The image of migrating water fowl as a natural sign of the changing of the seasons. But sometimes, there’s more to the picture. This year, a form of avian flu spread by those gracefully migrating birds led to the deaths of millions of Midwestern turkeys and laying hens—and a subsequent shortage of eggs.
Avian flu, in this case the one designated Strain H5N2, is carried by water fowl with minimal mortality. However, during migration, the virus is shed in the water via saliva and excrement. It may be carried into contact with domestic fowl on the wheels of vehicles and the footwear of farm workers, resulting in infection and spread of the disease.
Unfortunately this flu is highly virulent in domestic turkeys and hens. Worse than Ebola in humans, mortality rates for H5N2 run as high as 98%. Even free-range/cage-free domestic fowl have been hit hard by this disease.
Given the high natural mortality rates, the steps taken to control the spread of the disease in domestic flocks are strict. Once avian flu is diagnosed in a flock, the entire flock must be put down to halt the spread of the disease. If the flock is in a barn on a farm with 25 barns, all 25 barns are put down.
To further complicate this situation, once a laying barn or farm has been identified and purged of infected hens, it takes as long as half a year to clean and disinfect the facility to ensure active avian flu has been eliminated. Even then, new birds introduced will be pullets, which require as long as six months to mature into egg-laying hens. This means an infected facility could be off-line for a year or longer.
The current avian flu outbreak could be the worst case in US history. To give an idea of the size of the crisis here are a few relevant facts and figures, courtesy of John Howeth, senior vice president of foodservice and egg product marketing at the American Egg Board.
There are an estimated 303 million laying hens in the US. The eggs from about 100 million of these hens go to the food processing industry, while the other two-thirds go the table-egg market.
About 12%—or some 35 million birds—have been affected by the flu so far. Of these, 31 million were producing eggs for the food processing industry. This means the industry was disproportionately affected, losing nearly a third of its production capabilities. There are factors which can help mitigate the current shortage—imports, diversion from table to processing, as well as egg replacement ingredients—might all play a part.
Food manufacturers face a situation where standard industrial egg ingredient supplies and pricing may not return until 2017. The last time there was a major outbreak of this proportion was 1983-1984. Then, it took two years to come back to pre-epidemic numbers, yet only from a comparative 7% loss vs. the aforementioned 12% noted so far this year.
On a positive note, the 1983-84 outbreak occurred in different times, and under different conditions and capabilities for correction. On the worrisome side, with the imminent fall migration, the outbreak could be rekindled.
Although the current egg situation is certainly significant, the egg shortage is a temporary one. Egg production will recover, as the industry works to address the issues raised by the flu outbreak. In the meantime, the problem for the food industry becomes what steps to take to deal with the shortage and higher prices of eggs right now. Since reducing the amount of egg used in a formulation is unlikely to produce satisfactory results, the more common response is to find suitable egg replacements.
It should be noted that there’s a difference between an egg replacement and an egg substitute. Egg substitute will not be used, because it is commonly used to denote products that are intended as substitutes for whole eggs. Egg replacement denotes the use of other ingredients to replace aspects of the functionality of eggs.
Eggs are used in a variety of products, including ready-to-eat (RTE) meals, batters and coatings, glazes and glosses, pastas, dairy products (ice cream, egg nog) and even in edible packaging. In these applications, eggs serve a number of functions, including structure (aeration/stability/whipping ability/foaming/latticework), emulsification (for sauces, etc.), texture (richness, tenderization, coagulation, thickening), adhesion/binding, color (natural yellow colorant, browning), clarification, film formation (finishing glazes and glosses), flavor, crystallization control (freeze/thaw stability), fortification (protein enrichment), pH stability, moisture control (drying, humectancy, water binding) and shelflife extension (antimicrobial agent).
Given the range of functions eggs can perform, it is challenging to find suitable replacements. The heart of the challenge rests in the fact that much of the functionality is attributable to the unique structure and function of the individual components of egg. While they cannot be completely duplicated, these functionalities can be mimicked by other food ingredients.
Many, if not most, of these functions derive from the protein content of the egg. Egg protein is capable of forming films and irreversible gels in cooking applications. These help to define the characteristic structure of some foods. Its ability to bind and control the movement of water introduces additional functionality.
