boiling

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A process in which a liquid phase is converted into a vapor phase. The energy for phase change is generally supplied by the surface on which boiling occurs. Boiling differs from evaporation at predetermined vapor/gas-liquid interfaces because it also involves creation of these interfaces at discrete sites on the heated surface. Boiling is an extremely efficient process for heat removal and is utilized in various energy-conversion and heat-exchange systems and in the cooling of high-energy density components. See also Boiler; Evaporation; Heat exchanger; Heat transfer.

Boiling is classified into pool and forced-flow. Pool boiling refers to boiling under natural convection conditions, whereas in forced-flow boiling the liquid flow over the heater surface is imposed by external means. Flow boiling is subdivided into external and internal. In external-flow boiling, liquid flow occurs over heated surfaces, whereas internal-flow boiling refers to flow inside tubes. Heat fluxes of 2 × 10⁸ W/m², or three times the heat flux at the surface of the Sun, have been obtained in flow boiling. See also Convection (heat).

Pool boiling

The illustration, a qualitative pool boiling curve, shows the dependence of the wall heat flux q on the wall superheat ΔT (the difference between the wall temperature and the liquid's saturation temperature). The plotted curve is for a horizontal surface underlying a pool of liquid at its saturation temperature (the boiling point at a given pressure). See also Boiling point.

Typical boiling curve, showing qualitatively the dependence of the wall heat flux q on the wall superheat ΔT. Schematic drawings show the boiling process in regions I–V, and transition points A–E.

Several heat transfer regimes can be identified on the boiling curve: single-phase natural convection, partial nucleate boiling, fully developed nucleate boiling, transition boiling, and film boiling.

Forced-flow boiling

Forced flow, both external and internal, greatly changes the boiling curve in the illustration. The heat flux is increased by forced convection at temperatures below boiling inception, and after that the nucleate boiling region is extended upward until a flow-enhanced higher maximum flux (corresponding to point C) is achieved. Forced flow boiling in tubes is used in many applications, including steam generators, nuclear reactors, and cooling of electronic components. See also Steam-generating unit.

adjective

Marked by much heat: ardent, baking, blistering, broiling, burning, fiery, heated, hot, red-hot, roasting, scalding, scorching, searing, sizzling, sultry, sweltering, torrid. See hot/cold/lukewarm.

Definition: angered
Antonyms: happy

adj

Definition: very hot
Antonyms: freezing

The admission of the novice cook that he or she "cannot even boil water" has perpetuated the idea that boiling water is one of the simplest tasks in the kitchen. In reality, it is also a frequently misunderstood and mislabeled culinary technique. Boiling is one of the moist (as opposed to dry) heat processes of cooking, which include pressure cooking, scalding, simmering, poaching, stewing, fricasseeing, braising, casserole-making, double-boiling, and steaming, as well as partial moist-heat processes, like blanching. Through the years, however, these traditional terms for different kinds of moist heat cooking have been variously interpreted and, of necessity, combined with other culinary methods. For example, a braise, fricassee, and brown stew have their origin in dry heat sautéing but are finished by long moist-heat cooking in stock. Even foods that are specifically labeled "boiled," such as boiled eggs, boiled potatoes, and boiled coffee, are not entirely cooked in boiling water but rather simmered after being brought to a boil. The pores of food are sealed by being dropped into rapidly boiling liquid, but then the temperature is usually reduced to a simmer (185–200°F)—the suitable temperature for cooking soups, stews, and braises.

Boiling, or bouiller, is cooking in boiling water. Water boils at 212°F (sea level), and simmers at 190°F. To fully understand the heating process, Julia Child advises the cook to observe water in its various cooking stages, from tepid to real boil, by testing it and using an immersable thermometer and noting the following temperature changes:

Tepid:

85 to 105°F. The water is comparable to the temperature of the human body.

Warm:

115 to 120°F. The water is touchable but not hot.

