Vegetable starches gelatinize 310F / 154C.

Maillard reactions become noticeable 356F / 180C.

Sugar (sucrose) begins to caramelize visibly

104F / 40C and 122F / 50C: Proteins in Fish and Meat Begin to Denature Chances are, you haven't given much thought to the chemical reactions that happen to a piece of meat when the animal supplying it is slaughtered. The primary change is, to put it bluntly, that the animal is dead, meaning the circulatory system is no longer supplying the muscle tissue with glycogen from the liver or oxygen-carrying blood. Without oxygen, the cells in the muscle die, and preexisting glycogen in the muscle tissue dissipates, causing the thick and thin myofilaments in the muscle to fire off and bind together (resulting in the state called rigor mortis rigor mortis).

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Denaturation temperatures of various types of proteins (top portion) and standard doneness levels (bottom portion).

Somewhere around 8 to 24 hours later, the glycogen supply is exhausted and enzymes naturally present in the meat begin to break down the bonds created during rigor mortis (postmortem proteolysis). Butchering before this process has run its course will affect the texture of the meat. Sensory panels have found that chicken b.r.e.a.s.t.s cut off the carca.s.s before rigor mortis was over have a tougher texture than meat left on the bone longer. And since time is money, much ma.s.s-produced meat is slaughtered and then butchered straightaway. (I knew knew there was a reason why roasted whole birds taste better!) there was a reason why roasted whole birds taste better!) Proteins in meat can be divided into three general categories: myofibrillar proteins (found in muscle tissue, these enable muscles to contract), stromal proteins (connective tissue, including tendons, that provide structure), and sarcoplasmic proteins (e.g., blood). We'll talk about myofibrillar proteins here and save the stromal proteins for the section on collagen later in the chapter. (We're going to ignore sarcoplasmic proteins altogether, because understanding them doesn't help in cooking many dishes, blood-thickened soups aside.) Muscle tissue is primarily composed of only a few types of proteins, with myosin and actin being the two most important types in cooking. About two-thirds of the proteins in mammals are myofibrillar proteins. The amount of actin and myosin differs by animal type and region. Fish, for example, are made up of roughly twice as much of these proteins as mammals.

Lean meat is mostly water (6580%), protein (1622%), and fat (1.513%), with sugars such as glycogen (0.51.3%) and minerals (1%) contributing only a minor amount of the ma.s.s. When it comes to cooking a piece of fish or meat, the key to success is to understand how to manipulate the proteins and fats. Although fats can be a significant portion of the ma.s.s, they are relatively easy to manage, because they don't provide toughness. This leaves proteins as the key variable in cooking meats.

Of the proteins present in meat, myosin and actin are the most important from a culinary texture perspective. If you take only one thing away from this section, let it be this: denatured myosin = yummy; denatured actin = yucky. Dry, overcooked meats aren't tough because of lack of water inside the meat; they're tough because on a microscopic level, the actin proteins have denatured and squeezed out liquid in the muscle fibers. Myosin in fish begins to noticeably denature at temperatures as low as 104F / 40C; actin denatures at around 140F / 60C. In land animals, which have to survive warmer environments and heat waves, myosin denatures in the range of 122140F / 5060C (depending on exposure time, pH, etc.) while actin denatures at around 150163F / 6673C.

Food scientists have determined through empirical research ("total chewing work" and "total texture preference" being my favorite terms) that the optimal texture of cooked meats occurs when they are cooked to 140153F / 6067C, the range in which myosin and collagen will have denatured but actin will remain in its native form. In this temperature range, red meat has a pinkish color and the juices run dark red.

The texture of some cuts of meat can be improved by tenderizing. Marinades and brines chemically tenderize the flesh, either enzymatically (examples include bromelain, an enzyme found in pineapple, and zingibain, found in fresh ginger) or as a solvent (some proteins are soluble in salt solutions). Dry aging steaks works by giving enzymes naturally present in the meat time to break down the structure of collagen and muscle fibers. Dry aging will affect texture for at least the first seven days. Dry aging also changes the flavor of the meat: less aged beef tastes more metallic, more aged tastes gamier. Which is "better" is a matter of personal taste preference. (Perhaps some of us are physiologically more sensitive to metallic tastes.) Retail cuts are typically 5 to 7 days old, but some restaurants use meat aged 14 to 21 days.

Soy Ginger MarinadeThe salt in the soy sauce and zingibain in the ginger give this marinade both chemical and enzymatic tenderizers. Mix this up, transfer it to a resealable bag, and toss in some meat, such as flank steaks. Allow to marinate for an hour or two in the fridge, and then pan sear the meat.

