t here are dozens of scientifi c principles at work in baking. As an introduction to the topic of food science, this section provides an overview of the most basic of these principles.
chapter four
Advanced baking principles
Baking science
Food science is an exacting study, dedicated to discovering and clarifying the complex re- actions involved in food preparation. A general knowledge of how basic ingredients can be changed through the effects of temperature, agitation, and acids or alkalis gives the baker or pastry chef the freedom to develop new items. It also aids the chef in problem solving, such as changing a formula’s original cooking method, fi nding a suitable shortcut for a long or complex recipe, or substituting one ingredient for another. These challenges may be inspired by a need to liven up or update a menu, cut costs, streamline production, or introduce a new technique or ingredient.
Books and articles on these topics should be part of every baker’s or pastry chef’s pro- fessional reading (see Appendix D, “Readings and Resources,” page 908).
Basic baking ingredients
Flour, eggs, water, fat, and usually sugar are necessary in all baking and pastry goods. The ways in which these ingredients interact with one another and other ingredients during mix- ing and baking dictate the qualities of the end product. For the purposes of understanding how these ingredients infl uence a fi nished product, they can be divided into two categories:
stabilizers and liquefi ers.
Stabilizers
A stabilizer is any ingredient that helps to develop the solid structure, or “framework,” of a fi nished product. Of the fi ve basic baking ingredients, fl our and eggs act as stabilizers. Flour and eggs both lend structure (and nutritional value) to a fi nished product, but the way each of these ingredients acts is different.
Flour represents the bulk of most of the formulas made in any bakeshop. It acts as a binding and absorbing agent, and it may be thought of as the “backbone” of the majority of bakeshop formulas. It is the gluten (the protein component in fl our) that builds structure and strength in baked goods. Different types of fl ours have different gluten-to-starch ratios, which will create vastly different results in the texture, appearance, and fl avor of the fi nal product if used in the same formula. A fl our with a higher gluten content will result in a tougher crumb, whereas a fl our with a lower gluten content will result in a more tender crumb.
Eggs lend additional stability during baking. They infl uence the texture and crumb as well; by facilitating the incorporation and distribution of air, they promote an even-grained and fi ne texture. Eggs also have leavening power. As eggs—whole, yolks, or whites—are whipped, they trap air, which will expand when heated, resulting in a larger and lighter product.
In addition, eggs help to develop fl avor and aroma in a product, mostly from the fat and nutrients contained in the yolk. Egg yolks also contribute to a drier fi nished product, and egg whites add volume and moisture.
Liquefi ers
The remaining three of the fi ve basic baking ingredients—water (along with milk and other liq- uids), fats, and sugar—act as liquefi ers. That is, they help to loosen or liquefy a dough or bat-
In the baking process, liquid provides the moisture neces- sary for hydration of the ingredients. The moisture aids in the development of the gluten in the flour, in gelati- nization of starches, and in dissolving other ingredients to achieve even distribution and consistency. Typically,
Products made with water are less expensive and have a longer shelf life. Those made with milk contain more nutrients and are more flavorful. The sugars pres- ent in milk also help these products develop a golden brown color in the oven.
hydration of a dough or batter
ter. Some liquefi ers such as sugar may actually tighten or bind a dough when fi rst added, but their interaction with other ingredients ultimately tenderizes or loosens the dough or batter.
Water acts to dilute or liquefy water-soluble ingredients such as sugar and salt. It also facilitates the even distribution of sugar, salt, and yeast in a dough if these ingredients are mixed thoroughly with the water before introducing the remaining ingredients in the formula.
In bread making, water is typically the primary liquefi er. A bread formula with a higher per- centage of water results in a more open-grained and softer crumb. In addition, water helps to develop the proteins in fl our, necessary for proper leavening. Water also acts as a leavener as it changes to steam and expands.
Gluten is formed by the proteins present in wheat flour (wheat is the only grain that forms measurable amounts of gluten, making it an indispensable grain in the kitchen or bakeshop). Flour gives strength to a batter or dough and acts to absorb the bulk of the moisture in most baked goods. As the flour takes up water, gluten strands begin to form. To further develop these strands, making them more cohesive and elastic, the mixture is agitated (mixed).
Gluten development is essential for certain baked goods such as breads, in which a somewhat chewy texture is desirable; in other baked goods such as cakes, which should be tender and moist, excessive gluten development is a flaw. The differences among desired outcomes for the textures of different types of baked goods led to the development of flours with varying gluten levels.
