Part 5 (1/2)

Salting Why Must Infants Not Be Fed Sausages?

Those nitrates that ecologists condemn for polluting streams and rivers are present in foods preserved with salt. Pota.s.sium nitrate, that is, saltpeter, has been used in this way empirically since the Middle Ages, even since Roman times. In 1891 the biologist H. Polenski demonstrated that bacteria transform saltpeter into nitrite in meat. Then in 1899 came the discovery that the characteristic color of salted products was due to these nitrites and not to the nitrates themselves. In 1901 the biologist John Scott Haldane found that this color resulted from the combination of the chemical group NO with the meat pigments. Finally, in 1929, nitrites were observed to inhibit the development of bacteria. Today, the description of the process is complete: salting, with the use of saltpeter, is an effective conservation method because the nitrate ions of the saltpeter are transformed into nitrite ions, which kill bacteria.

Unfortunately, nitrites are certainly not lacking in toxicity for humans as well. They react with the amino acids that make up proteins and form carcinogenic nitrosamines. Babies, especially, should not absorb nitrites, because these compounds are oxidants. They transform the hemoglobin in the blood into methemoglobin, which no longer transports oxygen. Adults possess an enzyme called methemoglobin reductase that retransforms methemoglobin into hemoglobin, but infants, who do not yet have this protective enzyme, must wait to indulge in sausage, dried meats, and the like.

How Do We Dry Meat Using Salt?

Though nitrited salt is available commercially, we should nevertheless remember that nitrites are not crucial for home salting. A well-implemented brining and drying process will suffice. The salt in a brine acts according to the phenomenon of osmosis already discussed. When a piece of meat is placed in a terrine with a little water and a lot of cooking salt, the water in the animal cells tends to leave the meat until the concentration of salt inside and outside the cells is equal. The salt does not enter the cells, but the water, small molecule that it is, is very mobile.

Thus drained, the meat hardens on the surface, and in this waterless meat bacteria have trouble developing. Why must a little water be added to the terrine? Isn't the cooking salt alone sufficient? With a bit of water, the meat is entirely soaked, so that contact with the salt is improved.40 After undergoing this treatment for some time, the meat is removed from the brine and dried. For a successful drying operation, it is advisable to place the meat in a dry, well-ventilated spot. An uninsulated attic with good ventilation serves well, as does a cool, dry cellar. The meat dries, and, after some time, it can be consumed ... with that great pleasure derived from slowly cured, long-awaited foods.

Microwaves Cooking with Internal Vapor Cooked in a microwave, beef is rejected by taste testers, who find fault with its grayish external color, the uniformity of its internal color, its toughness, its lack of succulence, and its bland taste. And they are right. Microwaves penetrate into the ma.s.s of the foodstuff for several dozen millimeters before being absorbed by the water molecules. These molecules are heated, then vaporized. The temperature never goes above 100C (212F). Now, as we have seen, heating in this way is fatal to meat, which must be heated intensely to achieve the browning produced by Maillard and other similar reactions.

On the other hand, microwaves are good for cooking eggs, for example, in which the proteins coagulation begins at 61C (141F). Placed in a bowl without an ounce of fat, an egg will cook rapidly; its taste is acceptable, and the figure benefits. Scrambled eggs, soft-boiled eggs, omelets, and even souffles can be cooked in this way. Microwaves are useful for fish as well, because they efficiently heat the poaching liquid over which the fish is placed. Similarly, vegetables can be cooked in boiling water, heated by microwaves.

Where Do Microwaves Act?

Let us review the basic principles in order to really understand where microwaves act. Inside a microwave oven is a device called a magnetron that emits electromagnetic waves (that is, vibrations in s.p.a.ce a.n.a.logous to light or to radio waves but with a different wavelength) with a frequency equal to 2400 megahertz. At each point in s.p.a.ce crossed by a microwave beam, the electromagnetic field oscillates 2400 times a second.

Without safeguards, such waves would heat the water in our bodies, and we would boil. Thus the waves are directed by an aluminum tube just inside the oven, and they are sealed within the oven (metallic grating in particular, like the kind used to reinforce microwave oven doors, stops microwaves).

When food is irradiated with microwaves, the waves interact through their electrical field with electrically asymmetric molecules, such as water molecules. The energy given to these molecules is transformed into motion, and the movement of these agitated molecules disturbs the other, unagitated molecules, so that the ma.s.s is put into motion, that is to say, heated. Gradually, the agitated molecules are calmed down by colliding with the surrounding molecules, through their random movement. Since most foods contain large quant.i.ties of water, they are heated because this water becomes agitated, and it is especially the parts of the food containing the most water that are heated the most. Hence the recipe for canard a l'orange canard a l'orange given at the start of this book. given at the start of this book.

