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2) Food Chemistry I > Lipids VIII > Flashcards

Lipids VIII Flashcards

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1
Q

What is the % of TG in milk fat?

A

96%

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2
Q

Why are sterols necessary in milk fat?

A

To maintain the fluidity of phospholipids

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3
Q

What are the main fatty acids in milk fat? (3)

A
  • Oleic
  • Stearic
  • Palmitic
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4
Q

How much linoleic and linolenic does milk fat contain?

A

Very little

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5
Q

Which product contains butyrate? What is the chemical abbreviation?

A

Milk fat (C4:0)

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6
Q

In milk fat, long chain fatty acids are preferred in which positions?

A
  • sn-1

- sn-2

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7
Q

In milk fat, short-chain fatty acids are preferred in which positions?

A

sn-3

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8
Q

What kind of TG are preferentially synthesized in milk fats?

A

TG with one short and two long-chain FA

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9
Q

How does the ratio of saturated to unsaturated FA vary in milk?

A
  • Does not vary

- Due to their typical diet

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10
Q

TG are contained within ___________ that are surrounded by a _________

A
  • fat globules

- membrane

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11
Q

_________ are synthesized by the microflora of the cow, and present health benefits

A

Conjugated linoleic acid (CLAs)

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12
Q

What are the components of the membrane that surround the fat globules in milk fats?

A
  • Protein (41%)
  • Phospholipids and glycolipids (30%)
  • Cholesterol (2%)
  • Neutral glycerides (14%)
  • Water (13%)
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13
Q

How much cholesterol does milk, shrimp, and eggs contain?

A
  • Milk: 27 mg
  • Shrimp: 125 mg
  • Eggs: 275 mg
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14
Q

What does the membrane that surrounds the fat globules in milk contain?

A
  • Double layer of lipoproteins

- Enzymes, including lipase

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15
Q

What is the function of the membrane of the fat globule

A

Prevents lipolysis

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16
Q

What is the consequence of the disruption of the membrane of fat globules? In which situation could this happen?

A
  • Homogenization of milk
  • Allows lipase to bind to the fat globules and to hydrolyze TG at a high rate
  • Milk becomes unpalatable
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17
Q

What must be done prior to homogenization? Why?

A

Lipases must be inactivated by pasteurization to avoid them hydrolyzing the TG

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18
Q

What is lactose degraded to during ripening? How?

A

Degraded to lactic acid by homofermentation

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19
Q

What does the type and extent of milk fat degradation depend on?

A

Depends on the microflora

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20
Q

What is a prerequisite for good aroma in cheese? What are the exceptions?

A
  • As little lipolysis as possible

- Exceptions: stinky cheeses (ex: roquefort)

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21
Q

More/less free fatty acids are released in homogenized milk than untreated milk.

A

More

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22
Q

What do the different aromas of various types of cheeses arise from?

A
  • From the different specificities of the lipases involved

- They exhibit specificity to hydrolyze certain substrates, which causes different aromas

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23
Q

Are the levels of saturated or unsaturated FA higher in red meat?

A

Unsaturated exceeds saturated

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24
Q

If the levels of unsaturated FA exceeds saturated FA in red meat, why are the lipid products solid?

A

Since they have more fully saturated fatty acids (GS3)

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25
Q

What is the % of total saturated lipids in red meat? Which fatty acids are the most present?

A
  • Total: 46%

- Palmitic (16:0) > Stearic (18:0) > Myristic (14:0)

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26
Q

What is the % of total monounsaturated lipids in red meat? Which fatty acids are the most present?

A
  • Total: 50%

- Oleic (18:1) > Palmitoleic (16:1)

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27
Q

What is the function of cholesterol in red meat? How much is found in 100 grams?

A
  • Integral component of cellular membranes

- 70-90mg/100 grams

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28
Q

What is the main monounsaturated fatty acids found in skeletal muscles of red meat?

A
  • Oleic acid (90% of MUFAs)

- 45% of total FA

29
Q

What is the main polyunsaturated fatty acids found in skeletal muscles of red meat? What is the main source of saturated? What is the main source of unsaturated?

A
  • Polyunsaturated: Linoleic acid
  • Monounsaturated: Oleic acid
  • Saturated: Palmitic and stearic acid (2:1 ratio)
30
Q

What is the main saturated fatty acids found in skeletal muscles of red meat?

A
  • Palmitic acid and stearic acid in a ratio of 2:1 (90%)

- 40% of total FA

31
Q

How many eggs do hens produce per year?

A

225

32
Q

What is the composition of the albumen of an egg?

A

10% protein, 0.03% lipids

33
Q

What is the composition of the yolk of an egg?

A

16% protein, 35% lipids

34
Q

What is the composition of the whole egg?

A

13% protein, 11% lipids

35
Q

Why are eggs nutrient rich?

