Why Sugar is in Food
Beyond its contributions as a sweetener and flavor-enhancer, sugar:
- Interacts with molecules of protein or starch during baking and cooking process.
- Act as a tenderizer by absorbing water and inhibiting flour gluten development, as well as delaying starch gelatinization.
- Incorporates air into shortening in the creaming process.
- Caramelizes under heat, to provide cooked and baked foods with pleasing color and aroma.
- Speeds the growth of yeast by providing nourishment.
- Serves as a whipping aid to stabilize beaten egg foams.
- Delays coagulation of egg proteins in custards.
- Regulates the gelling of fruit jellies and preserves.
- Helps to prevent spoilage of jellies and preserves.
- Improves the appearance and tenderness of canned fruits.
- Delays discoloration of the surface of frozen fresh fruits.
- Enables a wide variety of candies through varying degrees of recrystallization.
- Controls the reformation of crystals through inversion (breakdown to fructose and glucose).
- Enhances the smoothness and flavor of ice cream.
Sugar in Bakery Foods
During the mixing process, sugar acts as a tenderizing agent by absorbing water and slowing gluten development.
During the mixing of batters and doughs, flour proteins are hydrated (surrounded with water) forming gluten strands. The gluten forms thousands of small, balloon-like pockets that trap the gases produced during leavening. These gluten strands are highly elastic and allow the batter to stretch under expansion of gases. However, if too much gluten develops, the dough or batter becomes rigid and tough.
Sugar competes with these gluten-forming proteins for water in the batter and prevents full hydration of the proteins during mixing. As a consequence, less gluten is allowed to “develop,” preventing the elastic dough or batter from becoming rigid. With the correct proportion of sugar in the recipe, the gluten maintains optimum elasticity, which allows for gases to be held within the dough matrix. These gases, from leavening agents and mixing, expand and allow the batter or dough to rise. By preventing the gluten development, sugar helps give the final baked product tender crumb texture and good volume.
Sugar increases the effectiveness of yeast by providing an immediate, more utilizable source of nourishment for its growth.
Under recipe conditions of moisture and warmth, sugar is broken down by the yeast cells, and carbon dioxide gas is released at a faster rate than if only the carbohydrates of flour were present. The leavening process is hastened and the dough rises at a faster and more consistent rate.
Sugar crystals become interspersed among the shortening molecules when shortening and sugar are creamed together.
In cakes and cookies, sugar helps promote lightness by incorporating air into the shortening. Air is trapped on the face of sugar’s irregular crystals. When sugar is mixed with shortening, this air becomes incorporated as very small air cells. During baking, these air cells expand when filled with carbon dioxide and other gases from the leavening agent.
Sugar serves as a whipping aid to stabilize beaten egg foams.
In foam-type cakes, sugar interacts with egg proteins to stabilize the whipped foam structure. In doing so, sugar makes the egg foam more elastic so that air cells can expand and take up gases from the leavening agent.
Egg Protein Coagulation
In unshortened cakes, sugar molecules disperse among egg proteins and delay coagulation of the egg proteins during baking.
As the temperature rises, egg proteins coagulate, or form bonds among each other. The sugar molecules raise the temperature at which bonds form between these egg proteins by surrounding the egg proteins and interfering with bond formations. Once the egg proteins coagulate, the cake “sets,” forming the solid mesh-like structure of the cake.
During baking, sugar tenderizes by absorbing liquid and delaying gelatinization.
In cakes, the heat of baking causes the starch in flour to absorb liquid and swell. This process is called gelatinization. As more liquid is absorbed by the starch, the batter goes from a fluid to a solid state, “setting” the cake. Sugar acts to slow gelatinization by competing with the starch for liquid. By absorbing part of the liquid, sugar maintains the viscosity of the batter. As a result, the temperature at which the cake “sets” (turning from liquid to solid state) is delayed until the optimum amount of gases are produced by the leavening agents. Carbon dioxide, air and steam produced from leavening agents, heated water and air become entrapped and expand in the air cells. The result is a fine, uniformly-grained cake with a soft, smooth crumb texture.
As described above, sugar is effective in delaying starch gelatinization in cakes and provides good texture and volume. Little data is available concerning sugar’s function in delaying gelatinization in breads; therefore its influence on gelatinization in yeast-leavened breads is less clear. In theory, as breads with higher sugar content bake, gelatinization is delayed by the same mechanism described above in cakes. A bread with more tender crumb texture results.
Sugar caramelizes when heated above its melting point, adding flavor and leading to surface browning which improves moisture retention in baked products.
At about 175°C (or 347°F), melted dry sugar takes on an amber color and develops an appealing flavor and aroma. This amorphous substance resulting from the breakdown of sugar is known as caramel. In baking a batter or dough containing sugar, caramelization takes place under the influence of oven heat, and is one of two ways in which surface browning occurs. The golden-brown, flavorful and slightly crisp surface of breads, cakes, and cookies not only tastes good but helps retain moisture in the baked product.