A Few Questions and Answers Why have the manufacturers of microwave ovens adjusted the frequency of microwaves so that they are a bit lower than the frequency at which water best absorbs these waves?

Because if we want the inside of foods to be cooked as well as the outside, the microwaves must not be absorbed immediately by the outer layers of the food. If the water on the surface absorbs only some of the microwaves, the rest will permeate the food, where another share will be absorbed.

Why do salted foods heat more quickly than unsalted foods in a microwave oven? Because salt contains ions, and the water molecules that hydrate these ions, by surrounding them, heat more quickly than isolated water molecules.

Why should we not try to heat oil in a microwave oven? Because triglycerides have no chemical groups that can interact efficiently with microwaves. This can easily be demonstrated by putting two gla.s.ses, one filled with water, one filled with oil, in a microwave oven. When the water comes to a boil, the oil will still be cold.

Why does meat cooked by microwaves become grayish-brown? Because the temperature stays below 100C (212F); thus the oxymyoglobin is not denatured and retains its color.

And, to end with something sweet, remember that caramel can be prepared quite easily in a microwave oven. Take a small bowl, place sugar and a bit of water in it, and heat. Caramel rapidly results without any trouble whatsover.

Vegetables COLOR AND FRESHNESS.

A Matter of Water Vegetables, the jewels of the kitchen! Did they not give their names to the great Roman families? Fabius, in honor of faba faba, or feve feve, the broad bean; Lentulus, in honor of the lentil; Piso, in honor of the pea; Cicero, in honor of the chickpea.

Vegetables must be eaten fresh to be good. The soil in which they were cultivated, the climate that brought them to life will sing in one's mouth ... if they are not mangled in the cooking process. Cooking them is a delicate operation. How long must they cook to become sufficiently tender? Must they be tossed into cold or hot water? Must the cooking water be salted? How to retain their bright colors, which seem to be the mark of their freshness?

Before I launch into an examination of this last question, let me recall that a very fresh vegetable is generally tender, and cooking is not of great value to it. On the other hand, for certain older or even dried vegetables, like lentils, rehydration is essential.

In these two cases, the cooking methods are very different, since the object in the first is to retain the emollient moisture of the vegetable and in the second to reintroduce moisture that has been lost.

How Do We Avoid the Discoloration of Green Vegetables When Cooking Them?

The intense green that vegetables acquire after cooking for a few seconds in boiling water results from the release of gases trapped in the s.p.a.ces between the vegetable cells.

Generally, these pockets of air act as magnifying gla.s.ses that highlight the color of the chloroplasts, the green organelles that are responsible for the transformation of carbon dioxide into oxygen.

Vegetables, however, are usually cooked longer than a few seconds, thus destroying the atmosphere that shows these vegetables in their best light. Spinach cooked too long turns brown, sorrel as well; leeks lose their greenness, and so on. How to retain that appetizing color?

The cooks of antiquity were the first to make advances toward explaining this phenomenon. They observed that green vegetables remained very green when saltpeter or ashes were added to cooking water. Why?

When a green vegetable is heated, some of its cells burst, releasing various organic acids. The hydrogen ions of these acids react with chlorophyll molecules (which contribute to the green color of green vegetables) because these molecules contain a large square chemical pattern, the porphyrin group, at the center of which is a magnesium atom. Now, the hydrogen ions have a bad habit of taking the place of the magnesium ion in this porphyrin group and of thus transforming the various kinds of chlorophylls into pheophytins, which absorb different components of light. Instead of retaining all the light rays except those of the color green, pheophytins reflect a mixture of wavelengths that produce the perception of a horrible brown.

But from this a.n.a.lysis emerges a solution: not heating the vegetables for too long, so that the magnesium will remain in its chlorophyll cage.

A few corollaries are equally essential. To retain the color of green vegetables, avoid lidded earthenware pots and opt for steaming, because if they are not immersed in water, the vegetables are not in contact with the hydrogen ions. If vegetables are cooked in water, large quant.i.ties of water should be used. Finally, adding vinegar to the cooking water for green vegetables should be absolutely avoided, as it will enhance the bad effects you wish to avoid. Be aware, too, that many juices from fruits are very acidic (and that the acidity one perceives can be hidden by sugars).

Naturally, inventive cooks have thought of cooking green vegetables in the presence of salts, which provide ions that can occupy the positions hydrogen ions would otherwise take. That is why green vegetables were cooked in copper pans, called ”regreening pans,” and why, later in history, copper salts were used; with these methods, the green remained intense ... but the vegetables became toxic. Indeed, a law prohibited the practice of adding copper salts in 1902. More recently, processes using zinc ions have been patented.