Egg protein is the most bioavailable protein in the human diet. Thus, it contributes to the overall protein content in a formulation. As part of the Maillard browning reaction that occurs in the interaction of carbohydrates as sugar and starch with the amino acids in the protein under high heat, egg protein also can contribute color.
There are additional functionalities that can be obtained from whole eggs. The yolk can produce a natural yellow coloration, as with pasta, due to the presence of lutein and other xanthophylls. The yolk also contains phospholipids and lipoproteins which can provide emulsification and enhance mouthfeel in numerous applications.
As with the egg white protein, the yolk also contributes to the overall nutritional profile of the formulation, containing a significant portion of protein. But the yolks also are rich in B vitamins (including folate, thiamin, pantothenate, B12 and B6), minerals (selenium, calcium, potassium, iron, phosphorus and zinc) and each of the fat soluble vitamins (A, D, E and K).
The fat in an egg yolk is healthful and rich in essential fatty acids. Although a large egg yolk contains an average 210mg cholesterol, multiple studies have determined that this form of dietary cholesterol does not affect serum cholesterol in healthy persons. In fact, eggs can be an excellent source of the cholesterol the body needs for effective nerve and brain function.
A Matter of Function
Most egg-replacement systems tend to be combinations of ingredients that work together to mimic the specific functionality of eggs. However, these systems frequently must be tuned to specific applications, and, therefore, are not always a “one size fits all” replacement.
The approach most processors have taken is to identify the specific and critical functionality that eggs supply their formulations. Then, they seek ingredients that produce similar results and are suitable to the specific application.
In this process, care must be taken to utilize ingredients that can be accommodated by the operational and supply-chain capabilities of the facility; the cost constraints of the formula; and the label and performance demands of the consumers.
“Technologists have been working on the egg replacement puzzle since the 1970s but traditionally with limited success,” notes Mark Freeland, a hydrocolloid technology consultant with more than 40 years of industry experience. “Much of the earlier work focused on the use of carrageenan or alginate to mimic the gel-forming properties of egg protein. There were a number of technical hurdles. For instance, carrageenan does not dissolve well in water at temperatures below 120?F. In addition, both carrageenan and alginate require the presence of potassium ions to catalyze crosslinking of the carbohydrate chains leading to gel formation.”
Freeland points out that egg protein “provides irreversible gelation, contributing to structure and mouthfeel. In addition, as the food product is chewed, the shear and the warmth of the mouth cause the egg protein gel to soften and produce an effect akin to melting.”
This mouthfeel performance from eggs can be significantly different from that of other gelling ingredients. Some hydrocolloids, such as carrageenan and alginate, provide gelation, but the gel formed is often either too soft or too rubbery, creating a mouthfeel that is not natural to the original product.
“The gel from these hydrocolloids can break readily upon chewing, but the gel pieces do not soften and melt in the mouth the same way that the egg protein gel does,” adds Freeland. “In the case of strong gels, upon chewing, they break up into smaller pieces which retain a firmer texture. The effect on mouthfeel can be dramatic.”
Experimentation with combining carrageenan and guar gum has helped some technologists modify the firm texture, Freeland explains. Guar does not gel; it produces a softer texture.
Cases in Point
Angel food cake as is an example of one of the more difficult egg replacement challenges. Given the high ratio of egg to flour to sugar, the egg plays a dramatic role in the texture and flavor of the cake. The egg white is a fundamental part of the structure and makes a tenderer crumb. Egg yolk is not always used in angel food cake recipes, but when it is, it contributes a custard-like taste profile—resulting in richer flavor.
Part of the complexity of formulating to replace egg is that individual egg products can contain added ingredients or processing aides that modify and improve performance. Depending on the manufacturing process, for example, angel food cake can be made with liquid egg components or powdered egg components. It is not necessarily a simple “drop-in” to replace one with the other.
Also, powdered egg whites might contain a processing aide to enhance the whipping performance. Liquid egg whites can be formulated with hydrocolloids added to enhance whipping. These additional ingredients must be taken into account when searching for replacement ingredients in a reduced egg formulation.
