Sunday, January 12, 2014

The Physics of Cooking Meat: Your Quick Guide to Cooking your Favorite Meat

 

Meat is animal flesh that is eaten as food.  Meat is mainly composed of water and protein, and is usually eaten together with other food. It is edible raw, but is normally eaten after it has been cooked and seasoned or processed in a variety of ways. Unprocessed meat will spoil within hours or days. Spoilage is caused by the practically unavoidable infection and subsequent decomposition of meat by bacteria and fungi, which are borne by the animal itself, by the people handling the meat, and by their implements. For some reason, fish muscle is not considered meat by some people, but it should be.

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Meat Main Composition

Adult mammalian muscle flesh consists of roughly 75 percent water, 19 percent protein, 2.5 percent intramuscular fat, 1.2 percent carbohydrates and 2.3 percent other soluble non-protein substances. These include nitrogenous compounds, such as amino acids, and inorganic substances such as minerals.

Muscle proteins are either soluble in water (sarcoplasmic proteins, about 11.5 percent of total muscle mass) or in concentrated salt solutions (myofibrillar proteins, about 5.5 percent of mass). There are several hundred sarcoplasmic proteins. Most of them – the glycolytic enzymes – are involved in the glycolytic pathway, i.e., the conversion of stored energy into muscle power. The two most abundant myofibrillar proteins, myosin and actin are responsible for the muscle's overall structure. The remaining protein mass consists of connective tissue (collagen and elastin) as well as organelle tissue.

Fat in meat can be either adipose tissue, used by the animal to store energy and consisting of "true fats" (esters of glycerol with fatty acids), or intramuscular fat, which contains considerable quantities of phospholipids and of unsaponifiable constituents such as cholesterol.

How to Cook Meat to Safe Temperatures

As meat is heated, it undergoes physical and chemical changes called denaturing. It is a complex process, but a basic understanding is the first step in making an omnivore's delight.

The tricky part of cooking meat? It is that time when the meat is just right, at just the right temperature, because it lasts only about two minutes. And how do you avoid overcooking the outer parts? Food scientist looked into the matter and came up with the following guidelines:

1) Cook beef, pork, lamb and veal steaks, chops, and roasts to at least 145°F (63ºC) measured with a food thermometer in the thickest part. For safety and quality, allow meat to rest at least three minutes before carving or eating.

2) Use thin cuts of meat.

3) One of the special pleasures of a well-cooked bird is its crisp, rich skin. The skin of birds and other animals is mainly water (about 50%), fat (40%), and connective-tissue collagen (3%). In frying chicken meat, the key to crisp skin is the process of dissolving the leathery collagen into tender gelatin in the skin’s water, and then vaporize the water out of the skin. The high heat of a hot oven or frying pan does this most effectively; slow cooking at a low oven temperature can desiccate the skin while its collagen is intact, and preserve its leatheriness. A crisp skin is easier to obtain with a dry-processed bird — kosher or halal, for example — whose skin hasn’t been plumped with added water. It also helps to let the bird air-dry uncovered in the refrigerator for a day or two, and to oil the skin before roasting.  Oiling improves heat transfer from hot oven air to moist meat. The cooked bird should be served promptly, since crisp skin quickly reabsorbs moisture from the hot meat beneath, and becomes flabby as it sits on the plate.

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4) Cook ground beef, pork, lamb, and veal to an internal temperature of 160°F (71ºC) measured with a food thermometer.

5) Cook poultry to an internal temperature of 165°F (74ºC) measured with a food thermometer in the thickest part (inside the thigh).

6) Pre-warm the meat, for instance by immersing the (wrapped) meat in warm water, so that its temperature rises to about 40 °C (104 °F). This diminishes overcooking of the outer parts as it reduces the cooking time. Letting the meat warm to room temperature is much less effective! When you try this at home, you may notice that the color of the meat changes. The red color of meat is caused by myoglobin, an oxygen-storing protein. It denatures – breaks down - at higher temperatures and then turns grayish brown. Experiment with this and you may be pleasantly surprised by the results.

7) Keep the surface temperature below boiling. This minimizes the temperature gradient across the meat and it maximizes the time interval during which the center of the meat is close to its optimum temperature.

8) Since grilling and frying involve high heat, they tend to overcook the outer portions of meat while the interior cooks through. This overcooking can be minimized in two ways: prewarming the meat, and flipping the meat frequently. This is much gentler on the meat. Wrap pork shoulders and beef briskets at about 150°F, after about 2 hours in the smoke. By then it has absorbed as much smoke as is needed. If you wrap it then, the meat powers right through "the stall" on a steady curve and takes much less time. It also retains more juice.

