Egg Composition, Formation, and Quality Control in Poultry Science

Egg shell composition

Calcium carbonate

Egg white composition

~88% water, ~11% protein

Whole egg composition

~66% water, 12% protein, 10% fat

Eggshell color determined by

Genetics (breed)

Eggshell porosity

Eggshell is porous

Cuticle function

Protective layer sealing pores

Egg formation order

Ovary → Oviduct → Isthmus → Uterus → Vent

Air cell formation

Forms at large end as egg cools

Air cell size meaning

Larger air cell = older egg

Egg pH over time

Increases due to CO2 loss

Blood spots cause

Ruptured blood vessels

Meat spots cause

Tissue fragments in egg

Soft shell cause

Premature laying / insufficient time in uterus

Thin shell cause

Calcium deficiency or disease

Egg processing first steps

Collect, handle, cool

Egg washing rule

Water must be warmer than egg

Why warm wash water is needed

Prevents bacteria being pulled into egg

Egg processing steps

Wash → sanitize → dry → oil → grade → package

Egg grading AA

High quality, thick albumen

Egg grading A

Moderate quality

Egg grading B

Low quality, spread out

Grading requirement

90% must meet labeled grade

Cage

free definition - Indoor movement with enrichments

Free

range definition - Cage-free plus outdoor access

Main reason for animal products

Protein, vitamins, minerals

Complete protein definition

Contains all 9 essential amino acids

Complete protein requirement

Must be digestible and absorbable

Not required for complete protein

Palatability

Common limiting amino acids

Lysine, methionine, tryptophan

Animal protein advantage

Better amino acid balance and digestibility

Vitamin B12 source

Animal products

Vitamin A source

High in liver

Vitamin C in animal products

Not present

Heme iron source

Animal products

Heme vs non

heme iron - Heme iron is more bioavailable

Calcium source (animal)

Dairy products

Most increased meat consumption

Chicken

Beef consumption trend

Decreased relative consumption

Most consumed vegetable USA

Potatoes

Cheese consumption trend

Increased since 1979

Ovo

vegetarian - Eats eggs

Lacto

vegetarian - Eats dairy

Ovo

lacto vegetarian - Eats eggs and dairy

Vegan diet

No animal products

Correlation vs causation

Correlation does not equal causation

Why nutrition studies are difficult

Too many variables in humans

Cell

cultured meat status - Not widely commercial (lecture context)

Cell

cultured meat regulation - USDA and FDA

Grass

fed beef omega-3 - Higher than grain-fed

Grass

fed health claim - Difference is small, not significant

Best omega

3 source comparison - Fish (e.g., salmon) >> beef

Egg functional properties

Emulsify, coagulate, trap air

Why eggs are useful in cooking

Highly functional proteins

Egg albumen layers

Thin and thick albumen

High

quality egg white - Thick, stands tall

Low

quality egg white - Spreads out

Egg washing effect

Removes cuticle

Why US refrigerates eggs

Cuticle removed during washing

European egg handling

Not washed, can be room temp

Protein to calorie ratio meaning

Lower ratio = more efficient protein source

Burger vs plant protein example

Burger had lower calorie-to-protein ratio