At oven temperatures, sugar chemically reacts with proteins in the baking product, contributing to the food’s browned surface.
These Maillard reactions are the second way in which bread crusts, cakes, and cookies get their familiar brown surfaces. During baking of breads, cakes, and cookies, Maillard reactions occur among sugar and the amino acids, peptides or proteins from other ingredients in the baked products, causing browning. These reactions also result in the aroma associated with the baked good. The higher the sugar content of the baked good, the darker golden brown the surface appears. As described above, these browned surfaces not only taste good but help retain moisture in the baked product, prolonging freshness.
Sugar helps produce the desirable surface cracking of some cookies. Because of the relatively high concentration of sugar and the low water content in cookies, sugar crystallizes on the surface. As sugar crystallizes, it gives off heat that evaporates the water it absorbed during mixing and baking. At the same time, leavening gases expand and cause cracking of the dry surface.
Sugar in Canning and Freezing
Sugar is used in the canning and freezing of fruits to improve flavor and texture, and to preserve natural color and shape. Through osmosis, sugar replaces some of the water in the fruit. This natural process preserves the fruit’s inherent color, texture and shape by preventing the fruit’s remaining water from leaving its cellular structures. As a result, the fruit’s texture is protected against weakening during freezing and canning. In addition, sugar, upon entering the cells, also helps minimize oxidation, and prevents the fruit’s firm texture from becoming mushy. Sugar both enhances flavor and preserves the color of the fruit which makes it more appealing to eat.
Sugar is essential in the gelling process of jams, preserves and jellies to obtain the desired consistency and firmness. This gel-forming process is called gelation – the fruit juices are enmeshed in a network of fibers. Pectin, a natural component of fruits, has the ability to form this gel only in the presence of sugar and acid. Sugar is essential because it attracts and holds water during the gelling process. In addition, acid must be present in the proper proportions. This optimum acidity is a pH between 3.0 and 3.5. Some recipes include lemon juice or citric acid to achieve this proper acidity.
The amount of gel-forming pectin in a fruit varies with the ripeness (less ripe fruit has more pectin) and the variety (apples, cranberries and grapes are considerably richer in pectin than cherries and strawberries). In the case of a fruit too low in pectin, some commercial pectin may be added to produce the gelling, especially in jellies. In recipes that use commercial pectin, the proportions of sugar may be slightly higher or lower than the one part fruit to one part sugar ratio.
Sugar prevents spoilage of jams, jellies, and preserves after the jar is opened. Properly prepared and packaged preserves and jellies are free from bacteria and yeast cells until the lid is opened and exposed to air. Once the jar is opened, sugar incapacitates any microorganisms by its ability to attract water. This is accomplished through osmosis (the process whereby water will flow from a weaker solution to a more concentrated solution when they are separated by a semi-permeable membrane). In the case of jellies and preserves, the water is withdrawn from these microorganisms toward the concentrated sugar syrup. The microorganisms become dehydrated and incapacitated, and are unable to multiply and bring about food spoilage. In jellies, jams and preserves, a concentrated sugar solution of at least 65% is necessary to perform this function. Since the sugar content naturally present in fruits and their juices is less than 65%, it is essential to add sugar to raise it to this concentration in jellies and preserves.
Sugar helps retain the color of the fruit through its capacity to attract and hold water. Sugar absorbs water more readily than other components, such as fruit, in preserves and jellies. Thus, sugar prevents the fruit from absorbing water which would cause its color to fade through dilution.
Sugar in Non-sweet Foods
Caramelization of Meats and Vegetables
Sugar enhances browning and flavor development in sautéed vegetables and meats. Caramelization is the process of cooking sugar, to the browning stage. During sautéing, sugar helps brown vegetables and enhances their flavor. Sugar also increases the browning of meats, adding a depth of flavor to stew dishes featuring well-browned meat. Add sugar judiciously to sautéed vegetables and meats. Sucrose begins to brown at 338°F. Most foods will brown only on the outside and only through dry-heat methods (sautéing, roasting, grilling or broiling), which reach the high temperatures at which browning occurs. Foods cooked with moist-heat methods alone, as in some poached and braised recipes, do not become hot enough to brown or caramelize.
Sugar enhances or brings out the flavors that are already in the barbecue sauce. It enhances the tomato, vinegar or lime flavors that may be present in the sauces. Through its ability to caramelize, sugar also contributes to the browning process, which an artificial sweetener can’t do.
Sugar has an optimum taste between 100°F and 125°F and tastes better when heated. Because sugar can withstand high temperatures, it is a good choice for barbecue sauces. Additionally, sugar provides superior taste, consistency and performance over other sweeteners in barbecue sauce applications.