The warmer the meat starts out, the less time it takes to cook through, and so the less time the outer layers are exposed to high heat. The cooking and overcooking time can be reduced by a third or more by wrapping steaks and chops, immersing them for 30–60 minutes in warm water, so that they approach body temperature, 100°F/40°C, and then cooking immediately (bacteria grow quickly on warm meat).

How often should the cook turn a steak or hamburger when grilling or frying? If perfect grill marks are necessary, once or twice. If texture and moistness are more important, then flip every minute. Frequent turns mean that neither side has the time either to absorb or to release large amounts of heat. The meat cooks faster, and its outer layers end up less overdone.

9) Do not boil tender meats or fish. Simmering or poaching well below boiling is much better (at about 80 °C).

10) Do not stick to standard rules about cooking time per weight or thickness. They have nothing to do with physics and cooking meat is physics, and chemistry. When you have double the thickness of a cut of meat, for instance, the cooking time does not become twice as much but almost four times as much. That's Fourier's Law at work. The rate of heat flow in one dimension is proportional to the square of the thickness.

11) Remember the two-minute interval, when the meat is at its best. Most meat is properly done at temperatures between roughly 55 and 70 °C (130 to 160 °F). Most people cook meat to much higher temperatures, but only tough meats should be heated past 70 °C. Other meats turn very dry at those high temperatures.

12) At 70 °C (160 °F), Escherichia coli (E. coli) is destroyed. Browning, however, may already occur at lower temperatures and therefore is not a great indicator of temperature.

13) Cook the fish through with the gentlest possible heat, so that the outer portions aren’t badly overcooked. Oven baking and poaching well below the boil are two good ways to do this, after an initial and brief high-temperature treatment to brown and/or sterilize the surfaces.

14) Check the fish early and often for doneness. Simple formulas — 10 minutes to the inch is a popular one — and past experience can get you in the vicinity of the correct time, but there’s no substitute for checking the particular piece. This can be done by measuring the internal temperature with a reliable thermometer, peering into a small incision to see whether the interior is still translucent or already opaque, pulling on a small bone to see whether the connective tissue has dissolved enough to release it, or pushing a small skewer or toothpick into the flesh to see whether it encounters resistance from coagulated muscle fibers.

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15) Compensate for uneven thickness by cutting slashes in the thick areas every 1–2 cm. This effectively divides the thick areas into smaller portions and allows heat to penetrate more rapidly. Another strategy for relatively large portions is to cover thin areas loosely with aluminum foil, which blocks radiant heat and slows their cooking.

16) Heat transfer, that is what cooking is all about. Heat transfer comes in three kinds: conduction, convection and radiation. How the heat is transferred depends on whether the meat goes into an oven, a stewpot, a frying pan or a steamer. Heat transfer within the meat itself takes place mainly by conduction.

It does seem counterintuitive that a piece of meat just resting on the counter could grow hotter. That would violate the most fundamental law of physics: You can't get energy from nowhere. But while the meat rests, its internal temperature indeed rises from 5 to 15 degrees, depending on its size and shape. This effect is called "carryover cooking."

The source of the heat is the outer portions of the roast, which had been exposed most directly to the oven's hot air and are therefore hotter than the interior. The resting time allows some of the extra heat at the surface to work its way into the interior, thereby raising its temperature and, as a result, cooking it further.

A roast should always be taken out of the oven before its interior reaches the desired final temperature. That's not only to avoid overcooking, but also to allow the juices to redistribute themselves throughout the roast.

17) What determines how good your steak is going to taste? The main reasons are:

a) The difference between the temperature of the meat and the temperature of the heating source. It is the reason why heat goes into the meat, just like water flows downstream, not upstream.

b) The type of meat. How good it is (its texture, and whether it has inhomogeneities).

c) The temperature of everything in your kitchen and the initial temperature of the meat.

d) The presence of water, which lowers the effective cooking temperature. Regular meat consists of about 75 weight percent water. If you think that loss of water has something to do with juiciness, you guessed right.

e) The heating path. That’s the time a piece of meat spends at a particular temperature. Or in plain English: how quickly or slowly you heat it and the way you turn up or turn down the heat when cooking your meat.

After reading the above tips and knowing the basic physics of cooking meat, you may need decide to spend a few bucks on an accurate meat thermometer . Meat thermometers are not very expensive, and you can order one online from companies like Amazon.com.

Guidelines for Succulent Meat Braises and Stews

1) The most important rule: never let the meat interior get anywhere near the boil. Keep the meat as intact as possible to minimize cut surfaces through which fluids can escape.

2) When doing braises or stews, if the meat must be cut, cut it into relatively large pieces, at least an inch/2.5 cm on a side.

