The short answer is very important. Eggs are a cornerstone ingredient in the world of baking, essential to countless recipes from cakes and cookies to custards and soufflés. Their unique properties make them indispensable, providing structure, leavening, richness, color, and flavor to baked goods. Understanding the roles eggs play in baking can help home bakers and professionals alike achieve consistent and superior results in their creations.
However, before we begin to get into how eggs work in baking, let’s start at the beginning – with the egg.
The Shell
The outermost layer of an egg, the shell, is composed primarily of calcium carbonate (CaCO3). Despite its hard appearance, the shell is porous, allowing for the exchange of gases and the retention of moisture. These pores also provide a barrier against microbial contamination while maintaining the integrity of the egg’s contents. The shell’s strength protects the egg from physical damage, making it a crucial component for both storage and use in baking.
Shell Membranes
Beneath the shell are two thin layers known as the inner and outer shell membranes. These membranes are made of keratin-like proteins and serve as additional defense mechanisms against bacterial invasion. They also help in retaining the moisture within the egg, which is vital for maintaining the egg’s quality over time.
Air Cell
Located at the larger end of the egg, the air cell forms between the inner and outer shell membranes as the egg cools after being laid. This pocket of air is essential for the developing chick in fertilized eggs, providing the first breath of air during hatching. In baking, the presence of an air cell can indicate the egg’s freshness, with smaller air cells signifying a fresher egg.
Albumen (Egg White)
The albumen, commonly referred to as egg white, consists mostly of water (about 90%) and proteins such as ovalbumin, conalbumin, and ovomucin. Sixty percent of the egg’s protein comes from the egg white. There have been 12 different types of proteins that make up the albumen protein. The most abundant are the ovalbumin, which accounts for over 50% of the egg white. It is easily denatured by heat.
Other proteins in the egg white that contribute to any successful bake are the Ovotransferrin (Conalbumin) – which is about 12-13% of the whites. It’s has antimicrobial properties due to its ability to bind iron, depriving bacteria of the iron they need to grow. It also contributes to the gel formation when egg whites are cooked.
Ovomucoid, which is 11% of the egg white, inhibits trypsin, a digestive enzyme. This protein helps stabilize egg white foams, which is essential for their use in baking and other culinary processes.
Lysozyme, 3.5%, is an unusual albumen protein, because, according to Foods Experimental Perspectives, “it has a fraction (G1 globulin) that has an isoelectric point of 10.7. Only avidin, among other albumen proteins, has an isolextric point in the alkaline range.” It is also has strong antibacterial properties because it can break down the cell walls of certain bacteria. This protein is also used in food preservation and pharmaceuticals.
Other proteins include Glycoprotein (Ovomucin), around 1.5-3.5%. It is responsible for the gel-like consistency of egg whites and plays a significant role in the stability and viscosity of egg white foams. This property is critical for creating stable foams in dishes like soufflés and meringues.
Avidin: (about 0.05%) binds biotin (vitamin B7) strongly, preventing its absorption. However, cooking deactivates avidin, rendering it harmless. In raw eggs, this protein can inhibit biotin absorption if consumed in large amounts. Flavoprotein, found in small amounts, binds riboflavin (vitamin B2) and participates in various biochemical reactions, contributing to the nutritional content of egg whites.
Ovoglycoprotein, also found in small amounts, has protective and structural functions in the egg white, contributing to overall stability and functionality.
It is also crucial for the thickening and gelling properties when egg whites are heated. It also helps stabilize foams, which is important for creating light and airy textures in meringues and soufflés.
The albumen is divided into two main layers: the outer thin albumen and the inner thick albumen. The egg white acts as a protective layer for the yolk and provides water and protein, crucial for the structure and stability of many baked goods. It is responsible for the foaming and leavening properties in recipes, contributing to the light and airy texture of cakes and meringues.
Chalazae
Within the albumen are the chalazae, two twisted, cord-like structures that anchor the yolk in place. These cords ensure that the yolk remains centered and stable, preventing it from touching the shell. The chalazae provide cushioning and support, helping to maintain the yolk’s position and integrity, which is especially important when handling and mixing eggs for baking.
