Download The Incredible Egg

The Incredible Egg
Egg Production
• Closely controlled breeding programWhite Leghorns preferred favorite.
– Early maturity
– Large producer
– White shelled eggs
– 100,000 size flocks common
– Each hen produces 250-300 eggs a year
Processing
• Physical and chemical changes begin
immediately after hen lays egg
• Production is automated
• Eggs refrigerated immediately
• Temperature 40-45 F
• Humidity kept high to minimize moisture
loss
Egg Carton Dating
• USDA requires Julian Dating, number between 1- 365
• May also have an expiration date- beyond which eggs
can be sold.
• USDA plants expiration date cannot exceed 30 days
after pack date.
• Plants not under USDA- under state laws.
• Fresh shell eggs store 4-5 weeks beyond Julian date
without significant loss of quality.
Structure and Characteristics
Diagram of an Egg
Membranes
Color
• Color- egg shell and yolk color vary.
• Color does not alter nutrition,
– quality,
– flavor,
– cooking characteristics
– shell thickness.
Shell
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Breed of hen determines color of shell
Color comes from pigments in outer layer
Ranges from white to deep brown.
Shell first line of defense against bacteria
Shell largely calcium carbonate- 94%
Rest small amounts of- magnesium
carbonate, calcium phosphate and protein
Egg White
• Egg albumen in raw egg opalescent or
clear
• Appears white when cooked or beaten
• Yellowish cast may indicate presence of
riboflavin
• Cloudiness- due to presence of carbon
dioxide. Indicates a very fresh egg.
Air Cell
• Empty space
between white
and shell
• Forms after egg
is first laid.
• Inner membrane
cools and
separates from
the cell.
Chalazae
•Ropey strands of
egg whites
•Anchors egg yolk in
center of egg white.
•Not beginning
embryos or
imperfections
•More prominent,
fresher the egg.
Germinal Disc
Membranes
Vitelline- covers the yolk
Inner and outer membranes.
• Channel leading to
center of yolk.
•Sperm enters egg
through disc.
•Embryo forms
Egg Yolk
• Yolk color depend on diet of
hen
• Gold or lemon color
preferred by consumers
• Color is stable- not lost in
cooking.
Nutritional Value
• Yolk 33% of liquid weight
– All of fat in the egg
– Less than ½ protein
– Higher % of most vitamins, except ribolflavin
and niacin
– Yolk large egg 59 calories, whole egg 75
• Albumen or egg white contains half of total
egg protein
– Contains all essential amino acids
Grading Eggs.
• Classified by interior
and exterior qualityAA, A, or B.
• Sorted according to
weight and size
• No difference in
nutritional quality
and size or color of
eggs.
Sizing of Eggs
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Jumbo
Extra large
Large
Medium
Small
Peewee
30 oz.
27 oz.
24 oz.
21 oz.
18 oz.
15 oz.
Other Egg Characteristics
• Blood spot- not an embryo, often called
meat spots.
• Fertile eggs- develop into chicks. They are
not more nutritious than unfertilized.
• Organic eggs not more nutritious than non
organic.
– Must be free from hens not fed by rations that
have pesticides, fungicides or herbicides.
Storage of Eggs
• Stored at 30 F for up to six months in
the shell
• Stored out of the shell for extended
storage.
• Food manufacturing freezes most eggs
they use.
• Eggs stored as yolks, or whites, or
whole eggs.
• Eggs can be dehydrated or powered.
Samonella
• Salmonella enteritidis found in some eggs.
• 2-3 eggs infected per 10,000 eggs
produced.
• Eggs need proper handling, storage and
adequate cooking.
• Watch eggs in uncooked products such as
cookie dough.
Egg Substitutes
• Average egg has 240 mg of cholesterol
• Egg substitutes reduce cholesterol
• Made by separating the yolk from albumen
or white
• Yolk color added back in to albumen, but
with reduced or no cholesterol.
Cooking Functions
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Breakfast entrees
Binder for other dishes- meatloaf, croquettes
Leavening agent- soufflés, sponge cakes
Thickening agent- custards, sauces
Emulsified in mayonnaise, salad dressings
Coating agent- breads, cookies
Clarify soups and coffee
Boiled candies and frostings, retards crystallization
Garnishment as hard cooked eggs.
Grade AA, A and B
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Nutritional value the same for all grades.
Grade AA stands up tallLarge portion of thick white to thin white
Grade A yolk stands up, but white is well
spread out.
• B grade eggs used in
food manufacturing.
Reference
• Parker, R.O. (1999). Food science sample
lesson FS117. Retrieved September 22,
2005 from http://www.agednet.com/
• Mehas, K. & Rodgers, S., (2002). Food
science. Peioria. Glencoe/ McGraw-Hill