3) Brown the meat very quickly in a hot pan so that the inside of the meat warms only slightly. This kills microbes on the meat surfaces, and creates flavor.

4) Start the pot with meat and cooking liquid in a cold oven, the pot lid ajar to allow some evaporation, and set the thermostat to 200ºF/93ºC, so that it heats the stew to around 120ºF/50ºC slowly, over two hours.

5) Raise the oven temperature to 250ºF/120ºC so that the stew slowly warms from 120ºF to 180ºF/80ºC.

6) After an hour, check the meat every half hour, and stop the cooking when it is easily penetrated by the tines of a fork. Let the meat cool in the stew, where it will reabsorb some liquid.

7) The liquid will probably need to be reduced by boiling to improve flavor and consistency. Remove the meat first.

Temperature Guideline for Cooking Meat

32°F. This is water (H2O) freezing point. Meat stored frozen keeps much longer. Because water in meat is combined with proteins, the actual freezing temperature of meat is often as low as 26°F. Water expands as it freezes and sharp-edged crystals form that can rupture cell walls creating "purge" when it is thawed, a spilling of liquid, mostly the pink protein fluid called myoglobin. Faster freezing makes smaller crystals resulting in less purge.

34-39°F. Ideal refrigerator temperature. Water is not frozen and microbial growth is minimized. You do have a good refrigerator thermometer don't you?

40-122°F. This is the temperature range where enzymes that tenderize meat are most active. Enzymes called calpains become ineffective at about 105°F. Other enzymes called cathepsins keep working up to about 122°F. Slow cooking can keep meats in this range longer so enzymes can be effective and tenderize. But slow cooking can be hazardous for ground meats and poultry. Read on:

41-135°F. As defined by United States Department of Agriculture (USDA), this is the microbial "danger zone" in which bacteria grow most rapidly, sometimes doubling in number in as little as 20 minutes. According to USDA, cold foods must be stored below 41°F, and hot foods above 135°F. That's why we don't leave meats sitting around to come to room temperature.

60°F. When chilling cooked meat, liquid gelatin from form a solid gel called aspic. Gelatin happens with the melting of connective tissues that wrap muscle fibers and connect them to bones, called collagen. Yep, it's the same stuff they inject under your skin to hide wrinkles.

95°F. Aspic starts melting.

95-122°F. Meat fats start to soften, melt, and drip away.

120°F. Myosin protein, a protein involved in muscle contraction within fibers, begins to lose its natural structure. It unwinds or unfolds, a process called denaturing. It starts to clump, gets milky, and starts to firm up the muscle fibers. Purple meats, called "rare", start turning red.

130°F. Pathogenic bacteria begin to die, slowly at first, but as the temperature rises, they croak more rapidly. At this temperature it takes more than two hours to pasteurize meat. At 165°F it takes just seconds.

130-135°F. "Medium rare" for most mammal meats, they are at optimum tenderness, flavor, and juiciness at this temperature. If you eat your meat well-done, you need to snap out of it.

130-140°F. Fats begin to melt and liquefy, a process called rendering. This is a slow process and can take hours if meat is held at this temperature.

140°F. Collagens begin to contract and squeeze juice from within muscle fibers into the spaces between the fibers and out to the surface. Myoglobin, the pink protein liquid within muscle cells, denatures rapidly and red or pink juices begin to turn clear or tan and bead up on the surface. Meat gets noticeably tougher and drier.

150°F. Actin, another protein important to muscle contraction in live animals, begins to denature making meat tougher and drier still.

155°F. Known as "well done", meats are overcooked at this internal temperature. Much moisture has been squeezed out and fibers have become tough. Most (but not all) bacteria are killed in less than 30 seconds but spores can survive to much higher temperature.

150-165°F. This is "the stall zone", when large cuts such as pork butt and beef brisket seem to get stuck for hours when cooked at low temperatures like 225°F. In this range, moisture evaporates and cools the meat like sweat on an athlete. Inexperienced cooks panic. Eventually temperature start rising again.

160-165°F. Normal cooking temperature kill microbes on the outside of meats rapidly so solid muscle meats are not likely dangerous since contamination is almost always on the surface. But ground meats and poultry often have bad guys beyond the surface so you must cook them beyond to the "instant kill zone" within which pathogenic bacteria die in seconds. That's why the recommended internal temperature for ground meats is 160°F and for poultry is 165°F. When you reheat foods you should take them up to 165°F.

160-195°F. Tough collagens melt and form luscious tender gelatin. The process can take hours so low and slow cooking creates the most gelatin. Dehydrated fibers begin to fall apart and release from the bones. Meat becomes easy to shred. Even though the fibers have lost a lot of water, melted collagen and fat make the meat succulent.

