Sauces, dressings, and condiments, such as mayonnaise, benefit in obvious ways from the emulsifying properties of the egg yolk. While it is easy to observe the importance of a stable emulsion in mayonnaise or a dressing where one can witness the battle between immiscible liquids (typically water and fat) as they strive to separate from each other, emulsifiers play an important although less obvious role in other formulations.
Egg yolks can supply emulsification in baked goods, especially within the batter of sweeter formulations, such as cakes. Egg yolks also lend their emulsification properties to premium ice creams that look to natural ingredients to supply their decadent and delicious texture and taste.
Despite the challenges of the past year—or perhaps because of them—consumers continue to seek out products that use more natural, authentic ingredients. The International Food Information Council Foundation’s 2020 Food & Health Survey found that the “natural” label claim remains the most widely sought, influential health claim above all others, including locally sourced, non-GMO, etc.
People perceive food products more positively when they are free from artificial ingredients. But it isn’t simply perception. Various studies have proven that natural ingredients often help create a superior product. Conversely, ingredient substitutions often pose myriad challenges with the increase or decrease of any specific traditional ingredient affecting the texture, stability, and sensory attributes, not to mention label length. A natural emulsifier such as the egg can aid multiple product categories.1
Attaining a proper emulsion
An emulsion is the combination or blending of two immiscible liquids with one of the liquids dispersed into the other in the form of small droplets through mixing or whipping, with the speed of blending dependent on the application. The droplets must remain dispersed for the mixture to be considered a stable emulsion; yet the very nature of immiscible liquids means they want to separate. In order to achieve a stable emulsion, surface-active components via emulsifiers need to adsorb into the mixture.
Egg yolk contains a large number of surface-active components, which possess both hydrophilic (water attracting) and lipophilic (fat attracting) qualities. The surface-active components in an egg yolk, the various proteins and phospholipids acting together, form an interfacial film between the oil phase and the water phase in formulation, or almost a protective coating around the dispersed droplets. This action helps supply kinetic stability.
Droplet size also is important, as smaller droplets make for more stable emulsions. The phospholipids within the egg yolk (approximately 30% of its composition) act as the surface-active agents and may lower the interfacial tension “significantly” facilitating the formation of small droplets during emulsification.2
Environmental conditions and ingredient handling can impact additional factors such as droplet size or adsorption. An egg yolk typically enables stable emulsions at a lower pH than other food emulsifiers — one of its more unique properties compared to other ingredients — to help form acidic food emulsions.
The role of an emulsifier within ice cream is almost contrary to its usual role. Within ice cream, emulsifiers are used to make an emulsion that is more susceptible to controlled destabilization or partial coalescence.
This partial coalescence has a significant impact on multiple touchpoints for ice cream quality and the eating experience, including dryness, a smooth and creamy mouthfeel, resistance to shrinkage during storage, and resistance to meltdown during consumption. A small percentage of egg yolk — just 1% to 2% — induces a “sufficient structure similar to (the use of) monoglycerides” or a sufficient amount of partial coalescence.3
In baked goods — especially in sweet baked goods, such as cake batter, which often is comprised of a large amount of water and fat — emulsifiers help maintain the quality and integrity of the finished product by stabilizing the emulsion of these disparate ingredients in the batter phase.
Within cake batter formulations, the egg protein combined with its emulsifying capabilities lends multiple structural and textural benefits to the finished product. Egg proteins contribute a great deal to the structure, texture, appearance, crumb, and taste of baked goods, but so does the emulsification supplied by the yolk’s phospholipid content.
Improperly emulsified cake batter may have a number of issues. It might fall or sink while baking or simply have less rise than properly emulsified batter. This leads to an uneven texture and a flat, flavorless outcome. Properly emulsified cake batter traps air within the fat, resulting in a fluffier, lighter, and springy texture, an even crumb, and better flavor.
Adding extra yolks to cake batter enables it to hold extra liquid and therefore a greater amount of sugar. This helps create a moist, sweet cake with good structure. Adding the eggs slowly helps promote an even suspension of liquid in fat.
Egg yolk products are available in multiple forms for use in emulsification, including fresh, frozen or dried, or as whole eggs in the same forms.
Learn more about the emulsifying capabilities of egg yolk.
Egg ingredients don’t stop with a single functional property. They contribute more than 20 functional benefits to food formulations. Read about the additional 20-plus functional properties of egg ingredients on the American Egg Board website.
To locate a supplier of refrigerated, frozen, or dried egg yolk products, visit the American Egg Board’s Egg Product Buyers’ Guide.
Hasenhuettl, G., and Hartel, R. W., 2019. Food Emulsifiers and Their Applications. 2nd ed. Switzerland: Springer
Elisa Maloberti is director of egg product marketing at the American Egg Board.
About the American Egg Board (AEB)
Home of the Incredible Egg, the AEB is the U.S. egg industry’s national commodity marketing board. The AEB’s mission is to increase demand for eggs and egg products through research, education and promotion. The AEB is located in Chicago.