- 1 cup (290g) soy sauce - 2 tablespoons (15g) grated fresh ginger or ginger paste - 1 teaspoon (2g) ground black pepper Then there are the mechanical methods for "tenderizing," which aren't actually so much tenderizing as they are masking toughness: for example, slicing muscle fibers against the grain thinly, as is done with beef carpaccio and London broil, or literally grinding the meat, as is done for hamburger meat. (Some industrial meat processors "tenderize" meat by microscopically slicing it using very thin needles, a method called jacquarding.) Applying heat to meats "tenderizes" them by physically altering the proteins on the microscopic scale: as the proteins denature, they loosen up and uncurl. In addition to denaturing, upon uncurling, newly exposed regions of one protein can come into contact with regions of another protein and form a bond, allowing them to link to each other. This process is called coagulation coagulation, and while it typically occurs in cooking that involves protein denaturation, it is a separate phenomenon.

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Temperatures required for various levels of doneness. Note that seafood cooked very rare or medium rare and chicken cooked medium must be held for a sufficiently long period of time at the stated temperature in order to be properly pasteurized. See the section on sous vide cooking in Chapter7 Chapter7 for time and temperature charts. for time and temperature charts.

Salmon Poached in Olive OilFish, such as salmon and Atlantic char, becomes dry and loses its delicate flavor when cooked too hot. The trick with poaching fish is to not overcook it. Poaching fish is an easy way to control the rate of heat being applied, and it is amazingly easy and tasty.[image]Place a fillet of fish, skin side down, in an oven-safe bowl just large enough for the fish to fit. Sprinkle a small amount of salt on top of fish. Cover with olive oil until the fillet is submerged. Using a bowl that "just fits" the fish will cut down on the amount of olive oil needed.Place into a preheated oven, set to medium heat (325375F / 160190C).Use a probe thermometer set to beep at 115F / 46C and remove the fish when the thermometer goes off, letting carryover bring the temperature up a few more degrees.NoteConsider this fish as raw/undercooked. See Chapter7 Chapter7's section on sous vide cooking for a discussion on pasteurization and time-at-temperature rules.[image]Notes - Try serving on top of a portion of brown or wild rice and spooning sauteed leeks, onions, and mushrooms on top. (A squirt of orange juice in the leeks is really good.) Or serve with string beans sauteed with red pepper flakes and white rice, with a splash of soy sauce drizzled on top.

- Salmon contains a protein, alb.u.min, that generates a white congealed mess on the outside of the flesh, as shown on the bottom piece in the following photo. This is the same protein that leeches out of hamburgers and other meats, typically forming slightly gray "blobs" on the surface. You can avoid this by brining the fish in a 510% salt solution (by weight) for 20 minutes, which will set the proteins. The top piece in the first photo below was brined; you can see the difference.

[image]Salmon contains a protein, alb.u.min, that is expressed out of the flesh and leads to an un-sightly, curd-like layer forming on the surface of the fish when poached, as shown in the bottom piece in this photo.[image]If your fish doesn't fit in your pan, you can fold the tail bit over in a pinch, or cut it and poach it face down. This won't win you any Foodie Points, but as long as you don't take a photo and publish it in a book, who's going to know?Seared Tuna with c.u.min and SaltPan searing is one of those truly simple cooking methods that produces a fantastic flavor and also happens to take care of bacterial surface contamination in the process. The key to getting a rich brown crust is to use a cast iron pan, which has a higher thermal ma.s.s than almost any other kind of pan (see the Metals, Pans, and Hot Spots Metals, Pans, and Hot Spots sidebar in sidebar in Chapter2 Chapter2). When you drop the tuna onto the pan, the outside will sear and cook quickly while leaving as much of the center as possible in its raw state.You'll need 34 oz (75100 grams) of raw tuna per person. Slice the tuna into roughly equal-sized portions, since you'll be cooking them one or two at a time.On a flat plate, measure out 1 tablespoon c.u.min seed and teaspoon (2g) salt (preferably a flaky salt such as Malden sea salt) per piece of tuna per piece of tuna. On a second plate, pour a few tablespoons of a high-heat-stable oil, such as refined canola, sunflower, or safflower oil.Place a cast iron pan on a burner set as hot as possible. Wait for the pan to heat up thoroughly, until it just begins to smoke.For each serving of tuna, dredge all sides in the c.u.min/salt mix, and then briefly dip all sides in the oil to give the fish a thin coating.Sear all sides of the fish. Flip to a new side once the current facedown side's c.u.min seeds begin to brown and toast, about 30 to 45 seconds per side.Slice into (1 cm) slices and serve as part of a salad (place fish on top of mixed greens) or main dish (try serving with rice, risotto, or j.a.panese udon noodles).Notes - Keep in mind that the temperature of the pan will fall once you drop the tuna in it, so don't use a piece of fish too large for your pan. If you're unsure, cook the fish in batches.

- Use coa.r.s.e sea salt, not rock (kosher) salt or the table salt you'd find in a salt shaker. The coa.r.s.e sea salt has a large, flaky grain that prevents all of the salt from touching the flesh and dissolving.

