Leavening Acid

Time of Reaction Time of Reaction

Cream of tartar, tartaric acid

Immediately, during mixing Immediately, during mixing

Monocalcium phosphate (MCP)

Immediately, during mixing Immediately, during mixing

Sodium aluminum pyrophosphate (SAPP)

Slow release after mixing Slow release after mixing

Sodium aluminum sulfate (SAS)

Slow release and heat-activated Slow release and heat-activated

Sodium aluminum phosphate (SALP)

Heat-activated, early in cooking (100104F/3840C) Heat-activated, early in cooking (100104F/3840C)

Dimagnesium phosphate (DMP)

Heat-activated, early in cooking (104111F/4044C) Heat-activated, early in cooking (104111F/4044C)

Dicalcium phosphate dihydrate (DCPD)

Heat-activated, late in cooking (135140F/5760C) Heat-activated, late in cooking (135140F/5760C)

Baking Soda The most common alkaline component of chemical leavenings is sodium bicarbonate (or sodium acid carbonate, NaHCO The most common alkaline component of chemical leavenings is sodium bicarbonate (or sodium acid carbonate, NaHCO3), usually called baking soda.

Baking soda can be the sole added leavening if the dough or batter contains acids to react with it. Common acid ingredients include sourdough cultures, fermented milks (b.u.t.termilk, yogurt), brown sugar and mola.s.ses, chocolate, and cocoa (if not dutched, p. 705), as well as fruit juices and vinegar. A general rule of thumb: teaspoon/2 gm baking soda is neutralized by 1 cup/240 ml of fermented milk, or 1 teaspoon/5ml of lemon juice or vinegar, or teaspoons/5 gm cream of tartar.

Baking Powders Baking powders are complete leavening systems: they contain both alkaline baking soda and an acid in the form of solid crystals. (The active ingredients are mixed with ground dry starch, which prevents premature reactions in humid air by absorbing moisture, and gives the powder more bulk so that it's easier to measure.) When added to liquid ingredients, the baking soda dissolves almost immediately. If the acid is very soluble, it too will dissolve quickly during mixing and react with the soda to inflate an initial set of gas bubbles. Cream of tartar, for example, releases two-thirds of its leavening potential during two minutes of mixing. If the acid is Baking powders are complete leavening systems: they contain both alkaline baking soda and an acid in the form of solid crystals. (The active ingredients are mixed with ground dry starch, which prevents premature reactions in humid air by absorbing moisture, and gives the powder more bulk so that it's easier to measure.) When added to liquid ingredients, the baking soda dissolves almost immediately. If the acid is very soluble, it too will dissolve quickly during mixing and react with the soda to inflate an initial set of gas bubbles. Cream of tartar, for example, releases two-thirds of its leavening potential during two minutes of mixing. If the acid is not not very soluble, then it will remain in crystal form for a characteristic length of time, or until cooking raises the temperature high enough to dissolve it - and then it reacts with the soda to produce a delayed burst of gas. There are several different acids used in baking powders, each with a different pattern of gas production (see box, p. 533). very soluble, then it will remain in crystal form for a characteristic length of time, or until cooking raises the temperature high enough to dissolve it - and then it reacts with the soda to produce a delayed burst of gas. There are several different acids used in baking powders, each with a different pattern of gas production (see box, p. 533).

Most supermarket baking powders are "double-acting"; that is, they inflate an initial set of gas bubbles upon mixing the powder into the batter, and then a second set during the baking process. Baking powders for restaurant and manufacturing production contain slow-release acids so that leavening power doesn't dissipate while the batter sits before being cooked.

Chemical leavenings can have adverse effects on both flavor and color. Some leavening acids have a distinctly astringent taste (sulfates, pyrophosphates). When acid and base are properly matched, neither is left behind in excess. But when too much soda is added, or when the batter is poorly mixed and not all the powder dissolves, a bitter, soapy, or "chemical" flavor results. Colors are also affected in even slightly alkaline conditions: browning reactions are enhanced, chocolate turns reddish, and blueberries turn green.

Breads There are four basic steps in the making of yeast bread. We mix together the flour, water, yeast, and salt; we knead the mixture to develop the gluten network; we give the yeast time to produce carbon dioxide and fill the dough with gas cells; and we bake the dough to set its structure and generate flavor. In practice, each step involves choices that affect the qualities of the finished loaf. There are many ways to make basic bread! The following paragraphs explain some of the more significant choices and their effects. Breads made with special ingredients or methods - sourdoughs, sweet breads, flatbreads - are described later.

The Choice of Ingredients Bread making begins with the ingredients, especially the flour and the yeasts. Because proportions are important, and the weight of a given volume of flour can vary by as much as 50% depending on whether it has been fluffed up (sifted) or packed down, it's best to weigh ingredients rather than measure them in cups.

Flour The texture and flavor of bread are strongly influenced by the kind of flour used. "Bread flours" are milled from high-protein wheats, require a long kneading period to develop their strong gluten, and produce well-raised loaves with a distinctive, slightly eggy flavor and chewy texture. Lower-protein "all-purpose" flours give breads with a lower maximum volume, more neutral flavor, and less chewy texture, while flours from soft wheats with weak gluten proteins make denser loaves with a tender, cake-like crumb. The more of the outer aleurone, bran, and germ that makes it into the flour, the darker and denser the bread and the stronger the whole-grain flavor. The baker can mix different flours to obtain a particular character. Many artisan breadmakers prefer flours with a moderate protein content, 1112%, and an extraction rate somewhere between standard white and whole wheat flours. The texture and flavor of bread are strongly influenced by the kind of flour used. "Bread flours" are milled from high-protein wheats, require a long kneading period to develop their strong gluten, and produce well-raised loaves with a distinctive, slightly eggy flavor and chewy texture. Lower-protein "all-purpose" flours give breads with a lower maximum volume, more neutral flavor, and less chewy texture, while flours from soft wheats with weak gluten proteins make denser loaves with a tender, cake-like crumb. The more of the outer aleurone, bran, and germ that makes it into the flour, the darker and denser the bread and the stronger the whole-grain flavor. The baker can mix different flours to obtain a particular character. Many artisan breadmakers prefer flours with a moderate protein content, 1112%, and an extraction rate somewhere between standard white and whole wheat flours.

