Taylor Made: Sugar engineering
In baking, granulated sugar is considered a weakening ingredient because it weakens the structure of the dough or batter. This is especially applicable in cookie dough, where sugar plays a large role in the outcome of the cookie’s texture and appearance. Sugar caramelizes during baking, darkening the tone of the cookies. It also absorbs some of the moisture in the dough, causing the cookies to crisp if other ingredients or procedures aren’t present to keep them soft. A higher sugar : flour ratio in the dough means that the dough will spread out as it heats in the oven—this is caused by the sugar melting. For those who are wondering, butter and other fats are also weakening ingredients, while flour and eggs are strengthening.
From a molecular standpoint, sugars, also called saccharides, are classified by their structures. Our classical sugars (aka simple carbohydrates) are broken into three groups: monosaccharides, disaccharides, and polyols. A common polyol is the sugar alcohol sorbitol, which is used as both a sweetener and a laxative. Glucose (C6H12O6) and fructose (found in berries and root vegetables) are both monosaccharides. Disaccharides can be broken down into two monosaccharides; one common example is sucrose, made up of glucose bonded to fructose. Complex carbohydrates like cellulose, which makes up our insoluble dietary fiber, and starch, are classified as polysaccharides. Polysaccharides are made of chains of monosaccharides and take longer to be broken down by the metabolism.
Granulated sugar, classified as sucrose, makes a good building material. Sugar crystals are easily assembled into cubes by being mixed with water, packed into a mold, and dried. More complex sugar structures are often seen on holidays such as Day of the Dead and Easter.
For Day of the Dead skulls, granulated white sugar is mixed with meringue powder, which contains cornstarch and dried egg whites. Water is sprinkled in to achieve the texture of wet sand. If you think of the resulting mixture like concrete, the sugar is the aggregate, the meringue powder is the cement, and the water mixes with the cement to create glue that holds together the aggregate and hardens into a finished product (TAM 324, anyone?). The mixture is pressed into molds, one each for the face and back of the skull, then removed and allowed to dry overnight. Since the outer layers of sugar harden first, a hollow area can be scraped out of the back of each half before full hardening is achieved. Thus a hollow skull is made.
For sugar eggs, white granulated sugar is mixed with egg whites (i.e. pre-wetted cement). Much like for the skulls, the mixture is pressed into the mold, then removed and allowed to begin hardening. Sugar is scraped out of the halves to form hollows before the pieces have fully hardened. Because of the presence of the egg white, the pieces should not be refrigerated.
For both, royal icing is used to glue the halves together and to decorate. Royal icing is made from powdered sugar, egg whites, and cream of tartar. Also known as potassium hydrogen tartrate (KC4H5O6), cream of tartar is a byproduct of wine production, as it crystallizes in fermenting grape juice. It serves to stabilize the egg whites, allowing for larger volume to be obtained during whipping. The ingredients are combined and then whipped until stiff. Adding more powdered sugar can thicken the icing to make it stiffer still. The finished product will react with air and hardening immediately, which is why it needs to either be used right away or be kept temporarily in a humid container (achieved by using a fully drenched cloth as a lid).
When made properly, structures built from sugar become very hard and brittle. If treated and handled like the fragile ceramic they resemble, and kept at room temperature in dry air, these structures can last for decades.