[image]Coat all sides of the tuna in c.u.min seeds and salt by pressing the tuna down onto a plate that has the spice mixture evenly spread out on it.[image]Make sure the pan is really hot. Some smoke coming off the fish as it sears is okay![image]Pan-seared tuna will be well-done on the outside and have a very large "bull's eye" where the center is entirely raw.

144F / 62C: Eggs Begin to Set The lore of eggs is perhaps greater than that of any other food item, and more than one chef has gone on record judging others based on their ability-or inability-to cook an egg. Eggs are the wonder food of the kitchen-they have a light part, a dark part, and bind the culinary world together. Used in both savory and sweet foods, they act as binders holding together meatloaf and stuffing; as rising agents in souffles, certain cakes, and cookies like meringues; and as emulsifiers in sauces like mayonnaise and hollandaise. Eggs provide structure to custards and body to ice creams. And all of this so far doesn't even touch on their flavor or the simple joys of a perfectly cooked farm egg. Simply put, I cannot think of another ingredient whose absence would bring my cooking to a halt faster than the simple egg.

Egg whites are composed of dozens of different types of proteins, and each type of protein begins to denature at a different temperature. In their natural "native" state, you can think of the proteins as curled-up little b.a.l.l.s. They take this shape because portions of the molecular structure are hydrophobic hydrophobic-the molecular arrangement of the atoms making up the protein is such that regions of the protein are electromagnetically repulsed by the polar charge of water.

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Important temperatures in eggs.

Because of this aversion to water, the protein structure folds up on itself. As kinetic energy is added to the system-in the form of heat or mechanical energy (e.g., whipping egg whites)-the structure starts to unfold as kinetic energy overtakes potential energy. The unfolded proteins then get tangled together, "snagging" around other denatured proteins and coagulating to form a linked structure. This is why a raw egg white is liquid, but once cooked becomes solid. (Well, technically, raw egg white is a gel that coagulates into a solidlike substance when heated. We'll get to gels in Chapter6 Chapter6.) [image]

Hydrophobic proteins in their native state (left) remain curled up to avoid interacting with the surrounding liquid. Under heat, they denature (center) and uncurl as the kinetic energy exceeds the weaker level of energy generated by water molecules and regions of the proteins that repel each other. Once denatured and opened up, the hydrophobic parts of the protein that were previously unexposed can interact and bond with other proteins.

The most heat-sensitive protein is ovotransferrin, which begins to denature at around 144F / 62C. Another protein, ovalb.u.min, denatures at around 176F / 80C. These two proteins also are the most common in egg whites: ovotransferrin accounts for 12% of the proteins in an egg white and ovalb.u.min 54%. This explains the difference between soft-boiled and hard-boiled ("hard-cooked") eggs. Get that egg up to about 176F / 80C for sufficient time, and voila, the white is hard cooked; below that temperature, however, the ovalb.u.min proteins remain curled up, leaving the majority of the egg white in its "liquid" state.

NoteMost of the proteins in egg yolks set at between 149F / 65C and 158F / 70C, although some set at lower temperatures.

Proteins in foods such as eggs don't denature instantaneously once they reach denaturation temperature. This is an important point. Some cooking newbies have the mental model that cooking an egg or a piece of meat is something like melting an ice cube: all ice below a certain temperature, ice and water at the freezing/melting point, and all water above that temperature. From a practical perspective in the kitchen, it's not an entirely incorrect picture, because heat pours into the foods so quickly that the subtle differences between a few degrees aren't obvious. But as heat is transferred into the food more slowly, the subtleties of these chemical reactions become more noticeable. And unlike melting an ice cube, where increasing the heat transfer by a factor of two causes the ice to melt in half the time, cooking foods do not respond to additional energy in a linear fashion.

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You might find it easiest to think of the different proteins in foods as having particular temperatures at which they denature, and try to shoot for a target temperature just above that of the proteins you do want denatured. Just remember: there's more to a piece of meat or egg than one type of protein or connective tissue, and the different proteins have different temperature points at which they're likely to denature.

Here are some examples of cooking eggs that show how to take advantage of the thermal properties of different portions of the egg.

Hard-Cooked Eggs, Shock and Awe Method There's a silent war of PC-versus-Mac proportions going on over the ideal way to make hard-cooked eggs. Should you start in cold water and bring the water up to a boil with the eggs in them, or should you drop the eggs into already boiling water? The cold-start approach yields eggs that taste better, while the boiling-water approach yields eggs that are easier to peel. But can you have both?

Thinking about the thermal gradient from sh.e.l.l to center of egg, it would make sense that cooking an egg starting in cold water would result in a more uniform doneness. The delta between the center and outer temperatures will be smaller, meaning that the outer portion won't be as overcooked once the center is set compared to the boiling-water method.

The conjecture for ease of peeling in the boiling water approach is that the hot water "shocks" the outer portion of the egg. Into industrial-grade cooking? Steam 'em at 7.5 PSI over atmospheric pressure and quick-release the pressure at the end of cooking to crack the sh.e.l.l. (Hmm, I wonder if one could do this in a pressure cooker...) But what about the rest of us? What if we shock the outside, and then cook in cold water?