Yolk
The yolk is the nutrient-rich core of the egg, encased in the vitelline membrane. It contains fats, proteins, vitamins (such as A, D, E, and K), and minerals, making it an essential ingredient for enriching the flavor and texture of baked goods. The yolk also provides emulsifying properties, which help blend fats and liquids smoothly, contributing to the creamy texture of custards and sauces.
Vitelline Membrane
The vitelline membrane surrounds the yolk, keeping it intact and separate from the albumen. This membrane is crucial for maintaining the structural integrity of the yolk during mixing and baking, ensuring that the yolk can perform its functions effectively.
Germinal Disc (Blastodisc)
On the surface of the yolk, there is a small, white spot called the germinal disc or blastodisc. In fertilized eggs, this is where the embryo begins to develop. In baking, the germinal disc does not play a significant role, but it is an interesting aspect of egg anatomy.
Cuticle (Bloom)
The cuticle, or bloom, is a thin, outermost layer that covers the shell. It serves as an additional protective barrier against microbial invasion and helps reduce moisture loss. While the cuticle is often washed away in commercially processed eggs, its presence in fresh eggs adds an extra layer of protection.
The average whole egg (58% is composed of the white and 31% is the egg yolk) is made up of 65.5% water. Out of that 88% is found in the egg while and 48% in the egg yolk.
The United States Department of Agriculture (USDA) oversees this process, evaluating both external and internal attributes to categorize eggs into distinct grades.
Egg Grading Process
Egg grading involves comprehensive assessment of various factors. Externally, eggs must be clean, free from stains, dirt, or defects such as cracks. Internally, freshness is determined by the size of the air cell, which indicates the age of the egg. Fresh eggs have smaller air cells that expand over time due to moisture and carbon dioxide loss. The yolk should be well-centered and barely visible under candling, indicating freshness. Fresh eggs also have clear, firm whites that maintain their shape.
The date when eggs were graded will appear on the carton as a three-digit number corresponding to the day of the year. If an egg was graded on January 1 it would appear as 001 and ending with December 31 – 365.
USDA Egg Grades
The USDA classifies eggs into three grades based on these criteria. Grade AA eggs are ideal for applications requiring pristine appearance, with intact shells, minimal air cell depth, and firm whites. Grade A eggs are suitable for most culinary uses, featuring clean shells, slightly larger air cells, and reasonably firm whites. Grade B eggs, primarily used in baking and processed egg products, may have minor shell imperfections, larger air cells, and thinner whites.
Consumer shell eggs in the United States are classified into weight classes based on the average weight per dozen eggs. These weight classes, regulated by the USDA (United States Department of Agriculture), include:
- Jumbo: eggs weighing more than 30 ounces per dozen (70.9g each)
- Extra Large: eggs weighing between 27 ounces and 30 ounces per dozen (63.8g each)
- Large: eggs weighing between 24 ounces and 27 ounces per dozen (56.8g each)
- Medium: eggs weighing between 21 ounces and 24 ounces per dozen (42.5g each)
- Small: eggs weighing less than 18 ounces and 21 ounces per dozen (42.5g each)
- Peewee: eggs weighing 15 ounces or less per dozen (35.4g each)
“It is important to note that egg packers are allowed by the USDA to include eggs that are larger than the package indicates when packing eggs,” writes Miranda Kohout in Pastry Arts Magazine. “Any container labeled ‘large eggs’ can also contain extra-large (XL) and even jumbo eggs. Any chef using fresh eggs in a recipe will want to measure them by weight rather than by the piece, as natural variations within a size, coupled with these variations in size within a case, will mean that one egg can be very different in size from the next.”
The differences between various types of eggs, such as regular eggs, grain-fed, pasture-raised, and free-range, primarily lie in the living conditions and diets of the hens that lay them. Sometimes confusion lies in what’s the difference between a cage-free hen, a free-range hen, and a pasture-raised hen. Here are the distinction between each of the terms commonly used:
- Regular Eggs (Conventional Eggs): These are the most common eggs found in supermarkets. The hens are typically raised indoors in large-scale commercial facilities. They may have limited space and access to natural light. Their diet often includes a formulated feed that may include grains, soybeans, and other supplements.
