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1) Food Fundamentals > Dispersion Systems > Flashcards

Dispersion Systems Flashcards

1
Q

Define a dispersion system.

A

A system in which particles are dispersed in a continuous phase of a different matter

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2
Q

Define true solutions.

A
  • Small molecules or ions, such as sugar, salt, and vitamins dispersed homogenously in true solutions in food
  • Very well mixed
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3
Q

Define colloid dispersions.

A
  • Larger molecules such as proteins, pectic substances, cellulose and cooked starch are colloidaly dispersed
  • Seemingly mixed
  • They can all be separated out
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4
Q

Define suspensions.

A
  • Large fat globules and uncooked starch granules form suspensions
  • Readily separate from the dispersion medium upon standing
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5
Q

Provide true solutions examples.

A
  • honey
  • sugar in water
  • vitamins in water
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6
Q

Provide colloid dispersion example.

A
  • gas in liquid: whipped cream
  • liquid in solid: gummy bears
  • liquid in liquid: homogenizing milk, cellulose, cooked starch
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7
Q

Provide suspension examples.

A
  • Flour in Water

- Vinegar in Oil

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8
Q

How large are the dispersed medium in true solutions, colloids and suspensions?

A

True solutions: under 1 nanometer
Colloids: 1 nanometer to 0.2 micrometer
Suspensions: > 0.2 micrometer

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9
Q

If the dispersed medium is gas, and the dispersion medium is liquid, what is the type of dispersion?

A

Foam

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10
Q

If the dispersed medium is gas, and the dispersion medium is solid, what is the type of dispersion?

A

Solid foam

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11
Q

If the dispersed medium is liquid, and the dispersion medium is liquid, what is the type of dispersion?

A

Emulsion

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12
Q

If the dispersed medium is liquid, and the dispersion medium is solid, what is the type of dispersion?

A

Solid Emulsion or gel

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13
Q

If the dispersed medium is solid, and the dispersion medium is liquid, what is the type of dispersion?

A

Suspension

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14
Q

Name 3 ways you can change the degree of dispersion.

A
  • Heat
  • Mechanical Treatment
  • Adding Acid
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15
Q

Is heating a sugar solution, a gelatin gel, and egg whites reversible?

A
  • Sugar and gelatin geel: reversible

Egg whites: irreversible

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16
Q

Does heating a sugar solution, a gelatin gel, and egg whites increase or decrease the degree of dispersion?

A
  • Sugar and gelatin geel: increase

Egg whites: decrease

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17
Q

How does raw egg white change with heat?

A

1) Folded proteins (raw) - hydrophilic –> denature
2) Unfolded proteins (hydrophilic and hydrophobic) –> aggregate
3) Aggregated proteins (cooked) - hydrophilic and hydrophobic

18
Q

Name 3 kinds of mechanical treatment.

A
  • Beating egg whites
  • Grinding meat
  • Homogenization of milk
19
Q

Does mechanical treatment of beating egg whites, grinding meat, and homogenizing milk increase the degree of dispersion? What coagulates/disperses?

A

Egg whites: decreases, protein coagulation
Grinding meat: increases, dispersion of connective tissue
Homogenization of milk: increases, dispersion of fat globules

20
Q

If you add an acid to milk and the pH decreases below 4.6, what will happen? Will that increase of decrease the degree of dispersion?

A
  • Casein particles will coagulate and separate from whey

- Decrease degree of casein dispersion

21
Q

What is an example of a colloid?

A

Homogenized milk (butter fat globules dispersed through a water solution)

22
Q

Arrange the dispersion systems in order of least stable to most stable.

A

Least: suspensions, colloids, solutions: Most

23
Q

What are the main 3 factors responsible for the stabilization of colloidal systems?

A
  • Brownian movement of the dispersed particles
  • Like Electric charges of the dispersed particles
  • Water of hydration around the dispersed particles
24
Q

What is the brownian movement?

A

Continuous movement of colloid particles due to bombardment from dispersion medium molecules
- Improves colloid stability (can’t set since they’re zig zagging)

25
Q

What would result in a greater dispersion due to more movement of colloid particles?

A

Smaller colloid particles + less viscous dispersion medium

26
Q

How does the brownian movement change with temperature?

A

Increases with temperature

27
Q

Do repulsive or attractive forces improve colloid stability? What would disrupt?

A
  • Repulsive forces improve stability (like charges)

- Addition of acid or base disturbs the charges on the colloid molecules: acid coagulation of milk proteins

28
Q

If the dispersed medium is hydrophilic, how will that affect stability? What will you need to add?

A
  • Decrease stability, will separate out (non-homogenized milk)
  • Need to add an emulsifying agent
29
Q

What is an emulsion? What does it require?

A

A mix of 2 or more liquids that are normally immiscible (non-mixable)
Requires an emulsifier

30
Q

What are the 3 phases in an emulsion?

A
  1. The dispersed (discontinuous)
  2. The dispersion (continuous)
  3. The emulsifier (stabilizer)
31
Q

Name some common emulsifiers.

A 
 Lecithin
 Milk proteins
 Soy proteins
 Gelatin
 Gluten
 Vegetable gums  Starches
 Ground paprika  Dry mustard
32
Q

What are the two types of emulsions?

A
  • Oil in water: oil is dispersed, water is dispersion

- Water in oil: water is dispersed, oil is dispersion

33
Q

What is a foam?

A

Agglomeration of gas bubbles separated from each other by thin films (liquid or solid)

34
Q

What are liquid foams? Give examples.

A
  • Gas in liquid dispersion

- Whipped cream, whipped egg whites, draft beer foam, mousse

35
Q

What are solid foams? Give examples.

A
  • Gas in solid dispersion

- Sponge toffee, bread, marshmallows, aero

36
Q

What is gelatin?

A

Proteins extracted from collagen, hides, and connective tissues of animals

37
Q

What is a sol? What is the dispersed and the dispersion medium?

A
  • a dispersion of solid colloidal particles in a liquid dispersion medium
38
Q

Are sols pourable, can they gel?

A
  • Pourable

- Gel transformations can occur under appropriate conditions

39
Q

What is a gel? How many phases are there? How can it be made firmer?

A
  • 2 phase system

- High degree of interface between the continuous phase (solid) and the dispersed phase (liquid) = firmer gel

40
Q

How is gelatin prepared?

A

Protein separate out, line up, break up into strands, curl up again, join up with other strands, make an unbreakable irreversible matrix.

41
Q

What effects gelation?

A
  • Gelatin concentration
  • Temperature
  • Sugar
  • Acid
  • Enzymes
  • Salts
  • Solid ingredients

1) Food Fundamentals (17 decks)

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