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FDSC300 > 7-lipids > Flashcards

7-lipids Flashcards

1
Q

Lipid: soluble in ______ but insoluble in ____

A

organic solvents

water

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2
Q

FDA definition of lipids: total fat is the ___ of ____from C__ to C___, calculated as _______.

A

total fat is the sum of fatty acids from C4 to C24, calculated as triglycerides.

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3
Q

Oils: _____ that are ____ at room temperature (oil and olive oil)

A

Oils: triacylglycerols that are liquid at room temperature (oil and olive oil)

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4
Q

Fats: _______that are _____ at room temperature

A

Fats: triacylglycerols that are solid at room temperature

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5
Q

lipid are classification to ____lipids, _____lipids,_____lipids

A

simple, compound, derived

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6
Q

Simple lipids: ester of _____ with _____ (i.e.,____, _____)

A

Simple lipids: ester of fatty acids with alcohol

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7
Q

2 ex of simple lipids

A

(i.e., fats, waxes)

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8
Q

Compound lipids: compounds containing ____ in addition to an ____ of a ____ with an _____

A

Compound lipids: compounds containing groups in addition to an ester of a fatty acid with an alcohol

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9
Q

3 ex of compound lipids

A

(i.e., phospholipids, cerebrosides, and sphingolipids)

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10
Q

Derived lipids: substances derived from ______ or _____

A

substances derived from neutral lipids or compound lipids

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11
Q

5 ex of derived lipids

A

(e.g., fatty acids, long- chain alcohols, sterols, fat-soluble vitamins, and hydrocarbons)

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12
Q

Why is it important to measure Fat content in food materials? 4 reasons

A
  • Nutritional evaluation
  • Health / diet restrictions
  • Food quality (mouth feel texture)
  • Economic consideration
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13
Q

list 2 food high in fat content

A

almond and avocados

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14
Q

The ________of lipids in water makes possible their separation form ____and ________ in foods.

A

The insolubility of lipids in water makes possible their separation form proteins and carbohydrates in foods.

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15
Q

Lipids have a wide range of relative _________ depending on their _______.

A

Lipids have a wide range of relative hydrophobicity depending on their molecular constituents.

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16
Q

what are lipids in foods? 8 ex.

A

Triglycerides (TG), Free fatty acids (FFA), Phospholipids,

monoglycerides (MG), diglycerides (DG), sterols, complex lipids and waxes.

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17
Q

what is crude fat?

A

Crude fat represents mainly non polar lipids, Triglycerides (TG) because of using non polar organic solvents.

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18
Q

Crude fat is extracted by ____________

A

Crude fat is extracted by dry extraction techniques

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19
Q

give 2 ex of dry extraction techniques

A

Soxhelt method and Goldfish method

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20
Q

what does total lipid represent?

A

Total lipids represent non polar and polar lipids,

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21
Q

give an ex of total lipid

A

e.g. Fat content of milk TG (non polar) + phospholipids (polar lipids).

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22
Q

Total lipids are extracted by _______ techniques

A

Total lipids are extracted by wet extraction techniques

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23
Q

4 methods of wet extraction techniques

A

Babcock Method
Gerber Method
Majonnier Method
Bligh & Dyer method

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24
Q

which is intermittent method?

A

soxhelt

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25
Q

which is continues method?

A

goldish

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26
Q

which is discontinuous method?

A

majonnier

bligh&dyer

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27
Q

which belongs to solvent extraction?

A

soxhelt
goldfish
majonnier
bligh&dyer

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28
Q

which belongs to non solvent extraction?

A

babcock

gerber

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29
Q

The non polar organic solvent only extracts _________ materials (mainly _______).

A

The non polar organic solvent only extracts non polar materials (mainly TGs).

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30
Q

use non polar organic solvent to extract ___________. GET _____________.

A

dry food sample

solution of fat in the solvent

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31
Q

how to get the residue? (crude fat)

A

evaporation of organic solvent from the solution of fat in the solvent

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32
Q

what are 8 ideal solvent properties?