Hot:

130 to 135°F. The water is too hot to touch without injury.

Poach:

160 to 180°F. The water is beginning to move, to shiver.

Simmer:

185 to 200°F. There is movement, and little bubbles appear in the water.

Slow boil:

205°F. There is more movement and noticeably larger bubbles.

Real boil:

212°F. The water is rolling, vigorously bubbling, and steaming.

Boiling is affected by altitude. At sea level, water boils at 212°F; at 3,000 feet, it boils at 205°F; 5,000 feet, at 203°F; and 7,500 feet, at 198°F. Because certain foods, like soup, pasta, and vegetables, will cook at a lower temperature, they will take longer to cook.

The boiling process serves two purposes: it destroys organic impurities, and it transforms raw ingredients into cooked foods. Boiling water hardens the albumen in eggs; toughens fibrin and dissolves tissues in meat; and bursts starch grains and softens cellulose in cereals and vegetables. One of the great advantages of water as a cooking medium is that it needs only a vessel and heat to reach and maintain its boiling point, no matter how long or how hard it is heated.

The food scientist Harold McGee maintains that during the boiling process, it is the convection currents in hot water that heat food. The "moist" cooking methods, however, cannot brown foods; consequently, meat and vegetables are normally sautéed in a frying pan before they are simmered in broth or water. Despite this limitation of the technique, by which boiling in water is conducted at a substantially lower temperature level than that of broiling, baking, and frying, boiling is a very efficient process. As McGee notes in On Food and Cooking, "The entire surface of the food is in contact with the cooking medium, which is dense and turbulent enough that the water molecules continuously and rapidly impart their energy to the food" (p. 615).

The old adage "a stew boiled is a stew spoiled" can be applied to almost every other kind of food because lengthy cooking at high temperatures toughens the proteins in meats, fish, and eggs, and the rapid bubbling breaks up delicate foods. While recipes either call for foods to be immersed in cold water and brought to the boiling point or plunged into boiling water, they almost never indicate boiling for a protracted period of time. Even so-called "boiled" eggs should be simmered after the initial contact with boiling water. Simmering, then, is often used in tandem with boiling because simmering liquid gently cooks fragile foods and tenderizes tough ones.

Only certain foods, such as vegetables, pasta, cereals, and other grains, are truly boiled in water. In these cases, it is necessary to maintain the boil to ensure their proper cooking. Because adding foods to boiling water lowers the boiling point, it is usually stipulated that the quantity of water must be at least three times the volume needed to cover the ingredient to offset the lower temperature caused by their addition. In cooking vegetables, particularly, the amount of salted water will insure rapid boiling, thereby shortening the time of cooking and preserving color.

According to Fannie Merritt Farmer, milk should never be allowed to boil because at boiling temperature the casein is slightly hardened, and the fat is rendered more difficult to digest. She advises the use of a double boiler to "scald (196 degrees)" milk heated over boiling water.

History of Boiling

McGee theorizes that, as a culinary technique, boiling probably followed roasting and preceded baking. Because boiling requires containers that are both water-and fireproof, the development of pottery at least ten thousand years ago had to precede boiling. And the large pots hanging in the fireplaces of the earliest kitchens attest to the fact that many meals were slowly simmered, sometimes over a period of days. In Taillevent's Viandier (c. 1364) the cook's activities centered on a fireplace that featured an adjustable pothook from which large cooking pots hung filled with meats, poultry, game, and vegetables. To control temperatures, the pot's position could be stationary over temperate ashes or could be swung over the hottest coals. Hot coals or logs could also be moved beneath it. This method of hearth cooking continued into the eighteenth century and even later in rural areas. Chef and author John Thorne eulogizes the pot as the emblem of the kitchen and quotes the noted French chef Alain Senderens, who suggests in his Figues sans barbarie (1991) that unlike "spit cooking" or the kind of roasting associated with the early "gatherers," "the cooking of the pot symbolized the feminine domain of the kitchen, family, economy, and, by extension, the civilizing process itself." By preparing food in boiling water in a pot, the cook took what nature provided and transformed it into thoroughly cooked food. "From this instant," Senderens believes, "cooking came to indicate the cultural, intellectual, and technological level of a society" (Thorne, p. 239).