Water The chemical composition of the water used to make the dough influences the dough's qualities. Distinctly acid water weakens the gluten network, while a somewhat alkaline water strengthens it. Hard water will produce a firmer dough thanks to the cross-linking effects of calcium and magnesium. The proportion of water also influences dough consistency. The standard proportion for a firm bread dough capable of good aeration is 65 parts water to 100 parts all-purpose flour by weight (40% of the combined weight). Less water will produce a firmer, less extensible dough and a denser loaf, while more water produces a soft, less elastic dough and an open-textured loaf. Wet doughs that are barely kneadable - for example the Italian The chemical composition of the water used to make the dough influences the dough's qualities. Distinctly acid water weakens the gluten network, while a somewhat alkaline water strengthens it. Hard water will produce a firmer dough thanks to the cross-linking effects of calcium and magnesium. The proportion of water also influences dough consistency. The standard proportion for a firm bread dough capable of good aeration is 65 parts water to 100 parts all-purpose flour by weight (40% of the combined weight). Less water will produce a firmer, less extensible dough and a denser loaf, while more water produces a soft, less elastic dough and an open-textured loaf. Wet doughs that are barely kneadable - for example the Italian cia-batta cia-batta - may be 80 parts water or more per 100 flour (45%). High-protein flours absorb as much as a third more water than all-purpose flours, so water proportions and corresponding textures also depend on the nature of the flour used. - may be 80 parts water or more per 100 flour (45%). High-protein flours absorb as much as a third more water than all-purpose flours, so water proportions and corresponding textures also depend on the nature of the flour used.

Salt Though some traditional breads are made without salt, most include it, and not just for a balanced taste. At 1.52% of the flour weight, salt tightens the gluten network and improves the volume of the finished loaf. (The tightening is especially evident in the autolyse mixing method, below.) Unrefined sea salts that contain calcium and magnesium impurities may produce the additional gluten strengthening that mineral-rich hard water does. In sourdoughs, salt also helps limit the protein-digesting activity of the souring bacteria, which can otherwise damage the gluten. Though some traditional breads are made without salt, most include it, and not just for a balanced taste. At 1.52% of the flour weight, salt tightens the gluten network and improves the volume of the finished loaf. (The tightening is especially evident in the autolyse mixing method, below.) Unrefined sea salts that contain calcium and magnesium impurities may produce the additional gluten strengthening that mineral-rich hard water does. In sourdoughs, salt also helps limit the protein-digesting activity of the souring bacteria, which can otherwise damage the gluten.

Yeast The baker can incorporate yeast in very different forms and proportions. For a simple dough to be fully leavened and baked in a few hours, the standard proportion for cake yeast is 0.54% of the flour weight, or 2.520 gm per pound/500 gm flour; for dried yeast, approximately half these numbers. If the dough is to be fermented slowly overnight, only 0.25% of flour weight, barely a gram per pound/500 gm is needed. (One gram still contains millions of yeast cells.) As a general rule, the less prepared yeast goes into the dough, and the longer dough is allowed to rise, the better the flavor of the finished bread. This is because the concentrated yeast has its own somewhat harsh flavor, and because the process of fermentation generates a variety of desirable flavor compounds (p. 543). The baker can incorporate yeast in very different forms and proportions. For a simple dough to be fully leavened and baked in a few hours, the standard proportion for cake yeast is 0.54% of the flour weight, or 2.520 gm per pound/500 gm flour; for dried yeast, approximately half these numbers. If the dough is to be fermented slowly overnight, only 0.25% of flour weight, barely a gram per pound/500 gm is needed. (One gram still contains millions of yeast cells.) As a general rule, the less prepared yeast goes into the dough, and the longer dough is allowed to rise, the better the flavor of the finished bread. This is because the concentrated yeast has its own somewhat harsh flavor, and because the process of fermentation generates a variety of desirable flavor compounds (p. 543).

Durum BreadsDurum wheat flour forms an inelastic dough that doesn't rise well, but has nevertheless been used to make dense, distinctively flavored, golden breads in the Mediterranean region for thousands of years. Durum flour absorbs nearly 50% more water than bread flour does, a fact that is part of the reason for the longer shelf life of durum bread.

Starters A general method for incorporating yeast into bread dough that maximizes the effective fermentation time and flavor production is the use of A general method for incorporating yeast into bread dough that maximizes the effective fermentation time and flavor production is the use of pre-ferments pre-ferments or or starters, starters, portions of already fermenting dough or batter that are added to the new ma.s.s of flour and water. The starter may be a piece of dough saved from the previous batch, or a stiff dough or runny batter made up with a small amount of fresh yeast and allowed to ferment for some hours, or a culture of "wild" yeasts and bacteria obtained without any commercial yeast at all. This last is called a "sourdough" starter because it includes large numbers of acid-forming bacteria. Starters go by many names - French portions of already fermenting dough or batter that are added to the new ma.s.s of flour and water. The starter may be a piece of dough saved from the previous batch, or a stiff dough or runny batter made up with a small amount of fresh yeast and allowed to ferment for some hours, or a culture of "wild" yeasts and bacteria obtained without any commercial yeast at all. This last is called a "sourdough" starter because it includes large numbers of acid-forming bacteria. Starters go by many names - French poolish, poolish, Italian Italian biga, biga, Belgian Belgian desem, desem, English English sponge sponge - and develop different qualities that depend on ingredient proportions, fermentation times and temperatures, and other details of their making. Sourdough breads are described on p. 544. - and develop different qualities that depend on ingredient proportions, fermentation times and temperatures, and other details of their making. Sourdough breads are described on p. 544.

Preparing The Dough: Mixing and Kneading Mixing The first step in making bread is to mix the ingredients together. The moment flour meets water, several processes begin. Broken starch granules absorb water, and enzymes digest their exposed starch into sugars. The yeast cells feed on the sugars, producing carbon dioxide and alcohol. The glutenin proteins absorb some water and sprawl out into their elongated coils; the coils of neighboring molecules form many weak bonds with each other and thus form the first strands of gluten. We see the dough take on a vaguely fibrous appearance, and feel it cohere to itself. When it's stirred with a spoon, the protein aggregates are drawn together into visible filaments and form what has been vividly described as a "s.h.a.ggy ma.s.s." At the same time, a number of substances in the flour cause breaks in and blocking of the end-to-end bonds of the gluten molecules, and so an initial shortening of the gluten chains. As oxygen from the air and oxidizing compounds from the yeasts enter the dough, the breaking and blocking stop, and the gluten molecules begin to bond end-to-end and form long chains. The first step in making bread is to mix the ingredients together. The moment flour meets water, several processes begin. Broken starch granules absorb water, and enzymes digest their exposed starch into sugars. The yeast cells feed on the sugars, producing carbon dioxide and alcohol. The glutenin proteins absorb some water and sprawl out into their elongated coils; the coils of neighboring molecules form many weak bonds with each other and thus form the first strands of gluten. We see the dough take on a vaguely fibrous appearance, and feel it cohere to itself. When it's stirred with a spoon, the protein aggregates are drawn together into visible filaments and form what has been vividly described as a "s.h.a.ggy ma.s.s." At the same time, a number of substances in the flour cause breaks in and blocking of the end-to-end bonds of the gluten molecules, and so an initial shortening of the gluten chains. As oxygen from the air and oxidizing compounds from the yeasts enter the dough, the breaking and blocking stop, and the gluten molecules begin to bond end-to-end and form long chains.