While the gluten level of the flour has a very sig- nificant role in the final texture of a product, the amount of mixing a dough or batter undergoes, particularly if the flour has a moderate to high percentage of gluten, will also have a marked impact.
Gluten is composed of two distinct proteins: glutenin and gliadin. When flour is mixed with water, the glutenin and gliadin begin to join together (with the water intermingled) to form strands or sheets of gluten. The glutenin provides the elasticity; the gliadin, the extensibility. The formation of these strands provides the structure for many baked goods. If a flour with too little (or no) gluten is used in bread making, the bread will not rise. Yeast is the catalyst for risen bread, but it is also necessary to have well-developed gluten to trap the gases produced by the fermenting yeast for bread to rise.
proteins in flour
BUTTER
Butter is made from cow’s milk. It is approximately 80 percent fat, 10 to 15 percent water, and 5 percent milk solids. The advantages of using butter in baking are its flavor and lower melting point.
LARD
Lard is rendered pork fat. It is most often used in con- junction with other fats.
OILS
Oil is seldom used in baked goods. Solid fat is more typi- cally a requirement for baking formulas that are made using the creaming method (see page 62); it is necessary for aeration, which lends leavening power and structure to the finished baked item.
SHORTENINGS
Solid shortenings are hydrogenated vegetable fats created for baking. They are made by injecting hydrogen gas into purified oil as it is heated. Hydrogenated fats will have varied melting temperatures depending on the purpose for which they were manufactured. Most are designed to cream well, and thus have a higher melting point.
To create emulsified shortening, mono- and diglyc- erides are added to shortening, resulting in increased absorption and retention of moisture. Recipes using emulsified shortening have higher ratios of milk, sugar, fat, and eggs to flour, resulting in richer cakes that are less prone to drying out. Emulsified shortening is typi- cally used when the quantity of sugar in a recipe is equal to or greater than the amount of flour.
shortening agents
• IMPROVE EATING QUALITIES.
Products are more tender and less chewy; in addition, some fats or oils add flavor.
• IMPROVE APPEARANCE.
Shortening agents do not dissolve in doughs or batters, but instead become evenly dispersed and incorporate air, resulting in a soft crumb in breads and flakiness
in pastries, which make them more appealing to the eye.
• IMPROVE KEEPING QUALITY.
Fats delay the retrogra- dation, or breakdown, of starches, which helps to delay staling.
• ADD FOOD VALUE.
Fats constitute a concentrated source of energy.
• ADD VOLUME.
Used in conjunction with the cream- ing method, fats can facilitate the incorporation of air, which expands during baking, into a batter, contributing to leavening.
additional functions of fats and oils in baking
Milk performs many of the same functions as water, but because of its additional com- ponents (fat, sugar, minerals, and protein), it serves a number of other functions and adds fl avor as well. As the sugar (lactose) in milk caramelizes, it gives a rich color to the product’s surface, and can also aid in development of a fi rm crust. The lactic acid in milk has a tightening effect on the proteins in fl our, which serves to increase stability, resulting in a product with a fi ne grain and texture.
Fats also fall into the category of liquefi ers. If the total amount of fat added to a dough or batter equals no more than 3 percent of the weight of the fi nished dough or product, it acts to increase the elasticity of the proteins in the fl our, thereby helping the bread or other product
to expand during baking. In baking, fats and oils are also classifi ed as shortening agents, a term derived from their ability to split the long, elastic gluten strands that can toughen doughs and batters. This tenderizing effect renders the strands more susceptible to breaking, or shorten- ing, resulting in a more tender and less dense crumb.
Although sugar has a tendency to tighten up a mixture when it is fi rst incorporated, by its nature it attracts moisture, a characteristic that causes it to ultimately loosen or liquefy a batter or dough. For the gluten in fl our to develop, it needs moisture; because sugar attracts moisture, it acts to inhibit gluten development in the batter or dough, preventing it from be- coming too tough or elastic. Furthermore, when used in the correct proportion, sugar can help to maintain the elasticity of the gluten strands present in a dough or batter. With maxi- mum elasticity, the gluten can expand more easily so the item is more effi ciently leavened, allowing for the proper development of volume and the creation of a moist and tender crumb.