Try it. Place your eggs into rapidly boiling water. After 30 seconds, transfer the eggs to a second pot containing cold tap water, bring to a boil, and then simmer. The second-stage cooking time will take about two minutes less than the normal cold-start approach. Cook for 8 to 12 minutes, depending upon how well cooked you like your eggs.

The 30-Minute Scrambled Egg This method involves ultra-low heat, continuous stirring, and a vigilant eye. I wouldn't suggest this as an everyday recipe, because it takes a while to make, but after however many years of eating eggs, it's nice to have them cooked a new way. Cooking the eggs over very low heat while continuously stirring breaks up the curds and allows for cooking the eggs to a point where they're just cooked, giving them a flavor that can be described as cheese or cream-like. It's really amazing, and while the thought of "cheese or cream-like" eggs might not have you racing off to the kitchen, it's really worth a try!

In a bowl, crack two or three eggs and whisk thoroughly to combine the whites and yolks. Don't add any salt or other seasonings; do this with just eggs. Transfer to a nonstick pan on a burner set to heat as low as possible.

Stir continuously with a silicone spatula, doing a "random walk" so that your spatula hits all parts of the pan. And low heat means really low heat: there's no need for the pan to exceed 160F / 71C, because enough of the proteins in both the yolks and whites denature below that temperature and the proteins will weep some of their water as they get hotter. If your heat source is too hot, pull the pan off the stovetop for a minute to keep it from overheating. If you see any curds (lumps of scrambled eggs) forming, your pan is getting too hot.

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Stir continuously to avoid hot spots so that the eggs are kept at a uniform temperature. If you have an IR thermometer, make sure your pan doesn't exceed 160F / 71C.

Continue stirring until the eggs have set to a custard-like consistency. When I timed myself, this took about 20 minutes, but you might reach this point in as few as 15 minutes or upward of half an hour.

Oven-Poached Eggs Here's a simple way to cook eggs for a brunch or appetizer. In an individually sized oven-safe bowl (ideally, one that you can serve in), add:

Breakfast version Dinner version 1 cup (30g) fresh chopped spinach cup (100g) crushed tomatoes 3 tablespoons (20g) grated mozzarella cheese cup (50g) black beans (canned are easiest) cup (50g) black beans (canned are easiest) 3 tablespoons (40g) heavy cream cup (50g) grated mozzarella cheese 4 teaspoons (20g) b.u.t.ter

Create a "well" in the center of the ingredients by pushing the food into a ring around the edges of the bowl. Crack two eggs into the well, add a pinch of salt and some fresh ground pepper, cover with aluminum foil, and bake in a preheated oven set to 350F / 180C until the egg is set, about 25 minutes. (You can use a probe thermometer set to beep at 140F / 60C.) Try adding some crushed red pepper flakes to the breakfast version or sriracha sauce to the dinner version.

Pasteurized Eggs While salmonella is quite rare in uncooked eggs, with estimates being somewhere around 1 in 10,000 to 20,000 eggs carrying the bacteria, it does occur in the laying hen populations of North America. If you're cracking a few dozen eggs into a bowl for an omelet brunch at your local hacker house every week, let's just say that odds are you'll eventually crack a bad egg. Luckily, this isn't a problem if those eggs are properly cooked and cross-contamination is avoided.

The real risk for salmonella in eggs is in dishes that use undercooked eggs that are then served to at-risk populations (e.g., infants, pregnant women, elderly or immunocompromised people). If you're making a dish that contains raw or undercooked eggs-Caesar salad, homemade eggnog, mayonnaise, raw cookie dough-and want to serve that dish somewhere where there might be at-risk individuals, you can pasteurize the eggs (a.s.suming your local store doesn't happen to carry pasteurized eggs, but most don't). Pasteurized eggs do taste a little different, and the whites take longer to whip into a foam, so don't expect them to be identical to their raw counterparts.

Since salmonella begins to die at a noticeable rate around 136F / 58C and the proteins in eggs don't begin to denature until above 141F / 61C, you can pasteurize eggs to reduce the quant.i.ty of salmonella, should it be present, to an acceptable level by holding the egg at a temperature between these two points. The FDA requires a 10,000-fold reduction (5 log10 in food safety lingo), which can be achieved by holding the egg at 141F / 61C for 3.5 minutes (according to Margaret McWilliams's in food safety lingo), which can be achieved by holding the egg at 141F / 61C for 3.5 minutes (according to Margaret McWilliams's Foods: Experimental Perspectives, Foods: Experimental Perspectives, Fifth Edition, from Pearson Publishing). Most consumers won't have the necessary hardware to do this at home, but if you do have a sous vide setup, as described in Fifth Edition, from Pearson Publishing). Most consumers won't have the necessary hardware to do this at home, but if you do have a sous vide setup, as described in Chapter7 Chapter7, you're golden.

