ANSCI 201--Eggs

Pray for us please

What is the term for an animal that requires large amounts of parental care after birth?

Altricial

What is the term for an animal that requires little parental care after birth?

Precocial

Do altricial birds have eggs with less or more yolk content than precocial eggs?

Hint: do they need less or more energy for developement?

Less

Do altricial birds have eggs with less or more albumen than precocial eggs?

Hint: do altricial birds need more or less protection in the egg?

More

What is the technical term for egg whites?

Albumen

What % of the total egg do the shell and shell membranes comprise?

11%

What % of the total egg does the yolk comprise?

31%

What % of the total egg does albumen comprise?

58%

What is another name for the spongy layer?

Calcareous layer

What are the five components of a shell?

1. Cuticle

2. Spongy layer

3. Mammillary layer

4. Shell membranes

5. Pores

What are the four functions of a shell?

1. Strength

2. Permit gaseous exchange (pores)

3. Prevent loss of egg contents and entrance of bacteria (cuticle)

4. Nutrient source (mainly minerals)

What is the geometric design of a shell?

Crosshatching

What is the thickness of a shell correlated with?

Weight of bird

What is a shell mainly composed of?

Calcium carbonate (calcite)

What are the tough mats of protein fibers that give structure to eggs?

Shell membranes

What forms when the inner and outer membranes of a shell separate at the blunt end?

Air cell

How does an air cell form?

As the egg cools, liquids contract

Where is an air cell located?

Blunt end of egg, between inner and outer shell membranes

What structure supplies air to the embryo when respiration is initiated?

Air cell

What are the three functions of albumen?

1. Insulation

2. Shock absorption

3. Nutrient source

Which layer makes up the highest % of albumen (57%)?

Firm/dense

Which layer makes up 23% of albumen?

Outer thin

Which layer makes up 17% of albumen?

Hint: the number 17 kind of looks like the initials of the answer

Inner thin

Which layer makes up 3% of albumen?

Chalaziferous (thick white)

Which layer of albumen stabilizes the position of the yolk in the egg?

Chalazae

Which albumen layer extends into the firm/dense albumen?

Chalazae

Which part of the egg houses the living center?

Yolk

What is the function of the yolk?

Provides nutrients for embyro

Is a blastodisc present on a fertilized or unfertilized egg?

Unfertilized

What shape is a blastodisc?

Circular

What is the size of a blastodisc?

3-4 mm

Is a blastoderm present on a fertilized or unfertilized egg?

Fertilized

What shape is a blastoderm?

Oval

What is the tubelike structure in the middle of an egg yolk?

Latebra

How does an egg yolk form?

Layers of nutrients deposit on the outside of latebra

What is the name of the membrane that surrounds the yolk?

Vitelline membrane

Which layer of the albumen is highlighted in pink?

Firm/dense

Which layer of the albumen is highlighted in blue?

Outer thin

Which part of the egg is highlighted in green?

Latebra

Which part of the egg is highlighted in yellow?

Blastoderm

Which part of the egg is represented by the black and white swirls?

Yolk

Which part of the egg is represented by the gray whispies on either side of the yolk?

Chalazae

Which part of the egg is represented by the gray highlighting surrounding the yolk?

Inner thin

What egg defect forms when vessels rupture in the yolk follicle at the time of ovulation?

Blood spot

What egg defect forms when two yolks meet in the oviduct and are included in the same shell?

Double yolk

What is the most common egg defect?

Double yolk

What do the germicidal properties of eggs do?

Help kill/prevent the growth of bacteria

What are the four germicidal properties of eggs?

• Shell

• Shell membranes

• Avidin

• Lysozyme

What is the first line of defense for an egg?

Shell

What compound does a shell contain that acts as a drying agent?

Calcium carbonate

How do shell membranes act as germicides?

Act as filters (pores are smaller than those in shell)

Which germicidal enzyme in the albumen interferes with bacterial growth?

Avidin

Which germicidal enzyme in the albumen dissolves/lyses bacteria and is also found in tears?

Lysozyme

Egg contents are what % water?

74%

Egg contents are what % dry matter?

26%

Egg contents are what % proteins?

13%

Egg contents are what % fats (same as shell)?

11%

Egg contents are what % carbohydrates?

1%

Egg contents are what % minerals?

1%

Egg yolks are what % dry matter?

52%

Egg yolks are what % fat?

33%

Albumen is what % water?

88%

Albumen is what % protein?

10%

Egg shells and membranes are what % minerals?

92%

What are causes for variations in egg composition?

• Type and strain of bird

• Day-to-day variation

• Weather/climate

• Nutrition

• Disease status

What are the nine egg minerals?

Ca, Cl, Fe, Mg, S, K, P, Na, I

Which egg minerals are found mainly in the shell?

Ca, Mg, P

What are the four egg proteins found in the albumen?

• Ovalbumin

• Ovoconalbumin

• Ovoglobulin

• Ovomucin

What are the two egg proteins found in the yolk?

• Ovovitellin

• Ovolivetin

What is the one egg protein found in the membranes?

Ovokeratin

Which egg protein makes up 75% of albumen?

Ovalbumin

What is the nutritional quality of egg proteins?

Very high → nature’s best proteins

Where are most egg lipids located?

Yolk

What are the four lipids present in eggs?

• Triglycerides

• Phospholipids

• Sterols (cholesterol)

• Cerebrosides

What % of egg lipids do triglycerides comprise?

62%

What % of egg lipids do phospholipids comprise?

33%

What % of egg lipids do sterols comprise?

5%

What % of egg lipids do cerebrosides comprise?

Trace

What % of fatty acids in eggs are saturated (opposite of milk)?

34%

What % of fatty acids in eggs are unsaturated (opposite of milk)?

66%

Where are most of the carbohydrates in eggs located?

Albumen

Are there lots of carbohydrates in eggs? What is their purpose?

No → only purpose is to provide sugar for embryo

Eggs are a good source of vitamins except for which?

Vitamin C

What are the two enzymes present in eggs?

Avidin and lysozyme

From a consumer viewpoint, what makes an egg good quality?

• Intact and clean shell

• No blood spots

• No off-flavors

• Uniform size, shape, and color

• Uniform yolk color

• Large amount of firm albumen

What are the three internal factors that influence egg quality?

• Genetics

• Physiology

• Nutrition

What are the three external factors that influence egg quality?

• Temperature

• Humidity

• Contamination

When is an egg’s quality highest?

Immediately after it is layed by the hen

What is shrinkage?

Loss of water when stored in low humidity

What happens to the air cell during shrinkage?

Enlarges

During liquefaction, which gas is lost from the albumen?

CO₂

During liquefaction, due to CO₂ loss, what happens to the amount of water the albumen binds?

Decreases

During liquefaction, due to water released from albumen, what happens to the size of the yolk?

Enlarges → runnier

How can liquefaction of eggs be reduced?

Pump CO₂ into the atmosphere

Liquefaction is directly related to which factor of proper egg storage?

Temperature

What is the temperature storage requirement for eggs?

45-55°F

What is the humidity requirement for eggs?

>80%

Storing eggs at a low temperature prevents what?

Liquefaction

Storing eggs at a high humidity prevents what?

Shrinkage

What are the three egg grades?

• AA

• A

• B