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2) Food Chemistry I > Lipids - Summary > Flashcards

Lipids - Summary Flashcards

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1
Q

What are the three groups of lipids?

A
  • Simple lipids
  • Compound lipids
  • Derived lipids
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2
Q

What are the two groups of simple lipids?

A
  • Triglycerides

- Waxes

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3
Q

What are the three groups of compound lipids?

A
  • Phospholipids
  • Glycolipids
  • Lipoproteins
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4
Q

What is jojoba oil?

A

An ester (simple lipid)

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5
Q

Why does an edible fat melt over a much wider range than a pure triglyceride?

A

Because it consists of many different pure TG molecules, each with different melting points

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6
Q

What are waxes?

A

Esters of fatty acids esterified with an alcohol, other than glycerol

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7
Q

Give examples of compounds in the wax category.

A
  • Cholesterol

- Esters of vitamin A

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8
Q

When X is OH, what is the phospholipid called?

A

Phosphatidic acid

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9
Q

When X is O-CH2-CH(NH2)-COOH, what is the phospholipid called?

A

Phosphatidylserine

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10
Q

When X is a sugar, what is the phospholipid called?

A

Phosphatidylinositol

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11
Q

When X is O-CH2-CH2-N+(CH2)3, what is the phospholipid called?

A

Phosphatidylcholine (lecithin)

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12
Q

When X is O-CH2-CH2-NH2, what is the phospholipid called?

A

Phosphatidylethanolamine (cephalin)

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13
Q

What is the fundamental unit of terpenes? How many carbons does it contain?

A

Isoprenes (5 carbons)

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14
Q

How many isoprene units and carbons do monoterpenes contain?

A

2 isoprene units, 10 carbons

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15
Q

Name the terpene classes in chronological order.

A
  • Monoterpenes
  • Sesquiterpenes
  • Diterpenes
  • Sesterterpenes
  • Triterpenes
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16
Q

What chain length of fatty acids are slightly miscible with water?

A

C4-C8

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17
Q

What is the systematic name of myristic acid?

A

Tetradecanoic acid (14:0)

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18
Q

What is the systematic name of stearic acid?

A

Octadecanoic acid (18:0)

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19
Q

What is the systematic name of palmitic acid?

A

Hexadecanoid acid (16:0)

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20
Q

What are the names for 18:1, 18:2, and 18:3 fatty acids?

A
  • Oleic
  • Linoleic
  • Linolenic
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21
Q

Give the systematic names of fatty acids from C2 to C22 (even-numbers only).

A
  • Ethanoic (C2)
  • Butanoic (C4)
  • Hexanoic (C6)
  • Octanoic (C8)
  • Decanoic (C10)
  • Dodecanoic (C12)
  • Tetradecanoic (C14)
  • Hexadecanoic (C16)
  • Octadecanoic (C18)
  • Eicosannoic (C20)
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22
Q

What are C2:0, C4:0, and C12:0 fatty acids?

A
  • C2:0 - acetic
  • C4:0 - butyric
  • C12:0 - lauric
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23
Q

How do you indicate the presence of a double bond in nomenclature?

A

By the suffix “enoic”

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24
Q

What are unconjugated double bonds?

A

Separated by a methylene group (natural state)

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25
Q

What is a conjugated double bond?

A

Double bonds are next to each other (more susceptible to autoxidation)

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26
Q

Which fatty acid is readily converted to a mixed bonding system? What does that lead to?

A
  • Linolenic acid
  • Formation of an active methylene group, positioned between a conjugated and unconjugated double bonds
  • Very susceptible to autoxidation
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27
Q

What is largely responsible for reversion in soybean and fish oils?

A

The active methylene group of linolenic acid

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28
Q

Where do you start counting in Omega-nomenclature? What does 10:23 mean?

A
  • Methyl end

- 10 carbons with two double bonds, the first positioned at 3 from the methyl end

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29
Q

What is 20:46?

A

Arachidonic acid

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30
Q

What are the distinguishing features of the milkfat group?

A
  • High levels of long-chain saturated fatty acids

- Unique and substantial portion of short-chain fatty acids (ex: butyric acid)

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31
Q

What is responsible for the “rancid like” odor from lipolysis in milkfats?