A

 Should have a high solvent power for lipids and low or no solvent power for proteins, amino acids, and carbohydrates
Should evaporate readily and leave no residue  Should have a relatively low boiling point
 Should not leave behind any residue
Should be nonflammable and nontoxic
 Should penetrate sample particles readily
 Should be nonhygroscopic
 Should be cost effective

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33
Q

high solvent power for protein aa and cho is good properties

A

false

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34
Q

high solvent power for lipids is good properties

A

true

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35
Q

evaporate readily is good properties

A

true

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36
Q

leave residue is good properties

A

false

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37
Q

low boiling point is good properties

A

true

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38
Q

flammable and nontoxic is good properties

A

false. nonflammable and nontoxic is good properties

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39
Q

penetrate sample particles readily is good properties

A

true

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40
Q

hygroscopic is good properties

A

false. nonhygroscopic

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41
Q

low cost is good properties

A

true

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42
Q

what are 3 common non polar organic solvent used for crude fat determination?

A

hydrocarbon
diethyl ether
n-Butanol

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43
Q

what are the properties of petroleum ether?

A

common, low BP, volatile, very non polar

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44
Q

3 ex of hydrocarbons

A

Hexane, heptane and pentane

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45
Q

what does petroleum ether belongs to?

A

hydrocarbon

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46
Q

is diethyl ether more polar or hydrocarbon?

A

diethyl ether

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47
Q

what reaction can diethyl ether happen with O2?

A

absorb O2 form peroxide

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48
Q

what happen if peroxide meet heat?

A

explode-as safety concern

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49
Q

n-Butanol is more _____than other solvents

A

polar

50
Q

the higher the C, the____the BP

A

higher

51
Q

what is the bp of diethyl ether?

A

35 oc

52
Q

what is the bp of n-Butanol?

A

118oc

53
Q

what is the bp of pentane?

A

36oc

54
Q

what is the bp of hexane?

A

69oc

55
Q

what is the bp of heptane?

A

98oc

56
Q

Petroleum Ether.
is the _____ boiling point fraction (bp _____0C) of
petroleum.

A

Petroleum Ether.
is the low boiling point fraction (bp 35-380C) of
petroleum.

57
Q

what does petroleum ether contain?

A

hexane and pentanes

58
Q

is petroleum ether or diethyl ether more selective for hydrophobic lipids?

A

petroleum ether, more hydrophobic

59
Q

what are the 3 basic way to carry out dry extraction?

A

discontinuous extraction
continuous extraction
intermittent extraction

60
Q

what is discontinuous extraction?

A

a high ratio of organic

solvent to sample.

61
Q

what is intermittent extraction?

A

solvent is in contact with

the sample intermittently, e.g. Soxhlet.

62
Q

what is continuous extraction?

A

solvent is always in contact with the sample for a given period of time, e.g. Goldfish.

63
Q

how to avoid lipid oxidation?

A

Using inert atmosphere (with nitrogen)
Preparing sample under low temperature
Avoiding excessive light

64
Q

what are the general steps in sample preparation?

A

Removal of water
Reduction of particle size
Separation of the lipid from bound proteins and/or
carbohydrates

65
Q

why remove water?

A

enhance penetration of non-polar solvents

66
Q

why reduce particle size?

A

enhance SA

67
Q

how to separate the lipid from bound proteins and CHO?

A

by alkaline or acid hydrolysis

68
Q

how to extract meat sample?

A

hydrolysis with HCL, then solvent extraction for crude fat

69
Q

Lipids in foods such as ____, ____, ____ and ____ products is bound to ______ and ______

A

Lipids in foods such as dairy, bread, flour, and animal products is bound to proteins and carbohydrates

70
Q

is lipids in food direct extraction with non-polar solvents is efficient?

A

no

71
Q

what is the usage of acid hydrolysis?

A

enable the penetration of solvent into the sample.

72
Q

acid hydrolysis can break both ____ and ______ bound lipids into ___________ forms.