During baking, sugar also interacts with the starch component of fl our to delay its gelatini- zation, enabling batters and doughs to stay softer longer, allowing greater spread and rise before setting.
Leaveners
To leaven is to raise, or to make lighter. There are several ways to accomplish this in baking: with yeasts (also known as organic leaveners), with chemical agents such as baking powder or baking soda, or with steam (mechanical leavening). Each method is best suited for specifi c applications and produces very different results. The different leavening methods may be used alone or in conjunction with one another (as in croissants, for example) to yield different effects.
• AIDS IN THE CREAMING PROCESS.
The crystalline structure of granulated sugar makes it an effective agent for the incorporation of air into batters mixed by the creaming method. The incorporated air is then held by the shortening agent, the other main ingredient in any creaming-method formula.
• RETAINS MOISTURE AND PROLONGS FRESHNESS.
Sugar absorbs moisture from other ingredients as well as from the atmosphere, thereby helping to keep fin- ished products moist and delay drying out or staling.
• IMPARTS COLOR TO CRUSTS.
Through caramelization and the Maillard reaction (for more information on browning reactions, see page 63), sugar aids in the development of deep golden crust color during baking, which also adds flavor.
• CONTRIBUTES FOOD VALUE.
Sugar in moderate amounts can supply some of the carbohydrate requirements of a normal diet.
additional functions of sugar in baking
Yeast
Yeast is a living organism that needs suitable conditions to thrive. Commercially sold baker’s yeast is of the strain Saccharomyces cerevisiae, which has been determined to be the best suited for bread baking.
Yeast needs warmth, moisture, and food (carbohydrates) to begin fermenting. By defi ni- tion, fermentation is the anaerobic respiration of microorganisms. The process converts car- bohydrates into alcohol and carbon dioxide. The carbon dioxide acts to leaven a dough or batter as the gas is trapped in the web of protein (gluten) strands that developed during the mixing process. The alcohol acts to tenderize the gluten strands, improving the overall texture of the product; it cooks out during baking, leaving no undesirable fl avor.
The fermentation process is important in building the internal structure and fl avor of the dough. Given the proper environment, yeast cells will continue to ferment until they run out of food, or until the by-products of fermentation begin to poison them and they die. For these reasons, as well as the necessity of maintaining production schedules, it is easy to see why time is an important element in making quality yeast-raised products. Consequently, it is important to understand how the fermentation of yeast can be controlled.
Yeast cells are sensitive to the temperature of the environment. The ideal temperature for fermentation is between 80° and 90°F/27° and 32°C. Lower temperatures will retard or arrest yeast development. Temperatures at or above 105°F/41°C will also slow fermentation.
Yeast dies at 138°F/58°C.
While sugar provides an immediate food source for yeast to begin fermentation, too much sugar can act to slow the fermentation process. High concentrations of sugar can have the same dehydrating effect as salt, causing yeast cells to die.
Salt plays many roles in baking, but its contributions are most evident in bread baking. It helps to slow yeast growth and, when used in the correct proportions, will help to control the rate of fer- mentation. However, too much salt can damage or kill the yeast by dehydrating the cells, resulting in a heavier, denser product. For this reason, salt should never come in direct contact with yeast.
Chemical leaveners
Baking soda and baking powder are the primary chemical leaveners. With these leaveners, an alkaline ingredient—the baking soda or baking powder (which also contains an acid and a starch)—interacts with an acid. The alkali and acid, when combined with a liquid, react to produce carbon dioxide, which expands during baking, leavening the dough or batter.
• STRENGTHENS THE GLUTEN STRANDS.
• CONTRIBUTES TO ELASTICITY,
which in turn acts to improve the texture of the final product.
• IS AN IMPORTANT FLAVOR COMPONENT IN BREADS.
It enhances both the subtle flavors in the other ingre- dients and those that result from the fermentation process. Without salt, bread tastes flat.
other functions of salt in bread baking
Baking soda, or sodium bicarbonate, is a common leavening agent for cakes, quick breads, and cookies. Sodium bicarbonate is an alkali and is, therefore, positively charged and seeks to be in a neutral state. (For more information on alkalis, see “Acid, Base, and pH,”above.) As sodium bicarbonate reacts with an acid, it breaks down and releases carbon dioxide, which is captured in the dough or batter and causes it to rise (leaven) as it is baked. To break down and be relieved of its charge, sodium bicarbonate requires the presence of an acidic ingredi- ent, such as chocolate, vinegar, a cultured dairy product, fruit juice, or molasses.