Whether gender driven, as Senderens implies, or a matter of historical temperament, the cooking process became more complex and varied because of the invention of pottery at least ten thousand years ago. Furthermore, the word "pot," contrary to popular belief, does not seem to reflect the Latin potare (to drink) or be related to the Spanish olla or Italian pentolone or marmitta—the words for large cooking vessels. Etymologically, "pot" can be traced to Celtic origins: Irish pota; Gaelic poit; and Welsh pot, and there is reason to believe that the word "pot" may have developed initially in northern lands.

Traditionally, boiled dinners and one-pot cooking seemed to be a congenial way of dining in cold climates. From broth-based fondues in Switzerland to the soup kettle that used to hang over the open hearth in the old farmhouses of Japan's snow country, variations on sustaining one-pot meals can be found in almost every ethnic cuisine, including the Italian bollito misto, Spanish cocido, and the French potee lorraine. The cold regions of China had a communal dish known in the West as the Mongolian hot pot, named for its distinctive cooking utensil, and a popular contemporary Japanese modification is called shabu-shabu.

Asian cooking also has a communal one-pot meal, called nabemono, literally "things in a pot," which is served at home and in restaurants. Diners do their own cooking, choosing whatever meat, poultry, fish, and vegetables they like from platters overflowing with raw ingredients that they cook over a communal pot of sizzling broth. The broth is continually enriched in flavor as the ingredients are dipped into it. Although the donabe, an earthenware casserole with thick pottery walls and distinctive shape, requires a portable and substantial heat source to maintain the temperature of the dipping broth, everything from gas rings to an alcohol or canned-heat burner can be used effectively during the traditional lengthy meal.

Pot-au-feu, or "pot on the fire," consisting of meat, poultry, and vegetables in their cooking liquid, has also been a fixture of French gastronomy since the Middle Ages, and it was dramatized by King Henri IV, who promised his subjects a chicken in their pot every Sunday. In some French cookbooks a distinction is sometimes made between a pot-au-feu, a boiled beef and vegetable dinner; and a poule-au-pot, in which a whole stewing hen was used; and a potée or mixed pot of ingredients, including pork and veal shoulder and various sausages. Used in every French household, the tall earthenware cylindrical pots known as marmites were the ideal cooking utensils for this meal of meat, poultry, and vegetables, which was brought to a boil in water and then simmered for hours over the fire. A good consommé was thereby produced and a full-course dinner served—clear broth first, the boiled meat and vegetables presented separately. A dish called petite marmite was almost identical with pot-au-feu except that its primary purpose was to be served and eaten all together.

By the time Pierre François de la Varenne's cookbook was published in 1651, the fine broth that hours of simmering had produced in these one-pot meals had an intrinsic value, and separate recipes for bouillon began to appear for the purpose of enhancing soups and entrees. As did medieval cooks before him, La Varenne kept in reserve one meat stock and one fish stock to make a roux, flavor a soup or stew, and combine with other ingredients for a sauce.

On the other side of the Atlantic, boiled dinners have always been popular in New England, Pennsylvania, and other parts of the country. Prepared like a pot-au-feu, the New England boiled dinner is made traditionally with either corned or fresh beef, and boiled beets on the side, while other sections of the country feature an Irish boiled dinner that includes cabbage, onions, and new potatoes simmered with the corned beef. Boiled crab dinner, the signature seafood dish of the Chesapeake Bay region, consists of blue crabs placed into seasoned boiling water, cooked, cracked open, and accompanied by melted butter. And Wisconsin boasts a famous Door County white-fish boil.