Mixing can be done by hand, in a stand mixer, or in a food processor. The processor works in less than a minute, a fraction of the time required for hand or mixer kneading, and therefore offers the advantage of minimizing exposure to air and oxygen, an excess of which bleaches the remaining wheat pigments and alters flavor. The high energy input heats the dough, which should be allowed to cool before fermentation.

Two-Stage Mixing: AutolysisAn alternative to mixing all the dough ingredients at once is the autolyse autolyse or "autolysis" method championed by a legendary French bread authority, Raymond Calvel, to compensate for some of the disadvantages of rapid industrial production. It has also been adopted by many artisan bakers. Autolysis involves combining only the flour and water and letting them sit for 1530 minutes before adding the leavening and salt. According to Calvel, this initial preparation gives the starch and the gluten proteins a chance to absorb as much water as possible without the interference of salt, and allows the gluten chains to shorten more ( or "autolysis" method championed by a legendary French bread authority, Raymond Calvel, to compensate for some of the disadvantages of rapid industrial production. It has also been adopted by many artisan bakers. Autolysis involves combining only the flour and water and letting them sit for 1530 minutes before adding the leavening and salt. According to Calvel, this initial preparation gives the starch and the gluten proteins a chance to absorb as much water as possible without the interference of salt, and allows the gluten chains to shorten more (autolysis means "self-digestion"). The result is a dough that's easier to manipulate, requires less kneading and therefore less exposure to oxygen, and so better retains the wheat's light golden color and characteristic taste. means "self-digestion"). The result is a dough that's easier to manipulate, requires less kneading and therefore less exposure to oxygen, and so better retains the wheat's light golden color and characteristic taste.

Dough Development: Kneading Once the ingredients have been mixed and the dough is formed, the process of dough development begins. Whether the dough is kneaded by hand or in an electrical mixer, it undergoes a similar kind of physical manipulation: it is stretched, folded over, compressed, stretched, folded, and compressed many times. This manipulation strengthens the gluten network. It unfolds the proteins further, orients them side by side and encourages the development of many weak bonds between neighbors. The glutenin molecules also form strong end-to-end bonds with each other and thus a cohering network of extensive gluten chains. The dough gradually gets stiff, harder to manipulate, and takes on a fine, satiny appearance. (If the dough is worked so hard that many end-to-end bonds start breaking, its overall structure breaks down, and the dough becomes sticky and inelastic. Overdevelopment is a real problem only when kneading is done mechanically.) Once the ingredients have been mixed and the dough is formed, the process of dough development begins. Whether the dough is kneaded by hand or in an electrical mixer, it undergoes a similar kind of physical manipulation: it is stretched, folded over, compressed, stretched, folded, and compressed many times. This manipulation strengthens the gluten network. It unfolds the proteins further, orients them side by side and encourages the development of many weak bonds between neighbors. The glutenin molecules also form strong end-to-end bonds with each other and thus a cohering network of extensive gluten chains. The dough gradually gets stiff, harder to manipulate, and takes on a fine, satiny appearance. (If the dough is worked so hard that many end-to-end bonds start breaking, its overall structure breaks down, and the dough becomes sticky and inelastic. Overdevelopment is a real problem only when kneading is done mechanically.) Gluten formation. The view of wetted flour through a light microscope. Left: Left: When water is first added to flour, the gluten proteins are randomly oriented in a thick fluid. When water is first added to flour, the gluten proteins are randomly oriented in a thick fluid. Right: Right: As this fluid is stirred, it quickly develops into a tangle of fibers as the glutenin proteins form elongated bundles of molecules. As this fluid is stirred, it quickly develops into a tangle of fibers as the glutenin proteins form elongated bundles of molecules.

Gluten orientation. When flour is initially mixed with water, the glutenin molecules form a random network of gluten chains. Kneading helps orient the gluten chains in orderly arrays.

Kneading dough. Kneading repeatedly stretches and elongates the gluten, helping to orient the long chains and encourage the side-by-side bonding that contributes to gluten strength.

Kneading also aerates the dough. As it's repeatedly folded over and compressed, pockets of air are trapped and squeezed under pressure into smaller, more numerous pockets. The more pockets formed during kneading, the finer the texture of the final bread. Most of the air pockets are incorporated as the dough reaches its maximum stiffness.

Some bread recipes call for a bare minimum of kneading. This generally results in fewer and larger air cells, and so a coa.r.s.e, irregular texture that has its own appeal. The gluten of such doughs is less developed as they begin fermentation, but the rising of the dough continues to develop gluten structure (below), so little-kneaded doughs can eventually rise well to give an airy, tender crumb.

Fermentation, or Rising Fermentation is the stage during which the dough is set aside for the yeast cells to produce carbon dioxide, which diffuses into the air pockets, slowly inflates them, and thus raises the dough. This gentle stretching action continues the process of gluten orientation and development, as does the oxidizing effect of other yeast by-products, which continue to help the glutenin molecules to link up end-to-end. As a result, even initially wet, barely cohesive doughs become more manageable after fermentation.

Yeasts produce carbon dioxide most rapidly at around 95F/35C, but they also produce more noticeable quant.i.ties of sour and unpleasant-smelling by-products. A fermentation temperature of 80F/27C is often suggested for a relatively quick rising time of a couple of hours. Lower temperatures may extend fermentation times by an hour or more, and with them the generation of desirable yeast flavors.

The end of the fermentation period is signaled by the dough's volume - it approximately doubles - and by the condition of the gluten matrix. When poked with the finger, fully fermented dough will retain the impression and won't spring back: the gluten has been stretched to the limit of its elasticity. The dough is now gently handled to reconsolidate the gluten, divide the gas pockets, redistribute the yeast cells and their food supply, and even out the temperature and moisture (fermentation generates heat, water, and alcohol). Thanks to the added moisture and to the gluten-interrupting bubbles, fermented doughs feel softer and easier to work than newly kneaded dough.

Food Words: Knead KneadThe word knead knead comes from an Indo-European root meaning "to compress into a ball"; related words are comes from an Indo-European root meaning "to compress into a ball"; related words are gnocchi, quenelle, knoll, gnocchi, quenelle, knoll, and and knuckle. knuckle.

