Overview
This lecture explains how emulsifiers and stabilizers work in food emulsions, highlights their types and mechanisms, and introduces common kitchen examples.
Emulsification Basics
- Emulsification combines fat and water by reducing surface tension, forming a temporarily stable mixture.
- Emulsions are naturally unstable and tend to separate unless stabilized.
Emulsifiers: Types and Mechanisms
- Emulsifiers link fat and water molecules to stabilize emulsions.
- Two main kitchen emulsifier types: amino acid chains (proteins) and phospholipids (like lecithin).
- Amino acid chains have fat-friendly and water-friendly ends, allowing them to connect both phases.
- Proteins, such as casein found in egg yolks and milk, act as natural emulsifiers.
- Phospholipids (e.g., lecithin) have water-soluble heads and fat-soluble tails, linking fat and water.
- Surfactants are emulsifiers with water-soluble heads and fat-soluble tails; they lower surface/interfacial tension.
- Some phospholipids (lecithin) have positively charged fat tails that repel each other, preventing fat droplets from merging.
Common Kitchen Emulsifiers
- Egg yolks are powerful emulsifiers due to lecithin and casein content (used in hollandaise, aioli, mayonnaise).
- Milk and cream also stabilize emulsions because of casein protein.
- Mustard contains a surfactant in its seed coat, commonly used in vinaigrettes to emulsify oil and vinegar.
Stabilizers: Types and Function
- Stabilizers prevent the dispersed phase (typically fat) from regrouping and breaking the emulsion.
- Most stabilizers are water-soluble and include proteins, starches, pectin, plant purees, and food-grade gums.
- Stabilizers increase viscosity, creating drag that helps break fat into smaller droplets for more stable emulsions.
- Adding stabilizers to the water phase before emulsifying enhances stability.
Xanthan Gum as a Stabilizer
- Xanthan gum is effective for stabilizing water-based emulsions, requiring only small amounts (~0.5% by weight).
- It works in a range of pH levels and hydrates in both hot and cold water.
- Xanthan gum is "shear thinning": it's thicker at rest and thins when stirred, aiding the stability and texture of sauces.
Key Terms & Definitions
- Emulsifier — a substance that links fat and water to form a stable emulsion.
- Surfactant — an emulsifier with a water-soluble head and fat-soluble tail, reducing surface tension.
- Phospholipid — a molecule like lecithin with both water and fat-friendly parts, used as an emulsifier.
- Stabilizer — a large molecule that increases viscosity and prevents dispersed fat from recombining.
- Viscosity — the thickness of a fluid; higher viscosity slows particle movement.
- Shear thinning — property of a substance to become less viscous when force is applied.
Action Items / Next Steps
- Watch the upcoming video on making a stabilized beurre blanc with xanthan gum.
- Review examples of emulsifiers and stabilizers used in common kitchen recipes.