Part 4 (1/2)

Roasting First Principle: Succulence A quick cooking process that is not meant to tenderize the meat, roasting is reserved for choice pieces that come from young, tender animals. It leaves the characteristic flavor of the meat intact, adding only a delicate touch on the surface. The juices, most of which remain in the flesh, flood the mouth with subtle flavors when one bites into the meat.

A roast retains its succulence only when it is seared. The oven must be preheated, the meat must be coated with oil, which conducts heat better than water, and ideally steam must be eliminated. Without allowing too many of the juices to be released, the heat produces new sapid and odorant compounds by destroying various molecules at the surface and thus blending the contents of various cell compartments, which react with one another. The lipids (fats), amino acids, and sugars bind together into large, dark-colored odorant and sapid molecules.

Traditional French cooking requires beef, for example, to be roasted in such a way that the center remains rare. The surface is covered with oil or b.u.t.ter so that, seared more rapidly, it forms the thin crust so prized by gourmands.

A long time ago, it was believed that searing produced an impermeable layer that would keep the juices from escaping. But it has been demonstrated that the juices escape regardless. If meat should be roasted in a hot oven, it is to limit the roasting time and thus the time during which the juices can escape. When the roast comes out of the oven, tender, odorant, and juicy, it must rest a few minutes so that the juices in the center migrate toward the dry periphery. Then it must be cut with a good knife that will not maul it, allowing the juices to be retained within.

Other countries, other customs: the English are renowned for their boiled meats but also for their well-done roasts. Across the English Channel, a roast remains respectable when the temperature at its center reaches 60 (140F) or even 80C (176F). In France, the temperature at the center of a roast sometimes does not even attain 30C (86F).

How Does a Roast Cook?

Let us recall the paragraphs devoted to cooking and review one by one the various kinds of heat transfers in order to see which one applies to roasts. We will consider three of them: radiation, convection (the hot air ensures the distribution of heat in the oven), and conduction (within the meat).

How does a roast cook? First of all, note that the thermic conductivity of meat diminishes considerably with temperature. Meat conducts heat very poorly (it is an insulating material) at low temperatures (at 0C [32F], for example), but it becomes a better conductor at higher temperatures. We can examine the consequences of these properties by a.n.a.lyzing how a Christmas turkey cooks.

THE CHRISTMAS TURKEY.

How to cook a turkey correctly? A turkey's sphericity holds some interest for physicists, who know how to calculate heat transfers within bodies with simple forms. In 1947 Horatio Scott Carslaw and John Conrad Jaeger studied the relations.h.i.+p between the radius of an ideal, spherical turkey and cooking time. They a.s.sumed that a turkey was a mixture of water, fats, and proteins in the ratio of 60/20/20, and they sought the optimal cooking temperature.

Why does the cooking temperature matter? When a turkey is roasted, its fibers contract until, at about 70C (158F), the individual muscle cells begin to deteriorate. During heating, the weakest bonds between the atoms of certain molecules are broken, so that the proteins are denatured. These long threads, folded back on themselves in specific configurations, unwind and move in all directions. Because the proteins can thus come into contact with one another, they bond and coagulate. The meat hardens, but not very much.

When the cooking is too prolonged, the water that remains bound to the proteins is released, and the meat becomes tough. Conversely, we have often seen that, the longer the cooking, the more the rigid network of collagen is broken down. In short, the cook who roasts a turkey must find a compromise in order to break down the collagen and at the same time avoid letting the proteins dry out and toughen after they have coagulated.

COOKING CALCULATIONS.

Since it is juicy, tender meat that we want, it is clear why there is no question of opening the oven while the meat is roasting. The water vapor that is released in a limited quant.i.ty could escape and then be replaced by the vaporization of a certain quant.i.ty of the juices. Opening the oven dries out the turkey. Neither, however, should one humidify the oven before putting the turkey in. In the presence of too much water, the surface water cannot evaporate, and the skin will not get crispy.

Having thus resolved the problem of the surface, the serious problem of tenderness within remains. We cannot disappoint our guests, who fear the proverbial dryness of the Christmas turkey.

Since tenderness results necessarily from the deterioration of the connective tissue, let us consider this tissue. It princ.i.p.ally contains three kinds of proteins: collagen, already discussed many times, reticulin, and elastin. Neither reticulin or elastin are notably altered by the heat of the oven, but the triple helixes of the collagen molecules can be broken up and form gelatin, which is soft when it is in water, as we all know.