A

break both covalently and ionically bound lipids into easily extractable lipid forms.

73
Q

what 2 ex method of discontinuous extraction?

A

majonnier

bligh&dyer method

74
Q

Discontinuous Extraction is the ______ version of extraction
There is ___________of solvent.
The sample is extracted with a _______ of solvent.

A

Discontinuous Extraction:
Simplest version of extraction
There is no continuous flow of solvent.
The sample is extracted with a fixed volume of solvent.

75
Q

which one is the simplest version of extraction?

A

discontinuous extraction

76
Q

which one is extracted by a fixed volume of solvent?

A

discontinuous extraction

77
Q

what is the disadvantages of discontinuous extraction?

A 
Needs large amount of solvent (1 sample: 10 solvent).
Low efficiency (As solvent extract fat, its ability to extract fat decreases)
78
Q

what is the ex of intermittent extraction?

A

soxhlet extraction

79
Q

describe the soxhelt instrument?

A

Consist of a flask (2) for holding the solvent (1), a section containing the siphoning unit (Soxhelt flask) (6,7), paper thimble for holding food (4), and a condenser (9).

80
Q

describe the soxhelt extraction steps

A
  1. The sample is placed in filter paper thimble.
  2. The solvent builds up in the extraction chamber.
  3. The solvent accumulates in the extraction chamber (soxhelt flask) for 5- 10 mins that facilitate the extraction
    of crude fat from the sample.
  4. The solvent + crude fat siphons back to the boiling flask.
  5. Dismantle the unit, place the bottom flask containing solvent and fat on a heating mantle and evaporate the solvent to obtain crude fat
  6. Measure the crude fat (weight or volume) left in the flask.
81
Q

put in the right sequence for soxhelt extraction steps
a. The sample is placed in filter paper thimble.
b. Dismantle the unit, place the bottom flask containing solvent and fat on a heating mantle and evaporate the solvent to obtain crude fat.
c. The solvent + crude fat siphons back to the boiling flask.
d. The solvent accumulates in the extraction chamber (soxhelt flask) for 5- 10 mins that facilitate the extraction
of crude fat from the sample.
e.The solvent builds up in the extraction chamber..
f. Measure the crude fat (weight or volume) left in the flask.

A

aedcbf

82
Q

what variables need to be consider when determine of crude fat?

A
  • Sample preparation (dried sample)
  • Choice of solvent (i.e. petroleum ether and diethyl ether)
  • Extraction (temperature, time and particle size)
83
Q

what does continuous extraction based on? ex?

A

goldfish method

closed loop of solvent evaporating, being condensed.

84
Q

describe the steps of continuous extraction

A

The procedure involves placing the sample between the boiling solvent and a cold surface.
The solvent from a boiling flask (Baker) continuously flows over the sample placed in a ceramic thimble.
As boiling continuous, the solvent vaporizes, condenses on the cold surfaces and washes back through the samples to the boiling flask.

85
Q

what is the limitation of continuous extraction?

A

form a solvent channel in the sample, and fire hazard

86
Q

2 ex of non solvent wet extraction method?

A

babcock and gerber method

87
Q

2 ex of solvent wet extraction?

A

majonnier, bligh and dyer method

88
Q

is babcock solvent/non solvent , wet/dry extraction?

A

non solvent

wet

89
Q

is majonnier solvent/non solvent , wet/dry extraction, continuous/discontinuous?

A

solvent
wet
discontinuous

90
Q

is bligh&dyer solvent/non solvent , wet/dry extraction, continuous/discontinuous?

A

solvent
wet
discontinuous

91
Q

is gerber solvent/non solvent , wet/dry extraction?

A

non-solvent

wet

92
Q

is soxhelt solvent/non solvent , wet/dry extraction, continuous/discontinuous?

A

intermittent
solvent
dry

93
Q

is goldfish solvent/non solvent , wet/dry extraction, continuous/discontinuous?

A

continuous
solvent
dry

94
Q

which 2 methods is discontinuous?