A

Short-chain fatty acids

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32
Q

What are sources of the lauric acid group?

A
  • Palm kernal oil (extracted from oilseed)
  • Coconut
  • Tropical oils
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33
Q

What is palm oil?

A
  • Extracted from palm FRUIT

- Much more unsaturated, not a lauric acid

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34
Q

What is the distinguishing feature of the lauric acid group?

A
  • High content of lauric acid (C12:0)

- Mostly saturated

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35
Q

Why are lauric acids oils at room temperatures?

A

Despite their saturation, they are oils due to lauric acids short-chain (C12)

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36
Q

Which group is resistant to oxidative rancidity?

A

Lauric acid, due to their low degree of unsaturation

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37
Q

Give examples of the oleic-linoleic acid group.

A
  • Cottonseed
  • Olive
  • Peanut
  • Corn
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38
Q

Why don’t oleic-linoleic group fatty acids suffer from reversion?

A

Negligible amount of linolenic fatty acids

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39
Q

Give examples of linolenic acids.

A

Soybean, hempseed

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40
Q

Which group’s fatty acids are qualified as drying oils?

A
  • Linolenic acids

- Because of their ability to polymerize into a hard film if applied as a thin layer

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41
Q

Why are animal fat depot group fats rather than oils?

A
  • Despite their high content of unsaturated fatty acids,

- They are fats because they have a higher ratio of GS2 (disaturated) and GS3 (trisaturated) glycerides

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42
Q

What is the distinguishing feature of marine oils?

A
  • High in long-chain unsaturated fatty acids (C16-C22)
  • Very highly unsaturated (up to 6 double bonds)
  • High in omega-3 fatty acids
  • REVERSION and autoxidation
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43
Q

Give examples of erucic fatty acids.

A
  • Rapeseed oil

- Mustard oil

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44
Q

What is erucic acid?

A
  • C22:1

- Health hazard

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45
Q

What is canola oil?

A

Low erucic acid edible oil

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46
Q

Corn oil, safflower oil, and sunflower oil are examples of what?

A

Omega-6 fatty acids

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47
Q

Olive oil, avocados, peanuts, and almonds are examples of what?

A

Omega-9 fatty acids

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48
Q

What does lipase catalyze?

A
  • Lipolysis

- Hydrolysis of the ester linkage between glycerol and a fatty acid in a TG

49
Q

What does lipoxygenase catalyze?

A
  • The oxidation of polyunsaturated fatty acid chains that have a cis-cis-1,4-pentadiene group
50
Q

What are the three ways to obtain oil from a plant source? How are they different?

A
  • Hydraulic pressing: poor quality, long time, more enzyme damage
  • Expelling: press cake still contains oil, followed by solvent
  • Solvent extraction: organic solvent (hexane), efficient
51
Q

What are the four steps to the refinement of oil?

A

1) Settling and degumming
2) Refining
3) Bleaching
4) Deodorization

52
Q

What does settling and degumming extract? How?

A
  • Mixing the oil with water and allowing it to stand

- Carbohydrates, proteins, and phospholipids dissociate (aqueous)

53
Q

What does refining extract? How?

A
  • Treatment with dilute alkali, to convert FAs into soap

- Removal of free fatty acids from the oil

54
Q

What does bleaching extract? How?

A
  • Oil is passed through dry bentonite or clay

- Removal of coloured material from the oil

55
Q

What does deodorization extract? How?

A
  • Steam stripping

- Removal of volatile compounds

56
Q

What is biodiesel?

A

Methyl esters

57
Q

How can fatty acid composition/distribution be determined?

A

Gas chromatography

58
Q

What is winterization? What was it developed with?

A
  • Cooling down the oil to remove saturates

- Cottonseed oil

59
Q

What are the functions of hydrogenation? (2)

A
  • Convert an oil into a fat

- Reduce the susceptibility of an oil to oxidative rancidity

60
Q

What are the double bonds formed by hydrogenation capable of? What does that result in?

A
  • Wandering (positional isomerism)

- Conversion of unconjugated double bonds to mixed bonding systems

61
Q

What is selectivity?