Calculating the cooking time requires some skill, because the denaturation of the collagen and the coagulation of the muscle proteins (actin and myosin, mainly) take place at different temperatures and different speeds in the different parts of the turkey. It is necessary to know that the temperature of 70 (158F) is essential for transforming the collagen into gelatin and tenderizing the muscles. But the longer the turkey remains at a high temperature, the more water it loses and the more its proteins risk coagulating. The optimal cooking time, consequently, is the minimum time it takes to attain the temperature of 70C (158F) at the center of the turkey.

Thus defined, the problem is simplified because physicists are experts on heat transmission in different materials, even animal tissues. They make their calculations a.s.suming the temperature is h.o.m.ogeneous and the animal is cylindrical, h.o.m.ogeneous, and so on, and they end up with precise if complex results involving the radius of the animal, the coefficient of the thermic diffusion, the temperature of the turkey, and the temperature of the oven.

Fortunately, there is a simpler means for calculating the cooking time for turkeys. We can apply the Fick law, which stipulates that, for the center of the turkey to attain a given temperature, the time of heating (t) is proportional to the square of the radius of the turkey. Since the ma.s.s (M) of a sphere is proportional to the cube of its radius, we can determine the cooking time by applying the simple formula t t = ( = (M/Mo)2/3to.

My friend Peter Barham, a physicist and molecular gastronomer from Bristol, has calibrated this equation and calculated the following values: * at 180C (356F), a turkey weighing five kilograms (11 pounds) must cook two hours and twenty-five minutes, and a turkey weighing seven kilograms (15.43 pounds) must cook three hours;* at 160C (320F), a turkey weighing five kilograms (11 pounds) must cook three hours and thirty-five minutes, and a turkey weighing seven kilograms (15.43 pounds) must cook four hours and thirty minutes.33 One Can Become a Cook, but One Is Born a Roaster Brillat-Savarin's aphorism paraphrases an old Latin adage: poeta nascitur, orator fit poeta nascitur, orator fit (one can become an orator, but one is born a poet). I will end this chapter by attempting to prove Brillat-Savarin wrong; to that end, let me succinctly a.n.a.lyze the cla.s.sic rules of roasting, adherence to which will allow anyone to roast as to the manner born. (one can become an orator, but one is born a poet). I will end this chapter by attempting to prove Brillat-Savarin wrong; to that end, let me succinctly a.n.a.lyze the cla.s.sic rules of roasting, adherence to which will allow anyone to roast as to the manner born.

You want to obtain meat that is just right, that is to say, nicely browned, every bit of the flesh enhanced by the cooking, and oozing with juices when carved. To retain the juices, shorten the cooking time by placing the roast in a preheated oven, as hot as possible (too hot, and the meat will char).

As in the case of stew, season the roast only after completely cooking it, a few moments before taking it off the spit or out of the oven, because, once on the meat, the salt will draw the water from it, hamper browning, and dry out the inside (through the phenomenon of osmosis). Likewise, do not add pepper until the end of cooking. Pepper, when overheated, gives meat a strong, unpleasant taste.

Lard the meat with strips of pork fat or wrap it in a caul or strips of bacon; this enhances the browning by releasing fat, which will aid the transfer of heat and protect against overheating.

Finally, remember that the only true roasting takes place on a spit, because this is the only way to ensure that all parts have equal contact with the heat. Meat in a metal pan, for example, cooks more quickly at the points of contact than elsewhere.

THE STUFFING AND THE SAUCE.

While the turkey slowly roasts, let us examine how the stuffing we have put inside it cooks.

Remember that the stuffing, placed where the temperature is lower, will have a harder time cooking than the turkey. It is especially for this reason that stuffing is often forcemeat mixed with egg. Prepared in this way, the meat filling the turkey forms one coherent ma.s.s. The 70C (158F) attained at the center at the end of the cooking time is high enough to coagulate the egg and bind the various components in the stuffing.

Additionally, in order to avoid burning the outer layer of the meat, let us baste it for about three full minutes with the melted fat (not liquid, which would soften the outside crust). This forms a screen, stopping some kinds of radiation. Sometimes the roast can be protected by covering it with paper coated with oil, but basting is more effective. Naturally, we should not begin to baste before a crisp crust has formed on the surface.

The fat that drips over the meat falls back into the bottom of the roasting pan (or, if one is using spit, into a pan set below the roast to collect the drippings), bringing with it a bit of the browned juices of the meat.34 At the end of cooking, these delicious juices are recovered in what is called a glaze. Once the pan is removed from the oven, the meat is lifted out of it, a little boiling water is poured into the pan to dissolve these juices, the mineral salts from the meat, and the gelatin that emulsifies the fat. With a little whisking, a thickened sauce with a good consistency is quickly obtained.