The 60-Minute Slow-Cooked Egg Going back to our earlier discussion of time and temperature, when food is left in an environment long enough, its temperature will come to match that of its environment. Therefore, if we immerse an egg in water held at 145F / 62.7C, it follows that the proteins in the white and the yolk that denature at or below that temperature will denature and coagulate, and those that denature above that temperature will remain unaltered.

The added benefit of this method is that the egg cannot overcook cannot overcook. "Cooking" is effectively the occurrence of chemical reactions in the food at different temperature points, and holding the egg at 145F / 62.7C will not trigger any reactions that don't occur until higher temperatures are reached. This is the fundamental concept of sous vide cooking. We'll cover the details of sous vide in Chapter7 Chapter7, so you may want to take a peek at that chapter now or make a mental note to come back to this section when you get there. For a sous videstyle cooked egg, immerse an egg in water that is maintained at 145F / 62.7C for one hour. As you'll see, sous vide cooking has some incredible properties that greatly simplify the time and temperature rule.

NoteYour average, run-of-the-mill (or is that run-of-the-yard?) chicken laid only 84 eggs per year a century ago. By the turn of the millennium, improvements in breeding and feed had pushed this number up to 292 eggs per year-almost 3.5 times more. And, no, science has not yet figured out which came first.

154F / 68C: Collagen (Type I) Denatures An animal's connective tissues provide structure and support for the muscles and organs in its body. You can think of most connective tissues-loose fascia and ligaments between muscles as well as other structures such as tendons and bones-as a bit like steel reinforcement: they don't actively contract like muscle tissue, but they provide structure against which muscles can pull and contract.

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Temperatures related to collagen hydrolysis and the resulting gelatin.

The most common type of protein in connective tissue is collagen, and while there are several types of collagen in animals, from a culinary perspective, the main chemical difference between the different types of collagen is the temperature at which they denature. In cooking, collagen shows up in two different ways: either as discrete chunks (e.g., tendons, silverskin) outside of the muscle, or as a network that runs through the muscle. Regardless of its location, collagen is tough (it provides structure, after all) and becomes palatable only given sufficient time at sufficiently high temperatures.

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It's easy to deal with collagen that shows up as discrete pieces: get rid of it by cutting it off. For cuts of meats that have a thin layer of connective tissue on them (called silverskin silverskin, presumably because of its somewhat iridescent appearance), cut off as much as possible and discard it. Beef tenderloin cuts commonly have a side with this layer; trim off as much as possible before cooking.

Chicken b.r.e.a.s.t.s also have a small but noticeable tendon connected to the chicken tenderloin. Uncooked, it's a pearlescent white ribbon. After cooking, it turns into that small white rubber-band-like thing that you can chew on endlessly yet never get any satisfaction from. Generally, this type of collagen is easy to spot, and if you miss it, it's easy to notice while eating and can be left on the plate.

However, for the other kind of collagen found in some cuts of meat-collagen that forms a 3D network through the muscle tissue-the only way to remove it is 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 are in the animal), denatured, or hydrolyzed state-collagen, once hydrolyzed, can enter a coagulated (gelled) state. This property opens up an entirely new world of possibilities, because gelatin gives meats a lubricious, tender quality and provides a lip-smacking goodness.

In its native form, collagen is like a rope: it's a linear molecule composed of three different strands that are twisted together. The three strands are held together by weak secondary bonds (but there are a lot of them!) and stabilized by a small number of crosslinks crosslinks, which are stronger covalent bonds.

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Collagen in its native form is a triple helix, held together in its helical structure by secondary bonds (left) and stabilized by crosslinks. Under heat, the secondary bonds break and the protein becomes denatured, but the crosslinks between the strands continue to hold the structure together (second from left). Given sufficient heat and time, the strands in the triple helix themselves break down via hydrolysis (third from left) and, upon cooling, convert to a loose network of molecules (right) that retains water (a gel).

NoteCovalent bonds are bonds where the electrons from an atom in one location are shared with another atom. are bonds where the electrons from an atom in one location are shared with another atom.

In addition to being crosslinked, the strands also form a helical structure because of secondary bonds between different regions of the same molecules. You can think of it something like a braided rope, where each strand wraps around the other two strands. It has a "curl" to it because the internal structure finds its optimal resting place in that shape.

Under the right conditions-usually, exposure to heat or the right kinds of acids-the native form of collagen denatures, losing its linear structure and untwisting into a random mess. With the addition of sufficient heat, the molecules in the structure will vibrate enough to overcome the electromagnetic energy that caused the structure to twist up in the first place, leading it to lose its helical structure and denature.

Acids can also denature the collagen protein: their chemical properties provide the necessary electromagnetic pull to disrupt the secondary bonds of the helical structure. It's only the twisting that goes away during denaturing in collagen; the crosslinks remain in place and the strands remain intact. In this form, collagen is like rubber-it actually is a rubber from a material science point of view-and for this reason, you'll find its texture, well, rubbery.

