Animal Science: Chicken Eggs Quiz

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Questions and Answers

What is the primary function of the chalazae within an egg?

To protect the egg from bacterial contamination.

To increase the viscosity of the albumen.

To provide nutritional support to the yolk.

To serve as anchors keeping the yolk centered. (correct)

What is the average weight of a chicken egg?

58 grams (correct)

65 grams

45 grams

75 grams

Which component comprises the largest percentage of a chicken egg's weight?

Yolk

Egg white

Water (correct)

Shell

Which part of the eggshell is responsible for providing initial protection against microbial invasion?

Cuticle or bloom Signup and view all the answers

How does the protein content of the egg yolk compare to that of the egg white?

Higher in yolk (16.6%) than in white (10.6%). Signup and view all the answers

What role doesavidin play in relation to biotin?

It binds one mole of biotin per subunit. Signup and view all the answers

Which protein functions as a proteinase inhibitor in egg white?

Ovoinhibitor Signup and view all the answers

What is the predominant carbohydrate presence in egg white?

Glucose and mannose Signup and view all the answers

What is the estimated mineral content of egg white?

0.6% Signup and view all the answers

How many amino acid residues are present in chicken egg Cystatin C?

120 Signup and view all the answers

Which bird's eggs are considered the least significant compared to chicken eggs?

Plover Signup and view all the answers

Which continent produced the highest number of chicken eggs in 1996?

Asia Signup and view all the answers

What is the approximate thickness range of an egg shell?

0.2-0.4 mm Signup and view all the answers

Which country is listed as the top producer of other eggs?

China Signup and view all the answers

What structural feature of the egg helps determine its age during storage?

Air cell size Signup and view all the answers

Which country produced approximately 680 (1,000 t) of chicken eggs?

Italy Signup and view all the answers

Which type of egg has a shell that can be described as characteristically spotted?

Wild birds Signup and view all the answers

What is the approximate diameter of the air cell in fresh eggs?

5 mm Signup and view all the answers

Which vitamin is found exclusively in the egg yolk?

Retinol (A) Signup and view all the answers

What is the main component of yolk droplets in egg yolk?

Lipids Signup and view all the answers

What mineral has the highest percentage in egg yolk compared to egg white?

Phosphorous Signup and view all the answers

What method is currently used for yolk studies to prevent lipoprotein destruction?

Ultracentrifugation Signup and view all the answers

Which mineral is present in both egg white and yolk but in a higher concentration in yolk?

Magnesium Signup and view all the answers

According to the composition percentages, which vitamin has the highest concentration in egg yolk?

Pantothenic acid Signup and view all the answers

What characteristic best describes the viscosity of egg yolk?

Non-Newtonian fluid Signup and view all the answers

What size range do yolk droplets typically fall within?

40-40 um Signup and view all the answers

What is the primary role of conalbumin in egg products?

It slows the growth of microorganisms. Signup and view all the answers

Which of the following features is true about ovomucoid?

It is stable against heat coagulation. Signup and view all the answers

Which protein is responsible for the red discoloration of egg products?

Conalbumin Signup and view all the answers

What structural elements are predominantly found in ovomucoid?

Alpha-helix and beta-structure Signup and view all the answers

Which of the following statements correctly describes lysozyme?

It is an N-acetylmuramidase enzyme. Signup and view all the answers

Which of the following best describes ovomucin?

It contributes to the viscosity of egg white. Signup and view all the answers

What distinguishes conalbumin from ovalbumin in terms of denaturation?

Conalbumin does not denature at the interphase. Signup and view all the answers

Which of the following is a characteristic of ovoglobulins G2 and G3?

They function as effective foam builders. Signup and view all the answers

What percentage of lipid content is found in egg yolk granules?

6.9% Signup and view all the answers

Which component is primarily responsible for binding metal ions in egg yolk?

Phosvitin Signup and view all the answers

At what pH do lipovitellins occur as dimers?

< 7 Signup and view all the answers

What is the primary lipid composition of lipovitellins?

60% Phospholipids and 35% Triglycerides Signup and view all the answers

Which fraction corresponds to the high-density lipoproteins in egg yolk?

Lipovitellins Signup and view all the answers

What is the molecular weight of lipovitellins mentioned in the content?

Several million dal Signup and view all the answers

How can lipovitellins be separated based on their protein content?

Chromatographic and electrophoretic methods Signup and view all the answers

What type of proteins can livetins be separated into through electrophoresis?

Alpha, beta, and gamma livetins Signup and view all the answers

Study Notes

Eggs - General Information

Eggs are nearly perfect protein foods, containing high-quality nutrients.
They are easily digested and provide a significant portion of daily nutrients for growth and body tissue maintenance.
Eggs are widely used in both the food industry and at home.
Chicken eggs are the most important type. Other birds' eggs (e.g., geese, ducks, quail, plovers, seagulls) are less significant.

