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1) Introduction to Food Science > Chapter 10: Lipids: Nature's Flavour Enhancers > Flashcards

Chapter 10: Lipids: Nature's Flavour Enhancers Flashcards

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1
Q

What elements do lipids contain?

A

C, H, O

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2
Q

Name the 3 types of lipids.

A
  • Triglycerides
  • Phospholipids
  • Sterols
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3
Q

What are the 2 basic parts of glycerides?

A

Glycerol molecule and fatty acid(s)

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4
Q

What is the base of a glyceride?

A

Glycerol molecule with 3 hydroxyl groups that readily react with other compounds

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5
Q

What are fatty acids?

A

Carbon chains with a carboxyl group (COOH) at one end

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6
Q

How will the glycerol and the fatty acids react? What will it form? What are their charges? How will they change?

A

Carboxyl group of a fatty acid will react with the hydroxyl group of a glycerol producing a lipid and water
They are both charged (COOH+, OH-) and polar, but will become nonpolar after combining

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7
Q

Which glycerides are partially soluble in water? What are they used for?

A

Mono and diglycerides are partially soluble in water and soluble in fat
They are added to processed foods to keep mixtures of water and fats stable (emulsion)

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8
Q

What are phospholipids made of?

A

A glycerol base + 2 fatty acids (diglyceride) + phosphorus-containing acid attached

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9
Q

What part of the phospholipid dissolves in fat? What dissolves in water?

A

Fatty acid dissolves in fat (nonpolar)

Phosphorus-containing acid dissolves in water (polar)

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10
Q

Name 2 functions of phospholipid

A
  • Part of cell membranes, help transport fats in and out of cells (phospholipid bilayer)
  • Help fats stay mixed in water-based solutions (emulsifying agents)
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11
Q

Name some examples of sterols

A

Vitamin D, steroid hormones, cholesterol

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12
Q

What’s the first consideration when categorizing lipids based on molecular structure?

A

How saturated the carbon chains are with Hatoms (0, 1 or many double bonds)

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13
Q

What are saturated fatty acids?

A

Fatty acids that have max nb of H atoms (no double bonds)

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14
Q

What are unsaturated fatty acids?

A

Do not have the max number of H atoms (double bonds present)

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15
Q

Name monounsaturated fatty acid sources.

A

Olive and canola oils, almonds, walnuts

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16
Q

Name polyunsaturated fatty acid sources.

A

Safflower, sunflower and corn oils

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17
Q

What determines the temperature at which a lipid will liquify?

A

The number of carbon and hydrogen atoms

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18
Q

What lowers the temperature at which a lipid becomes solid?

A

Double bonds

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19
Q

Define the melting point of a lipid.

A

The temperature at which all the different fats and oils it contains are liquid

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20
Q

Define hydrogenation.

A

The process of adding hydrogen atoms to an unsaturated lipid to increase its saturation levels

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21
Q

Describe the hydrogenation process

A
  • H is bubbled through liquid oil in the presence of a nickel catalyst
  • Double bonds in the fatty acid chain break and pick up extra H atoms
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22
Q

Name 3 advantages to hydrogenation.

A
  • Longer shelf life than oil or lard (less oxidation)
  • Greater stability and lower production cost than lard
  • Faster dissolving and setting properties in chocolate production
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23
Q

What are milkfats?

A

Contain short chain fatty acids and come from cows, goats and sheep

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24
Q

What are lauric acids?

A

Lipids found in the oils of fruits and seeds from tropical palm trees, low melting point, most saturated of the oils found in plants

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25
Q

What are vegetable butters?

A

Come from seeds of tropical plants (ex: cocoa butter)

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26
Q

Name sources of oleic-linoleic acids.

A

Corn, peanuts, sunflowers, olives, cottonseed: largest group of triglycerides and contain less than 20% saturated fatty acids

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27
Q

Name sources of linolenic acids.

A

Soybeans, wheat germ

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28
Q

What kind of lipid requires refrigeration?

A

Linolenic acids

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29
Q

What is marbling?

A

More marbling = more animal fat
High marbling = good quality cut
Marbling is an indicator of flavour and tenderness and higher fat content

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30
Q

Define marine oils.

A

Unsaturated oils from fish

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31
Q

Why do lipids melt and solidify over a temperature range?

A

Because of the mixture of fatty acids

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32
Q

Define solidification point.

A

Temperature at which all lipids in a mixture are in a solid state

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33
Q

What influences the melting point?

A

The more saturated the fatty acid and the longer the length of the carbon chain, the higher the melting point

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34
Q

Why don’t fats mix with water?