190-205°F. Beef brisket, beef ribs, pork ribs, and pork shoulder are at their best because they are so full of collagen and fat.

212°F. Water boils at sea level. The boiling point declines about 2°F for every 1,000 feet above sea level.

225°F. The temperature I recommend for low and slow cooking of tough cuts. High enough so water evaporates from the surface to help form the desired crust called "bark", but low enough to get the most out of enzymes, collagen melting, and fat rendering.

230°F. Fructose, the predominant sugar in fruit and honey, begins to caramelize. Its chemical structure changes and it turns brown and develops richer, more complex flavors.

250-300°F. Butter starts to burn and smoke.

310°F. The Maillard reaction accelerates. This is the browning of the surface caused by chemical changes in proteins and sugars resulting in thousands of new molecules and the flavor we love in crusty brown meat. The Maillard reaction begins at lower temperature, but really takes off at 310°F.

320°F. Sucrose (table sugar) begins to caramelize.

325°F. The temperature I recommend for crisping chicken and turkey skins because the Maillard reaction and caramelization move quickly at this temperature.

350°F. Table sugar and brown sugar, which is just white sugar with molasses, in spice rubs and sauces begin to burn.

325°F. Pork fat begins to smoke.

400°F. Beef fat begins to smoke.

450-500°F. Nonstick surfaces begin to emit toxic gases.

570-750°F. Primary combustion temperature of wood. Hardwood smolders and releases large quantities of unburned gases including smoke.

600-700°F. The flash point or fire point, the temperature at which smoke from burning fat can burst into flame. Never use water to extinguish burning fat.

1,110°F. Secondary combustion of wood begins. Gases, cellulose, and lignin in wood burn rapidly if sufficient oxygen is present.

Red Meat vs. White Meat

Blade steaks are an example of "red" meat.

Meat can be broadly classified as "red" or "white" depending on the concentration of myoglobin in muscle fibre. When myoglobin is exposed to oxygen, reddish oxymyoglobin develops, making myoglobin-rich meat appear red. The redness of meat depends on species, animal age, and fibre type: Red meat contains more narrow muscle fibers that tend to operate over long periods without rest, while white meat contains more broad fibers that tend to work in short fast bursts.

Generally, the meat of adult mammals such as cows, sheep, goats, and horses is considered red, while chicken and turkey breast meat is considered white.

Nutritional Information of Meat

All muscle tissue is very high in protein, containing all of the essential amino acids, and in most cases is a good source of zinc, vitamin B12, selenium, phosphorus, niacin, vitamin B6, choline, riboflavin and iron. Several forms of meat are high in vitamin K2 (the menaquinones), which is only otherwise known to be found in fermented foods, with natto having the highest concentration. Vitamin K2 includes several menaquinones (MK-n, with the ‘n’ determined by the number of prenyl side chains), such as MK-4 found in meats, MK-7, MK-8, and MK-9 found in fermented food products like cheese and natto. Natto is typically fermented  from soybeans or chickpeas by using a healthy bacteria called bacillus subtilus that may also serve as a probiotic.

Muscle tissue is very low in carbohydrates and does not contain dietary fiber. The fat content of meat can vary widely depending on the species and breed of animal, the way in which the animal was raised, including what it was fed, the anatomical part of the body, and the methods of butchering and cooking. Wild animals such as deer are typically leaner than farm animals, leading those concerned about fat content to choose game such as venison. Decades of breeding meat animals for fatness is being reversed by consumer demand for meat with less fat.

While each kind of meat has about the same content of protein and carbohydrates, there is a very wide range of fat content. It is the additional fat that contributes most to the calorie content of meat, and to concerns about dietary health.



REFERENCES:

Aidells, Bruce. 2001. The Complete Meat Cookbook. Rux Martin/Houghton Mifflin Harcourt. ISBN-10: 061813512X

McGee, Harold. 2004. On Food and Cooking: The Science and Lore of the Kitchen. Scribner; Rev Upd edition. ISBN-10: 0684800012

Phillips, Jeff. 2012. Smoking Meat: The Essential Guide to Real Barbecue. Whitecap Books Ltd. . ISBN-10: 1770500383



Have you tried Sous Vide cooking technique? Nope... get the 9 Best Cookbooks for Sous Vide Cooking Technique. If yes, then try this... sous vide recipes.


Now you know how to cook you favorite meat, do you how to keep cooked broccoli green? Please go to... How to Keep Cooked Broccoli Bright Green to know more.


You can download a complete PDF version (with table of Temperature Guideline for Cooking Meat and Fish) of this cooking guide at https://docs.google.com/file/d/0B8SlglBF4EknVXI0cThXcERwbWM/ for future reference.

Happy cooking and keep healthy always...! ;-)

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