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1) Introduction to Food Science > Chapter 9: Complex Carbohydrates: Starches, Cellulose, Gums, Pectins > Flashcards

Chapter 9: Complex Carbohydrates: Starches, Cellulose, Gums, Pectins Flashcards

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1
Q

What are complex carbohydrates also called?

A

polysaccharides

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2
Q

How many glucose molecules make up starches?

A

100 to several thousand glucose units linked in chains

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3
Q

Name examples of polymers of sugar.

A

wheat, flour, rice, corn

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4
Q

Define amylose.

A

The linear structure of starches

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5
Q

Define amylopectin.

A

The branched structure of starches

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6
Q

What are starch pockets called?

A

Granules

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7
Q

How do starches perform differently in food mixtures?

A

The ratios of amylose to amylopectin within granules

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8
Q

What are waxy structures made of?

A

Mostly amylopectin

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9
Q

What is cellulose made of?

A

Polysaccharide made from large amounts of beta-glucose

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10
Q

Why can’t we digest cellulose

A

We lack the enzyme to digest it

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11
Q

What is cellulose known as in the diet?

A

Fibre

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12
Q

Give characteristics of gums.

A

Soluble in H2O, extracted from plants

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13
Q

Name 2 functions of gums.

A
  • Thickens and stabilizes mixtures

- Traps colour and flavour

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14
Q

Give 2 examples that use gums.

A

Salad dressings and gummy candies

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15
Q

Where are pectins found? What are they made of?

A
  • Found in plant cells (naturally occur in fruit)

- Made of sugar acids

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16
Q

What are pectins used for?

A

Jams/Jellies

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17
Q

Name the 3 functions of complex carbs in food preparation.

A

1) They provide structure
2) They act as binding agents
3) They thicken liquids

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18
Q

Name 3 examples in which complex carbs provide structure.

A
  • Flour = structure of baked goods
  • Cellulose = structure of fruits and veg
  • Pectins = structure of jams/jellies
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19
Q

What happens when starches are heated? Cooled?

A

Heated: thickens
Cooled: gels

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20
Q

What do amylose molecules bind best for?

A

Binding batters to meat, fruit and vegetable pieces for deep frying

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21
Q

Name 3 examples of carbs as binding agents.

A
  • Amylose to bind batters and produce for deep-frying
  • Carageenan (gum) stabilizes cocoa in milk, dairy products, ice cream
  • Guar gum and xanthan gums improve consistency of gluten free baked products
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22
Q

How do complex carbs react when heated with H2O? What happens?

A

Starch pockets open, allowing H2O molecules to slide into spaces in the starch molecules -> H-bonds with sugar OH groups (thickens)

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23
Q

When complex carbs are heated with H2O, what happens when there’s too much heat?

A

starch molecules break apart (hydrolyze)

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24
Q

Define gelatinization.

A

Thickening liquid with starch

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25
Q

Define gelatinization point.

A

Temp at which max swelling occurs - point at which the starch will hold the most water and have the greatest thickening power

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26
Q

What interferes with gelling? Why?

A

Salt and sugar compete for water (because polar) so large amounts interfere with gelling.

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27
Q

Name the 4 types of combinations of complex carbs.

A
  • Slurries
  • Sols
  • Pastes
  • Gels
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28
Q

Define slurries.

A

Uncooked mixtures of starch and water (acids and bases are added to the mixture to chemically alter the structure of the starch molecules)

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29
Q

Define sols

A

Pourable thickened liquids (pancake, waffle, muffin batter and white sauce, gravy)

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30
Q

Define pastes.

A

Thickened starch/liquid mixtures with very little flow

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31
Q

Define gels.

A

Rigid starch mixtures in which molecules of hydrogen bonds together and form a junction

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32
Q

What is retrogradation?

A

Firming of a gel during cooling and standing

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33
Q

When is retrogradation desirable? What can it form if it continues for too long?

A

When it causes thickening during cooling, it can form cracks if it continues

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34
Q

Define syneresis.

A

Condition of water leaking from a gel over time

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35
Q

Define viscosity.

A

The resistance of a mixture to flow or a measure of starch’s thickening ability.

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36
Q

What makes you more resistance to flow?

A

The more solid you are

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37
Q

What does viscosity change with?

A

With temperature

38
Q

How does cornstarch’s viscosity change?

A

When pressure is applied

39
Q

Which is more viscous: amylose or amylopectin?

A

Amylose

40
Q

Define stability.

A

The ability of a thickened mixture to remain constant over time and temperature

41
Q

What can stable sauces do?

A

They can be frozen and reheated with very little change in appearance or taste

42
Q

How do cornstarch and flour compare in terms of stability and thickening?

A

Cornstarch has more thickening power, but flour is more stable over time and temp

43
Q

Define opacity.

A

The degree of light blockage

44
Q

Define translucency.

A

The degree of how much light passes through objects

45
Q

Define texture.

A

The feel of graininess or smoothness of a mixture on the tongue and palate

46
Q

Why is cornmeal not used for gravy?

A

Since it has a grainy mouthfeel

47
Q

How are modified starched changed?

A

Structurally by chemical or mechanical means

48
Q

What are modified starches often made from?

A

Wheat, corn, soy

49
Q

What can you change when you modify a starch?

A

Sweetness, viscosity, mouthfeel and appearance

50
Q

How are cross-linked starches made?

A

Cross-linked starch is changed chemically so bonding takes place between starch molecules

51
Q

What do cross-linked starches form? When are they most stable?

A

a molecular network, more resistant to acids and more stable during freezing/thawing, will not lead water on standing, and do not continue to thicken during food storage

52
Q

What are cross-linked starches more resistant to?

A

Acids

53
Q

In what are cross-linked starches used?