Doughs made from high-protein flours may be put through a second rising to develop their tougher gluten fully. Either way, the fermented dough is then divided, gently rounded into b.a.l.l.s, rested for a few minutes to allow the gluten to relax somewhat, and then molded into loaves. The loaves are then allowed another partial rise, or "proof," to prepare them for the final and dramatic rise during baking.

r.e.t.a.r.ding the Fermentation Traditional breadmaking can last many hours, and bakers would often have to work through the night in order to sell fresh bread in the morning. In the 1920s, bakers in Vienna began to experiment with breaking the work into two periods, a daytime stint for mixing, fermentation, and molding into loaves, and then an early-morning baking. During the night, the formed loaves were kept in a refrigerated chamber. Cool temperatures slow the activity of microbes substantially; yeasts take 10 times longer to raise bread in the refrigerator than at warm room temperature. Refrigeration of dough is therefore called Traditional breadmaking can last many hours, and bakers would often have to work through the night in order to sell fresh bread in the morning. In the 1920s, bakers in Vienna began to experiment with breaking the work into two periods, a daytime stint for mixing, fermentation, and molding into loaves, and then an early-morning baking. During the night, the formed loaves were kept in a refrigerated chamber. Cool temperatures slow the activity of microbes substantially; yeasts take 10 times longer to raise bread in the refrigerator than at warm room temperature. Refrigeration of dough is therefore called r.e.t.a.r.ding, r.e.t.a.r.ding, and the cold chamber a and the cold chamber a r.e.t.a.r.der. r.e.t.a.r.der. r.e.t.a.r.ding is now a common practice. r.e.t.a.r.ding is now a common practice.

In addition to giving the baker greater flexibility, r.e.t.a.r.ding has useful effects on the dough. Long, slow fermentation allows both yeasts and bacteria more time to generate flavor compounds. Cold dough is stiffer than warm dough, so it's easier to handle without causing a loss of leavening gas. And the cycle of cooling and rewarming redistributes the dough gases (from small bubbles into the water phase, then back out into larger bubbles), and encourages the development of a more open, irregular crumb structure.

Baking Ovens, Baking Temperatures, and Steam The kind of oven in which bread is baked has an important influence on the qualities of the finished loaf. The kind of oven in which bread is baked has an important influence on the qualities of the finished loaf.

Traditional Bread Ovens Until the middle of the 19th century, bread was baked in clay, stone, or brick ovens that were preheated by a wood fire, and that could store a large amount of heat energy. The baker started the fire on the floor of the oven, let it burn for hours, cleaned out the ashes, and then introduced the loaves of dough and closed the oven door. The oven surfaces start out at 700900F/350450C, the domed roof radiating its stored heat from above, the floor conducting heat directly into the loaves from beneath. As the dough heats it releases steam, which fills the closed chamber and further speeds the transfer of heat to the loaves. Slowly the oven surfaces lose their heat, and the temperature declines during the bake, at the same time that the loaf is browning and therefore becoming more efficient at absorbing heat. The result is a rapid initial heating that encourages the dough to expand, and temperatures high enough to dry the crust well and generate the color and flavors of the browning reactions (p. 778). Until the middle of the 19th century, bread was baked in clay, stone, or brick ovens that were preheated by a wood fire, and that could store a large amount of heat energy. The baker started the fire on the floor of the oven, let it burn for hours, cleaned out the ashes, and then introduced the loaves of dough and closed the oven door. The oven surfaces start out at 700900F/350450C, the domed roof radiating its stored heat from above, the floor conducting heat directly into the loaves from beneath. As the dough heats it releases steam, which fills the closed chamber and further speeds the transfer of heat to the loaves. Slowly the oven surfaces lose their heat, and the temperature declines during the bake, at the same time that the loaf is browning and therefore becoming more efficient at absorbing heat. The result is a rapid initial heating that encourages the dough to expand, and temperatures high enough to dry the crust well and generate the color and flavors of the browning reactions (p. 778).

Modern Metal Ovens The modern metal oven is certainly easier to bake in than the wood-fired oven, but it isn't as ideally suited to breadmaking. It usually has a maximum cooking temperature of 500F/250C. And its thin walls are incapable of storing much heat, so its temperature is maintained by means of gas flames or electrical elements that get red-hot. When these heat sources switch on during baking, the effective temperature temporarily rises well above the target baking temperature, and the bread can be scorched. Because they are vented to allow the escape of combustion gases (carbon dioxide and water), gas ovens don't retain the loaves' steam well during the important early stage. Electric ovens do a better job. Some of the advantages of the traditional stored-heat oven can be obtained from the use of ceramic baking stones or wraparound ceramic oven inserts, which are preheated to the oven's maximum temperature and provide more intensive and even heat during baking. The modern metal oven is certainly easier to bake in than the wood-fired oven, but it isn't as ideally suited to breadmaking. It usually has a maximum cooking temperature of 500F/250C. And its thin walls are incapable of storing much heat, so its temperature is maintained by means of gas flames or electrical elements that get red-hot. When these heat sources switch on during baking, the effective temperature temporarily rises well above the target baking temperature, and the bread can be scorched. Because they are vented to allow the escape of combustion gases (carbon dioxide and water), gas ovens don't retain the loaves' steam well during the important early stage. Electric ovens do a better job. Some of the advantages of the traditional stored-heat oven can be obtained from the use of ceramic baking stones or wraparound ceramic oven inserts, which are preheated to the oven's maximum temperature and provide more intensive and even heat during baking.

Steam Steam does several useful things during the first few minutes of baking. It greatly increases the rate of heat transfer from oven to dough. Without steam, the dough surface reaches 195F/90C in 4 minutes; with steam, in 1 minute. Steam thus causes a rapid expansion of the gas cells. As the steam condenses onto the dough surface, it forms a film of water that temporarily prevents the loaf surface from drying out into a crust, thus keeping it flexible and elastic so that it doesn't hinder the initial rapid expansion of the loaf, the "oven spring." The overall result is a larger, lighter loaf. In addition, the hot water film gelates starch at the loaf surface into a thin, transparent coating that later dries into an attractively glossy crust. Steam does several useful things during the first few minutes of baking. It greatly increases the rate of heat transfer from oven to dough. Without steam, the dough surface reaches 195F/90C in 4 minutes; with steam, in 1 minute. Steam thus causes a rapid expansion of the gas cells. As the steam condenses onto the dough surface, it forms a film of water that temporarily prevents the loaf surface from drying out into a crust, thus keeping it flexible and elastic so that it doesn't hinder the initial rapid expansion of the loaf, the "oven spring." The overall result is a larger, lighter loaf. In addition, the hot water film gelates starch at the loaf surface into a thin, transparent coating that later dries into an attractively glossy crust.