A

Hydrogenation prefers highly unsaturated fatty acids

62
Q

Why is interesterification used in lard?

A
  • GS2U component is made of oleopalmitostearin, which has a propensity to form large crystals
  • Interesterification solves that problem
63
Q

What are the two ways to determine the solid fat content?

A
  • Dilatometry

- Nuclear magnetic resonance (NMR)

64
Q

What is plotted in a dilatometry graph?

A

Specific volume, inverse of density (y) as a function of temperature (x)

65
Q

What do the three sigmoidal represent in dilatometry?

A

1) Thermal expansion of the solid fat
2) Expansion due to a change in state
3) Thermal expansion of the ilquid only

66
Q

What is the equation of the solid fat index?

A
  • (X/Y) x 100
  • X is the measurement between the curve and the liquid line
  • Y is the measurement between the liquid line and the solid line
67
Q

Which polymorphic form has the highest and lowest melting point?

A
  • Highest: beta

- Lowest: alpha

68
Q

What polymorphic form arises from the rapid cooling of liquid fat?

A

Alpha

69
Q

What polymorphic form arises from the slow cooling of liquid fat?

A

Beta

70
Q

Beta-Prime is the polymorphic transformation of what?

A

Alpha

71
Q

Coconut, corn, and olive oil prefer the _____ crystal form

A

beta

72
Q

Cottonseed, milk fat, and palm oil prefer the ______ crystal form

A

beta-prime

73
Q

What are the four methods for conversion from beta to beta-prime?

A
  • Interesterification
  • Interesterification and hydrogenation
  • Winterization
  • Addition of cottonseed oil and/or tallow flakes
74
Q

Differentiate interesterification and intraesterification.

A
  • Interesterification: exchange among TG molecules

- Intraesterification: exchange WITHIN a TG molecule

75
Q

What are high temperature base catalysts for interesterification? What is the low-temperature catalyst?

A
  • High: KOH and NaOH

- Low: NaOCH3 (sodium methoxide)

76
Q

What are the three steps to interesterification?

A

1) Formation of enolate ion
2) Formation of B-keto ester
3) Interesterification

77
Q

What is the definition of catalyst activity?

A

Decrease in iodine number per unit of time during a hydrogenation under a specific set of conditions

78
Q

What is the iodine number? What does it indicate?

A
  • The number of grams of iodine absorbed by 100 grams of fat

- Indicates the degree of unsaturation of the fatty acid

79
Q

What are the independent variables affecting the reaction rate of hydrogenation?

A
  • Nature of the substance
  • Concentration of the catalyst
  • Pressure
  • Temperature
  • Agitation
80
Q

What are the dependant variables affecting the reaction rate of hydrogenation?

A
  • trans fatty acids
  • Selectivity ratio
  • Hydrogenation rate
81
Q

How does an increase in temperature affect the selectivity ratio, trans content, and reaction rate in hydrogenation?

A

Selectivity ratio: increases
Trans content: increases
Reaction rate: increases

82
Q

How does an increase pressure affect the selectivity ratio, trans content, and reaction rate in hydrogenation?

A

Selectivity ratio: decreases
Trans content: decreases
Reaction rate: increases

83
Q

How does an increase in agitation affect the selectivity ratio, trans content, and reaction rate in hydrogenation?

A

Selectivity ratio: decreases
Trans content: decreases
Reaction rate: increases

84
Q

How does an increase in catalyst affect the selectivity ratio, trans content, and reaction rate in hydrogenation?

A

Selectivity ratio: increases
Trans content: increases
Reaction rate: increases

85
Q

What is saponification?

A

Hydrolysis of an ester under alkaline conditions

86
Q

How do you use gas chromatography?

A

1) Saponify
2) Chromatograph methyl esters
3) Determine peak areas

87
Q

What are the two methods to obtain the iodine value?

A
  • Wijis

- Hanus

88
Q

What is cocoa butter composed of?

A
  • 80% is DISATURATED

- SOS, POS, POP

89
Q

What determines the characteristic cocoa butter texture?

A

POS

90
Q

What happens when POS in cocoa butter is transformed from the beta-prime form to the beta form?