Given even more heat or acid, though, the collagen structure undergoes another another transformation: the strands themselves get chopped up and lose their backbone, and at this point the collagen has no real large-scale structure left. This reaction is called transformation: the strands themselves get chopped up and lose their backbone, and at this point the collagen has no real large-scale structure left. This reaction is called hydrolysis hydrolysis: thermal hydrolysis in the case of heat, acid hydrolysis in the case of, you guessed it, acid. (Think ceviche. See the section on acids in Chapter6 Chapter6 for more.) for more.) It's possible to break up the collagen chemically, too: lysosomal enzymes will attack the structure and "break the covalent bonds" in chem-speak, but this isn't so useful to know in the kitchen.

NoteFor fun, try marinating a chunk of meat in papaya, which contains an enzyme, papain, that acts as a meat tenderizer by hydrolyzing collagen.

One piece of information that is critical to understand in the kitchen, however, is that hydrolysis takes time. The structure has to literally untwist and break up, and due to the amount of energy needed to break 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 also converts a portion of it to gelatin. When the collagen hydrolyzes, it breaks into variously sized pieces, the smaller of which are able to dissolve into the surrounding liquid, creating gelatin. It's this gelatin that gives dishes such as braised ox tail, slow-cooked short ribs, and duck confit their distinctive mouthfeel.

Since these dishes rely on gelatin for providing that wonderful texture, they need to be made with high-collagen cuts of meat. Trying to make a beef stew with lean cuts will result in tough, dry meat. The actin proteins will denature (recall that this occurs at temperatures of 150163F / 6673C), but the gelatin won't be present in the muscle tissue to mask the dryness and toughness brought about by the denatured actin. Don't try to "upgrade" your beef stew with a more expensive cut of meat; it won't work!

"Great," you might be thinking, "but how does any of this tell me whether I need to slow-cook a piece of meat?" Think about the piece of meat (or fish or poultry) that you're working with and consider what part 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 weight-bearing portions have a higher load, they need more structure, so they'll have more connective tissue. This isn't a perfect rule of thumb, though, and cuts of meat generally have more than one muscle group in them.

For animals like fish, which don't have 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.

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When cooking a piece of meat, if it's from a part that is responsible for supporting the animal's weight (primarily muscles in the chuck, rib, brisket, and round), it'll probably be higher in collagen and thus need a longer cooking time.

NoteOlder animals have higher levels of collagen. As animals age, the collagen structure has more time to form additional crosslinks between the strands in the collagen helix, resulting in increased toughness. This is why older chickens, for example, are traditionally cooked in long, slow roasts. (The French go so far as to use different words for old versus young chickens: poule poule instead of instead of poulet poulet.) Most commercial meat, however, is young at time of slaughter, so the age of the animal is no longer an important factor.

The other easy rule of thumb for collagen levels is to look at the relative price of the meat: because high-collagen cuts require more work to cook and come out with a generally drier texture, people tend to favor other cuts, so the high-collagen cuts are cheaper.