Professional bakers often inject steam under low pressure into the oven for the first several minutes of baking. In home ovens, spraying water or throwing ice cubes into the hot chamber can produce enough steam to improve the oven spring and crust gloss.

Early Baking: Oven Spring When the bread first enters the oven, heat moves into the bottom of the dough from the oven floor or pan, and into the top from the oven ceiling and the hot air. If steam is present, it provides an initial blast of heat by condensing onto the cold dough surface. Heat then moves from the surface through the dough by two means: slow conduction through the viscous gluten-starch matrix, and much more rapid steam movement through the network of gas bubbles. The better leavened the dough, the faster steam can move through it, and so the faster the loaf cooks. When the bread first enters the oven, heat moves into the bottom of the dough from the oven floor or pan, and into the top from the oven ceiling and the hot air. If steam is present, it provides an initial blast of heat by condensing onto the cold dough surface. Heat then moves from the surface through the dough by two means: slow conduction through the viscous gluten-starch matrix, and much more rapid steam movement through the network of gas bubbles. The better leavened the dough, the faster steam can move through it, and so the faster the loaf cooks.

As the dough heats up, it becomes more fluid, its gas cells expand, and the dough rises. The main cause of this oven spring is the vaporization of alcohol and water into gases that fill the gas cells, and that expand the dough by as much as half its initial volume. Oven spring is usually over after 68 minutes of baking.

Mid-Baking: From Foam to Sponge Oven spring stops when the crust becomes firm and stiff enough to resist it, and when the interior of the loaf reaches 155180F/6880C, the temperature range in which the gluten proteins form strong cross-links with each other and the starch granules absorb water, swell, gelate, and amylose molecules leak out of the granules. Now the walls of the gas cells can no longer stretch to accommodate the rising pressure inside, so the pressure builds and eventually ruptures the walls, turning the structure of the loaf from a closed network of separate gas cells into an open network of communicating pores: from an aggregation of little balloons into a sponge through which gases can easily pa.s.s. (If the dough were not transformed into a sponge, then cooling would cause each isolated gas cell to shrink, and the loaf would collapse.) Oven spring stops when the crust becomes firm and stiff enough to resist it, and when the interior of the loaf reaches 155180F/6880C, the temperature range in which the gluten proteins form strong cross-links with each other and the starch granules absorb water, swell, gelate, and amylose molecules leak out of the granules. Now the walls of the gas cells can no longer stretch to accommodate the rising pressure inside, so the pressure builds and eventually ruptures the walls, turning the structure of the loaf from a closed network of separate gas cells into an open network of communicating pores: from an aggregation of little balloons into a sponge through which gases can easily pa.s.s. (If the dough were not transformed into a sponge, then cooling would cause each isolated gas cell to shrink, and the loaf would collapse.) Bread dough before and after baking. As the dough heats up, starch granules absorb moisture from the gluten, swell, and leak some starch molecules, creating reinforcement for the dough walls that surround the gas pockets.

Late Baking: Flavor Development and Cooking Through Baking is continued for some time after the bread center approaches the boiling point. This gelates the starch as thoroughly as possible, thus preventing the center from remaining damp and heavy, and slowing subsequent staling. Continued baking also encourages the surface browning reactions that improve both color and flavor. Though limited to the hot, dry crust, these reactions affect the flavor of the whole loaf because their products diffuse inward. A light-colored loaf will be noticeably less flavorful than a dark one. Baking is continued for some time after the bread center approaches the boiling point. This gelates the starch as thoroughly as possible, thus preventing the center from remaining damp and heavy, and slowing subsequent staling. Continued baking also encourages the surface browning reactions that improve both color and flavor. Though limited to the hot, dry crust, these reactions affect the flavor of the whole loaf because their products diffuse inward. A light-colored loaf will be noticeably less flavorful than a dark one.

Bread is judged to be done when its crust has browned and its inner structure has become fully set. The second condition can be verified indirectly by tapping on the bottom of the loaf. If the interior still contains a continuous gluten ma.s.s with embedded bubbles, it will sound and feel heavy and dense. If it has cooked through and become an open sponge, the loaf will sound hollow.

Cooling Immediately after being removed from the oven, the loaf's outer layer is very dry, around 15% water, and close to 400F/200C, while the interior is as moist as the original dough, around 40% water, and around 200F/93C. During cooling, these differences partly even themselves out. Moisture diffuses outward, and much of the loaf's moisture loss occurs now. It ranges from 10% to 20% of the dough weight, depending on surface area, with small rolls losing the most and large loaves the least.

As the temperature declines, the starch granules become firmer and so the loaf as a whole becomes easier to slice without tearing. This desirable firming continues over the course of a day or so, and turns out to be the first step in the process called staling.

The Staling Process; Storing and Refreshing Bread Staling Staling takes place in the days following baking, and seems to involve the loss of moisture: the bread interior gets dry, hard, and crumbly. It turns out that bread will stale even when there's no net loss of moisture from the loaf. This was shown in the landmark study of bread staling in 1852, when the Frenchman Jean-Baptiste Boussingault showed that bread could be hermetically sealed to prevent it from losing water, and yet still go stale. He further showed that staling is reversed by reheating the bread to 140F/60C: the temperature, we now know, at which starch gelates. Staling takes place in the days following baking, and seems to involve the loss of moisture: the bread interior gets dry, hard, and crumbly. It turns out that bread will stale even when there's no net loss of moisture from the loaf. This was shown in the landmark study of bread staling in 1852, when the Frenchman Jean-Baptiste Boussingault showed that bread could be hermetically sealed to prevent it from losing water, and yet still go stale. He further showed that staling is reversed by reheating the bread to 140F/60C: the temperature, we now know, at which starch gelates.

Staling is now understood to be a manifestation of starch retrogradation, the recrystallization, water migration out of the granules, and hardening that take place when cooked starch is then cooled (p. 548). The initial firming of the freshly baked bread loaf, which improves its ability to be sliced, is caused by the retrogradation of the simple straight-chain amylose molecules, and is essentially complete within a day of baking.