Baking powder is a mixture of sodium bicarbonate, an acid, and cornstarch. The sodium bicarbonate (soda) will react with the acid to create carbon dioxide when combined with a liquid, and the carbon dioxide acts to leaven the product. The cornstarch in baking powder absorbs moisture and keeps the acid and alkaline components from reacting with each other before they are mixed into a dough or batter.
There are two types of baking powder: single-acting and double-acting. Single-acting baking powder contains sodium bicarbonate and cream of tartar (called a dry acid). Because cream of tartar is easily dissolved, this type of baking powder needs only to be combined with a liquid for the two substances to react and release the carbon dioxide that will leaven the dough or batter. Double-acting baking powder combines sodium bicarbonate with dry acids that have different solubility rates. One of the acids is easily soluble and will begin to react with the sodium bicarbonate when wet. The other needs heat for it to completely dissolve, delay- ing its reaction until the product is in the oven.
Mechanical leavening
Mechanical leavening occurs when air or moisture, trapped during the mixing process, ex- pands as it is heated during baking in pockets created by cooking proteins, causing “balloon- like” expansion that aids in the leavening process. This method of leavening occurs when one of three distinct methods is used: foaming, creaming, or lamination.
The foaming mixing method requires that eggs, eggs yolks, or egg whites be beaten to incorporate air until they form a foam. This foam is then added to the batter, folded in so as to disrupt as few of the air bubbles as possible and maintain the volume of the foam. The air trapped in these bubbles then expands during baking and causes the product to rise.
The pH of a solution is the measure of its acidity or alkalinity. A pH of 7 denotes a neutral solution, which indicates a balance between the negative and positive ions within the solution. If a solution has a pH higher than 7, it is alkaline or base and has a positive charge. If a solu- tion has a pH lower than 7, it is acidic and has a negative
charge. Compounds that are charged are unstable, mean- ing that they have a natural affinity to become neutral.
They may break down on their own when heat is applied, or they may break down in reaction to the presence of a compound or element that has the opposite charge.
acid, base, and pH
The creaming method of mixing blends fat and sugar together to incorporate air. The creamed mixture is then combined with the remaining ingredients, and as the product bakes, the air trapped during the creaming process expands and leavens it.
In lamination, alternating layers of fat and dough are created through different fold- ing and rolling techniques (for more information on lamination techniques, see “Laminated Doughs” in Chapter 9, page 217). When the dough is baked, the fat melts, releasing water in the form of steam, which acts to leaven the dough. The steam fi lls the pockets left by the melting fat and expands, causing the product to rise; the fat then “fries” the dough so that the spaces are retained.
Sweeteners
Sweeteners come in many forms, and are an integral part of most baked goods and pastries.
They serve a number of important functions including fl avor, moisture, leavening, extended shelf life, and color.
Monosaccharides and oligosaccharides
A monosaccharide, or single sugar, is the basic building block of all sugars and starches.
Fructose and dextrose are both monosaccharides. These are the simplest sugars. When fruc- tose and dextrose are bonded together, they form a disaccharide, or double sugar, called sucrose—that is, table sugar. Many monosaccharides linked together in long chains are called polysaccharides. Starches such as cornstarch are made up of such chains, thousands of sac- charides long. Although starches are also made up of sugar molecules, they do not taste sweet, and they do not dissolve in water when they are in long chains.
Oligosaccharides lie somewhere in between table sugar and the starches present in corn- starch and fl our that we are so familiar with. They are chains of sugar molecules—not so long as those in starches, but longer than those in sugars. Like starches, they do not taste sweet; unlike starches, they dissolve in water. All of these terms are vital to understanding corn syrup and glucose, because they are the ingredients in our humble bucket of glucose syrup.
Crystallization of sugar
Crystallization is a process that occurs when sugar is deposited from a solution. This type of deposition allows the sugar molecules to assume their characteristic geometric form. Sugar crystallization is infl uenced by many things: saturation levels, agitation, temperature, cooling, seeding, invert sugar, and acid. Through manipulation of these factors, the process of crystal- lization may be controlled to create the typical crystalline and noncrystalline structures used in the bakeshop or pastry kitchen, such as fondant, rock candy, hard candies, and caramel.
