Shortenings are essential components of most crackers and cookies. The type and amount of shortenings and emulsifiers in a formula affect both the machining response of a dough or batter and the quality of a finished product. Coatings (such as chocolate) and fillings (such as sandwich cremes) depend on specific fats and oils to furnish the structural part of such components.
Natural fats and oils suitable for shortenings include butter, lard, beef fats, and vegetable oils. The latter material includes refined and modified soybean, cottonseed, coconut, palm, and corn oils. The processing of shortenings may include some or all of the steps of refining (to remove contaminants), deodorizing, winterizing (to remove high-
melting-point fats), bleaching, hydrogenation, fractionation, and blending. The purpose of these operations is to yield a shortening that is bland in flavor, essentially colorless, and free of aromas; has a melting point and solid fat content within the desired ranges for the application for which it is destined; and has other characteristics desired by the purchaser. Butter, and to a lesser extent lard and beef fats, have natural flavors and physical qualities that are considered desirable in some applications.
Recently, new fat systems that are non- or poorly digestible have been developed. One of these fat systems is a combination of sugar esters that is nondigestible in the body. Another fat system, which contributes a reduced calorie load, modifies the triglyceride composition through es-terification with nondigestible fatty acids.
The function of shortenings in baked goods is primarily to modify the physical properties or texture of the finished product, making it more tender or flakier and, in some cases, giving it a glossier, more appealing appearance. Shortenings may also affect the rheological characteristics of doughs. Most crackers have a topping or spray oil applied after baking, to add flavors or solids (cheese, spices and/or herbs) that improve the eating qualities.
Emulsifiers are specialized fats or fat systems that act as surfactants between various systems (eg, oil and water). Emulsifiers are specialized fats that can be composed of mono-, di-, or triglycerides or their combinations. Chemically, an emulsifier is a molecule composed of a water-soluble or hydrophilic portion and a water-insoluble or hydrophobic portion. Different solubility tendencies thus exist within the same molecule. This leads to the phenomenon of incomplete solubility in both water and oils. Emulsifiers partition, or orient, themselves at the interface between oil and water phases (3). Naturally occurring emulsifiers include egg yolk or fluid lecithin. Fluid lecithin is derived from either soybeans or corn during the milling process.
All cookies and many crackers contain some form of sweetener. The quantity of sweetener is usually such that it has significant effects on the texture and appearance of the product, as well as on its flavor. Machining properties and response of the dough piece to oven conditions are also related to the type and quantity of sweetener employed. In fermented goods, sugars serve as substrates from which yeast and other microorganisms form carbon dioxide and the flavoring substances characteristic of these products. Commercial sucrose (cane or beet sugar) functions not only as a nutritive sweetener but also as a texturizer, coloring agent, and as a means of controlling spread during baking. However, differences in the crystallization properties between cane and beet sugars can be quite significant. In marshmallow, jellies, and fruit jams with relatively high moisture content, sucrose has the valuable property of delaying microbiological spoilage, when it is present in a high-enough concentration.
Sucrose can be obtained in various particle sizes or in the form of syrups. When added to a dough as granulated or powdered sugar, its particle size influences the dimen sions of the finished cookie, by controlling the extent to which the dough piece spreads as it is baking.
Syrups are easier to handle, being adaptable to fluid-transfer systems of pumps, pipes, valves, and meters. Syrups can crystallize in handling systems, causing problems. Sucrose will not form a stable aqueous solution of greater than 67% concentration at room temperature, and this is not high enough to ensure resistance to all forms of microbiological growth. Treating a solution of sucrose with an acid or an enzyme known as invertase hydrolyzes the sucrose into fructose and dextrose (3). Invert sugar solutions are sweeter than pure sugar solutions of the same concentration. Invert syrups are less likely to crystallize and are more resistant to spoilage.
Corn syrups are sweeteners prepared by hydrolyzing cornstarch with acids or enzymes. The standard types contain glucose and varying amounts of maltose, larger oligomers, polymers, and other carbohydrates, plus minor amounts of impurities. In preparing the high-fructose corn syrup (HFCS) varieties, manufacturers isomerize part of the glucose to fructose. Because fructose is sweeter than glucose, a substantial increase in sweetening power results. HFCS can be substituted for invert sugar syrups in many applications, but they are not identical.
Regular corn syrup is categorized by type, according to dextrose equivalent (DE), which is a measure of reducing sugar content. A second parameter is total solids content of a syrup. Cookies made with syrups with higher-reducing sugar contents have a greater sweetness that those made with a similar content of low-DE syrup. In addition, the browning of the crust and, for that matter, the interior of the cookie is affected by high contents of reducing sugar from any source. Low-DE corn syrups can increase the apparent viscosity of doughs and batters and make a finished product chewier.