“Dominos Pizza uses whole cracked eggs, and some of Dominos’ suppliers use eggs in their processes,” says Mike Weber, manager of dough quality and R&D for Dominos Pizza Inc. In Weber’s experience, citrus fiber can be used to replace whole egg in cakes at levels up to 20% before organoleptic characteristics are affected.
“One key to the functionality of the citrus fiber is water binding,” Weber explains. “Some fiber products bind up to twenty times their weight of water. This assists with creating a structure similar to egg, while maintaining acceptable shelflife.” He adds that there can be “a bit of color loss, due to reduction in total color from the egg yolk.”
Weber finds citrus fiber useful as an all-natural ingredient and less expensive on a cost-in-use basis. “In a brownie formulation, for example, citrus fiber was used as a means of improving shelflife by controlling water migration associated with staling. Testing was done at as much as 50% egg replacement, which resulted in improved shelflife.”
Shear and Smooth
Sauces and dressings are a key application area for egg replacement, as egg—especially egg yolk—plays a critical role in the formulation of such products. Spoonable and pourable dressings are a prime example, while mayonnaise is perhaps the most challenging.
The lipoproteins, proteins and phospholipids in egg yolk provide emulsification, texture, viscosity and flavor. Of these, emulsification is perhaps the most critical functionality that must be duplicated if egg is to be replaced.
Extensive work has been done on using lipophilic starches (such as from oat, potatoes and other sources) as egg replacement ingredients in dressings. These starches have been modified specifically to provide strong emulsification properties, binding together the water and oil phases of the formulation. Application work has also shown it is desirable to include a protein source to compliment these lipophilic starches. The protein works in conjunction with the starch to provide an egg-like texture and body.
The choice of protein is important, because it can influence the allergen content of the final formulation. For example, whey protein and soy protein isolate have been shown to work in these applications; yet they, as well as egg, are known allergens.
Egg yolk replacement in mayonnaise-like dressings can bring other challenges. The egg yolk contains naturally occurring color components, such as the aforementioned lutein. The replacement ingredients do not. Additionally, when the egg-free formulation is processed through a colloid mill, it tends to whiten more noticeably. It could be necessary to add color to obtain a more characteristic appearance. Annatto and turmeric are commonly used for this purpose.
It is important to remember that, in the case of mayonnaise, there is a standard of identity which closely defines what can be present in the product.
This means, for this application, replacing the egg yolk results in a product that can no longer be called mayonnaise. The use of modified starch as egg replacement in dressing applications is not usually an issue, because modified starch is already commonly used in these applications to provide viscosity.
A Matter of Structure
The protein in eggs is used to provide structure and stability in food foams. In fact, the stabilization of foams derives from the film-forming functionality of egg protein. Common applications in this area include marshmallows and meringues.
During whipping, the egg whites coat the surface of the air bubbles being incorporated, preventing them from coalescing and dissipating. There are other ingredients which can perform this function with varying degrees of efficiency. For example, certain modified starches, some grades of gum Arabic and other protein ingredients, such as modified soy protein and gelatin, are all capable of forming films to greater or lesser degrees.
The challenge involves identifying the ingredient, or combination of ingredients, that produces textural and structural characteristics best matching those provided by the egg protein in the specific application.
Such matching is generally done on an application-by-application (and sometimes formula-by-formula) basis to achieve the best results.
Emulsification is another key function of egg proteins. Some modified starches, certain grades of gum Arabic, gelatins and many small molecule surfactants (monoglycerides, polysorbates, etc.) can perform similar functions. Still, it’s important to recognize there can be inherent incompatibilities in some ingredient combinations.
Today’s ingredient suppliers typically have scientists in-house who have the expertise to work with processors in developing customized ingredient systems fine-tuned to specific formulation needs.
Eggs can control the movement of moisture, modify viscosity and provide structure—and so do many starches. Native starches, modified starches and hydrocolloids effectively are being used for similar purposes. Their contribution to texture, emulsification and film-forming varies greatly, depending on the specific ingredient, format, or combination of ingredients or formats used.