In order for sugars to crystallize out of solution, the solution must be suffi ciently saturat- ed for precipitation to occur. Typically, in a bakeshop or pastry kitchen, sugar will be dissolved in water through the introduction of heat, which facilitates the dissolving and incorporation of more sugar. The solution may then be heated to a specifi c temperature, thereby evaporat- ing water and serving to further increase the density, or saturation, of the solution. The more saturated, or “densely packed,” a solution, the more likely and more easily it will begin to
crystallize. Crystallization occurs as the particles in solution collide with one another; hence agitation is a key contributor to the process. If agitation is initiated while the solution is still hot, large crystals will form as molecules become attached at a slower rate. As the mixture cools, crystals form more readily, promoting rapid growth of many tiny crystals when stirred or otherwise agitated. If the mixture is allowed to cool without agitation and is then stirred, it will crystallize rapidly but will form small crystals rather than large ones.
The introduction of a “seed” will cause crystallization. A seed is anything, from whole sugar crystals to air bubbles to a skewer (as when making rock candy), that will act as a surface for the sugar crystals to adhere to and grow on.
Controlling or delaying crystallization allows the sugar solution to be manipulated or pulled without graining. It allows the confectioner to make chewy caramels that will not crystallize.
Certain ingredients may be introduced into a sugar solution to inhibit crystallization. A small amount of glucose syrup or another invert sugar is often added to the solution. The mo- lecular structure of glucose and other invert sugars is different from that of sucrose. This dif- ference means the invert sugar will inhibit crystallization by getting in the way of the sucrose molecules that start to attach to each other as they begin to crystallize out of the solution. A second way to inhibit crystallization is to introduce a small amount of an acid into the solution.
When sucrose (table sugar) is boiled with dilute acids, the acids will cause the inversion of some of the sucrose molecules. The resultant invert sugars will interfere with the crystalliza- tion process just as glucose syrup does.
Hygroscopic properties of sugar and salt
Sugar and salt are both hygroscopic, meaning they will readily take up water under certain conditions of humidity. In baked products, they act to retain moisture, extending shelf life. In items such as hard candies, however, this attraction of moisture acts to begin to break down the structure of the candy or other item, causing it to become soft and sticky.
Browning reactions
There are two types of processes that create browning in food: caramelization and the Mail- lard reaction. Browning occurring from either of these processes results in a rich color and en- hances both the fl avor and aroma of the food. Caramelization occurs when sucrose is present, and only at high temperatures. As sugar is heated, it melts and then begins to break down. As the temperature continues to increase, different compounds will form and then break down, creating different fl avors and colors throughout the cooking process. The Maillard reaction (for example, the browning of bread crust in the oven) occurs between the reducing sugars and proteins; it can occur at low temperatures more slowly, and at high temperatures over short periods of time. It is a complex browning reaction that results in the particular fl avor and color of foods that do not contain much sugar.
Saturation and supersaturation are vital concepts for the confectioner, as they are directly linked with the process of crystallization. At a given temperature, a specific quantity of water can dissolve only a finite quantity of sugar. The warmer the water, the more sugar it can dis- solve. When no more sugar can be dissolved in a certain amount of water at a certain temperature, the solution is said to be saturated. When a saturated solution is then
heated to evaporate some of the water, the solution be- comes supersaturated. Supersaturated solutions contain a higher concentration of sugar than could have been initially dissolved in the same amount of water. Super- saturated solutions are delicate systems. Sugar molecules are attracted to each other, and with so many of them in such a small amount of liquid, they are quite likely to join together. This action results in the formation of crystals.
saturated and supersaturated sugar solutions
The term invert sugar refers to a sugar (sucrose or table sugar) whose optical or refractory properties have been altered. This altering occurs when it is boiled together with a dilute acid, such as cream of tartar (in solution), lemon juice, vinegar, and so on. In the presence of the acid, the sucrose breaks down into its two components, dextrose and fructose.
There are also naturally occurring invert sugars, such as honey. However, many, if not most, of these natu- ral invert sugars contain other components, or impurities, which make them ill-suited for use in the sugar-cooking and candy-making processes, as the impurities typically burn at a much lower temperature than is required to cook the sugar.
invert sugar
• MAKES COOKED CONFECTIONS SOFTER AND EASIER TO WORK WITH.
Added to cooked sugar in the proper amount, it will increase its elasticity.
• IS A HUMECTANT.
That is, when it is added to baked goods, it helps to retain moisture, resulting in a moister product and a longer shelf life.