A

baby foods, salad dressings, cream-style corn, fruit pie fillings

54
Q

Name the 3 basic methods to thicken sauces with starch.

A

1) Cold Water Paste
2) Starch and Fat
3) Starch and Sugar

55
Q

How is cold water paste made? How much starch to water?

A

Made by quickly stirring the starch while adding at least an equal amount of cold water
Must be heated while stirring

56
Q

Give examples of cold water paste.

A

Gravy, soups

57
Q

How do starch and fat thicken sauces?

A

Separates starch granules with melted fat, uses equal amounts of fat and starch

58
Q

Give examples of starch and fats used to thicken sauces.

A

White sauce and gravy

59
Q

What is roux?

A

Gravy made from starch heated in fat until the starch turns a reddish brown
Mixture of equal amounts by weight of flour and fat that is cooked to varying degrees of doneness.

60
Q

What does roux add? What does it require?

A

Adds distinctive flavours to gravies and sauces

Requires low heat and constant stirring

61
Q

How can starch and sugar thicken sauces?

A

Sugar helps separate starch granules and prevents them from sticking

62
Q

Why are digestible starches needed?

A
  • Abundant and economical source of E

- Needed in the diet to allow fat to be used for E and prevent ketosis

63
Q

Why is glucose needed?

A

The brain’s only E source

64
Q

What is fibre also called?

A

Fibre, bran, bulk on food labels

65
Q

What does fibre provide for food texture?

A

Crispiness/Mouthfeel

66
Q

Why is fibre added to bread products?

A

Slow staling and improve loaf volume

67
Q

Name 2 functions of indigestible fibre.

A

Aids in digestion/elimination of waste

Helps maintain a feeling of fullness

68
Q

Name 4 functions of fibre in the body.

A
  • Provides bulk for digestive processes
  • Decreases bile reabsorption
  • Lowers cholesterol levels in blood
  • Promotes the utilization of fats
69
Q

What is the ratio of natural sources of starch?

A

Amylose: 15-35%
Amylopectin: 65-85%

70
Q

Which polysaccharides are not generally available to the home cook?

A

Gums and pectins

71
Q

Which gum is the most common and widely used? What does it do?

A

Gum arabic: surrounds flavour particles, protecting them from moisture absorption, evaporation, or chemical oxidation.

72
Q

What happens to pectin molecules in the presence of sugar?

A

Pectin molecules will dehydrate, then acid will cause hydrogen bonding to occur between negatively charged molecules, thus creating a thickened structure

73
Q

Why must starch first be heated in order to act as a thickener?

A

To break intermolecular bonds. Starch molecules relax and expose polar structures to water, which allows H-bonds to form between the starch molecules and water. It increases the amount of water the molecule can trap.

74
Q

How does the starch differ in instant puddings?

A

Pregelatinized: allows it to gel, or set, at the T of cold milk. The starch in regular pudding mixes will not gelatinize until the mixture is hot enough to boil. Then it will not gel until it is chilled

75
Q

What happens when sugar is combined with flour or any other starch in a gel?

A

It will decrease the strength and viscosity of the gel and increase the translucency of the paste

76
Q

What is the pH of jams and jellies?

A

2.0 to 3.5

77
Q

List four physical properties food scientists evaluate before selecting a starch for thickening.

A

Retrogradation, viscosity, stability, opacity versus translucency and texture

78
Q

How are molecules bonded in a gel?

A

In a three-dimensional network which keeps the molecules from shifting positions.
Two Hs bond together: junction
Long starch chains form firmer gels that are more stable in heat

79
Q

How do amylose and amylopectin molecules form gels?

A

Amylose: set rapidly and form firm gels upon cooling (elastic)
Amylopectin: forms thinner gels or no gels at all (rigid)

80
Q

What is a main cause of bread becoming stale?

A

Tendency of amylopectin starches to become rigid (combined with moisture loss)

81
Q

List the four types of starch and liquid mixtures from least to most viscous.

A

Least – Sols, Pastes, Gels - Most

82
Q

Why does lemon pie filling call for more starch than coconut cream or chocolate pie filling?

A

Since acids hydrolyze starch, which will weaken or break down gels. Lemon juice is added after the starch has thickened the lemon pie’s filling. The filling is then cooled rapidly to minimize the thinning effect of acid in lemon.

83
Q

What makes viscosity vary?

A

Molecular size, shape, and charge

84
Q

Are linear or branched molecules more viscous?

A

Linear are more viscous because they will not roll over easily unless they are parallel to the direction of flow.

85
Q

How can pure wheat starch help achieve evenly shaped cookies?

A

Substituting 30% of the flour in cookies with pure wheat starch (protein removed) will increase the spreading action of the batter

86
Q

Give an example of a starch that is stable when frozen or heated.

A

Waxy maize starch

87
Q

Which starch would you use to make a translucent sauce? To make an opaque sauce?

A

Translucent sauce: cornstarch, potato starch, and arrowroot

Opaque: wheat flour

88
Q

Define beurre manie.

A

Mixture of equal amounts by weight of butter and flour. The mixture can be added to hot soups to thicken the broth. The heat of the broth melts the fat. This allows the starch from the flour granules to disperse into the broth with little risk of lumping.

89
Q

Describe the structure of glycogen.

A

Large, heavy and branched

The more branched the glycogen is, the more glucose units the body can release at a time

90
Q

What does the size of the glycogen store depend on?

A

The amount of carbohydrates consumed and how frequently the individual exercises. The more you exercise, the more energy the muscles will store

91
Q

Why do beans make you gassy?

A

The fibre tetrasaccharide stachyose -> gas
Minimize by taking a special digestive enzyme, but less positive fibre effects
So, eat high fibre foods and eat yogurt -> growth of beneficial bacteria

1) Introduction to Food Science (20 decks)

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