FUNCTIONAL

PROPERTIES OF EGG
INTRODUCTION

Egg ingredients supply foods with more than 20 functional properties, including aeration, binding,
coagulation, emulsification, foaming and whipping, to name just a few.
Not only do they have all this functionality, egg ingredients perform these functions under rigorous
processing conditions, demonstrating their reliability during decades of modern food manufacturing.
ADHESION

• The proteins in egg products, specifically in the whites, assist with adhesion and ingredient binding.
When they are heated or exposed to acid, they coagulate, causing the egg product to change from a
liquid to a semisolid or sold.
• When the proteins solidify, they function as an adhesive, connecting ingredients or food components
with each other.
• An egg wash for example, can be brushed onto the surface of baked foods in order to hold topically
applied nuts or seeds. The proteins help these decorative elements adhere to the surface of the baked
good during baking.
• An egg wash can also help control moisture depending on the type of egg mixture used for the egg
wash. Egg yolks or whole eggs will seal in moisture while egg white proteins will draw moisture out.
AERATION/FOAMING/STRUCTURE

• Certain food formulations, particularly in baking, rely on aeration to provide proper product structure.
Aeration can be achieved in several ways including biological (yeast), chemical (baking soda),
mechanical (methods of mixing certain ingredients or the batter through whipping or beating), physical
(lamination or steam), or a combination of those methods.
• Each is designed to introduce a gas, such as air, into a liquid or viscous solution.
• In baking for example, cake batter as an emulsion requires proper aeration in order not to become “very
thin and sloppy.”
• Dough viscosity can affect processing and machinability as well as end product texture and appearance.
• In cake varieties including yellow, white and pound cakes, if the cake is to have proper volume, grain
and texture, the baker must incorporate “considerable” amounts of air into the batter.
• When air is incorporated into a liquid or viscous solution, the solution traps the air bubbles, forming a foam.
If proteins stabilize the foam, it leavens a food, increasing its height and reducing its density.
• Eggs supply aeration to baking applications through the mechanical method, with the viscosity of all egg
products ideal for incorporating air cells during the whipping or beating process.
• As whipping or beating progresses, air bubbles decrease in size and increase in number, surrounded by egg
proteins. Liquid egg products have low air-liquid interfacial tension, therefore when eggs are beaten or
whipped, the proteins denature, or simply, they unfold.
• This exposes two oppositely charged ends of the protein molecule: the hydrophobic, or water hating end,
and the hydrophilic or water loving end.
• The proteins line up between the air and water, securing the air bubbles with their hydrophilic end and
pointing the hydrophobic end in the other direction. During baking, these proteins bond with each other,
forming a delicate, yet reinforced network.
• Egg whites form foams greater in volume than yolks due to the unique proteins found in the white.
• In fact, even though the term foam technically refers to any system where there are entrapped air
bubbles, in the food industry, when discussing egg products, the term tends to be exclusive to egg white
foams.
• This is because egg whites, unlike any other natural food ingredient, are able to create the largest
possible food foam, six to eight times greater in volume than unwhipped, non-aerated liquid egg white.
• The egg white proteins that enable such impressive foaming are ovalbumin and ovomucin.
• Ovalbumin is responsible for original foam volume when egg whites are whipped, while ovomucin holds
onto the air bubbles during heating and has elastic qualities that allow the protein to stretch as the air
bubbles enlarge.
ANTIMICROBIAL

• An antimicrobial by definition is an agent that either kills or stops the growth of microorganisms. Among
the various identities the egg can claim, antimicrobial is one of them.
• Various egg white proteins exhibit antimicrobial properties. One example is lysozyme, which attacks the
polysaccharide cell walls of Gram-positive bacteria.
• Lysozyme exhibits no significant functional property on its own, however it interacts easily with other
components in food system, and as such could influence actions such as gelation, foaming or
emulsification and coagulation.
• Gels for example, within mixed protein systems producing stronger networks than pure proteins.
• The hen’s egg is actually the richest source of lysozyme among other sources, accounting for 3.5 percent
of the albumen proteins.
• Lysozyme is a very stable enzyme.
BINDING