Egg Production

Global egg production in 1996: approximately 47,338 thousand tons (chicken eggs), along with 4,249 thousand tons (other eggs).

Egg Production per Country

Key countries and their estimated chicken egg production in 1996 are summarised in the attached data.

Egg Structure, Physical Properties, and Composition

The egg shell is calcified, porous, and 0.2-0.4mm thick.
Chicken egg shells are white-yellow to brown. Duck eggs are greenish-white, and most wild bird eggs are noticeably spotted.
The egg shell's inner surface is lined with two inner and outer membranes.
Air cell (approximately 5mm in fresh eggs) forms at the large end of the egg and grows larger during storage. The air cell size can be used to determine egg age.

Egg White (Albumen)

Egg white is an aqueous, faintly straw-tinted gel-like liquid.
It consists of three fractions with varying viscosities.

Egg Yolk

The egg yolk is the inner portion of the egg and is surrounded by the albumen.
The yolk contains an arrangement of alternating layers of dark and light-colored material, which is arranged concentrically.

Chalazae

The chalazae anchor the yolk, resembling twisted rope-like cords.
They are twisted clockwise at the large end and counterclockwise at the small end of the egg.

Germinal Disc (Blastoderm)

The germinal disc (blastoderm) is located on top of the yolk (at the wide end).
It has a club-shaped latebra (lateral part) form.

Egg Composition

Data regarding the percentage of total weight, dry matter, and protein content of eggs (shell, white, yolk) is provided in tabular form.
The shell comprises calcite crystals within an organic framework. It also contains minimal levels of magnesium carbonate and phosphates.

Egg Shell Structure

The shell structure is divided into the cuticle/bloom, spongy layer, mammillary layer, and pores.
The cuticle is an extremely thin (10μm) protein layer that's transparent and mucilaginous, coating the outer shell part.
The spongy layer, which comprises about two-thirds of the shell's thickness, is the main calcareous layer below the cuticle.
The mammillary layer has small knob-like particles cemented to the spongy layer, with the other side adhering to the shell membrane.
Tiny canals known as pores run through the shell, apparent as openings (7,000 to 17,000 per egg).

Egg Albumen Proteins

Egg albumen is comprised of various proteins, at around 10% solution.
The thick, gel-like albumen has significantly more ovomucin (around four times) when compared to the thin albumen.
It's a viscous pseudoplastic fluid and its viscosity is dependent on the shearing force.

Egg Albumen Proteins (Detailed)

Key proteins found in egg white: ovalbumin, ovoglobulin G3, avidin, conalbumin, ovoinhibitor, ovomucoid, flavoprotein ovomucin, ficin inhibitor, ovoglycoprotein, and lysozyme G1, ovomacroglobulin.
Several albumen proteins exhibit biological activity. Examples include enzymes (lysozymes), enzyme inhibitors (ovomucoid, ovoinhibitor), and complex-forming agents for coenzymes (flavoprotein, avidin).

Ovalbumin

Ovalbumin is a glycophosphoprotein that contains 3.2% carbohydrates, with 0 to 2 molecules of serine-bound phosphoric acid per protein molecule.
It has 4 thiols and 1 disulfide group, capable of forming heat-stable S-ovalbumin during egg storage via a thiol-disulfide exchange reaction.
Relatively susceptible to denaturation (e.g., by shaking or whipping its aqueous solution) through protein unfolding and aggregation during interphase denaturation.

Conalbumin

Conalbumin (also known as ovotransferrin) resists denaturation at the interphase but undergoes coagulation at lower temperatures.

Ovomucoid

It consists of a single peptide chain with 3 carbohydrate units bound via asparagine residues.
It contains 9 disulfide bonds, leading to heat stability.

Egg White Proteins: Lysozyme

Lysozyme (also named ovoglobulin G1), a widely distributed protein occurring in various animal tissues, secretions, plant latex exudates, and some fungi.
It's an N-acetylmuramidase enzyme.
It breaks down cell walls of Gram-positive bacteria by hydrolyzing them.
It is a polypeptide chain with 129 amino acid residues and 4 disulfide bonds.

Egg White Proteins (Other)

Ovoglobulins G2 and G3: good foam builders
Ovomucin: forms fibrils, contributing to a significant increase in the viscosity of egg white at higher concentrations compared to thin albumen.

Carbohydrates, Lipids, and Minerals in Eggs

Egg yolk contains 32.6% lipids.
Free carbohydrates are part of the 1% of the dry matter in egg yolk.
Egg white contains about 0.6% minerals.

Mineral Composition of Eggs

Data on mineral composition of egg whites and yolks in varying percentages is provided.

Vitamin Content of Eggs

A tabular summary detailing various vitamin levels (e.g., retinol, thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, tocopherols, and α-tocopherol) in whole eggs, egg white, and egg yolk is given.

