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Questions and Answers
What must be removed from egg whites prior to dehydration to improve storage stability?
What must be removed from egg whites prior to dehydration to improve storage stability?
What process occurs when denatured protein molecules in eggs form a solid mass?
What process occurs when denatured protein molecules in eggs form a solid mass?
Which ingredient raises the temperature required for coagulation in egg-based recipes?
Which ingredient raises the temperature required for coagulation in egg-based recipes?
What effect does added salt have on the process of egg protein?
What effect does added salt have on the process of egg protein?
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Which of the following nutrients is found in egg yolks?
Which of the following nutrients is found in egg yolks?
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Why are older eggs less likely to coagulate effectively?
Why are older eggs less likely to coagulate effectively?
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What type of egg products are processed to have no yolk and are often lower in fat?
What type of egg products are processed to have no yolk and are often lower in fat?
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What is the primary characteristic of eggs regarding their protein content?
What is the primary characteristic of eggs regarding their protein content?
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What percentage of an average hen egg's weight is composed of the egg yolk?
What percentage of an average hen egg's weight is composed of the egg yolk?
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Which component of an egg is primarily responsible for its high-quality protein content?
Which component of an egg is primarily responsible for its high-quality protein content?
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What is the primary lipid found in egg yolk?
What is the primary lipid found in egg yolk?
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What effect does avidin have when consumed raw in egg whites?
What effect does avidin have when consumed raw in egg whites?
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What is the main composition of eggshells?
What is the main composition of eggshells?
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How does egg shell color relate to its quality?
How does egg shell color relate to its quality?
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What happens to the contents of an egg as it ages?
What happens to the contents of an egg as it ages?
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Which vitamin is exclusively not found in egg yolk?
Which vitamin is exclusively not found in egg yolk?
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What is a major factor that determines the size of an egg?
What is a major factor that determines the size of an egg?
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What is the purpose of candling eggs?
What is the purpose of candling eggs?
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How long can an egg be stored on cold storage if the shell pores are closed?
How long can an egg be stored on cold storage if the shell pores are closed?
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What temperature range is required for the pasteurization of egg products?
What temperature range is required for the pasteurization of egg products?
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What effect does applying mineral oil to egg shells have?
What effect does applying mineral oil to egg shells have?
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What happens to uncooked egg whites after freezing and thawing?
What happens to uncooked egg whites after freezing and thawing?
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Which grading of eggs is highest in quality?
Which grading of eggs is highest in quality?
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What process is required for all commercial liquid, dry, or frozen egg products?
What process is required for all commercial liquid, dry, or frozen egg products?
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Study Notes
Eggs and Egg Products
- Eggs from various birds are consumed globally, but the focus here is on hen eggs.
- Hen eggs are a natural biological structure with shells that protect developing embryos.
- The World Health Organization (WHO) considers hen eggs a reference protein for comparison with other proteins.
- Egg quality and freshness are important to regulatory agencies, processors, and consumers.
Physical Structure of Eggs
- An average hen egg weighs approximately 57g (including the yolk, white, and shell).
- The yolk comprises approximately 31% of the egg's weight; it contains most of the egg's fat and all the vitamins except vitamin C.
- Egg yolks also contain all three lipids (triglycerides, fats, and oils), phospholipids, and sterols.
- The primary phospholipid is phosphatidylcholine (or lecithin), and the key sterol is cholesterol, found only in the yolk.
- Protein in the yolk accounts for about 10% of total egg protein.
- Yolk pigments (xanthophylls, carotene, and lycopene) originate from animal feed (e.g., yellow corn and green plants).
- The egg white (albumen) makes up about 58% of the egg's weight.
- Egg whites are a complete protein, containing all essential amino acids in a balanced proportion.
- A sizable portion of the protein in egg whites is ovalbumin.
- Egg whites contain lysozyme, an enzyme that can break down some bacteria.
- Avidin is another egg white protein. It binds to biotin, making it unavailable if consumed raw.
The Shell
- The eggshell comprises the remaining 11% of the egg's weight.
- The eggshell is primarily calcium carbonate (94%).
- The shell has thousands of pores, particularly concentrated at the larger end.
- The shell's porosity is essential for the developing embryo inside the egg.
- Washing eggs is not recommended as it could remove the outer cuticle or open pores.
Egg Color and Aging
- Egg shell color is determined by the hen breed and doesn't affect egg flavor or nutritional value.
- As an egg ages the internal contents shrink, and the air cell grows larger.
- The pH of the egg increases to a more alkaline level (7.6 to 9.6), making the egg more susceptible to bacterial growth.
- The chalazae (cord-like strands of white) become less prominent with increasing age.
Inspections and Grading
- Egg grading involves assessing the exterior shell (shape, texture, cleanliness) and interior (yolk, white, air cell).
- Candling is a non-destructive method to view the interior of the eggs.
- Letter grades (AA, A, B) are voluntary and based on candled quality.
Egg Size
- Hen age is the principal factor in determining egg size, with older hens laying larger eggs.
- The breed and weight of the hen are also secondary factors affecting egg size.
- Factors like feed quality, and henhouse overcrowding and stress impact size.
- A range of sizes is available in the market (e.g. jumbo, extra large, large, medium, small, pee wee).
Processing and Preservation
- Eggs are laid at body temperature and require subsequent refrigeration.
- Eggs are stored in cold conditions for up to 6 months if shell pores are sealed.
- Mineral oil can be sprayed onto shell eggs to seal pores to reduce microbial permeability, retain moisture, and reduce pH shifts.
- Pasteurization is required for commercial liquid, dry, or frozen eggs to destroy microorganisms like Salmonella.
- Pasteurized eggs are processed at a certain temperature for a minimum amount of time.
- Freezing eggs requires prior pasteurization.
Dehydration
- Dehydration techniques like spray drying reduce egg water content.
- Dehydrated eggs (whole, white, yolk) can be packaged and sold in different forms.
- Removing glucose from egg whites beforehand prevents browning and flavor changes during storage.
- Dried eggs should be stored under cold conditions to maintain food safety.
Egg Products and Substitutes
- Egg products include pasteurized, processed, refrigerated liquid, frozen, and dried eggs.
- Egg substitutes usually contain no yolk, a high proportion of egg white, and a variety of other ingredients.
- Egg substitutes have lower cholesterol and fat content than whole eggs.
- Egg substitutes use less processing temperature than whole eggs
Functional Use of Eggs in Foods
- Eggs bind ingredients in foods like meatloaf, croquettes, breading.
- Egg yolks emulsify ingredients like oil and water (in mayonnaise).
- Egg whites foam and aerate to make items like meringues and angel food cake.
- Coagulation of egg proteins forms gels, useful in custards.
Nutritive Value of Eggs
- Eggs are an excellent source of vitamins (A, D, E, various B vitamins) and minerals (iron, phosphorus, zinc, iodine, potassium, sulfur).
- A large egg has approximately 75 calories.
- Eggs are a complete protein with a biological value of 100%.
- Egg yolks contain cholesterol.
Egg Safety
- Egg safety concerns include contamination (e.g., Salmonella).
- Production methods (cages, free-range) and inspection are crucial for egg safety.
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Description
Test your knowledge about eggs, particularly hen eggs, and their nutritional structure. This quiz covers various aspects from the protein quality recognized by the WHO to the physical makeup of hen eggs. Understand the importance of egg freshness and learn about the components that make up an egg.