• IS USUALLY LESS SWEET THAN SUGAR.
For example, 42 DE corn syrup is only about 60 percent as sweet as cane sugar. By substituting this syrup for a percentage of the sugar in a formula, the sweetness of baked goods or frozen desserts can be decreased without sacrificing the textural advantages afforded by sugar.
benefits of glucose syrup
Thickeners
Sauces, puddings, fi llings, mousses, and creams can be thickened or stabilized by many ingre- dients, including gelatin, eggs, and starches such as fl our, cornstarch, tapioca, and arrowroot.
These thickeners may be used to lightly thicken a mixture, such as a sauce, or to produce something set to a sliceable consistency, like Bavarian cream.
The quantity and type of thickener, as well as how it is stirred or otherwise manipulated, will determine the properties of the fi nished product. For example, if a custard is cooked over direct heat and stirred constantly, the result will be a sauce that pours easily. Baked in a water bath with no stirring at all, the same custard base will set into fi rm custard.
Gelatinization of Starches
When starch granules suspended in water are heated, they begin to absorb liquid and swell, causing an increase in the viscosity of the mixture. This reaction, known as gelatinization, al- lows starches to be used as thickening agents.
Polysaccharides
Polysaccharides are starches that are commonly used as thickening agents in preparations such as sauces and fi llings. They are complex carbohydrates composed of two types of starch mol- ecules, both of which are made of long chains of dextrose. One type, known as amylose, exists in long linear chains, and the other, amylopectin, in dendritic (branched) patterns. The ratio in which the two types of starch molecules occurs in a starch will dictate its use. The higher the percentage of amylose, the more prone the starch is to gel. The more amylopectin present, the more the starch will act to increase viscosity or thicken without causing a gel to form. Starches high in amylose are derived from grain sources such as wheat and corn, while starches with a high percentage of amylopectin are derived from roots and tubers, such as tapioca.
It is only after a starch in liquid is heated that the granules can absorb the liquid and begin to thicken it. As the starch is heated, the molecules within each granule begin to move faster and their bonds begin to loosen, allowing liquid to work its way into the normally tightly bound granules. As the granules absorb the liquid, they swell, making it easier for more liquid to be absorbed. All starches have different temperatures at which they begin to thicken.
A Gel Has Not Formed
Unbound hydrocolloids in a continuous phase of water
A Gel Has Formed
A gel is formed when hydrocolloids bind to form a three-dimensional network that traps water, preventing motion.
Retrogradation
Starches high in amylose that have been gelatinized and then undergo freezing, refrigera- tion, or aging may begin to retrograde, or revert to their insoluble form. This reaction causes changes in food texture and appearance (staling in breads and similar products; cloudiness or graininess in sauces, puddings, and creams). But not all starches have the same tendency toward retrogradation. It is important to choose the correct starch for the application. For example, when making pies to be frozen, it is best to use modifi ed food starch to thicken the fi lling, rather than cornstarch.
GELLING AND THICKENING AGENTS AND THEIR USES
STARCH SOURCE CHARACTERISTICS USES
Modifi ed food starches Various Flavorless; freezes well Fruit fi llings
Cornstarch Grain Prone to retrogradation; must be
heated to a boil to remove fl avor Sauces, puddings, and fruit fi llings
Flour Grain Prone to retrogradation; must be
heated to a boil to remove fl avor Puddings and fruit fi llings
Arrowroot Tuber
Flavorless; makes a translucent paste that will set to a gel; if over- agitated, overcooked, or used in too large a quantity, may make the product stringy and gooey
Soups and sauces
Tapioca/Cassava Root Doesn’t set to a gel; doesn’t
retrograde Puddings and fruit fi llings
Potato Tuber
If overagitated, overcooked, or used in too large a quantity, may make the product stringy and gooey
Kosher baking
Agar-agar Sea vegetable
Strong thickening properties; sets to a fi rm gel; has a very high melt- ing point
Gelées and vegetarian desserts
Pectin Citrus skins, apples, and other high-pectin fruits
Requires a low pH and high sugar
content to form a gel Jellies, jams, preserves, and gelées
Gelatin Animal
Melts below body temperature;
boiling may reduce its strength;
enzymatic reactions with certain fruits will prevent setting
Mousses, aspics, and gelées
Eggs Animal
If not used in conjunction with a starch, will curdle when over- cooked; yolks create a soft velvety set, whites create a resilient set
Custards, custard sauces, and puddings
Pectin
Pectin is a carbohydrate derived from the cell walls of certain fruits. Some common sources of pectin are apples, cranberries, currants, quince, and the skins of citrus fruits, all of which are high in pectin. Pectin may be used as a gelling agent or as a thickener. To gel, it requires the correct balance of sugar and an acid. Pectin molecules have a natural attraction to water molecules; when pectin is put in solution alone, the molecules will become surrounded by water molecules and will not gel the solution. The addition of an acid interrupts this attraction, and sugar further acts to draw the water away from the pectin molecules, allowing them to connect together and form a three-dimensional network.