Among the nutrition conscious, there is growing concern about whether cooking, especially the lengthened cooking of boiling, robs foods of their vitamins and enzymes. The cult of raw food, for instance, has rapidly gained momentum. For such adherents, 116°F is the point beyond which components of the original human diet become "dead," unhealthy victuals. But nutritionists generally come down on the side of cooked food, both to rid ingredients like mushrooms and meats of toxins and to enhance the pleasures of the table. Boiling and its related moist heat cooking techniques, therefore, are worthy of mastering and a challenge to the cook.

Bibliography

Child, Julia. From Julia Child's Kitchen. New York: Knopf, 1975.

Corriher, Shirley O. Cookwise: The Hows and Whys of Successful Cooking. New York: William Morrow, 1997.

Culinary Institute of America. The New Professional Chef. Edited by Linda Glick Conway. New York: Van Nostrand Reinhold, 1991.

Farmer, Fannie Merritt. The Original Boston Cooking-School Cook Book. New York: New American Library, 1988. The original edition was published in 1896.

McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribners, 1984.

Peterson, James. The Essentials of Cooking. New York: Artisan, 1999.

Thorne, John, with Matt Lewis Thorne. Pot on the Fire: Further Exploits of a Renegade Cook. New York: North Point, 2000.

Tsuji, Shizuo. Japanese Cooking: A Simple Art. Tokyo: Kodansha International, 1980.

—Joan Reardon

Bringing to the boil.

• b. fowl — a mature hen of about 2 years of age, suitable for eating but requires prolonged cooking.
• b. test — meat that has a taint or which is beginning to decompose can have its bad odor intensified, for the purpose of convincing the doubters, by boiling a sample of it. Meat that is less than 24 hours old does not perform well in this test.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2009)

Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure. While below the boiling point a liquid evaporates from its surface, at the boiling point vapor bubbles come from the bulk of the liquid. For this to be possible, the vapor pressure must be sufficiently high to win the atmospheric pressure, so that the bubbles can be "inflated". Thus, the difference between evaporation and boiling is "mechanical", rather than thermodynamical. The boiling point is lowered when the pressure of the surrounding atmosphere is reduced, for example by the use of a vacuum pump or at high altitudes. Boiling occurs in three characteristic stages, which are nucleate, transition and film boiling. These stages generally take place from low to high heating surface temperatures, respectively.

Contents 1 Nucleate boiling 2 Transition boiling 3 Film boiling 4 Applications 4.1 Distillation 4.2 Boiling for water sterilization 4.3 Boiling in cooking 4.3.1 Levels of boiling 5 See also 6 References

Nucleate boiling

Nucleate boiling is characterized by the growth of bubbles or pops on a heated surface, which rise from discrete points on a surface, whose temperature is only slightly above the liquid’s. In general, the number of nucleation sites are increased by an increasing surface temperature.

An irregular surface of the boiling vessel (i.e. increased surface roughness) can create additional nucleation sites, while an exceptionally smooth surface, such as plastic, lends itself to superheating. Under these conditions, a heated liquid may show boiling delay and the temperature may go somewhat above the boiling point without boiling.

Transition boiling

Transition boiling may be defined as the unstable boiling, which occurs at surface temperatures between the maximum attainable in nucleate and the minimum attainable in film boiling.

The formation of bubbles in a heated liquid is a complex physical process which often involves cavitation and acoustic effects, such as the broad-spectrum hiss one hears in a kettle not yet heated to the point where bubbles boil to the surface.

Film boiling

Main article: Leidenfrost effect

If a surface heating the liquid is significantly hotter than the liquid then film boiling will occur, where a thin layer of vapor, which has low thermal conductivity, insulates the surface. This condition of a vapor film insulating the surface from the liquid characterizes film boiling.

Applications

Distillation

In distillation, boiling is used in separating mixtures. This is possible because the vapor rising from a boiling fluid generally has a ratio of components different from that in the liquid.