Food Words: Stale StaleThough stale stale now suggests a food that is past its prime, old and dried out, it hasn't always had these negative connotations. It is a medieval Teutonic word, and originally meant "to stand" or "to age." It was applied to wines and liquors, which became clarified and stronger in flavor when they were allowed to stand for some time and settle. A kind of settling and strengthening also takes place among the starch molecules in bread, but these have toughening effects that are undesirable, at least for bread to be eaten fresh. Stale toughened bread does have its uses (see box, p. 542). now suggests a food that is past its prime, old and dried out, it hasn't always had these negative connotations. It is a medieval Teutonic word, and originally meant "to stand" or "to age." It was applied to wines and liquors, which became clarified and stronger in flavor when they were allowed to stand for some time and settle. A kind of settling and strengthening also takes place among the starch molecules in bread, but these have toughening effects that are undesirable, at least for bread to be eaten fresh. Stale toughened bread does have its uses (see box, p. 542).

The majority of starch molecules, the branched amylopectins within the granul, also retrograde. But thanks to their irregular structure, they form crystalline regions and expel water much more slowly, over the course of several days. This is the process responsible for the undesirable firming in texture after after the bread has become sliceable. For some reason, both the rate and the extent of staling are lower in lighter, less dense breads. the bread has become sliceable. For some reason, both the rate and the extent of staling are lower in lighter, less dense breads.

Certain emulsifying agents have been found to r.e.t.a.r.d staling substantially and for this reason have been added to ma.s.s-produced bread doughs for about 50 years. True b.u.t.termilk (p. 50) and egg yolks are rich in emusifiers and have the same effect. It's thought that these substances complex with starch or in some other way interfere with water movement, thereby inhibiting recrystallization.

Reheating Reverses Staling As long as much of the water released by the starch granules remains in the surrounding gluten - that is, as long as the loaf isn't too old, or has been wrapped and refrigerated - staling can be reversed by heating the bread above the gelation temperature of wheat starch, 140F/60C. Once more the crystalline regions are disrupted, water molecules move in between the starch molecules, and the granules and amylose gels become tender again. This is why toasting sliced bread makes the interior soft, and why a loaf of bread can be refreshed by heating it in the oven. As long as much of the water released by the starch granules remains in the surrounding gluten - that is, as long as the loaf isn't too old, or has been wrapped and refrigerated - staling can be reversed by heating the bread above the gelation temperature of wheat starch, 140F/60C. Once more the crystalline regions are disrupted, water molecules move in between the starch molecules, and the granules and amylose gels become tender again. This is why toasting sliced bread makes the interior soft, and why a loaf of bread can be refreshed by heating it in the oven.

Storing Bread: Avoid the Refrigerator Staling proceeds most rapidly at temperatures just above freezing, and very slowly below freezing. In one experiment, bread stored in the refrigerator at 46F/7C staled as much in one day as bread held at 86F/30C did in six days. If you're going to use bread in a day or two, then store it at room temperature in a breadbox or paper bag, which reduces moisture loss while allowing the crust to remain somewhat crisp. If you need to keep bread for several days or more, then wrap it well in plastic or foil and freeze it. Refrigerate bread (well wrapped) only if you're going to toast or otherwise reheat it. Staling proceeds most rapidly at temperatures just above freezing, and very slowly below freezing. In one experiment, bread stored in the refrigerator at 46F/7C staled as much in one day as bread held at 86F/30C did in six days. If you're going to use bread in a day or two, then store it at room temperature in a breadbox or paper bag, which reduces moisture loss while allowing the crust to remain somewhat crisp. If you need to keep bread for several days or more, then wrap it well in plastic or foil and freeze it. Refrigerate bread (well wrapped) only if you're going to toast or otherwise reheat it.

Bread Spoilage Compared to many foods, bread contains relatively little water, and so it often dries out before it becomes infected by spoilage microbes. Keeping bread at room temperature in a plastic bag allows moisture from the staling starch granules to collect on the bread surfaces and encourages the growth of potentially toxic molds, especially blue-green species of Compared to many foods, bread contains relatively little water, and so it often dries out before it becomes infected by spoilage microbes. Keeping bread at room temperature in a plastic bag allows moisture from the staling starch granules to collect on the bread surfaces and encourages the growth of potentially toxic molds, especially blue-green species of Aspergillus Aspergillus and and Penicillium, Penicillium, gray-white gray-white Mucor Mucor species, and red species, and red Monilia sitophila. Monilia sitophila.

The Virtues of Stale BreadCooks have long known that stale bread is a very useful ingredient in its own right. It is more robust than fresh bread, and retains its sponge-like structure in wet preparations that would cause fresh bread to disintegrate, such dishes as bread salads, bread puddings, and pain perdu. pain perdu. Similarly, bread crumbs retain their individual ident.i.ty when wetted, and can serve as tender binding agent in stuffings, panades, and breadings for frying. The source of dry bread's structural integrity is its starch. When it retrogrades, it forms some regions that are extremely ordered and stable and that hold the rest of the starch network strongly together (p. 458). Similarly, bread crumbs retain their individual ident.i.ty when wetted, and can serve as tender binding agent in stuffings, panades, and breadings for frying. The source of dry bread's structural integrity is its starch. When it retrogrades, it forms some regions that are extremely ordered and stable and that hold the rest of the starch network strongly together (p. 458).

Bread Flavor The incomparable flavor of simple wheat bread has three sources: the flavor of wheat flour, the products of yeast and bacterial fermentation, and the reactions caused by oven heat during baking. The aroma of low-extraction white flour is dominated by vanilla, spicy, metallic, and fatty notes (from vanillin, a furanone, and fatty aldehydes), while whole-meal flour is richer in most of these and in addition has cuc.u.mber, fried, "sweaty," and honey notes (from other fatty aldehydes and alcohols and phenylacetic acid). Yeast fermentation generates a "yeasty" character, a large part of which comes from fruity esters and eggy sulfur compounds. Baking contributes the toasty products of browning reactions. Starters add general complexity and a distinctive sour note from acetic and other organic acids.

Ma.s.s-Produced Breads The manufacture of commercial breads bears little resemblance to the process described above. Ordinary mixing, kneading, and fermentation require several hours of work and waiting from the bread maker. In bread factories, high-powered mechanical dough developers and chemical maturing agents (oxidizers) can produce a "ripe" dough, with good aeration and gluten structure, in four minutes. Yeast is added to such doughs mainly as flavoring. The formed loaves are proofed briefly and then baked as they move through a tunnel-like metal oven. These breads tend to have a very fine, cakelike texture, because machines are far more efficient at aerating dough than are hands or stand mixers. The flavor of manufactured bread can sometimes be marked by such unpleasant aroma compounds as sour, sweat-like isovaleric and isobutyric acids, which are produced by flour and yeast enzymes in unbalanced amounts during intensive mixing and high-temperature proofing.