- Grain-Fed Eggs: These eggs come from hens that are fed a diet primarily composed of grains, such as corn or wheat, along with other feed supplements. The hens may still be raised in indoor facilities typical of conventional egg production.
- Pasture-Raised Eggs: Hens that produce pasture-raised eggs have continuous access to outdoor pasture areas where they can forage for grasses, insects, and other natural foods. They typically have more space compared to conventional or free-range systems. The diet of pasture-raised hens includes what they find outdoors supplemented with grains or other feed.
- Free-Range Eggs: Free-range hens have access to the outdoors, although the specifics of the outdoor area can vary. They are not confined to cages and have more space to move around compared to conventional systems. Their diet may include grains, forage, and natural supplements.
- Organic Eggs: Organic eggs come from hens that are raised according to USDA organic standards. This includes access to the outdoors (free-range or pasture-raised), organic feed (free of synthetic pesticides, herbicides, and genetically modified organisms), and adherence to strict animal welfare standards.
- Cage-Free Eggs: Hens producing cage-free eggs are not confined to cages but may still be raised indoors in a barn or warehouse environment. They have more space to move around compared to caged hens but may not necessarily have access to the outdoors.
- Omega-3 Enriched Eggs: These eggs come from hens fed a diet supplemented with sources of omega-3 fatty acids, such as flaxseed. This results in eggs with higher omega-3 content compared to conventional eggs.
Factors Affecting Egg Quality
Several factors influence egg quality. Freshness is evident in thicker whites and centered yolks, while aging enlarges air cells and alters texture. Proper storage conditions, such as a cool environment below 45°F (7°C) with the pointed end down, help maintain egg quality. Gentle handling during transport and storage prevents shell damage and maintains structural integrity. Additionally, a hen’s diet and health significantly impact egg quality, with nutrient-rich diets supporting shell strength and nutritional content.
Expiration dates for eggs can be confusing, because federal law does not mandate an expiration date for eggs; however, according to Food Arts Magazine, individual states may enforce such requirements, and most egg processors opt to include a “sell-by” or expiration date. Eggs packed under the USDA grading program must display the packing date, indicating they are safe for consumption for four to five weeks from that date.
Accounting for eggs in baker’s percentages involves calculating the proportion of eggs relative to the total flour weight in a recipe. Baker’s percentages are based on the weight of the flour, which is always considered 100%. Here’s how you can include eggs in baker’s percentages:
Understand Baker’s Percentage: In baker’s percentages, the weight of each ingredient in the recipe is expressed as a percentage of the flour weight. Flour weight is always set to 100%.
Weigh the Eggs: Determine the total weight of eggs used in the recipe. This includes both the egg yolks and whites.
Calculate the Percentage:
- Divide the weight of eggs by the weight of flour used in the recipe.
- Multiply the result by 100 to convert it to a percentage.
For example, if your recipe uses 500 grams of flour and 200 grams of eggs:
Include in the Total: Add the egg percentage to the percentages of other ingredients like water, sugar, salt, etc., to ensure they collectively do not exceed 100%. This helps maintain the balance of the recipe.
Adjust for Egg Yolks and Whites: If your recipe calls for separated eggs (yolks and whites used separately), calculate the percentage for each component separately based on their respective weights and the total flour weight.
Apply in Recipes: Use baker’s percentages to scale recipes according to desired batch sizes while maintaining consistent ingredient ratios. This method provides flexibility and precision in recipe formulation, especially in professional baking where accuracy is crucial.
One of the primary functions of eggs in baking is to provide structure and stability. When eggs are beaten or whisked, their proteins unfold and form a network that traps air. This process, known as coagulation, gives structure to baked goods. During baking, the proteins solidify, helping to set the shape of cakes, muffins, and other baked items. This structural support is crucial for maintaining the integrity of the final product.