Boiling for water sterilization

Boiling can be used as a method of water disinfection but is only advocated as an emergency water treatment method, or as a method of portable water purification in rural or wilderness settings without access to a potable water infrastructure. Bringing water to the boil is effective in killing or inactivating most bacteria, viruses and pathogens. Boiling is the most certain way of killing nearly all microorganisms. According to the Wilderness Medical Society^[1], water temperatures above 160°F (70°C) kill all pathogens within 30 minutes and above 185°F (85°C) within a few minutes. So in the time it takes for the water to reach the boiling point (212°F or 100°C) from 160°F (70°C), all pathogens will be killed, even at high altitude. To be extra safe, let the water boil rapidly for one minute, especially at higher altitudes since water boils at a lower temperature.^[1]

There are 100 degrees between water freezing point and boiling point, thus the initial name centigrade, later replaced by the name Celsius (°C).

Boiling in cooking

Transition boiling of water

In cooking, boiling is the method of cooking food in boiling water, or other water-based liquid such as stock or milk. Simmering is gentle boiling, while in poaching the cooking liquid moves but scarcely bubbles.

Boiling is a very harsh technique of cooking. Delicate foods such as fish cannot be cooked in this fashion because the bubbles can damage the food. Foods such as red meat, chicken, and root vegetables can be cooked with this technique because of their tough texture.

The boiling point of water is typically considered to be 100 °C or 212 °F. Pressure and a change in composition of the liquid may alter the boiling point of the liquid. For this reason, high elevation cooking generally takes longer since boiling point is a function of atmospheric pressure. In Denver, Colorado, which is at an elevation of about one mile, water boils at approximately 95 °C.^[2] Depending on the type of food and the elevation, the boiling water may not be hot enough to cook the food properly. Similarly, increasing the pressure as in a pressure cooker raises the temperature of the contents above the open air boiling point.

Adding a water soluble substance, such as salt or sugar also increases the boiling point. This is called boiling-point elevation. At palatable concentrations of salt, the effect is very small, and the boiling point elevation is difficult to notice. However, while making thick sugar syrup, such as for Gulab Jamun, one will notice boiling point elevation. Due to variations in composition and pressure, the boiling point of water is almost never exactly 100 °C, but rather close enough for cooking.

Bringing water to a boil is generally done by applying maximal heat, then shutting off when the water has come to a boil, which is known as bang–bang control. Keeping water at or below a boil requires more careful control of temperature, particularly by using feedback.

In places where the available water supply is contaminated with disease-causing bacteria, boiling water and allowing it to cool before drinking it is practiced as a valuable health measure. Boiling is the most certain way of killing all microorganisms in emergency situations.

Foods suitable for boiling include vegetables, starchy foods such as rice, noodles and potatoes, eggs, meats, sauces, stocks and soups.

Boiling has several advantages. It is safe and simple, and it is appropriate for large-scale cookery. Older, tougher, cheaper cuts of meat and poultry can be made digestible. Nutritious, well flavoured stock is produced. Also, maximum color and nutritive value is retained when cooking green vegetables, provided boiling time is kept to the minimum.

On the other hand, there are several disadvantages. There is a loss of soluble vitamins from foods to the water (if the water is discarded), and some boiled foods can look unattractive. Boiling can also be a slow method of cooking food.

Boiling can be done in several ways: The food can be placed into already rapidly boiling water and left to cook, the heat can be turned down and the food can be simmered; or the food can also be placed into the pot, and cold water may be added to the pot. This may then be boiled until the food is satisfactory.

Water on the outside of a pot, i.e. a wet pot, increases the time it takes the pot of water to boil. The pot will heat at a normal rate once all excess water on the outside of the pot evaporates.

Levels of boiling

In Chinese cuisine, particularly tea brewing, one distinguishes five stages of boiling:^[3] "shrimp eyes, the first tiny bubbles that start to appear on the surface of the kettle water, crab eyes, the secondary, larger bubbles, then fish eyes, followed by rope of pearls, and finally raging torrent [rolling boil]".