A

Since they are nonpolar and water is polar.

Nonpolar: equal or balanced sharing of electrons

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35
Q

Define auto-oxidation.

A

Complex chain reaction that starts when lipids are exposed to oxygen and results in deterioration

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36
Q

Define rancidity.

A

Form of food spoilage that poses no short term health risk

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37
Q

How can rancidity be prevented?

A

Vacuum sealing (removing O or replaced with N or CO2) or adding antioxidants (interact with O before the lipids do)

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38
Q

Name the 6 lipid functions in food preparation.

A

1) Lipids transfer heat quickly, evenly, and at high T
2) Lipids tenderize baked products
3) Lipids aerate batters
4) Lipids enhance flavours of other foods
5) Lipids lubricate food components
6) Lipids serve as liquids in emulsions

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39
Q

Define smoke point.

A

T at which fatty acids break apart and produce smoke

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40
Q

Define flash point.

A

T at which lipids will flame (grease fire), cannot put out with water

41
Q

What determinates flakiness in baked products?

A

fat to flour ratio

42
Q

What causes chewiness and toughness in baked products?

A

Fats shorten flour’s protein strands (which causes chewiness and toughness)

43
Q

What kind of lipid works best for biscuits, pies, and puff pastry?

A

With high melting point (solid fats - butter, regular margarine, lard, shortening)

44
Q

What can be used for quick mix batters?

A

Oils

45
Q

What do saturated fats form when beaten?

A

Allow tiny air pockets to form when beaten

46
Q

How can you aerate a cake batter?

A

Creaming fat and sugar together

47
Q

Name some common seasoning and moistening lipids.

A

Butter, margarine, mayonnaise

48
Q

Why do lipids help flavour?

A

Fats dissolve and disperse flavour compounds

49
Q

Name flavourless oils.

A

Cottonseed, vegetable shortening, soybean, canola

50
Q

Name 2 ways lipids can make food more moist.

A
  • Greasy texture feels slick and smooth, making foods seem moister
  • Spreads like butter, margarine and mayonnaise make sandwiches seem moister without the soggy bread
51
Q

Define an emulsion.

A

A mixture of a lipid and a H2O based liquid

52
Q

What can stabilize emulsions?

A

Phospholipids because they have a polar end that attracts water and a nonpolar end that attracts the lipid

53
Q

Name examples of emulsions.

A

Butter, margarine, mayonnaise, bottled salad dressings

54
Q

Name the 9 functions of lipids in the body.

A
  • Provide a concentrated source of E
  • Give a longer feeling of fullness due to digestion time
  • Help regulate body temperature
  • Provide an energy reserve from lipids stored in adipose tissue
  • Protect vital organs from injury
  • Participate in cell production
  • Transport vitamins A, D, E, and K
  • Produce hormones, vitamins, and other secretions
  • Provide essential fatty acids
55
Q

Name the 2 essential fatty acids. What can they become in the body?

A
  • Linoleic acid, can become Omega-6

- Linolenic acid, can become Omega-3

56
Q

Give examples of linoleic acid (Omega-6).

A

Corn, cottonseed, and soybean oils, as well as chicken

57
Q

Give examples of linolenic acid (Omega-3).

A

Canola and soybean oils, walnuts and fish

58
Q

What are the benefits of Omega-3s?

A

May slow the growth of plaque in arteries

59
Q

How much fish should we have to eat? What should we look out for?

A

8 ounces or more, we have to be careful for mercury

60
Q

Describe three ways lipids differ from carbohydrates.

A
  • Lipids are not polymers.
  • They do not provide structure to food products.
  • They cannot be dissolved in water.
61
Q

Name the saturated fatty acids found in butter and beef fat.

A

Butter: butyric acid

Beef fat: stearic acid

62
Q

What do double bonds create in the fatty acid chain?

A

A bend, making it tough to pack together tightly

63
Q

Why do trans fatty acids solidify at lower temperatures?

A

Because their trans confirmation (no bend) makes them linear

64
Q

Why do marine oils spoil or develop off flavours and odours very quickly?

A

The high degree of unsaturated, must be eaten or frozen

65
Q

List the seven main groups of triglycerides.

A

1) Milkfats
2) Lauric acids
3) Vegetable butters
4) Oleic-linoleic acids
5) Linolenic acid
6) Animal fats
7) Marine oils

66
Q

Identify three physical characteristics of lipids that affect the way lipids perform in food products.