In baking and cooking, various ingredients can enhance or inhibit the properties of eggs. Understanding these interactions is crucial for achieving the desired texture, flavor, and structure in recipes. Common ingredients in baking that either work with or against eggs are sugar, salt, fats, acid, water, heat, and alcohol.
Sugar stabilizes egg whites during whipping, allowing them to hold more air and create a more stable foam. This is crucial for meringues and soufflés. Pastry Arts Magazine says that in egg-white foams, sugar “increases the viscosity of the water in the foam” thereby allowing the “foam cell walls to become thicker and stronger. On the other hand, it also makes the egg white proteins to coagulate. If they have already coagulated, it will take the foam longer to whip up and it will become dense. The best time to add sugar is when the whites are at soft-peak stage.
As far as egg yolks are concerned, since when sugar is added to yolks several things happen. First, sugar dissolves in the water content of the yolks creating a thicker mixture. Sugar is hygroscopic, meaning it attracts and holds water. However if you add the sugar to the yolks too early you can get what pastry chefs refer to as “burning” the egg yolks. It is also known as “curdling” or “cooking” the yolks. This occurs because the sugar starts to denature the proteins in the egg yolks and they clump together- similar when heat is added. It creates a grainy, lumpy texture that will give any batter a gritty texture and it will negatively impact the final product’s consistency and appearance.
The best way to avoid “burning” is to do a couple of things. Add the sugar to the egg yolks and mix them immediately and thoroughly or gradually add the sugar while continuously whisking the yolks. Finally, once the sugar and yolks are combined, use the mixture in your recipe promptly.
Fats have a love/hate relationship with eggs. When mixed with eggs, fats can contribute to a tender and moist crumb in baked goods. In custards and sauces, fat helps create a smooth, rich texture. However, fat can prevent egg whites from whipping properly. Even a small amount of yolk or grease can interfere with the formation of a stable foam. The best way to insure that you will have perfect whipped egg whites every time is to throughly clean out your bowl. As an added measure, add a little white vinegar to the bowl and swirl it around, rinse it out with hot water, and wipe it completely dry with a towel.
Salt is another of those ingredients that can either be a friend or foe. In most cases, a small amount of salt will enhance the flavor of eggs and baked goods. In baked goods, egg proteins need an acid to set up.
It will also stabilize egg whites during whipping, however, like sugar it all depends on when you add them. Added during the soft peak stage, then it is fine. However, added too early it will coagulate the egg whites and make them less airy and stable.
“One can think of an acid added to whites at the beginning of the whipping process as creating conditions similar to lightly whipping them,” states Food Arts Magazine. “The protein molecules have broken apart and can begin trapping air and water.” The sugar then is able to strengthen the protein strands leading to “the arrest and most stable meringue.”
Acidic ingredients lower the pH of egg whites, which helps to stabilize the foam and make it less likely to collapse. This is particularly useful in meringues and angel food cakes. However, like sugar and salt, too much acid can break down the proteins, preventing proper foam formation.
Starch has significant effects on eggs when used in cooking and baking, particularly in recipes that require thickening or setting, such as custards, sauces, and puddings.
Starch serves as a thickening agent when combined with eggs, helping to stabilize the mixture and prevent curdling. This is especially useful in recipes like custards, pastry creams, and puddings. When heated, starch granules absorb water and swell, creating a network that thickens the liquid. This network helps support the egg proteins, providing a smoother, more consistent texture.
Starch helps to control the coagulation temperature of eggs, preventing them from cooking too quickly. This is crucial in custards and sauces, where gradual thickening is desired to avoid a curdled or grainy texture. By distributing heat more evenly, starch reduces the risk of the eggs scrambling or forming lumps, ensuring a smooth final product.
The addition of starch results in a creamier, more stable texture in egg-based dishes. It prevents the formation of a watery layer by binding excess moisture, thus enhancing the mouthfeel and consistency. Starch provides structural integrity, helping the mixture hold its shape once cooled, which is particularly beneficial in pie fillings and puddings.