In detail:^[4]

shrimp eyes

about 70-80 °C (155–175 °F) – separate bubbles, rising to top

crab eyes

about 80 °C (175 °F) – streams of bubbles

fish eyes

about 80-90 °C (175–195 °F) – larger bubbles

rope of pearls

about 90-95 °C (195–205 °F) – steady streams of large bubbles

raging torrent

rolling boil, swirling and roiling

See also

Look up boiling in Wiktionary, the free dictionary.

Wikibooks Cookbook has a recipe/module on Boiling

• Nucleate boiling
• Phase diagram
• Phase transition
• Boiling point

References

1. ^ ^{a b} OA Guide to Water Purification, The Backpacker's Field Manual, by Rick Curtis, first edition published by Random House March, 1998
2. ^ IAPWS. "What is the effect of pressure on the boiling of water? Why does water boil at a lower temperature at high altitudes?". FAQs About Water and Steam. http://www.iapws.org/faq1/boil.htm. Retrieved 2009-12-05. 
3. ^ James Norwood Pratt, The New Tea Lover's Treasury
4. ^ Boiling Water for Tea: Bubbles and Steam, by Bliss Dake, October 13th, 2009, Mighty Leaf Tea blog

v t e Cooking techniques Dry Conduction Dry roasting Hot salt frying Hot sand frying Searing Convection Baking Roasting (modern) Smoking Radiation Gridironing Grilling (charbroiling) Roasting (traditional) Rotisserie Toasting Wet High heat Blanching Boiling Decoction Parboiling Low heat Coddling Creaming Infusion Poaching Simmering Slow cooker Sous-vide Steeping Stewing Indirect heat Bain-marie Double boiling Double steaming Steaming Fat-based High heat Blackening Browning Frying Deep frying Pan frying Shallow frying Stir frying (bao) Sautéing Low heat Gentle frying Sweating Mixed medium Barbecuing Braising Griddling Stir frying (chao) Device-based Clay pot cooking Earth oven Masonry oven/Tandoor Microwaving Pressure cooking Pressure frying Vacuum flask/Haybox cooking Non-heat Curing Fermentation Pickling Souring See also Food preparation Food preservation Food safety

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Dansk (Danish)
adj. - kogende
n. - kogning

Nederlands (Dutch)
kokend, kokend heet

Français (French)
adj. - bouillant, furieux, (Culin) pour pot-au-feu
n. - ébullition, bouillonnement
adv. - tout bouillant, en rage

Deutsch (German)
adj. - kochend , siedend, wutschäumend
n. - Kochen, Gekochte
adv. - sehr

Ελληνική (Greek)
adj., -
adv. - ζεματιστός, καυτός

Italiano (Italian)
ebollizione, bollente, furibondo

Português (Portuguese)
adj. - fervente
adv. - muito

Русский (Russian)
кипение, кипячение, варка, кипящий

Español (Spanish)
adj. - hirviendo, hirviente
n. - ebullición, punto de ebullición
adv. - hirviendo, hirviente

Svenska (Swedish)
adv. - kokande, sjudande
adj. - brännhet

中文（简体）(Chinese (Simplified))
沸腾的, 激昂的, 煮沸, 起泡, 沸腾

中文（繁體）(Chinese (Traditional))
adj. - 沸騰的, 激昂的
n. - 煮沸, 起泡, 沸騰

한국어 (Korean)
adj. - 끓는, 격분하고 있는
n. - 끓음, 삶음

日本語 (Japanese)
adj. - 煮え立つ, 沸き返るような
adv. - 沸き立つほどに
n. - 沸騰, 一回分の煮物

العربيه (Arabic)
‏(ظرف) شديد, كثيف (صفه) يغلي‏

עברית (Hebrew)
adj. - ‮של רתיחה, רותח, חם מאד‬
n. - ‮רתיחה, שליקה‬

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