EXAM 2: Egg Function And Substitutions Flashcards
Eggs have over _____ functions in cooking!!
20
What are some of the functions of eggs in cooking
Structure (coagulation) - primary function (ex: custards, eggs coagulate and form a creamy gel)
Foaming/Aeration
Leavening agent
Thickening
Binding: breaded chicken bread crumbs
Emulsifying
Interfering
Clarifying
Color
Principles to keep in mind - eggs have many functions when used in recipes
The specific egg function depends on how it is used in the recipe
What is denaturation
Change in structure of the protein resulting in partial or complete loss of function
Brought about by heat, mechanical action or acids
Change in structure of the protein resulting in partial or complete loss of function
Brought about by heat, mechanical action or acids
What is coagulation
Clotting or precipitation of a protein in a liquid into a semisolid compound
Brought about by heat, acids and enzyemes
Coagulation is irreversible!
What are the steps of coagulation
1st step is denaturation
Disruption of hydrogen/amino acid bonds and ionic bonds between protein strands
Weakened strands cause amino acids to unwind and unfold
What is the coagulation process
Hydrogen molecules form bonds with amino acids link protein chains together during cooking
Proteins form network that traps water
With more heat, networks tighten squeezing out water (syneresis)
How does protein coagulation occur with heat
Protein Coagulation - Temperatures
- Egg white becomes jelly like at 140 F
- Egg white firms at about 149 F (before yolk)
- Egg yolk starts to set at 144 F
- Egg yolk is fully set at 158 F
- A whole egg coagulates at about 156 F
How does coagulation occur in a custard
Custards require slow, careful heating in water bath to avoid over-coagulation and curdling: 350 F
Ingredients affect the length of time under coagulation (sugar, extra protein, emulsifiers)
- sugar: increases temperature 175 F before coagulation begins
- addition of acid decreases coagulation time
What is foaming
When eggs are beaten to a foam that is 6-8 times its original volume
What are characteristics of foam
Mechanical energy is required to make a foam
- egg white foam: proteins provide structure
Stability of foams is important in baking
Requires the addition of sugar, acid, or heat (baking)
Eggs as foam uses: aerate and leaven
Tips for making foam
See lab manual and textbook
No plastic bowls (residues prevent foam formation), no yolk
What are recipes that rely on foaming
Soufflés, angel food cake, sponge cake, mousse and meringues
Focus on meringues: what is a meringues and what are the two types
Baked egg white foams containing sugar and acid
Two types:
- Hard
- cooked long period of time (1 to 1.5 hours)
- uses: meringue cookies (kisses), meringue pie shell or tartlet shell
- Soft
- cooked short period of time (15 to 30 mins)
- Uses: top pies and other desserts (rice and bread puddings), component of dessert soufflés, angel food cake and sponge cake
What are the factors that affect foam formation
Sugar, acid, fluid, salt and fat
How does sugar affect foam formation
Stabilizes foam
Inhibits mechanical coagulation of proteins needed for foam formation
Add at the end of whipping time so volume is not compromised
How does acid affect foam formation
Additional decreases pH, denatures proteins, allowing the egg white to be whipped easily into a foam
Types of acid: cream of tartar, lemon juice or white distilled vinegar
- Cream of tartar: 1 tsp cream per cup of egg white, or 1/8 tsp per egg white
- Lemon juice or vinegar: 1/8 tsp per egg white becomes jelly
How does fluid affect foam formation
Increases foam volume by 40% but decreases stability
How does salt and fat affect foam formation
Decreases stability and volume
How is egg used as a thickening agent in cooking
Emulsifiers in eggs assist w/ thickening properties (ex: Hollandaise sauce)
How do eggs act as a leavening agent
Baked goods - water in egg converts to steam during baking and rises
-> proteins form structure in foams and help with gluten/starch networks