A Scientific Definition of Bread QualityRaymond Calvel is an eminent figure in the world of baking, a researcher and teacher who made great contributions to the understanding and improvement of bread quality in postwar France. His definition of high quality in good French bread doesn't necessarily apply in detail to other bread styles, but it shows how much there is to appreciate in a well-made loaf.A good bread - a real quality loaf - ...will have a creamy white crumb. The proper creamy-white color of the crumb shows that the dough oxidation during mixing has not been excessive. It also presages the distinctive aroma and taste that are a subtle blend of the scent of wheat flour - that of wheat germ oil, along with the delicate hint of hazelnut aroma that comes from the germ. All of these are combined with the heady smell that comes from alcoholic dough fermentation, along with the discreet aromas that are the results of caramelization and crust baking.... the grain of French bread should be open, marked here and there by large gas cells. These should be thin-walled cells, with a lightly pearlescent appearance. This unique structure, resulting from the combination of numerous factors including the level of dough maturation and the loaf forming method, is basic to the eating qualities, flavor, and gustatory appeal of French bread.- The Taste of Bread, The Taste of Bread, transl. R. L. Wirtz. transl. R. L. Wirtz.

Special Kinds of Loaf Breads: Sourdough, Rye, Sweet, Gluten-Free Bakers make distinctive variations on the basic loaf bread from a variety of grains and other ingredients. Here are brief descriptions of some of them.

Sourdough Breads Sourdough breads get their name from the fact that both the dough and bread are acid. The acidity, along with other distinctive flavor components, is produced by bacteria that grow in the dough along with various yeasts. The bacteria often include some of the same lactic acid bacteria that make milk into yogurt and b.u.t.termilk (p. 44). The leavening for this kind of bread begins as a "wild" starter, a mixture of whatever microbes happened to be on the grain and in the air and other ingredients when flour was mixed with water. The mixture of yeasts and bacteria is then perpetuated by saving a portion of the dough to leaven the next batch of bread. Sourdough breads get their name from the fact that both the dough and bread are acid. The acidity, along with other distinctive flavor components, is produced by bacteria that grow in the dough along with various yeasts. The bacteria often include some of the same lactic acid bacteria that make milk into yogurt and b.u.t.termilk (p. 44). The leavening for this kind of bread begins as a "wild" starter, a mixture of whatever microbes happened to be on the grain and in the air and other ingredients when flour was mixed with water. The mixture of yeasts and bacteria is then perpetuated by saving a portion of the dough to leaven the next batch of bread.

The first breads probably resembled modern sourdoughs, and bread in much of the world is made with sourdough starters that give distinctive regional flavors. The bacteria somehow delay starch retrogradation and staling, and the acids they produce make the bread resistant to spoilage microbes: so sourdough breads are especially flavorful and keep well. Because browning reactions are slowed in acid conditions, sourdough breads tend to be lighter in color than straight yeast breads, and their flavor less toasty.

It isn't easy to make good bread with sourdough cultures. There are two reasons for this. One is that the bacteria grow faster than the yeasts, almost always outnumber them by factors of a hundred or a thousand, and inhibit the yeasts' gas production: so sourdoughs often don't rise very well. The other is that acid conditions and bacterial protein-digesting enzymes weaken the dough gluten, which makes it less elastic and the resulting bread more dense.

Guidelines for Working with Sourdoughs The key to successful baking with sourdough starters is to limit bacterial growth and acidification, and encourage a healthy yeast population. In general, this means keeping sourdough starters relatively cool, and "refreshing" them frequently by adding new flour and water and aerating them vigorously. Here are rules of thumb to keep in mind. The key to successful baking with sourdough starters is to limit bacterial growth and acidification, and encourage a healthy yeast population. In general, this means keeping sourdough starters relatively cool, and "refreshing" them frequently by adding new flour and water and aerating them vigorously. Here are rules of thumb to keep in mind.

Frozen and Par-baked Doughs and BreadsBread dough can be frozen, thawed, and baked into bread, but freezing kills a large proportion of the yeast cells, which means less leavening power, a slower rise, and the spread of yeast chemicals that weaken gluten. Sweet rich doughs turn out to freeze the best.The best stage at which to freeze bread dough is after the dough has risen and baked for 70 to 80% of its usual baking time. This frozen "par-baked" bread can be thawed and finished with just a few minutes in a hot oven. Yeast survival is no longer important, because the yeast cells have done their leavening and are killed during the initial bake.

Both yeasts and bacteria grow fastest in liquid starters, which allow the microbes easier access to nutrients; in a semisolid dough they grow more slowly and require less frequent attention. Because growing microbes consume nutrients rapidly, and produce acid and other growth-inhibiting substances, starters need to be divided and refreshed frequently, two or more times per day. Adding new water and flour dilutes the acc.u.mulated acids and other growth inhibitors, and provides a fresh supply of food. Aerating the starter - whisking a liquid one, or kneading a doughy one - supplies the oxygen that yeasts require to build cell membranes for new cells. The more frequently the starter is divided and refreshed, the better the yeasts will be able to grow, and the more leavening power the starter will have. Starters should be incorporated into a dough when they're actively growing and at their bubbliest. While bacteria thrive at warm temperatures, 8696F/3035C, yeasts in an acid environment grow better at a cooler 6878F/2025C; so both starters and rising doughs should be kept relatively cool.

Finally, sourdoughs should be well salted. Salt limits bacterial protein-digesting enzymes, and tightens the vulnerable gluten.

Rye Breads Though a minor grain compared to wheat, rye is still found in many breads in Germany and elsewhere in northern Europe and Scandinavia. Most rye breads baked today are made from mixtures of rye and wheat flours, with rye providing its distinctive, full flavor and wheat the rising power of gluten. Rye proteins simply don't form an elastic network like gluten, apparently because the glutenin molecules can't link up end-to-end into long chains. Rye has another major breadmaking liability: it tends to begin sprouting before harvest, so its starch-digesting enzymes are active during baking and break down the other major source of dough structure. Nevertheless bakers in northern Europe found a way of making a unique raised bread from pure rye flour. Though a minor grain compared to wheat, rye is still found in many breads in Germany and elsewhere in northern Europe and Scandinavia. Most rye breads baked today are made from mixtures of rye and wheat flours, with rye providing its distinctive, full flavor and wheat the rising power of gluten. Rye proteins simply don't form an elastic network like gluten, apparently because the glutenin molecules can't link up end-to-end into long chains. Rye has another major breadmaking liability: it tends to begin sprouting before harvest, so its starch-digesting enzymes are active during baking and break down the other major source of dough structure. Nevertheless bakers in northern Europe found a way of making a unique raised bread from pure rye flour.