A

majonnier and bligh&dyer

95
Q

what id the wet extraction method used for?

A

measure total lipids

96
Q

how is total fat measured?

A

volumetrically

97
Q

what kind of sample does babcock method measure? recognized as a reference method for _____?

A

sample contains water e.g. milk and dairy products

–milk fat

98
Q

describe the steps of babcock method.

A

wet sample+H2SO4–>Heat—>centrifugation—>fat coalesces/ fat measured volumetrically by graduated portion of the babcock bottle

99
Q

why use H2SO4 for babcock method?

A

H2SO4 digests protein to liberate fat, generate heat and release fat

100
Q

babcock method is not applicable to produce contain _______? why?

A

chocolate or added sugar without modification because of charring烧焦 of chocolate and sugar by sulfuric acid

101
Q

gerber method is similar to ____?

A

babcock

102
Q

beside H2SO4, ______ is added. what method?

A

isoamly alcohol

gerber

103
Q

why add isoamly alcohol

A

prevent charring of suagr. help release lipid from organic material e.g. CHO

104
Q

mojonnier method is acid/base method?

A

base/alkaline method

105
Q

what can mojonnier used for?

A

both liquid and solid sample milk, dairy products, fish and meat

106
Q

describe the steps of mojonnier

A

milk 1. NH4OH ethanol 2. Petroleum ether,diethyl ether—> centrifugation—> decant ether solution into previously weighed dish–> evaporation–> majonnier fat dish

107
Q

which 4 reagent does mojonnier need?

A

NH4OH
ethanol
diethyl ether
petroleum ether

108
Q

why use NH4OH?

A

dissolves protein of casein micelle membrane and fat globule membrane to separate any bond lipids from proteins; if the sample is sour, it neutralizes the acidic sample.

109
Q

why use ethanol?

A

prevents milk from becoming viscous (prevents possible gel formation).

110
Q

why use diethyl ether and petroleum ether?

A

solubilize and extract fat;

111
Q

why use petroleum ether with diethyl ether

A

prevent absorption of water by diethyl ether and dissolves more nonpolar lipids.

112
Q

bligh and dyer method used for?

A

Initially used for fish and sea foods and now for meat and meat products

113
Q

what is the principle of b&d method

A

Extraction of lipids with a mixture of Chloroform: Methanol: Water
CHCl3:CH3OH:H2O

114
Q

what is the method of B&D?

A

—Food samples are mixed/homogenized in a chloroform-methanol solution
and the homogenized mixture is filtered into a collection tube.
—A 0.88 % potassium chloride aqueous solution is added to the chloroform-
methanol mixture containing the extracted fats to form two phases: the aqueous
phase (top) and the chloroform phase containing the lipid (bottom).
—-The phases are further separated in a separatory funnel or by centrifugation.
—-Evaporation of the chloroform, to quantify total fat by weight.

115
Q

sample–>extraction fat by ______—>add _____ or water to change to _____ state—>aqueous phase contains non fat materials + _____ contains ______—>separation by separatory funnel–>removing ______

A

sample–>extraction fat by monophasic—>add CHCl3 or water to change to biphasic state—>aqueous phase contains non fate materials + CHCl3 contains fat—>separation by separatory funnel–>removing CHCl3

116
Q

what is monophasic?

A

extraction solvent

117
Q

why add CHCl3 or water

A

change to biphasic state

118
Q

what are 3 methods of instrumental methods?

A
  • -infrared method
  • -specific gravity(foss-let method)
  • -nuclear magnetic resonance NMR
119
Q

Infrared Method: fat can absorb IR energy at a wavelength ____ _m; The ____the energy absorption, the _____ is the fat content of the sample.

A

Infrared Method: fat can absorb IR energy at a wavelength 3.73μm; The more the energy absorption, the higher is the fat content of the sample.

120
Q

Fat is determined as a function of the _______ of a sample

solvent extract.

A

Fat is determined as a function of the specific gravity of a sample
solvent extract.

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