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Food Chemistry . Chapter 17 in Green / Damjii Chapter X in Nuess Chapter X in Oxford Study (no resource in Chang). Homework. F.6: Texture. Read F6– Texture pp . 487-488 Do Qs 38-42 on p 493. F.6.1 : Describe a dispersed system in food. TEXTURE depends on

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Food chemistry

Food Chemistry

Chapter 17 in Green / Damjii

Chapter X in Nuess

Chapter X in Oxford Study

(no resource in Chang)


Homework
Homework

F.6: Texture

  • Read F6– Texture pp. 487-488

  • Do Qs 38-42

  • on p 493


F 6 1 describe a dispersed system in food
F.6.1: Describe a dispersed system in food

TEXTURE depends on

  • Physical properties (hardness, elasticity)

  • Cooking

  • Moisture content

    CREAMY TEXTURES valued in many foods depend on

  • Disperse system

    • stablized (do not separate… or separate v. slowly)

    • macroscopically homogeneous mixture of 2 immiscible phases

    • A typical FOOD disperse system will involve a liquid as one of the immiscible phases.


F.6.2: Distinguish between the following types of dispersed systems – suspensions, emulsions, and foams in foods.

  • Dispersed system: LIQUID / SOLID

    • Suspension (sol)

      • Solid particles suspended in a liquid

        • EX: blood (solid red/white blood cells suspended in plasma)

    • Gel

      • Liquid particles suspended in a solid

        • EX: fruit jelly – water trapped in a protein matrix



  • Dispersed system: LIQUID / LIQUID

    • Emulsion

      • Stable blend of 2 immiscible liquids

        • EX: mayonnaise (oil droplets suspending in water)

      • Emulsifiers are often used to promote the mixing of 2 phases…


F 6 3 describe the action of emulsifiers
F.6.3: Describe the action of emulsifiers

Emulsifiers

  • molecules that can bond to both phases

  • found at the surface between the phases

  • often called surfactants

  • similar to what happens with soap !




F 6 3 describe the action of emulsifiers1
F.6.3: Describe the action of emulsifiers

Emulsifiers

  • Lecithin – a phospholipid which is found in egg yolks

  • Contains polar end… hydrophilic

    • Bonds to water

  • Contains nonpolarend… hydrophobic

    • Bonds to non aqueous phase

    • ex: mayo made by beating oil and

      vinegar with egg yolks

      • hydrophilic end of lecithin bonds to

        vinegar and hydrophobic end bonds

        to oil

      • Surfactant (lecithin) surrounds oil

        droplets… suspending them within the

        aqueous phase ( vinegar ).


F 6 3 describe the action of emulsifiers2
F.6.3: Describe the action of emulsifiers

Stabilizers

  • Often added to stablize dispersed states… keep them from separating.

  • Inorganic phosphates (trisodium phosphate) can stablize emulsions

  • Metal bowls – chefs prefer these to beat egg whites… minute traces of the metal are incorporated into the foam and actually stabilize it.


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