Custard and Puddings
When making custards or puddings, starch is often mixed with sugar and then combined with egg yolks before adding the liquid. This mixture is then gently heated until it thickens. The presence of starch ensures that the custard or pudding thickens uniformly without curdling, resulting in a silky, smooth texture.
Pastry Cream
In pastry cream, starch (often in the form of cornstarch or flour) is crucial for achieving the desired thickness and stability, allowing it to hold its shape when used as a filling for pastries and desserts.
Starch is a key ingredient in making egg-based dishes smooth and delicious. It helps thicken and stabilize mixtures, preventing curdling and ensuring the texture is just right. By adding starch to your recipes, you can achieve consistently great results in your cooking and baking.
Leavening
Eggs also contribute to the leavening process, which is essential for achieving a light and airy texture. When eggs are beaten, they incorporate air, which expands when heated, causing the batter to rise. This is especially important in recipes for soufflés, meringues, and sponge cakes, where the volume and fluffiness of the final product depend on the incorporation of air. The egg whites, when whipped, form a foam that provides lift, while the yolks add richness and moisture.
Moisture and Richness
Eggs add moisture and richness to baked goods. The water content in eggs helps to hydrate the dry ingredients, ensuring a smooth and cohesive batter. The fats in the egg yolks contribute to the overall richness and tenderness of the final product. This combination of moisture and fat is crucial for creating a moist and tender crumb in cakes, cookies, and pastries. The lecithin in egg yolks also acts as an emulsifier, helping to blend fats and liquids smoothly, leading to a uniform texture.
Color and Flavor
Eggs impart a natural color and flavor to baked goods. The yellow pigments in egg yolks give a golden hue to cakes, cookies, and pastries. This visual appeal is particularly desirable in items like brioche, challah, and custards. Additionally, the unique flavor of eggs enhances the overall taste of the final product, contributing a subtle richness that complements other ingredients.
Binding and Thickening
Eggs act as a binding agent, holding ingredients together and providing cohesiveness to the batter or dough. This is particularly important in recipes like meatloaf, meatballs, and certain types of cookies and cakes. The binding properties of eggs help to prevent crumbling and ensure a uniform texture. In custards, puddings, and pie fillings, eggs function as a thickening agent. When heated, the proteins in the eggs coagulate, thickening the mixture and giving it a smooth, creamy consistency.
Versatility
The versatility of eggs makes them a valuable ingredient in a wide range of baked goods. They can be used whole, separated into yolks and whites, or even just the whites or yolks, each providing different properties to the recipe. For instance, egg whites can be whipped into a stable foam for meringues and angel food cakes, while yolks can add richness to custards and pastry creams.
Nutritional Benefits
Beyond their functional properties, eggs also contribute nutritional benefits to baked goods. They are a good source of high-quality protein, vitamins, and minerals, including vitamin A, vitamin D, vitamin B12, and selenium. Incorporating eggs into baked items can enhance their nutritional profile, making them a more wholesome option.
Egg Substitutes
While eggs are essential in many recipes, there are instances where egg substitutes may be used, such as for those with allergies or dietary restrictions. Common egg substitutes include applesauce, mashed bananas, yogurt, and commercial egg replacers. These alternatives can mimic some of the functions of eggs, such as providing moisture and acting as a binding agent, but they may not fully replicate the structural and leavening properties of eggs.
Eggs play a multifaceted role in baking, contributing to the structure, leavening, moisture, color, flavor, binding, and nutritional value of baked goods. Their unique properties make them an indispensable ingredient in a wide range of recipes. Understanding the importance of eggs in baking allows bakers to make informed decisions about their use and explore creative alternatives when necessary. Whether you are baking a simple cake or a complex pastry, the role of eggs cannot be understated in achieving the desired texture, flavor, and overall quality of your baked creations.
References:
Foods Experimental Perspectives, McWilliams, Margaret, Prentice Hall, 2012
Pastry Arts Magazine, Spring 2024, Issue No. 23
Wikipedia
University of Nebraska-Lincoln, UNL Food
