers is related pretty much only to the temperature they are heated to.
*Some breakdown will take place at even lower temperatures, but it's so slow as to be completely impractical without the benefits of something like a sous-vide machine.
So the key to great carnitas (and French confit, for that matter) is to heat the meat to a specific temperature, and try and keep it there long enough for the collagen to break down, while minimizing the amount of moisture lost. The large quantity of fat helps to accomplish this in a few ways.
First off, it coats the food, making it more difficult for water to escape. The fact that fat is hydrophobic (it repels water) helps it perform this function even better. Secondly, it acts as a temperature buffer. A large quantity of oil will heat and cool very slowly, helping to deliver a more even, consistent temperature. Finally, it helps deliver fat-soluble flavor molecules, like the oils in orange zest or bay leaves.
N.B. A lot of you may be asking: Doesn't the fat actually penetrate into the meat and make it juicier? This idea has been pretty conclusively proven false, and is easy to prove to yourself: Weigh the fat in a pan before and after slow-cooking meat in it. The mass will actually increase, indicating that the meat is actually losing fat, not gaining it.
So the question is, is there a way to achieve all of those goals without resorting to buying a separate container of lard?
Lots of home recipe for carnitas attempt to solve this problem by replacing the lard with a liquid, usually a combination of stock and orange juice. I decided to give this method a go, comparing it side-by-side with the traditional. The pork on the left was cooked in lard, while the one on the right was braised in stock. Both batches were cooked in the same oven, at the same temperature (both of them came up to around 208°F during the cooking process).
The difference is not immediately obvious, but the stock-cooked pork on the right shows some telltale signs of dryness: It shreds into fine threads rather than moist chunks, and the top edges shows a flat, matte-like finish rather than the moist gloss of the fat-based version.
Tasting the samples confirmed what my eyes told me: The stock-based version was definitely dry and overcooked.
So how could two pieces of pork, cooked for the same amount of time at the same temperature have cooked to different degrees? A lot of it has to do with the hydrophobic property of the oil I already mentioned—it helps keep the liquid inside the meat. The other reason has to do with heat capacity—the amount of heat that is required to change the temperature of a body by a given amount. Water has a heat capacity of about 4 kilojoules per kilogram degree Kelvin, meaning that in order to raise one kilogram of water by one degree, you need 4 kilojoules of energy (for the record, that's 1/302,000 the amount of energy you'd need to provide per second in order to send a DeLorean back to the future). Oil, on the other hand, has a heat capacity of about half that amount.
Here's what it boils down to: Given a set mass of oil and water at the same temperature, the oil will have about half the amount of energy as the water. Since the density of oil and water are nearly identical (oil clocks in at about 91 percent the density of water), foods cooking in a given volume of oil at a specific temperature will cook more slowly than food cooking in water at the exact same temperature.
No wonder the stock-braised pork was coming out dryer than the oil-cooked version: Oil is a much better temperature buffer than water. To get moist and tender pork, my cooking medium would need to have a relatively high proportion of fat to water.
A Tight Fit
A new question entered my mind: Why do I need all the liquid in the first place? Is it possible that the only reason many home recipes use a lot of liquid is to emulate the real deal? Just because using lots of oil makes sense in a taqueria setting, does it necessarily mean that it makes sense in my own kitchen?
Here's what I was thinking: Rather than have my pork pieces swimming in a lot of fat, why not just cook them in a much small container, fitting them together tightly enough that they'll cook in their own fat as it renders out? As long as I'm careful with the temperature, it should have enough fat in it naturally to cook plenty slow, right?
I seasoned up another batch of pork and rather than placing it in a Dutch oven on the stove top to heat, I placed it directly in a casserole dish—the smallest one I could find that I could squeeze the pork into and added just enough oil to cover the top surface and prevent it from drying out—about a quarter cup. After tightly covering it with foil, I placed it directly into a 275° oven to slowly heat up. It reached 208° after about an hour, and held there until I pulled it out two hours later (a total of three hours). Here's what I got:
Looking pretty good.
Before I even tasted it, I wanted to make sure that my theory about fat ratio in the cooking liquid held, so I drained the pork in a fine-mesh strainer set over a bowl to figure out exactly how much fat and liquid were expelled in the cooking process.
Turns out that the ratio of the cooking medium was about 60 percent fat and 40 percent water-based liquid—much better than the nearly 90 percent water-based liquid I'd had in the stock-braised version! And the proof was in the pork: This batch was every bit as tender as the batch I'd cooked in lard.
What's more, it was actually even more flavorful than the lard-cooked version. With completely fresh lard, a lot of the flavor of the pork and the seasonings gets diluted. Only by repeatedly using the same ard over many many batches of carnitas will it actually become flavorful enough to enhance the flavor of the meat. By not adding any extra liquid and very little extra fat, all the flavor of the pork and seasoning stays right where it belongs: in the pork.
In order to further maximize flavor, I skimmed off the excess fat and added it back to the meat, which I shredded into large-ish chunks. The liquid I reserved to use as the base for a quick and easy tomatillo-based salsa. Look, Ma, no waste!
The final step: crisping the edges. Many lard-based recipes call for deep frying the pork pieces in the rendered lard. I couldn't do that for obvious reasons. Cooking them in a dry skillet on the stove top works pretty well—they've got enough fat that they'll crisp up without burning or sticking. It does, however, require you to cook in batches and lend a lot of attention to the pan.
By far the easiest method is to simply shred the pork, put it right back in the casserole dish, and throw it under the broiler. After it develops a nice crust, I like to stir it back in and broil it again, to double up on the crispy bits.
The best part of this method is that it allows you to crisp up a small portion of carnitas in the toaster oven, or to do a full party-sized batch in the regular broiler.
Since the meat is well seasoned and quite fatty, it also lasts quite a long time and freezes well: You can store it in the fridge for at least three days before the final crisping step, or in the freezer for several months. If you freeze it in the right shape (wide and flat), you can even broil it directly from the freezer with no real loss in quality. I wish I could say the same about my cat.
And oh, ok. Here's Dumpling coming out of a canon. This shot was not faked at all. Those are not his feet hanging out behind the canon. I swear.