Molasses is less-refined, concentrated sugar syrup containing some of the impurities, flavoring and coloring materials from the sugar-refining process. Molasses is available in various degrees of darkness; the darker the color, the more bitter and less sweet the syrup is. True blackstrap, the final residue of the refining process, is not suitable for human consumption and is used primarily as an animal feed additive.
Commercial brown sugar is granulated sugar that has been coated with a small percentage of molasses. No commercial brown sugar is produced by removing partially refined granulated sugar from the refining process. There are, however, less-refined sugars available from refiners (eg, Demarara) that occasionally provide some economic advantages over pure cane or beet sugar.
Honey is primarily invert syrup with various impurities that give typical flavors and color. Various concentrated fruit juices are used, as alternatives to sucrose and corn syrups, as natural sweeteners. These fruit juices are principally from grape, pear, or apple sources that have been treated to have low characterizing flavor. These fruit syrups are usually more expensive than sucrose or corn syrup.
Caramel color is a widely used brown pigment made from acid- or alkali-treated corn syrup (or sugar syrup). Caramel color is used in many types of cookies, in liquid or powder form, for its colorant properties and its low cost. It contributes no flavor to a finished product.
Synthetic sweeteners, such as saccharin and aspartame, can be used in certain dietetic cookies. However, sugar serves as a primary bulking agent in cookies. When significant reductions in sugar content are made, texture and other physical characteristics are affected. Most synthetic sweeteners are not heat stable, but recent developments are changing that limitation. New synthetic sugars are under development, which have up to 2000 times the sweetening power of sugar. Of course, most of these synthetic sweeteners are regulated by law and must pass stringent food and drug tests. Nonnutritive and reduced-calorie sweeteners are playing a more important role, as consumer demand requires such specialized products.
A leavening agent is a substance or system that expands or lightens a dough or batter at some stage of its processing. Leavening can be achieved in three ways: mechanically, biologically, or chemically. The leavening effect is absolutely essential to the formation of a finished product having the appearance and eating qualities that are required by consumers. Leaveners familiar to every baker are baking powder and yeast. Air and water vapor (steam) are also leaveners. They cause expansion of the product during baking, providing the dough or batter has a structure capable of retaining the gas. Ammonium bicarbonate is a chemical additive that has leavening and other effects on cookie and cracker doughs.
Yeast alters the physical properties of dough and its handling characteristics during mixing and fermentation. Yeast acts on certain sugars to form alcohol and carbon dioxide. Gluten from the flour absorbs water and forms extensible membranes that trap carbon dioxide and expand to decrease the density of the dough mass. The diffusion and accumulation of carbon dioxide throughout the dough mass generates powerful stretching action. These changes in gluten are described as the "mellowing," maturing, or conditioning of the dough (3).
An egg white meringue, which is the basis of angel food cake, relies on egg albumen to initially entrap the air that has been beaten into the mixture. The addition of flour strengthens the dough mass in the latter stages of mixing and baking.
Few cookies depend on yeast leavening. Crackers made by the sponge-and-dough method (eg, soda crackers, saltines, and certain snack crackers) require a fermentation period to develop their textures and characterizing flavors. Typical sponges contain flour, water, and yeast mixtures; the doughs usually contain the remaining ingredients, including sodium bicarbonate. The acids produced during sponge fermentation will react with sodium bicarbonate to neutralize the acid and yield additional leavening.
The great majority of cookies contain some sort of chemical leavening system such as baking powder, which is a mixture of sodium bicarbonate and a reactive acidic compound such as cream of tartar (potassium acid tartrate). In addition, fillers such as starch and other additives will be included in commercial baking powders to standardize their strength and delay storage deterioration.
When formulating cookie doughs, most food technologists add sodium bicarbonate in combination with a reactive acidic material, in proportions appropriate to the pH of the dough, rather than rely on premixed baking powder. Other types of chemical leaveners (eg, monocalcium phosphate, sodium acid pyrophosphate) have specific characteristics that can be tailored to the requirements of a given dough formula. The goal is usually to obtain a finished product with a pH close to neutrality, although this generality may not apply to certain products (eg, chocolate doughs containing Dutched cocoa, with a resulting higher pH).
Ammonium bicarbonate is a self-reacting leavener that decomposes as the dough is heated during the early stages of baking, giving off ammonia, carbon dioxide, and water. It is acceptable only for products baked to lower moistures (3-9%). In high-moisture products, the ammonia dissolves into the water, producing an unpleasant aroma and/or taste that most people find offensive. However, ammonium bicarbonate can be very effective in altering finished product characteristics (height, spread, and texture) for both cookies and crackers.
Many cookies undergo an increase in volume (decrease in density due to leavening) that is quite small compared with that of bread. For example, traditional shortbread cookies may contain no added soda and do not seem to increase in size during baking. An examination of their interior shows, however, that some expansion has taken place, as a result of air and water (steam) that have expanded during the baking process.
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