• The binding property supplied by eggs to food manufacturers proves valuable in numerous applications
ranging from appetizers through desserts.
• Binding may be related to its ability to coagulate and form gels, but in essence, it holds other
ingredients together. This binding action mainly benefits product structure, texture and mouthfeel.
• In meat or fish formulations for example, egg proteins react synergistically with these other proteins to
help bind ingredients together for greater product integrity.
• One reference states that the synergy between fish and egg white proteins makes egg white powder an
“indispensable ingredient” in surimi manufacturing, binding the ingredients together through gelling or
coagulation.
• Egg products form gels easily within certain meat matrices to hold together meat patties and sausages.
BROWNING/COLOR

• “We eat with our eyes first,” says one article on baking, with color so important for baking success that
companies actually make meters to measure it.
• Egg products can contribute to product color in two ways; browning on the product exterior in the case
of baked goods, or the product itself such as coloring mayonnaise or muffin interiors.
• The proteins within eggs can participate in the Maillard reaction when exposed to heat, producing a
desirable brown color.
• The Maillard reaction is responsible for the golden crust of baked products such as yellow batter
cake, meat browning and the dark color of roasted coffee.
• In addition, egg yolk contributes rich color to various foods via xanthophyll, a carotenoid with a yellow-
orange pigment that gives the yolk its characteristic color.
• Egg yolks impart a rich yellow color to cakes and are often used to fortify whole egg products within
formulations to yield a more intense color or increased emulsifying action.
• The pleasing color that eggs impart to baked foods has long been accepted as a mark of superior
quality.
CLARIFICATION

• Eggs, especially whites, can clarify or clear various fluid products, including consommé, broth and even
wine.
• When the fluid is heated, added egg white coagulates, capturing and holding minute particles.
• Depending on the size and weight of the encased particles, the cooked whites may sink to the bottom,
allowing the clarified mixture to be carefully poured off. Sometimes the whites may bubble to the top
where they are skimmed off, resulting in a crystal-clear product.
CRYSTALLIZATION CONTROL/FREEZABILITY

• Food crystals are neither good nor bad because some are beneficial to food while others are detrimental.1The key
is control.
• The formulator who masters crystallization can create the desired product taste and texture, with crystallization
an important aspect for both those qualities in applications such as frosting, nougat, truffles and ice cream, to
name a few.
• Egg products can help control crystallization in confections, frozen desserts and prepared foods. Two of the
functions eggs supply, emulsification and foaming, contribute to their ability to aid with crystallization control.
Many confections begin with a sugar solution in water.
• The proteins in egg whites slow down the crystallization process of this sugar solution, or interfere with the action
of sucrose molecules to reduce their size and to create a smoother texture and a more pleasant mouthfeel.
• Beaten egg whites allow for foam formation and incorporate air into an otherwise dense sugar/water solution, to
enhance the melting quality of the product in the mouth.
EDIBLE PACKAGING FILM

• Egg whites can be used to prepare edible packaging films, with the egg albumen similar in nature to
other types of proteins used for this type of film. “Egg albumen films are clearer and more transparent
than those made from wheat gluten, soy protein isolate and corn zein,” according to one source.
• Transparent egg white films are suitable as water-soluble packets or pouches for food ingredients. They
also have application in breath mint strips and pharmaceutical strips.
• The albumen content within egg products presents the most significant source of protein for films and
coatings, with the right type of treatment.
• Additives help enhance the egg white film’s workability, elasticity and flexibility, providing egg white
with its vast potential for commercial film and coating applications.
EMULSIFICATION

• An emulsion, as defined by Food Technology, is a “temporarily stable mixture of immiscible fluids, such
as oil and water, achieved by finely dividing one phase into very small droplets.”
• Nature designed multiple functions into the egg, including its ability to emulsify. While most commonly
associated with mayonnaise,2the emulsifying capacity of whole eggs, egg yolks and even egg whites
plays a role in baking and other applications. The absence of eggs in certain formulations such as
mayonnaise can affect emulsion stability and final product appearance.
• Fresh liquid eggs, frozen eggs and spray-dried all have the capacity to emulsify, there is no essential
difference found between them.3 The most popular forms however, include liquid, refrigerated whole
eggs or frozen yolks.
•
FLAVOR

