Egg Function and Processing

Functions of Eggs in Food Preparation

  • Emulsifying
  • Foaming
  • Color
  • Binding
  • Clarifying
  • Interfering

Changes in Eggs Due to Processing

  • Egg proteins denature and coagulate when exposed to heat or whipping.
    • Heating
      • Egg white coagulates at a lower temperature (140°F) than egg yolk (144°F).
      • Beaten egg mixture coagulates at 152°F.
      • High temperatures can lead to curdling and toughening of egg protein because the temperatures for coagulation and curdling are very close.
      • High heat can also lead to weeping in the gel structure, known as syneresis.
      • Cooking over water, using a water bath or double boiler, helps prevent curdling and control temperature.

Effect of Added Ingredients

  • Sugar and fat increase the temperature of coagulation.
  • Acid and salt decrease the temperature of coagulation.

Emulsifying

  • Egg yolks contain lecithin, which is amphiphilic with part of the molecule soluble in water and part soluble in fat.
  • This property allows egg yolks to hold oil and water together, creating a stable emulsion.
  • Examples Include:
    • Mayonnaise
    • Salad dressing

Foaming

  • Foam is primarily produced by egg whites.
  • Beating denatures the protein and expands it to form a film that holds air.

Foaming - Effect of Added Ingredients

  • Fat interferes with foam production.
  • Salt decreases the volume of beaten foam due to decreased elasticity.
  • Acid decreases alkalinity of egg whites and increases the stability of foam, cream of tartar is used for this function.
  • Sugar retards denaturation and coagulation of proteins, making the timing of addition important; it stabilizes the foam.
  • Fresh eggs foam better because they are less alkaline.

Color

  • Egg yolk pigments add color to:
    • Yellow cakes
    • Breads
    • Egg noodles
  • Egg wash on baked goods:
    • Egg white adds shine.
    • Egg yolk adds color and shine.

Binding

  • High protein content enables eggs to bind other ingredients together.
    • Battering foods with egg or egg whites before breading. Egg proteins coagulate during cooking and bind the breading to the food
    • Mixing foods with egg or egg white. Egg proteins coagulate during cooking and bind the ingredients together to give structure.
      • Examples: Meatballs, meat loaf, lasagna (used in cheese layer).

Clarifying

  • Egg whites are used in the preparation of clear soups (consommés) because they attract the agents that cloud the liquid.
  • Egg whites are added to cool liquids and heated, leading to coagulation, which traps particles that cause clouding.
  • This coagulated protein rises to the surface of the soup and can be skimmed off.

Interfering

  • Egg proteins interfere with the formation of unwanted crystals.
    • Ice cream: Fat and lecithin interfere with ice crystal formation to improve creaminess.
    • Candy: Albumen and fat interfere with sugar crystal formation, creating smaller crystals and a smoother texture.