Egg Yolk Composition

Egg yolk is a fat-in-water emulsion.
It contains about 50% dry water content, consisting of proteins and lipids.
It contains particles of distinct sizes that are categorized into two groups: yolk droplets, which are similar to fat droplets. Granules, substantially smaller than the yolk droplets, feature consistent size and shape with protein, lipid, and mineral content.

Egg Yolk Separation Methods

Older egg yolk separation methods involved defatting with various solvents.
Modern procedures employ ultracentrifugation aided by electrolytes, thereby ensuring the retention of native yolk constituents.

Composition of Egg Yolk Fractions

Data provides the lipid, protein, and mineral composition of various egg yolk fractions.

Proteins of Granules

Data details the composition and properties of lipoproteins.
Lipovitellins can be separated by electrophoretic and chromatographic techniques, based on distinctions in protein-bound phosphorus levels.

Phosvitin

Phosvitin is a glycophosphoprotein.
Characterized by a high amount of phosphoric acid bound to serine residues.
Effectively binds metal ions (e.g., Ca²⁺, Mg²⁺), forming inter-molecular complexes.

Plasma Proteins

Lipovitellin is a low-density lipoprotein obtained via ultracentrifugation of diluted yolk.
A variety of components with differing densities in the yolk are separated through fractional centrifugation.
The lipoid moiety constitutes about 84-90% of the dry matter and contains approximately 74% triglycerides and 26% phospholipids.
Additional contents like phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and lysophospholipids are also present.
Individual components of the plasma proteins may not be entirely characterized.

Livetin

Livetin is a soluble globular protein.
Electrophoretic procedures can effectively segment livetin into three fractions (α, β, and χ-livetins), which correspond to serum albumin, a₂-glycoprotein, and γ-globulin in chicken blood.

Other Egg Constituents

Egg yolk includes trace carbohydrates and free sugars (e.g., glucose), similar to egg white, with a proportionally low content (approx. 1%) bound to proteins.
Egg Yolks have less minerals than egg whites around 0.2%.

Egg Aroma Substances

The specific aroma substances in egg white and yolk are still not fully determined, although methylamine, with a sensory threshold of around 25 µg/kg, is linked to a "fishy" odor effect. This compounds forms from the breakdown of choline in fish or soy-based diets.

Egg Storage

During egg storage, changes occur due to the diffusion of CO₂ through shell pores resulting in an increase in egg white pH.
The evaporation of water through the shell lowers egg density, enlarging the air cell. This results in a gradual reduction of egg white viscosity and the egg yolk becoming flattened over time.
These changes affect egg quality and provide indicators for determining egg age (e.g., air cell size), or the presence of off-flavors("stale").
Cold storage is an important factor in egg preservation.

Egg Products

Eggs are utilized in many forms (liquid, frozen, dried) for both whole egg, white and yolk as food items, such as semi-finished products (baked goods, noodles), confectionery, pastry, mayonnaise, salad dressing, soup powders, margarine, meat products, ice cream and liqueurs.

Technically Important Properties of Eggs

Eggs' utility is tied to three key properties:
1. Coagulation when heated
2. Foaming ability
3. Emulsifying properties
Egg color and aroma are also significant aspects.

Thermal Coagulation of Eggs

Egg white begins to coagulate at 62 °C, and egg yolk at 65 °C.
The coagulation temperature is contingent on pH.
At pH levels above 11.9, egg white gels or sets even at normal temperature but later liquifies.
All egg proteins except ovomucoid and phosvitin undergo coagulation.
Conalbumin can be stabilized by complexing it using metal ions despite being sensitive to this process.

Foaming Ability in Eggs

Egg white whipping results in foam that holds air pockets, useful as a leavening agent in food preparation.
The increased surface area during whipping leads to protein denaturation and aggregation.
Particular substances, like ovomucin, create an insoluble barrier between the liquid and air bubbles, stabilizing the foam.
Egg globulin also plays a role, affecting foam stability through viscosity and surface tension.

Emulsifying Properties of Eggs

Eggs' emulsifying properties are utilized to produce mayonnaise, creamy salad dressings (using a combination of egg yolk, olive oil, lemon juice, or vinegar, and seasonings).
The emulsifying capacity is due to low-density lipoproteins and proteins in the egg yolk.

Dried Egg Products

Egg solids are churned either immediately or after separating egg white and yolk to create dried products.
A homogenization step is followed by a purification process (using a separator) and a final pasteurization step to create the finished product.
Carbohydrates are often removed to prevent undesirable color changes and unwanted flavors.

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Description

Test your knowledge on chicken eggs with this quiz focusing on their structure, composition, and production statistics. From understanding the function of chalazae to the protein content of egg yolk, this quiz covers various aspects of chicken eggs. Perfect for students of animal science or biology enthusiasts.