Lecture 3- Eggs Flashcards
Bird vs. mammalian eggs
Large vs. microscopic (egg is still largest cell in body)
What % of the egg is shell, shell membranes
11%
what % of egg is yolk
31%
What % of egg is albumen
58%
What % of altricial egg is yolk
20%
What is the shell structure made of?
Cross linking CaCO3 (calcium carbonate or calcite)
2 benefits of shell design
Permit gaseous exchange and nutrient (mineral) source
Shell membranes are made up of
Tough mats of protein
What is the formation, location, and function of air cells?
Liquid contracts as it cools, blunt end of egg btw inner + outer membranes, supply air to embryo at beginning of respiration
3 functions of albumen
Insulation
Shock absorption
Nutrient source
4 layers of albumen and % of total for each
Outer thin 23%
Firm/dense 57%
Inner thin 17%
Chalaziferous (thick white) 3%
Purpose of chalazae
Extend to dense albumen and stabilize yolk position
Yolk formation
Layers of nutrients for embryo surrounded by Vitelline membrane
Blastodisk
White, circular, opaque, infertile
Blastoderm
Oval, transparent center, opaque margins, fertile
Blood spot
Blood vessel rupture in yolk follicle during ovulation
Double yolk
2 yolks meet in oviduct (most common defect)
4 germicidal properties (physical defense)
Shell- CaCO3 is a drying agent
Shell membranes- pores work as filters
Avidin- bind of biotin to interfere bacterial growth (in albumen)
Lysozyme- dissolves/lyses bacteria (in albumen)
Where is most protein in an egg?
The yolk and albumen
Where is almost all fat in an egg?
Yolk
What % of egg contents is water
74%
What % of egg contents is dry matter?
26%
What % of egg contents is proteins?
13%
What % of egg contents is fats?
11%
What % of egg contents is carbohydrates?
1%
What % of egg contents is minerals?
1%
6 factors that vary egg composition
Type of bird, strain of bird, day-to-day variation, weather/climate, nutrition, disease
What three minerals are mainly found in the shell?
Ca, Mg, P
What 9 minerals are in eggs?
Ca, Cl, Fe, Mg, S, K, P, Na, I
Egg protein names start with
Ovo/ Ova
Egg’s are known as
Nature’s best protein
What % of egg fats are triglycerides?
62%
What % of egg fats are phospholipids?
33% (freezes less than milk)
What % of egg fat is sterols (cholesterol)?
5%
What is in trace amts. in egg fat?
Cerebrosides
What 5 fatty acids are most common in eggs?
Myristic 1%, Palmitic 27%, Stearic 6%, Oleic 50%, Linoleic 11%
What % of egg fatty acids are saturated?
34% (1/3)
Where are carbohydrates in eggs?
Little in albumen
What vitamins do eggs have?
All (especially B, not much of C)
What 5 aspects do consumers like in eggs?
Sounds + clean shells, no blood/meat spots, no off-flavors, uniformity, a lot of firm albumen
What 3 factors from the bird that influence egg quality?
Genetics
Physiology (blood/meat spots)
Nutrition
At higher temps it take ____ days for yolk to flatten?
Less
Egg shrinkage
Loss of water b/c of low humidity, air cell grows
Liquefaction
- CO2 lost to atmosphere
- Albumen binds less H2O
- Yolk enlarges
(No microorganisms involved)
Eggs should be stored at ____ temp and ____ humidity.
Low (4-12C/45-55F), high (80%+)
Grading is based on
Consumer preferences
Candling: an AA graded egg will have
A small air cell, faint/not visible yolk, firm albumen, no blood/meat spots, sound shell
Candling: a B graded egg will have
A large air cell, visible + mobile yolk, liquid albumen, blood/meat spots, bad shell
Breakout method: an AA graded egg will have
High yolk height and less spread albumen
Color has no effect on egg quality but…
People like uniformity