Adding a base to the cooking water in order to neutralize the acids as they form has also been considered. This solution was already familiar to the Romans. Apicius, famous for his gastronomical extravagances, wrote, ”Omne holus smarugdinum fit, si c.u.m nitro coquantur” (All vegetables will be the color of emerald if they are cooked with niter).41 The same effect occurs with ashes, where potash is present. Alas, niter, or saltpeter, and potash ruin the taste. The same effect occurs with ashes, where potash is present. Alas, niter, or saltpeter, and potash ruin the taste.42 How Long Must Vegetables Be Cooked?

Do not hope for a global response to such a question. Fresh asparagus will cook for less time than asparagus kept for a day or two after picking. And regardless of freshness, asparagus will not take as long to cook as potatoes. Still, as is so often the case, an a.n.a.lysis of the problem can guide us in our culinary transformation operations.

The objective is to tenderize the vegetables, the cells of which, unlike animal cells, are each protected by a hard, fibrous wall. Weakened by cooking (the cellulose is not altered chemically, but the pectins and the hemicellulose are), these walls becomes porous, and as their proteins are denatured, they lose their ability to regulate the movement of water from the interior of the cell to the exterior, and vice versa. Water can pa.s.s through the walls, while larger molecules are blocked.

We know that when we put vegetables into unsalted water, they swell because the water enters the vegetable cells as a result of osmosis. On the other hand, if the cooking water has too much salt, the vegetables harden (especially carrots), because the water does not enter the cells to reduce the salt concentration in them-the contrary!

The Mystery of Dried Vegetables The case of dried vegetables (lentils, etc.) is a little different, because the objective there is to reintroduce the water lost in drying them. As I just noted, the cooking water must not be salted. Nevertheless, this precept is not enough, and cooks have perfected a precise methodology for obtaining good results.

The first operation should be a soaking, the aim of which is to soften the external layer of the vegetable and facilitate the subsequent cooking. Often, two hours of soaking is enough to obtain a wrinkled skin. Warm water seems preferable to cold water, because the soaking is thus accelerated. The soaking water is then replaced for cooking.

The cooking water must not be calcareous, cooks say, because if a layer of calcium settles on the skins of the vegetables, it will harden them and prevent them from cooking. Authors like Madame Saint-Ange recommend adding bicarbonate of soda when the water is calcareous. In fact, no layer of calcium forms, but calcium should be avoided nevertheless because it acts as a cement between pectin molecules in the vegetable cell walls, hardening them rather than promoting softening. Madame Saint-Ange was right to recommend bicarbonate of soda. It has two benefits. First, the calcium is precipitated so that it cannot bind the pectins. Second, the water becomes basic, contributing to the pectin separation (we shall witness this effect again later, with regard to jams).

It is also specified that the cooking be gradual. This makes sense in principle, because cooking too rapidly from the outset cooks the exterior part too much, turning it to mush before the center of the vegetable is soft. Likewise, adding cold water if the cooking water boils away should be avoided. The sudden thermal discontinuity can explode the vegetable skins, thus releasing their contents into the cooking water.

Do Carrots Risk Losing Their Color in Cooking?

If the cook is careful, no carrot will ever lose its color. We must understand that the color of vegetables comes from various pigments: chlorophylls (green to blue pigments), carotenoids (yellows, oranges, and reds), and anthocyanins (reds, purples, and blues). If green vegetables are green, it is because they contain chlorophylls. If carrots are orange, it is because they contain, especially, carotenoids.

Now carotenoids, soluble in fat but insoluble in water, are little altered by boiling water. Normally, carrots remain brightly colored (the same is true for tomatoes, though their color is mainly due to lycopene, not carotenoids). In other words, carrots are easy to cook ... so long as a pressure cooker is not used. The pressure that builds in a pressure cooker alters the carotenoid molecules, which then lose their color.

How Do We Cook Potatoes?

Potatoes are made of cells that contain granules of starch. These starch granules become soft, inflated, and jelled when they are immersed in water at temperatures from 58 to 66C (136 to 150F). The perfectly cooked potato is full of these inflated, tender granules, all of which have uniformly reached the temperature of 66C (150F).

Thus sauteed potatoes are better when they have been cooked in water for a few minutes and acquired a jelled outer layer. During cooking, this layer prevents the starch granules from absorbing too much oil, while the external surface can be heated to 160C (320F). The starch contained there deteriorates and reacts, as we saw in the chapter on deep-frying, giving way to a crispy, golden casing.