If the sauce does not emulsify and remains in two phases, it can easily be h.o.m.ogenized with the help of gelatin.

Finally, remember that, depending on the kind of roast, the deglazing of the dripping pan can also be done with wine, milk, diluted cream, cognac, whatever you please.

Deep-Frying Why Is It Necessary to Fry in So Much Oil?

All cooks know that frying is cooking through contact with hot oil. They know that this operation creates a golden crust, but they distrust heated oil, which spatters, makes the kitchen greasy, and produces the taste and smell of burnt fat as it gradually darkens. And that is why some physicians condemn deep-frying on dietary grounds.

The makers of household appliances have already overcome the first two inconveniences of deep-frying by inventing deep-fryers equipped with a filter and in which the operation takes place in a closed vat. Is there a way to overcome the last inconvenience, of reconciling the pleasures of deep-frying with the concerns about health or even one's figure? How to fry well? What oil to use for deep-frying?

The principle of deep-frying is simple. The heated frying pan transmits its heat to the oil, which can rise in temperature well above the 100C (212F) maximum attainable with water. Brought to these very high temperatures, the cells on the surface of the foods to be fried, in drying, produce the characteristic crispness of good deep-fried food. Have you noticed that the surface of fried food seems dry? That is because the surface moisture, brought suddenly to a temperature higher than 100C (212F), has evaporated.

How to obtain good fried foods? By using oil as hot as possible, because if the crust is not formed very quickly, the oil penetrates the food. A dramatic release of vapor bubbles from the food's surface indicates that the frying process is going well.

Moreover, the initial temperature must be increased according to the size of the food. As it heats, the food cools the oil in which it is placed. A large piece of food cools the oil more than a small piece. Since the maximal temperature of the oil is limited, a good solution for cooking a large quant.i.ty of food is to use a large quant.i.ty of oil, in which a large quant.i.ty of heat will be stored.

It would be a serious mistake to use a small amount of oil for frying on the pretext of worrying that it will saturate the food. On the contrary, the food will fry in oil that is too cool to sear it and thus will become a horrible oil sponge.

It is equally important to realize that oil cannot withstand excessive heat. Just as overheated b.u.t.ter blackens and burns, too-hot oil deteriorates. A good deep-fry cook must remember that all oils do not have the same capacity for withstanding heat.

Try this experiment. Take oil and heat it quickly. It will eventually release a strong, sharp odor and a pungent smoke. A compound called acrolein is the source of this acridity that the cook must avoid. We can now turn to the farm-produce industry, which is working to produce special oils for deep-frying, that is to say, oils that have as high as possible a smoking point.

Why Must the Deep-Fry Oil Stay Clean?

Even the best oil can only produce good fried food if it is treated with care.

We know that reused oils smoke as soon as the temperature rises even the slightest bit. They have lost their frying properties because they have gradually become full of little particles, of meat, for example, which cook at 70C (158F) and blacken above that temperature, releasing acrid compounds. Moreover, the oil itself generates compounds that further increase its degradation. The solution is imperative: if an oil must be reused, it must be filtered in order to remain clear.

This same phenomenon of protein carbonization prevents the use of b.u.t.ter, without some preparation, for deep-frying. At the temperature of 45C (113F), b.u.t.ter melts; at 100C (212F), it sputters (because the water it releases evaporates); then, at 120C (248F), it decomposes unless someone has taken the precaution of clarifying it.

Even though it is simple, clarifying b.u.t.ter is an operation lost among the household arts. What does it consist of? Eliminating the proteins (especially casein) that the b.u.t.ter contains, in order to obtain a fatty substance as pure as possible that can withstand a good heating without turning black. Decomposing at a low temperature, the proteins in b.u.t.ter darken and impart a burnt flavor at the same time that they prompt the decomposition of the b.u.t.ter's lipids.

And, say what you like, deep-frying done with the aid of a good clarified b.u.t.ter is a true gastronomic pleasure. (This same clarified b.u.t.ter will be very useful in many other preparations, such as grilling.) How to set about clarifying b.u.t.ter? It is a matter of placing the b.u.t.ter in a saucepan and heating it a long time and very gently. After about thirty minutes, the caseins precipitate. The supernatant (the clarified b.u.t.ter), which can be recovered by simply pouring it into a container where it can be stored, retains the sapid and aromatic qualities of the original b.u.t.ter.