In addition to differences in functionality, differences in processing requirements can occur. Some modified starches and hydrocolloids require high shear and heat for proper dispersion and activation. If this cannot be accomplished with existing equipment, then either new equipment is required or these ingredients cannot be used—at least not cost-effectively. Incomplete dispersion or activation reduces the effectiveness of the ingredient.
It should be noted that many of the replacement options also are not allergens. Therefore, they have the added advantage of being able to be used to produce a formulation with broader appeal, from a food-safety standpoint.
Recently, carbohydrate-based, drop-in replacements for eggs have been developed for some formulations. For example, a new type of natural-fiber ingredient produced from edible-plant biomass was launched. It is marketed as a “cost-effective, single-ingredient replacement for eggs in some applications.”
The fiber has gelling and emulsification capability, and laboratory application tests demonstrated the ingredient was able to replace up to 100% of the egg in formulation without negatively affecting sensory attributes, product performance or shelflife in certain applications. The ingredient has been released as a natural, GMO-free, non-allergenic and kosher egg replacer.
In the rush to bring out new plant-derived protein sources (see “New Plant Protein Powerhouses,” page 98.), one novel and recently commercialized protein has the functionality attributes that make it surprisingly versatile for use in egg replacement applications. The humble potato is its source.
Potato is not traditionally thought of as a protein food, yet it compares to many vegetables at about 2% protein content. Still, the commercialization process has required development of innovative production tools to extract >90% pure protein isolates from the potato.
Protein derived from potatoes is reported to have surprising functional properties. It demonstrates foaming, emulsifying and gel-forming properties, and the thermal-set gel is irreversible. This makes it remarkably similar to similar to egg whites.
Two protein fractions are being isolated in that manner for use in ?commercial applications. The higher-molecular weight fraction has a slightly acid isoelectric point, while the lower-molecular weight fraction has an essentially neutral isoelectric point. Both fractions demonstrate good solubility in aqueous solutions. They offer functionality as an emulsifier; support foaming with high overrun; and offer good thermal gelation under the proper conditions. This allows contribution to the texture, mouthfeel, stability and appearance in an array of food applications where eggs are commonly used.
Application work with this new potato protein has been done on some challenging egg replacement formulations, such as meringue and “angel kisses.” In these applications, the egg is replaced 100% with excellent results. The protein supports the necessary air incorporation; stabilizes the foam produced; and withstands the temperatures necessary to complete the application.
In addition to offering such impressive functional properties, this potato protein product is a native, unmodified protein. It also is non-GMO, kosher, halal, vegan and non-allergenic. It offers clean label impact and can contribute to sustainability claims.
Potato protein ingredients currently are being used and tested as egg replacement ingredients in a variety of applications, including baked goods, pasta, emulsified sauces and dressings, gluten-free bread, meringue and others.
Another newly released protein is making as big an impact from a much smaller point. In fact, it’s nearly microscopic. Algal protein, along with algal flour, were granted GRAS status only a couple of years ago, yet algae ingredients have been used with great success as complete replacements for egg in several formulations, including dairy products, dressings and, impressively, in baked products.
In fact, whole-protein algae is a vegan, gluten-free ingredient that boasts functional fiber and, like eggs, contains lipids and micronutrients, such as lutein and zeaxanthin.
A wide array of potential egg replacement ingredients, familiar and quite new, are fresh on the market at an auspicious time. Coupling these ingredients with the ingenuity of food and culinary technologists will contribute to easing the impact of the current egg shortage.
It remains to be seen if egg replacement technology will impact the overall demand for eggs, once this temporary shortage is over. But it should be remembered that many of these ingredients came about as replacements suitable for vegan formulations—and that won’t change. For now, the fact that they can help out in a crisis makes them welcome additions to the food product developers’ tool kit.
For more information, be sure to watch the video "A Hard Break for Eggs".
Winston Boyd, PhD, is a food industry scientist and consultant and frequent contributor to Prepared Foods. He has authored numerous articles on food and ingredient technology, and provides management, technical, regulatory, food safety and business development services to clients in the food and beverage industry. He has worked with multiple national and international food and ingredient companies. Dr. Boyd can be reached at firstname.lastname@example.org.