The Incredible Egg

Egg Production

• Closely controlled breeding program- White Leghorns preferred favorite.– Early maturity– Large producer– White shelled eggs– 100,000 size flocks common– Each hen produces 250-300 eggs a year

• 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

Processing

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- egg shell and yolk color vary.

• Color does not alter nutrition, – quality, – flavor, – cooking characteristics – shell thickness.

Color

• 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

Shell

• 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.

Egg White

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 MembranesVitelline- covers the yolkInner 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 quality- AA, A, or B.

• Sorted according to weight and size

• No difference in nutritional quality and size or color of eggs.

Sizing of Eggs

• Jumbo 30 oz.

• Extra large 27 oz.

• Large 24 oz.

• Medium 21 oz.

• Small 18 oz.

• Peewee 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.

• 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.

Cooking Functions

Grade AA, A and B• Nutritional value the same for all grades.

• Grade AA stands up tall-

• Large 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