BPA 102: Ingredient Functions; Eggs

Eggs
-most commonly used birds eggs are chicken, duck goose
-size, protein content will vary
-most commercially produced chix eggs are unfertilized

Shell- 10% of weight
-made of calcium carbonate
-porus, odor exchange
-salmonella would be on outside
-shell color determined by breed of hen- no effect on flavor
-inner membrane creates air gap- sign of age

Yolk
-1/3 of volume, ¾ of calories
-contains lecithin, fat, vitamins + minerals
-coagulates at 149-150F
-chalazae- cord which anchors yolk in place

white
-2/3 of volume
-7/8 water and about 1/6 protein (albumin)
-contains sulfur, potassium, sodium, and chlorine

Coagulation temperatures
-egg white coagulates between 144 and 149F or 62-65C
-egg yolk coagulates between 149 and 158F, 65-70C
-whole eggs between 144- 158F

Temperature at which an egg coagulates can be changed
- to raise temp- add sugar, lower # of eggs used
Anglaise coagulates at 180-185F- lots of sugar
-to lower temp- add salt, raise # eggs used

Using eggs in baking
-Structure- protein hardens when cooked, holds shape, works this way in cakes
-Moistness- protein and water, when congeals can hold lot of water, milk, cream
-Aeration- albumin protein catches air when expands, denaturing process of forming bonds and structure with a lot of strength
-Shine/ glaze- egg wash before baking bread. Proteins and fats caramelize
-Binding- water holds ingredients together
-Thickening- by coagulation in custards
-Helps carry flavor- fats help carry flavor
-Imparts color to product due to carotene

Egg whites- thin albumin- more watery
Thick albumin- more elastic

Egg Market forms
-shell or fresh:
-dozens- retail, “loose” packed in flats, case of dozens
-Liquid- fresh, frozen, pasteurized (have a little sugar in them)
-dried- baking and processing
-whites- liquid or frozen
-yolks- liquid or frozen
-special blends- more yolks, salt, sugar
-hard boiled- 5 gal bucket

Contamination
-contamination by pathogenic bacteria like salmonella
-most experts advise people to cook thoroughly before eating, heat kills bacteria
-shells act as hermetic seals which guard against bacteria entering, but seal can be broken through improper handling or if laid by unhealthy chickens

Raw vs. cooked eggs
-protein in raw eggs only 51% bio available, cooked egg close to 91% bio available- 2x’s as absorbable

Changes in eggs during aging
-amount of think white increase
-yolk absorbs water from the white
-the chalazae disintegrate
-loss of water through shell
-increase in air cell size
-both white and yolk increase in pH

Tips in using eggs
-avoid pooling- break into small container then move to larger
-use room temp eggs
-sugar and eggs- exothermic reaction- start cooking
-cool quickly after cooking to avoid overcooking- if over boil will see green ring around yolk from iron sulfide
-no egg yolks mixed with whites
-store egg yolks and shelled eggs under refrigeration
-egg whites can be kept at room temp, keep open for a little bit before covering, let good bacteria form- lycism