A

1) Differing Melting and Solidification Points
2) Nonpolar Molecules
3) Tendency to Deteriorate

67
Q

Why don’t lipids have specific melting points?

A

Because most lipids are mixtures of different kinds of fatty acids. Since each fatty acid has a different melting point, the lipids in a mixture will melt at different temperatures.

68
Q

What is more dense: water or lipids?

A

Lipids are less dense that the water due to the shape of the fatty acid chain that creates space between the parts of the molecule - oil floats on water

69
Q

What must you add to mix oil and vinegar?

A

An emulsifier

70
Q

Why are unsaturated oils more susceptible to auto-oxidation than saturated fats?

A

Because unsaturated oils contain double bonds, which are more likely to react than single bonds

71
Q

Name some important dietary antioxidants.

A

Vitamins A,C, E

72
Q

What characteristic makes lipids get hot enough to brown food and make the exterior crisp?

A

The temperature of lipids will continue to increase as heat is added, unlike water

73
Q

What is the smoke point of lard?

A

185oC

74
Q

What is the usual flash point?

A

315oC

75
Q

What temperatures should deep frying occur at?

A

Between 175 (or else soggy) and 205 oC (or else outside burnt inside raw)

76
Q

Why should you let deep-frying batter sit for 20 to 30 minutes?

A

To allow the starch in the batter to bind to the food

77
Q

Should you add salt when deep frying?

A

No, since it pulls water to the surface of the food (increase splattering), also lowers the smoke point of the oil and will reduce the time the oil can be used

78
Q

How do lipids tenderize baked goods like cakes, pancakes, muffins, and waffles?

A

Fats aid in giving these products a fluffy, moist, texture. The separating of the flour keeps the products tender.

79
Q

Can oils replace solid fats in most cake recipes?

A

No, oils cannot provide the structure needed to trap air, which will result in a grainier texture

80
Q

Why is it important to time the creaming step?

A

Because beating increases friction, it increases the batter temperature. If the temp goes too high, the fat will melt and the trapped air will be lost. This results in a crumbly, grainy texture

81
Q

Can one stick of whipped butter replace one stick of butter?

A

No, since the whipped stick just has extra volume due to trapped air. They are good to help lower fat in the diet though

82
Q

Name some examples of emulsifying agents in food.

A

Lecithin (phospholipid) found in egg yolk

Butter, milk, and bottled salad dressings

83
Q

Name some benefits of EPA and DHA.

A

Strengthen brain-cell membranes improving cell-to-cell communication. They may also reduce joint inflammation and prevent heartbeat irregularities and mental decline.

84
Q

Name the 2 roles of cholesterol.

A

1) Used to produce hormones

2) Build cell membranes

85
Q

What causes atherosclerosis?

A
  • Too much cholesterol in the blood
  • Lipid and cholesterol deposits on artery walls (plaque)
  • Rough, rigid, narrow arteries = atherosclerosis, high blood pressure + heart attacks/strokes
86
Q

What is an optimal level for LDL? HDL?

A

LDL: Less than 100mg/dL
HDL: more than 40mg/dL (men) and 50mg/dL (women)

87
Q

Where is cholesterol found?

A

ONLY in animal sources: meats, dairy products, egg yolks

88
Q

Why are Mediterranean diets praised?

A
  • Very low levels of saturated fat (olive oil)

- High number of MUFAs

89
Q

What do PUFAs lower? MUFAs?

A

PUFA: lowers LDL and HDL
MUFA: lowers LDL, without lowering HDL

90
Q

Name the 2 disadvantages of olive oil.

A

1) Distinctive flavour

2) Low smoke point

91
Q

Where is cholesterol found?

A

only in animal products

92
Q

What is atherosclerosis?

A

Excess blood cholesterol leads to plaque buildup in arteries

93
Q

How do you keep LDL and HDL levels healthy?

A
  • Reduce intake of saturated fat and cholesterol
  • Regular exercise
  • Maintain healthy weight
  • Read food labels: limit trans, sat fats and added salt and sugar
94
Q

What are the dietary recommendations to reduce your risk of heart disease?

A

Fat: 20-35% daily calories

Mostly from PUFAs and MUFAs

95
Q

Name the 2 functions of cholesterol.

A
  • Produce hormones

- Build cell membranes

96
Q

How is cholesterol transported?

A

Lipoproteins

97
Q

Which lipoprotein is healthy? Which is atherogenic?

A

Healthy: HDL

Not healthy: LDL

98
Q

What does LDL do?

A

carry cholesterol to the liver

99
Q

What does HDL do?

A

find unneeded cholesterol and return it to the liver

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