Squid BruschettaSquid was a culinary mystery to me for a long time. You either cook it for a few minutes or an hour; anywhere in between, and it becomes tough, like chewing on rubber bands. (Not that I chew on rubber bands often enough to say what that's like.) Why is this?The collagen in squid and octopus is enjoyable in either its native state or hydrolyzed state, but not in its denatured state. It takes a few minutes to denature, so with just a quick pan sear it remains in its native state (tossed with some fresh tomatoes and dropped on top of bruschetta, it's delicious). And hydrolysis takes hours to occur, so a slowly simmered braised octopus turns out fine. Braising it in tomatoes further helps by dropping the pH levels, which accelerates the hydrolysis process.To make a simple squid bruschetta, start by preparing a loaf of French or Italian bread by slicing it into (1 cm) slices. You can create larger slices by cutting on a bias. (Save the triangular end piece for munching on when no one is looking.) Lightly coat both sides of the bread with olive oil (this is normally done with a pastry brush, but if you don't have one, you can either fold up a paper towel and "brush" with it or pour olive oil onto a plate and briefly dip the bread into the oil). Toast the bread. A broiler works best (the slices of bread should be 46 / 1015 cm from the heat). Flip as soon as they begin to turn golden brown. If you don't have a broiler, you can use an oven set to 400F / 200C. For small batches, a toaster also works.Once your bread is toasted, place it on a plate and store it in the oven (with the heat off) so that it remains warm.Prepare the squid: - 1 lb (500g) squid (either a mix of bodies and tentacles or just bodies) Slice the squid with a knife or, better yet, cut it into bite-sized pieces using kitchen shears.Bring a saute pan up to medium heat. You want the pan hot enough so that the squid will quickly come to temperature. Add a small amount of olive oil-enough to coat the pan thinly when swirled-and drop the squid into the pan.Use a wooden spoon or silicone spatula to stir the squid. Take note when it starts to turn white-it should become subtly less translucent-and cook for another 30 seconds or so. Add to the pan and toss to combine: - 1 cup (250g) diced tomato (about 2 medium tomatoes, seeds removed) - 1 tablespoon (2g) fresh herbs such as oregano or parsley - teaspoon sea salt - Ground pepper to taste Transfer squid and tomato topping to a bowl and serve with toasted bread.[image]Try using a pair of kitchen shears to snip the squid into small pieces directly into a hot pan. Add tomatoes and herbs, toss, and serve.Slow-Cooked Short RibsShort ribs and other high-collagen cuts of meat aren't difficult to work with, they just require time at temperature (collagen takes many hours to hydrolyze). The trick is to cook this type of meat "low and slow"-for a long time at low temperature. Too cold, and the collagen won't break down; too hot, and the water in the meat will evaporate, drying it out. Using a slow cooker cooks the meat in the ideal temperature range. After all, this is what they're designed for![image]This is an intentionally easy recipe, but don't let this fool you: slow-cooked meats can be amazingly amazingly good, and if you're cooking for a dinner party, they make for easy work when you go to a.s.semble the dinner. If you have a rice cooker, check to see if it has a "slow-cook" setting. In this mode, the rice cooker will heat foods to a temperature typically between 170190F / 7788C, which is warm enough to be safe from bacterial contamination and cool enough to not steam-dry the meat. good, and if you're cooking for a dinner party, they make for easy work when you go to a.s.semble the dinner. If you have a rice cooker, check to see if it has a "slow-cook" setting. In this mode, the rice cooker will heat foods to a temperature typically between 170190F / 7788C, which is warm enough to be safe from bacterial contamination and cool enough to not steam-dry the meat.Pour a bottle of barbeque sauce into the bowl of the rice cooker or slow cooker. Add the short ribs, arranging them in a layer so that the barbeque sauce covers the meat.Slow-cook for at least four hours (longer is fine). Try starting this in the morning before going to work-the slow cooker will keep the food safe, and the extra time will help ensure that the collagen is fully dissolved.Notes - Ideally, you should pan sear the short ribs (in a cast iron pan) for a minute or two before cooking. As discussed at the beginning of this chapter, this will cause browning reactions, bringing a richness to the final product.

- Keep in mind the danger zone rule covered earlier. Don't load up a slow cooker with so much cold meat that the cooker will be unable to raise the temperature above 140F / 60C within a two-hour period.

- Try adding other ingredients to the sauce, or making your own sauce if you like. I'll often pour a tablespoon or so of wine or port into the empty BBQ sauce jar to "rinse out" the thick sauce, then pour the port-sauce slurry into the slow cooker.

Duck ConfitDuck confit-duck legs cooked in fat-tastes entirely different from duck cooked almost any other way. It's like bacon and pork-to quote Homer Simpson, they're from "some wonderful, magical animal." Good duck confit is succulent, flavorful, tender, mouth-watering, and perhaps a bit salty. Even if you're not otherwise a fan of duck, give duck confit a chance.As you can probably tell, I'm a pragmatic cook. Traditional recipes for duck confit prescribe a long, drawn-out affair, which is fine for a leisurely Sunday afternoon spent in the company of friends and a bottle of good wine, but doesn't line up well with my idea of keeping things simple.Cooking duck "confit-style" is all about converting tough collagen proteins into gelatin. While this isn't a fast chemical reaction, it's a simple one to trigger: hold the meat at a low temperature for long enough, and the collagen proteins denature and eventually hydrolyze.The secret to duck confit is in the time and temperature, not the actual cooking technique. The upshot? You can 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 is.[image]Rub salt into the outside of the duck legs, covering both the side with skin and the side with meat exposed. I use roughly 1 tablespoon (18g) of salt per duck leg; you want enough to coat the outside thoroughly.Place the salted duck legs in a bowl or plastic bag and store them in the fridge for several hours to brine.NoteRemember: store raw meats in the bottom of the fridge so if they drip the runoff won't contaminate fresh produce or ready-to-eat foods.Salting the meat adds flavor and draws out a little bit of the moisture, but if you're in a real rush, you can skip this step and just lightly coat the duck legs with a few pinches of salt.After dry-brining the duck legs, wash off all the salt. At this point, you have a choice of heat sources. Duck confit is about cooking via convection heat with the energy being imparted into the meat by the surrounding fat. Regardless of heat source, the duck legs should be entirely submerged in oil. With careful arrangement and the right size pan, you'll find that it doesn't take much oil to cover them. I generally use olive or canola oil and save the oil after cooking for use in other dishes.NoteNote that the oil after cooking will be a blend of duck fat and your starting oil. You can also use it for things like sauteing greens and shallow-frying potatoes.Slow-cooker method - Arrange duck legs in bowl of slow cooker or multipurpose rice cooker. Cover with oil and set to slow-cook mode for at least 6 hours (preferably 10 to 12).