Gelatin
Gelatin is typically used to produce light, delicate foams (such as Bavarian creams, mousses, and stabilized whipped cream) that set so they may be molded or sliced. Available in both granulated and sheet form, gelatin must fi rst be rehydrated, or bloomed, in a cool liquid. Once it has absorbed the liquid, it is then gently heated to melt the crystals, either by adding the softened gelatin to a hot mixture, such as a custard sauce, or by gently heating it over sim- mering water.
Gelatin, a protein derived from the bones and connective tissue of animals, is composed of molecules that attract water. When they fi rst come in contact with water, they swell; then, as they are heated, they completely dissolve. As the mixture cools, the proteins join together to form a three-dimensional web (much as in coagulation) that holds in the moisture. This system is called a gel. When used in making a mousse or Bavarian, the gelatin solution is beaten into a mixture containing many air pockets. The proteins found in the gelatin are thus stretched to hold the air as well as the moisture, creating a stabilized product. Gelatin is also used commercially in the production of ice cream, as it interferes with formation of ice crystals.
Eggs as thickeners
Whole eggs, egg yolks, or whites may be used, alone or in conjunction with other thickeners, to thicken a food. Eggs act to thicken through the coagulation of proteins. As their proteins be- gin to coagulate, liquid is trapped in the network of set proteins, resulting in a smooth, rather thick texture. This is known as a partial coagulation, in which the proteins hold moisture; if the mixture were cooked or baked further, the proteins would fully coagulate and expel water,
When working with gelatin, it is important to remember
that there are a few fruits that contain proteases—enzymes that will break down the collagen in gelatin and not allow it to set (gel). Among these fruits are kiwi, pineapple, papaya, honeydew melon, and banana. To use these fruits
in any gelatin-based application, you must first allow the fruit or fruit purée to simmer for 2 to 3 minutes or use and ultra-pasturized purée, to destroy all of the protease enzymes, before adding the gelatin.
enzymes and gelatin
At the molecular level, natural proteins are shaped like coils or springs. When natural proteins are exposed to heat, salt, or acid, they denature—that is, their coils unwind. When pro- teins denature, they tend to bond together, or coagulate, and form solid clumps. An example of this is a cooked egg white, which changes from a transparent fl uid to an opaque solid. As proteins coagulate, they lose some of their capacity to hold water, which is why protein-rich foods give off moisture as they cook, even if steamed or poached. Denatured proteins are easier to digest than natural proteins.
Most commonly, proteins are denatured through the application of an acid, agitation, or heat. The addition of one or more of these elements will act to alter the structure of the protein by disrupting the bonds that shape its molecules. This change in structure permits the protein to behave in a different manner. For example, the proteins will extend in length, so that they are more likely to come in contact with one another and bond, forming a web (or coagulating). In this way proteins become useful as a thickening agent that can be used in many applications where starches may not, such as in frozen desserts.
Emulsions
An emulsion is a system of two immiscible liquids (liquids that are unable to be mixed together to form a true solution) that appears to be a completely homogenous mixture but is in fact what is known as a two-phase system, having a dispersed phase and a continuous phase.
When mixed to combine, one of the liquids breaks up into minute droplets (dispersed phase) and the other remains as a matrix for the droplets to be dispersed in (continuous phase).
There are two types of emulsions, temporary and permanent.
Uncoiling and denaturing proteins
LEFT: An emulsion is a suspension of the dispersed phase in the continuous phase.
MIDDLE: An excess of the dispersed phase forces the droplets together.
RIGHT: The result is separation; the droplets are no longer discrete, but coalesce into large drops that do not remain in suspension.