A

Chocolate “bloom” - white spots and dull surface appearance

91
Q

What is tempering?

A

Process which permits transformation to the proper polymorphic form

92
Q

What is reduced in the random interesterification of lard?

A

Proportion of palmitic acid in the 2-position is reduced –> improves its plastic range

93
Q

What is autoxidation? What is the overall result?

A
  • Reaction of unsaturated FAs with molecular oxygen

- Development of rancidity

94
Q

What does autoxidation require?

A

1) Hydrogen must be abstracted from the FA chain

2) Molecular oxygen must be present

95
Q

How can hydrogen be abstracted from the FA chain?

A
  • Light
  • Heat
  • Metallic cations
  • Lipoxygenase
  • Singlet oxygen
96
Q

What is propagation in autoxidation?

A

Reaction of the fatty acid free radical with oxygen

97
Q

What is the key to the self-propagating nature of the autoxidation reaction? What does that form?

A
  • The peroxy radical has a preference for terminating its free radical state by abstracting a hydrogen from another FA
  • Forms a hydroperoxide and a new FA radical
98
Q

What are the primary oxidation products?

A
  • Hydroperoxides (predominate)

- Peroxides

99
Q

What are the compounds responsible for off-flavors in autoxidation? What is their precursor?

A
  • Low-molecular weight aldehydes, alcohols, ketones

- Hydroperoxide

100
Q

When does the monomolecular hydroperoxide mechanism predominate?

A

When the hydroperoxide concentration is low

101
Q

When does the bimolecular hydroperoxide mechanism predominate?

A

When the hydroperoxide concentration is high

102
Q

What does the monomolecular reaction form?

A

Alkoxy and hydroxy radicals

103
Q

What three reactions can an alkoxy radical undergo? Which releases a free radical?

A
  • Aldehyde generation (radical)
  • Alcohol generation (radical)
  • Ketone generation (termination)
104
Q

What reactions can an aldehyde undergo? (2)

A
  • Oxidation to a carboxylic acid

- Reduction to an alcohol

105
Q

What does the bimolecular reaction form?

A

Alkoxy and peroxy radicals + H2O

106
Q

What do peroxy radicals prefer to do?

A

Abstract a hydrogen from a fatty acid

107
Q

What do alkoxy radicals prefer to do?

A

Decompose –> aldehydes, ketones, alcohols, carboxylic acids

108
Q

What does the peroxide value indicate? Does it accurately portray rancidity?

A
  • Measures the quantity of hydroperoxides

- No, since hydroperoxides decrease at the end of the reaction since they are degraded, which produces the off-flavours

109
Q

What is the slow accumulation of hydroperoxides called?

A

Induction period (primarily monomolecular reaction)

110
Q

What does the TBA test indicate?

A
  • Secondary breakdown products of autoxidation

- MALONALDEHYDE –> produces a red complex

111
Q

Is citric acid an antioxidant? Why/why not?

A
  • No, it is a chelating agent (synergistic agent)

- It does NOT interfere with primary autoxidation mechanism

112
Q

What are metal ions contribution to autoxidation?

A

Allow for the formation of more reactive singlet oxygen, which can attack lipids directly

113
Q

Give examples of synergists.

A
  • Ascorbic acid

- EDTA

114
Q

What are the detrimental effects of lipoxygenase?

A

1) Destruction of essential FAs
2) Free radicals produce damage
3) Development of off-flavour

115
Q

Give examples of preventative antioxidants.

A
  • Superoxide dismutase
  • Catalse
  • Glutathione peroxidase
  • EDTA
116
Q

Give examples of radical scavenging antioxidants.

A
  • Vitamin C
  • Tocopherol
  • Anthocyanin
117
Q

Does a hydroxy free radical have a low or high electron reduction potential?

A
  • High (2300)

- Greater affinity for electrons, will get reduced

118
Q

What should antoxidants not exceed?

A

200 ppm

119
Q

What is an ideal antioxidant?

A
  • No harmful physiological effects
  • Effective in low concentration
  • Readily-available
  • Economical
  • Fat-soluble

2) Food Chemistry I (31 decks)

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