The Science of Collagen-and The way to Make Mean Duck Confit-from Cooking For Geeks [Tastetest]

Duck confit tastes entirely different from duck cooked almost any wrong way. Cooking it’s all about converting tough collagen proteins-pound for pound tougher than steel-into gelatin.

While this isn’t a fast chemical reaction, it’s a straightforward one to trigger: hold the meat at a low temperature for long enough, and the collagen proteins denature and finally hydrolyze.

154°F / 68°C: Collagen (Type I) Denatures

An animal’s connective tissues provide structure and support for the muscles and organs in its body. You’ll be able to reflect on most connective tissues-loose fascia and ligaments between muscles in addition as other structures consisting of tendons and bones-as similar to steel reinforcement: they don’t actively contract like muscle groups, but they give structure against which muscles can pull and contract.

The most typical kind of protein in connective tissue is collagen, and while there are different types of collagen in animals, from a culinary perspective, the key chemical difference between the differing kinds of collagen is the temperature at which they denature. In cooking, collagen shows up in two other ways: either as discrete chunks (e.g., tendons, silverskin) outside of the muscle, or as a network that runs during the muscle. In spite of its location, collagen is difficult (it provides structure, in the end) and becomes palatable only given sufficient time at sufficiently high temperatures.

It’s easy to house collagen that shows up as discrete pieces: eliminate it by cutting it off. For cuts of meats that have a thin layer of connective tissue on them (called silverskin, presumably as a result of its somewhat iridescent appearance), bring to an end as much as possible and discard it. Beef tenderloin cuts commonly have a facet with this residue; trim off as much as possible before cooking.

Chicken breasts even have a small but noticeable tendon connected to the chicken tenderloin. Uncooked, it’s a pearlescent white ribbon. After cooking, it becomes that small white rubber-band-like thing that you could chew on endlessly yet never get any satisfaction from. Generally, this kind of collagen is simple to spot, and in case you miss it, it’s easy to notice while eating and might be left on the plate.

However, for the alternative form of collagen found in some cuts of meat-collagen that forms a 3D network throughout the muscle tissues-the sole option to remove it’s to convert it to gelatin via long, slow cooking methods. Unlike muscle proteins-which in cooking are either in a native (i.e., as they’re within the animal), denatured, or hydrolyzed state-collagen, once hydrolyzed, can enter a coagulated (gelled) state. This property opens up a completely new world of possibilities, because gelatin gives meats a lubricious, tender quality and gives a lip-smacking goodness.

One piece of knowledge which is critical to realize within the kitchen, however, is that hydrolysis takes time. The structure has to literally untwist and cut up, and because of the volume of energy needed to wreck the bonds and the stochastic processes involved, this reaction takes longer than simply denaturing the protein.

Hydrolyzing collagen not only breaks down the rubbery texture of the denatured structure, but in addition converts a element of it to gelatin. When the collagen hydrolyzes, it breaks into variously sized pieces, the smaller of which can be ready to dissolve into the encircling liquid, creating gelatin. It’s this gelatin that offers dishes which includes braised ox tail, slow-cooked short ribs, and duck confit their distinctive mouthfeel.

Since these dishes depend on gelatin for providing that wonderful texture, they must be made with high-collagen cuts of meat. Looking to make a beef stew with lean cuts will cause tough, dry meat. The actin proteins will denature (recall that this occurs at temperatures of 150–163°F / 66–73°C), but the gelatin won’t be present inside the muscular tissues to mask the dryness and toughness caused by the denatured actin. Don’t attempt to ” upgrade” your beef stew with a dearer cut of meat; it won’t work!

” Great,” you are thinking, ” but how does any of this tell me whether I must slowcook a chunk of meat?” Consider the piece of meat (or fish or poultry) that you just’re working with and view what component of the animal it comes from. For a land-based animal, those regions of the animal that bear weight generally have higher levels of collagen. This should make sense: because the load-bearing portions have a better load, they want more structure, in order that they’ll have more connective tissue. This isn’t a super rule of thumb, though, and cuts of meat generally have a couple of muscle group in them.

For animals like fish, which don’t have got to support their weight on land, the collagen levels are much lower. Squid and octopus are notable exceptions to this weight-bearing rule, because their collagen provides the equivalent support that bone structures do for fish.

Duck Confit, Oven method

The secret to duck confit is within the time and temperature, not the actual cooking technique. The upshot? You can also make duck confit in a slow cooker or in an oven set at an ultra-low temperature. The fat that the duck is cooked in doesn’t matter either; some experiments have shown that duck confit cooked in water and then coated in oil is indistinguishable from traditionally cooked duck confit. Regardless, definitely skip the exotic block of duck fat; duck legs are expensive enough as it’s.

Arrange duck legs in an oven-safe pan and cover with oil. Place in oven set at 170°F / 77°C for at least six hours. (200°F / 95°C will work, but avoid anything hotter to stop steaming the meat.)

The duck legs turns into more tender with longer cook times. I’ve cooked batches of 36 duck legs overnight using an enormous pot held at temperature in an oven. In case you do cook an enormous batch, remember the fact that the core temperature must get to about 140°F / 60°C within two hours. To that end, heat the oil up to ~250°F / 120°C before placing the duck legs in it. This kind, the hot oil will impart a solid thermal kick to get the cold legs up to temperature faster.

Notes
• Traditional recipes call for duck fat in preference to olive oil. One advantage to the duck fat is that, upon cooling to room temperature, it solidifies, encasing and sealing the duck leg in a sterilized layer of fat, somewhat like how some jams are preserved with a wax seal. In the event you were living in France a century ago, this will likely’ve been an easy way to preserve duck legs for a protracted winter, but with the invention of refrigeration and modern grocery stores, there’s no use for the duck fat to store the meat safely for the few days it could actually last. Use olive oil. It’s cheaper and healthier.
• While you pour off the oil and liquid into another container, a layer of gelatin will separate out on the bottom once it cools. Use that gelatin! Try tossing it into soups.

Cooking For Geeks just might get every geek you know fascinated by cooking. Written by Jeff Potter , a software engineer turned food writer, this cookbook is for anyone who likes to know how things work. An appropriate-selling book comes jam-packed with outstanding, well-thought out recipes recipes-and give readers enough information to enable them to move off-recipe. Indeed, once you give some thought to it, recipes are nothing but code.

Jeff Potter has done the cubicle thing, the startup thing, and the entrepreneur thing, and through it all maintained his sanity by cooking for friends. He studied Computer Science and Visual Art at Brown University.

Cooking for Geeks
By Jeff Potter
Copyright 2010 Atof Inc. All rights reserved.
Published by O’Reilly Media, Inc.

Cooking for Geeks is on the market for purchase at Amazon .

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This post is tagged: chemical reaction, connective tissue, connective tissues, high temperatures, low temperature, steel reinforcement