Pumpernickel True pumpernickel was apparently born during a famine in Westphalia in the 16th century. It starts with coa.r.s.e whole-grain rye flour and a several-stage sourdough fermentation; the acidity helps limit starch breakdown and also makes the dough more elastic. The dough manages to retain some carbon dioxide bubbles thanks to its high content of gummy cell-wall materials called pentosans (p. 470). The fermented rye dough is baked in a pan at a low oven temperature, or steamed, and for a very long time: 16 to 24 hours. The loaf develops only a thin crust, and turns a dark chocolate-brown and takes on a rich flavor thanks to the long cooking time and high concentration of free sugars and amino acids, which undergo browning reactions. Because the abundant starch-digesting enzymes are active for a long time during the slow baking, pumpernickel may end up very sweet, with a sugar content of 20%. True pumpernickel was apparently born during a famine in Westphalia in the 16th century. It starts with coa.r.s.e whole-grain rye flour and a several-stage sourdough fermentation; the acidity helps limit starch breakdown and also makes the dough more elastic. The dough manages to retain some carbon dioxide bubbles thanks to its high content of gummy cell-wall materials called pentosans (p. 470). The fermented rye dough is baked in a pan at a low oven temperature, or steamed, and for a very long time: 16 to 24 hours. The loaf develops only a thin crust, and turns a dark chocolate-brown and takes on a rich flavor thanks to the long cooking time and high concentration of free sugars and amino acids, which undergo browning reactions. Because the abundant starch-digesting enzymes are active for a long time during the slow baking, pumpernickel may end up very sweet, with a sugar content of 20%.

Food Words: Pumpernickel, Bagel, Pretzel, Brioche, Panettone, Pandoro Pumpernickel, Bagel, Pretzel, Brioche, Panettone, PandoroThree of these bread names are German in origin, three from Romance languages. Pumpernickel Pumpernickel comes from Westphalian dialect words for the devil (St. Nick) and for "fart": this is a high-fiber bread. comes from Westphalian dialect words for the devil (St. Nick) and for "fart": this is a high-fiber bread. Bagel Bagel comes via Yiddish from a German root meaning "ring," and comes via Yiddish from a German root meaning "ring," and pretzel pretzel directly from a German word of Latin origin meaning "little bracelet," so both are named for their shape. directly from a German word of Latin origin meaning "little bracelet," so both are named for their shape. Brioche Brioche is French, its root apparently is French, its root apparently broyer, broyer, meaning to grind or knead. It first appears in the 15th century to name breads enriched with b.u.t.ter but not yet with eggs. meaning to grind or knead. It first appears in the 15th century to name breads enriched with b.u.t.ter but not yet with eggs. Panettone Panettone and and pandoro pandoro are 19th-century Italian coinages meaning "grand bread" and "golden bread." are 19th-century Italian coinages meaning "grand bread" and "golden bread."

The distinctive, complex flavor of rye bread comes largely from the grain itself, which has mushroom, potato, and green notes (from octenone, methional, nonenal). The traditional sourdough fermentation adds malty, vanilla, fried, b.u.t.tery, sweaty, and vinegar notes.

Sweet and Rich Breads: Brioche, Panettone, Pandoro Bread doughs that contain substantial amounts of fat and/or sugar pose special challenges to the baker. Both fat and sugar slow gluten development and weaken it, sugar because it binds up water molecules and interrupts the gluten-water network, fat because it bonds to fat-loving portions of the gluten chains and prevents them from bonding to each other. Rich doughs are therefore relatively soft and fragile. Bakers often build them by holding back the fat and sugar and kneading these in only after developing the gluten network, and then bake the doughs in containers that support their weight and prevent them from sagging and flattening. Large amounts of sugar slow the growth of yeast by dehydrating the cells, so sweet doughs are often made with more yeast than ordinary breads, and they may take longer to rise. Sugar also makes sweet doughs p.r.o.ne to begin browning early in the baking, so they're usually baked at a relatively low oven temperature to prevent the surface from browning before the interior has set. Bread doughs that contain substantial amounts of fat and/or sugar pose special challenges to the baker. Both fat and sugar slow gluten development and weaken it, sugar because it binds up water molecules and interrupts the gluten-water network, fat because it bonds to fat-loving portions of the gluten chains and prevents them from bonding to each other. Rich doughs are therefore relatively soft and fragile. Bakers often build them by holding back the fat and sugar and kneading these in only after developing the gluten network, and then bake the doughs in containers that support their weight and prevent them from sagging and flattening. Large amounts of sugar slow the growth of yeast by dehydrating the cells, so sweet doughs are often made with more yeast than ordinary breads, and they may take longer to rise. Sugar also makes sweet doughs p.r.o.ne to begin browning early in the baking, so they're usually baked at a relatively low oven temperature to prevent the surface from browning before the interior has set.

French brioche dough is especially rich in b.u.t.ter and eggs. It's often r.e.t.a.r.ded (chilled, p. 539) for 618 hours to stiffen it, then rolled out and briefly rested. This makes the dough easier to handle and form before its final rise. Italian panettone and pandoro are remarkable holiday breads that are enriched with large quant.i.ties of sugar, egg yolks, and b.u.t.ter, but that keep well because they are built from a sourdough that starts with a naturally leavened sponge.

Gluten-Free Breads People whose immune systems are intolerant of gluten must avoid wheat and its close relatives, and therefore can't eat ordinary bread, where gluten plays a major role in texture. A reasonable facsimile of raised bread can be made with gluten-free flours or starches - rice flour, for example - that are supplemented with xanthan gum and emulsifiers. The gum, which is secreted by a bacterium and purified from industrial-scale fermenters, provides a modest gluten-like elasticity, while the emulsifiers stabilize the gas bubbles and slow the diffusion of carbon dioxide from the dough during baking. People whose immune systems are intolerant of gluten must avoid wheat and its close relatives, and therefore can't eat ordinary bread, where gluten plays a major role in texture. A reasonable facsimile of raised bread can be made with gluten-free flours or starches - rice flour, for example - that are supplemented with xanthan gum and emulsifiers. The gum, which is secreted by a bacterium and purified from industrial-scale fermenters, provides a modest gluten-like elasticity, while the emulsifiers stabilize the gas bubbles and slow the diffusion of carbon dioxide from the dough during baking.

Other Breads: Flatbreads, Bagels, Steamed Breads, Quick Breads, Doughnuts Light oven-baked loaves are the standard form of bread in Europe and North America, but there are many other versions of the staff of life. Here are brief descriptions of some of them.