A

Complete protein, essential FAs, vitamin D

36
Q

What is moderate egg consumption?

A

6 eggs/week does not increase coronary heart disease

37
Q

What is the macronutrient composition of an egg yolk?

A
  • Water: 48.7%
  • Fat: 32.9%
  • Protein: 16.4%
38
Q

Are egg yolks water-soluble?

A

Yes, even if they behave as lipids, eggs are “soluble” and can readily disperse in water

39
Q

Why can eggs readily “disperse” in water?

A
  • High lipid content
  • High proportion of phospholipids
  • More than 90% of the lipids in the yolk are associated with lipoproteins
40
Q

What is the ratio of LDL to HDL in egg yolks?

A

LDL: 68%
HDL: 14%

41
Q

What does cholesterol provide in egg yolks?

A

Flexibility

42
Q

How does the density of LDL and HDL compare?

A

LDL: 0.98
HDL: >1.0

43
Q

How does the composition of LDL compare to HDL?

A

LDL: large amounts of lipids (85%); mostly TG (69%) and phospholipids (26%)
HDL: small amounts of lipids (20%); mostly phospholipids (60%) and TG (40%)

44
Q

Where are LDL particles present in egg yolk? In what form?

A

In the form of tiny micelles suspended in the plasma fraction

45
Q

Does LDL or HDL contain phosvitin? What is it?

A
  • HDL

- Phosphorus-rich, lipid-free protein

46
Q

Associate these words:

1) LDL
2) HDL

A) Lipovitellin
B) Lipovitellenin

A

LDL: Lipovitellenin
HDL: Lipovitellin

47
Q

What influences the fatty acid composition of an egg yolk?

A

The breed and the diet

48
Q

What is the lipid composition in egg yolks?

A
  • TG (66%)
  • Phospholipids (28%)
  • Cholesterol (5%)
49
Q

What is the fatty acid composition of egg yolks?

A
  • Saturated FA: 30-35%
  • MUFAs: 40-45%
  • PUFAs: 20-25%
50
Q

What happens when the dietary PUFA is elevated in egg yolk?

A

Linoleic acid increases and oleic acid decreases

51
Q

What are the three main components of egg yolk phospholipids?

A
  • Phosphatidylcholine/Lecithin (73%)
  • Phosphatidylethanolamine/Cephalin (15%)
  • Lysophosphatidylcholine (6%)
52
Q

What is lysophosphatidylcholine?

A
  • Derivative of phosphatidylcholine

- One of the FA has been replaced by a hydroxyl group

53
Q

What are the deteriorative changes that occur in dried whole egg and egg yolk related to?

A

Maillard reaction

54
Q

What leads to discoloration of dried whole egg and loss of palatability?

A

The reaction between cephalin and glucose (Maillard)

55
Q

How is the development of off-flavour during storage eliminated in eggs?

A
  • Elimination of glucose

- Addition of glucose oxidase followed by catalase

56
Q

What are designer eggs?

A
  • Enhance the image of eggs as healthy and nutritional

- Omega-3 fatty acids eggs (feeding hens flax or fish oil); darker yellow colour to the yolk

57
Q

What is the fat content of fish depend on?

A
  • Species of fish
  • Maturity
  • Season
  • Food availability
  • Feeding habit
58
Q

Where does fat deposition occur in fish?

A

Muscle tissue, liver, intestines

59
Q

Fish is an important contributor to what types of omega-3 fatty acids? What are the benefits and downsides?

A
  • Omega-3-polyenic acids (5 or 6 double bonds)
  • Nutritional value
  • Preservation is difficult because of their easy peroxidation
60
Q

What is the typical fatty acid profile of fish oil?

A
  • Saturated (28%)
  • Unsaturated (28%)
  • Polyunsaturated (38%)
61
Q

What is the % of TG in soybeans? What about phospholipids?

A
  • TG (96%)

- Phospholipids (2%)

62
Q

What is the fatty acid profile of soybean oil?

A
  • Saturated FA (14%)

- Unsaturated FA (81%)

63
Q

What is the main saturated FA in soybean oil? What are the main unsaturated FA in soybean oil?

A
  • Palmitic acid (10%)
  • Linoleic acid (51%)
  • Oleic acid (23%)
64
Q

When are lecithins removed in the processing of oil? Why?

A
  • Removed from degumming

- To use their emulsifying power for other means

65
Q

What are the unsaponifiables contained in soybean oil? When are they removed?

A
  • Mostly tocopherol and sterols

- Partially removed in deodorization

66
Q

When are free fatty acids and pigments removed from soybean oil?

A

Refining and bleaching

67
Q

Why are soybean oils classified as semi-drying oils?

A

Due to their high linoleic and linolenic acid content

68
Q

What is responsible for the stronger tendency of soybean oil to undergo oxidative phosphorylation?

A

Linolenic acid

2) Food Chemistry I (31 decks)

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