Excessive Dispersed Phase Separation
= Continuous Phase (Water)
A Fat-in-Water Emulsion
= Dispersed Phase (Fat)
A temporary emulsion is one that will separate into two distinct layers in a short period of time. In a permanent emulsion, the two liquids do not separate as easily because of the presence of a third element, known as an emulsifi er. Emulsifi ers are naturally occurring sub- stances that are attracted to both fat and water and thus facilitate maintaining a stable emul- sion between two immiscible liquids.
Tempering chocolate
Tempered chocolate has a glossy fi nish, snap, and creamy texture. Cocoa butter, the fat found in chocolate, may set into one of four types of crystals: beta, gamma, alpha, or beta prime.
Only the beta crystals are stable and yield the gloss, snap, and proper texture. To temper chocolate, all of the crystals must fi rst be fully melted. For the chocolate to maintain gloss and snap, as it is cooling it must form stable beta crystals. They can be caused to form by gradu- ally reducing the temperature of the melted chocolate until it is at 80°F/27°C, while applying constant agitation. To encourage the formation of the beta crystals, some additional, already tempered chocolate (known as a seed) may be added to the mixture.
All chocolate you buy is in temper, if it has been properly stored since its time of manu- facture. But if you are going to dip centers, mold it, or use it for other confectionery or décor work, you will need to melt it and temper it again. See Chapter 21, Chocolates and Confec- tions, for more discussion of tempering.
Healthy baking
Today’s consumer is increasingly concerned about high-calorie, high-fat foods. Pastry chefs must be aware of this concern and look for ways to curb the fat and calorie content of their pastries and desserts when the market calls for it.
One method pastry chefs are using to cut back on calories is substituting fruit purées (such as apples, dates, and prunes) for pure sugar in their products. This will increase the sug- ar and moisture content of the product, but it may also change the baking methods. Yogurt is another product pastry chefs are using in their baked goods. Replacing oil or butter with yogurt in a recipe will change the acid, protein, and moisture content of the item, while add- ing a leavening agent and affecting taste and color. (Strain the yogurt through a cheesecloth overnight to get rid of any lumps or impurities.)
Methods to decrease fat are also quite common and easy for pastry chefs. For example, instead of using whole milk, substitute buttermilk, skim milk, evaporated milk, or even water.
A cheesecake can lose fat if it is made with reduced-fat cream cheese rather than regular cream cheese. Fat-free sour cream is available to substitute for regular sour cream. Replac- ing some eggs with egg whites is another way to cut back on fat; in many instances two egg whites can be used in place of one whole egg.
There are challenges when making substitutions in healthy baking. The moisture con- tent of your dough or batter might change. Baking time and temperature may also have to be adjusted. But the old adage that products with less calories and fat do not taste as good as the original is no longer true.
Gluten-free baking
Celiac disease is an autoimmune disorder of the small intestine that affects one in 133 people in the United States. It is caused by a reaction to a gluten protein found in wheat, rye, and bar- ley and anything derived from these grains. Oats also make this list because they often contain gluten as a result of cross contamination from packaging. In the most extreme cases, these grains could be deadly for a celiac. The only effective treatment is a gluten-free diet.
As celiac disease has become more common, pastry chefs have worked to develop baked goods without the use of wheat, rye, barley, or oats. When making gluten-free prod- ucts, it is important to make sure to use clean tools and surfaces, have separate cooking uten- sils, and, if possible, work in a room where wheat, barley, rye, or oats have not been present.
It is imperative that no contamination occur when making gluten-free products.
Since wheat fl our is not used in gluten-free baking, chefs must use different stabilizers as substitutes. Some of the possibilities include rice fl our, potato starch, tapioca starch, whey powder, bean fl ours, guar gum, and xanthan gum. Other ingredients that are safe to use are distilled alcohols and extracts, rather than fermented ones.
The strides made to allow celiac disease sufferers to enjoy breads and cakes and cook- ies are an important milestone in how far baking has come in the past decades.
Baking for vegans
A vegan is a person who consumes only products of the plant kingdom, excluding eggs, dairy, and any other animal products (including honey).
Baking for vegans may seem nearly impossible, but many products have been devel- oped that are vegan-friendly. Products that can be used for vegan baking include soy milk, soy margarine, vegetable oil, soy yogurt, tofu, fl axseed paste, arrowroot starch, whole wheat fl our, oats, mashed sweet and regular potatoes, tahini and nut butters, and agar-agar.