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Chapter 1: Emulsions and Foams

Pages 1-14
DOI: https://doi.org/10.1094/1891127020.001
ISBN: 1-891127-02-0


Topics Covered

  • Surface Activity
    • Surface Activity
    • Surfactants as Amphiphiles
    • Surface Free Energy and Interfacial Tension
    • Surface Excess of Emulsifier
    • Measuring Surface Tension
  • Formation, Stabilization, and Wetting
    • Formation of Emulsions and Foams
    • Emulsion Stabilization
    • Foam Drainage and Film Breakage
    • Wetting of Solid Particles
  • Microemulsions

Introduction to Chapter

Interfaces are ubiquitous features of foods. This is true during preparation of a cake batter or margarine blend, for example, as well as in finished products. Three specific kinds of interfaces are of particular importance in foods: liquid-liquid, or emulsions; air-liquid, or foams; and solid-liquid, or dispersions.

Controlling the physical nature of the interfaces is often crucial to making a high-quality food product and is frequently achieved by including emulsifiers (also called surfactants) among the ingredients. Emulsifiers may be components of an ingredient (e.g., egg yolk) or additives (e.g., monoglyceride).

From a technical point of view, the terms “emulsifier” and “surfactant” are synonymous. In practice, however, an emulsifier is usually considered to be a food-related material, while a surfactant is generally connected with other processes. For example, surfactants are added to detergents for washing and are used to aid in flotation during ore separation. Since this book is food-related, other uses of surfactants will not be discussed.