Oven method - Arrange duck legs in an oven-safe pan and cover with oil. Place in oven set at 170F / 77C for a minimum of six hours. (200F / 95C will work, but avoid anything hotter to prevent steaming the meat.) The duck legs will become more tender with longer cook times. I've cooked batches of 36 duck legs overnight using a large pot held at temperature in an oven. If you do cook a large batch, remember that the core temperature needs to get to about 140F / 60C within two hours. In this case, heat the oil up to ~250F / 120C before placing the duck legs in it. This way, the hot oil will impart a solid thermal kick to get the cold legs up to temperature faster.[image]Duck leg that has been cooked at low heat for a long time falls apart easily, because most of the collagen and connective tissues that normally hold muscles together are gone.After cooking, the duck skin will still be flabby and, frankly, gross. But the meat should be tender and yield with a bit of poking. You can either remove the skin (pan sear it by itself for duck lardons!) or score the skin with a knife and then pan sear the skin side of the duck to crisp it up.If you are not going to use the duck legs straightaway, store them in the fridge.Notes - Traditional recipes call for duck fat instead of 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. If you were living in France a century ago, this would've been a great way to preserve duck legs for a long winter, but with the invention of refrigeration and modern grocery stores, there's no need for the duck fat to store the meat safely for the few days it might last. Use olive oil. It's cheaper and healthier.

- If 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.

Collagen ExperimentIf all this talk about collagen and texture isn't gelling for you, do the following experiment.Take a few pieces of beef stew meat, and proceed as though you're making beef stew. (See Simple Beef Stew Simple Beef Stew in in Chapter2 Chapter2.) Once your beef is in the slow cooker, set a timer for 30 minutes.After 30 minutes, remove a few pieces of the beef. Use a probe thermometer on one to record the internal temperature; it should register somewhere around 160180F / 7182C, although it'll depend on your slow cooker. Stash the 30-minute sample in a container in your fridge.After six hours of stewing, repeat the procedure: remove a few pieces, verify that the temperature is about the same, and stash the second batch in a second container in the fridge. (You could heat up the 30-minute batch, but then we'd be changing more than one variable: who's to say that reheating doesn't change something?)Once both samples are cold, do a taste comparison. Got kids? Do a single-blind experiment to remove the placebo effect: blindfold the kids and don't let them know which is which. Got a spouse and kids? Do a double-blind experiment to control for both placebo effect and observer bias: have your significant other scoop the beef into the containers and label them only "A" and "B," not telling you which is which, and then go ahead and administer the blindfold test to your kids.

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158F / 70C: Vegetable Starches Break Down Whereas meat is predominately proteins and fats, plants are composed primarily of carbohydrates such as cellulose, starch, and pectin. Unlike proteins in meat, which are extremely sensitive to heat and can quickly turn into shoe leather if cooked too hot, carbohydrates in plants are generally more forgiving when exposed to higher temperatures. (This is probably why we have meat thermometers but not vegetable thermometers.) [image]

Temperatures related to plants and cooking.

Cooking starchy vegetables such as potatoes causes the starches to gelatinize (i.e., swell up and become thicker). In their raw form, starches exist as semicrystalline structures that your body can only partially digest. Cooking causes them to melt, absorb water, swell, and convert to a form that can be more easily broken down by your digestive system.

As with most other reactions in cooking, the point at which starch granules gelatinize depends on more than just the single variable of temperature. The type of starch, the length of time at temperature, the amount of moisture in the environment, and processing conditions all impact the point at which any particular starch granule swells up and gelatinizes. See the section Making gels: Starches Making gels: Starches in in Chapter6 Chapter6 for more about starches and gelatinization. for more about starches and gelatinization.

Leafy green vegetables also undergo changes when cooked. Most noticeably, they lose their green color as the membranes around the chloroplasts in the cells rupture. This same rupturing and damage to the cell structure is what improves the texture of tougher greens such as Swiss chard and kale.

For starchy plants (think potatoes), cook them so that they reach the temperature at which they gelatinize, typically in the range of 180190F / 9299C. For green leafy plants, saute the leaves above 140F / 60C to break down the plant cell structure.

NoteCellulose-a.k.a. fiber-is completely indigestible in its raw form and gelatinizes at such a high temperature, 608626F / 320330C, that we can ignore it while discussing chemical reactions in cooking.

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Starch levels in common vegetables.

Quick-Steamed AsparagusMicrowave ovens make quick work of cooking veggies. In a microwave-safe container, place asparagus stalks with the bottoms trimmed or snapped off, and add a thin layer of water to the bottom. Put the lid on, but leave it partially open so that steam has a place to escape. Microwave for two to four minutes, checking for doneness partway through and adding more time as necessary.[image]Notes - This technique cooks the food using two methods: radiant heat (electromagnetic energy in the form of microwaves) and convection heat (from the steam generated by heating the water in the container). The steam circulates around the food, ensuring that any cold spots (areas missed by the microwave radiation) get hot enough to both cook the food and kill any surface bacteria that might be present.