• Among all product attributes, taste outranks any other product attribute each and every year in an annual
survey conducted by the International Food Information Council Foundation. Taste or flavor is the deciding
factor for consumers who purchase foods and beverages.
• Though eggs contain more than 100 volatile flavor components, the end results may be described as mild
or bland. However, egg yolks contain fats that can carry and assist with the release of flavors of other
ingredients within a formulation.
• In fact, it is this ability to carry other flavors that helps create foods consumers recognize and enjoy since
fats impact multiple rheological and sensory properties such as flavor, mouthfeel and texture.
• It is difficult for reduced fat or low fat versions of traditional formulations to imitate traditional product
quality.
• For example, formulations with fat removed will release flavors like chocolate and vanilla more quickly than
in a formula made with traditional levels of fat, “dramatically changing” the perceived flavor of a product.
FORTIFICATION/PROTEIN ENRICHMENT

• Among other nutritional benefits, some formulations concentrate on protein fortification or enrichment
of foods that may or may not already contain protein.
• Consumers in the past few years indicate they are interested in increasing protein intake with the
majority selecting eggs as their preferred option for protein fortification
• One large egg contains a wide variety of nutrients for a relatively low calorie count, with just 70 calories
containing 6 grams of high-quality protein.
• For this reason, eggs and egg products are considered “nutrient-rich” according to the definition of the
USDA ARS. Nutrient dense foods and beverages provide vitamins, minerals and other substances that
may have positive health effects with relatively few calories.
• In addition, the definition states nutrients and other beneficial substances have not been ‘diluted’ by the
addition of energy from added solid fasts, added sugars or the solid fats naturally present in the food.
• Foods formulated with egg products contain all the nutrition originally found in the egg product, including high-quality protein,
trans-fatty acid free mono- and poly-unsaturated fats, vitamins, minerals and other highly bioavailable nutrients with
recognized health and wellness benefits.
• Of special note is the quality of protein. Eggs contain all nine essential amino acids, with whole egg protein having a biological
value of 93.7 on a 100-point scale.
• The essential amino acid composition of egg protein is similar to the human body’s requirement, allowing the body to use the
protein more efficiently to maintain muscle tone and strength as the body ages.
• The egg’s lipid portion, which is found primarily in the yolk, contains 5 percent of the Daily Value of fat-soluble vitamin D, a
nutrient associated with bone health.
• It is a source of lutein and zeaxanthin, two nutrients classified as xanthophyll carotenoids and have been shown to contribute
to eye health. While eggs contain only a small amount of these nutrients, research suggests that the lutein and zeaxanthin
from eggs may be more bioavailable, or more easily absorbed by the body, than from richer sources.
• The lipid portion is also a concentrated source of choline, a nutrient necessary for the normal functioning of all cells in all
people, with some segments of the population requiring more choline during certain life stages, such as pregnancy.
HUMECTANCY/MOISTURIZING

• Humectancy, particularly in baked goods, requires the formulator achieve a delicate balance between moist eating quality and
water activity control.
• Too much water activity will prompt mold growth, effectively ending the product’s shelf life. Too little water, in the case of staling
or retrogradation, and the product also is no longer suitable for consumption.
• Egg products can assist with moisture control by binding water, helping with humectancy or by adding a coating to help trap
moisture in the finished product.
• Each type of baked good, depending on the ratio of its individual ingredients, will exhibit a different relationship between its
moisture content and its water activity level or a w.
• Egg proteins bind water making it less available for microorganisms to grow and cause spoilage.
• Overall, eggs help reduce moisture loss from the baked product to extend shelf life by helping form proper cell structure of the
baked product. Proper cell structure traps moisture and holds it, whereas retrogradation or staling occurs when these cell
structures collapse.
• Particularly in gluten-free formulating, egg products help contribute humectancy, to help optimize moisture, not just for better
shelf life, but also for better product density and rise<sup.
WHIPPING ABILITY

• Eggs and egg whites can be whipped into a foam for aeration and to improve product texture and
appearance. Egg products’ whippability plays a role in baking and frozen desserts such as ice cream, in
addition to certain confections.
• The various types of egg products display varying levels of whippability, with differences between egg
white, whole egg and egg yolk. Dried eggs also perform in a different manner than liquid or frozen in
terms of whippability.
• Pasteurization, a process applied to all further processed egg products, does not impact whippability.
• Egg white for example is very stable in a dried state and its whipping properties remain unaffected
unless excessively high temperatures are applied.
• However the whipping properties of egg products containing yolk do witness a loss in efficacy when in
dried form, so refrigerated and frozen are recommended for certain applications.