Sugar creates a shiny, savory glaze on cooked vegetables. Glazing refers to cooking vegetables in a small amount of liquid (stock or water, usually with a little sugar and butter) over medium-low heat until the vegetables release juices, then reducing the liquid until it’s thick. Sugar tenderizes the vegetables and helps create a shiny, savory glaze.
Sauces and Salad Dressings
Sugar balances sour, bitter and spicy components in hot and cold applications. Sour sensations come from acids such as lemon or lime juice, tomato products and vinegars. Salty sensations come from sodium chloride and other salts. Bitterness is a reaction to alkaloids such as quinine and caffeine. The body is more tolerant of sweet sensations than sour, bitter or salty ones. The addition of sweetness to sour, salty and bitter foods can make them taste better. That’s why sugar is added to acidic dressings, salty brine solutions and coffee.
The interaction of taste and temperature produces various flavor sensations. Sucrose has an optimum taste between 100°F and 125°F. Fructose, the major component of honey, exhibits poor sweetening ability when hot, yet tastes very sweet in cold preparations.
Sugar softens and balances the flavor of delicate fish, poultry or meat in brine solutions. A brine is a very salty marinade that tenderizes foods, adds flavor and moisture, and reduces cooking time. Most brines have approximately 20% salinity or 1 pound salt per gallon water. Brines often contain sugar, herbs and spices. Other additions can include wine, beer, fruit juices and vinegar.
The chemistry behind brining is simple: Meat naturally contains salt water. By immersing meat in a liquid with a higher concentration of salt, the liquid (and its flavorings) is absorbed into the meat. The sugar in a brine also draws out some blood remaining in raw fish, beef and poultry. The longer a food is brined, the stronger the flavor will be. Poultry and seafood do not need to be brined as long as denser meats. After brining, the meat (or fish or poultry) contains extra moisture which will remain after cooking, producing a moist finished product.
Sugar adds flavor to salt-cured raw foods. Salt curing is the process of surrounding a food with salt or a mixture of salt, sugar, curing salt, herbs and spices. Salt curing dehydrates the raw food, inhibits the growth of bacteria and adds flavor. It preserves meats such as ham and makes it safe to consume raw. Sugar adds a sweet flavor to cured foods and balances the salt flavor. Most often used with pork or fish, salt curing is NOT a quick procedure and must be carefully managed to meet food safety regulations.
Sugar enhances flavor, browning, and crusting of meat, fish, and poultry, and contributes to osmosis during the smoking step in the barbecue process. A dry rub or dry marinade is a mixture of sugar (often white and brown), salt, and crushed herbs or spices that’s applied to a protein’s surface prior to cooking. Other additions such as minced garlic, onion and grated citrus zest can be added to form a paste which will adhere well to meat, fish or poultry. Unlike a wet marinade, a dry rub remains on the food during cooking.
A dry rub is an important flavor-building component of smoking, which is the first step in traditional barbecue. Through osmosis, the salt in the rub draws moisture from the surface of the meat. The dry surface, combined with the savory rub, create a crust that adds flavor, texture and eye-appeal to the cooked meat. Sugar contributes to osmosis and so to the creation of the crust as well as caramelization and flavor enhancement.
Dry rubs are recommended over marinating for large pieces of meat such as briskets and pork butts because a dry rub will not sear or burn on the grill the way marinades can during the long, slow cooking required for these large cuts. Marinades primarily flavor the surface of meats, and that’s sufficient for small cuts, which have large surface areas; but large meat cuts, with their smaller surface-to-interior ratios, benefit from the deeper flavor penetration of rubs.
Sugar balances acid flavor and helps maintain the texture of pickled vegetables. Pickling means preserving food in a brine or vinegar solution. It is one of the oldest methods of food preservation, perhaps starting with the Chinese in the 3rd century.
Pickled vegetables can be brined (fermented), which involves curing at room temperature for several weeks. Or pickles can be “quick” (unfermented), made in a day or two by adding vinegar to the brine solution. It’s critical to add enough vinegar to prevent bacterial growth.
Sugar is an important component in pickling. Besides balancing the flavor of the vinegar, sugar helps strengthen vegetable cell structures and makes vegetable fibers firmer. Either brown or white sugar can be used. Brown sugar produces a darker brine.
Sugar speeds browning in bread coatings. A combination of sugar and protein in a coating spurs browning. However, sugar must be carefully incorporated into a breading formula. Too much sugar can cause an onion ring coating, for example, to become overly brown before the onion has cooked.
Other Sugar Resources
- All About Sugar
- Sugar and Your Diet
- Types of Sugar
- Why Sugar is in Food
- Educational Materials
- Frequently Asked Questions