Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2) Food Chemistry I > Lipids III > Flashcards

Lipids III Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Gourmet Food flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Differentiate simple and mixed triglycerides.

A

Simple: one type of fatty acid
Mixed: more than one type of fatty acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the triglyceride “stearodilinolein”?

A

There are two types of fatty acids: mixed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a simple analytical method to separate, isolate and identify individual triglycerides?

A

There are none

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What allows the separation of cis from trans isomers?

A

Silver ion chromatography

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are triglycerides used as in plant seeds?

A

Used as a source of energy for germination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are some non-edible oils obtained from plant sources? What are they used for?

A
  • Castor oil, linseed (flax) oil

- Used for industrial (paint/chemical plasticizer) purposes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What can linseed (flax) oil can be transformed into using plant biotechnology?

A

To edible Linola

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What kind of lipid is biodiesel?

A

Methyl esters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is sesame oil high in according to GC?

A

High in palmitic acid, oleic acid and linoleic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do you get the percentage of fatty acids from GC?

A

Add all of the contributions (except the internal standard - IS) and then divide each by the total to get a percentage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which fatty acid group is useful in cosmetics?

A

Lauric acid group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the fatty acid breakdown of olive oil?

A
  • Oleic (75%) - M
  • Palmitic (10%) - S
  • Linoleic (10%) - U
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why does canola oil have 60% oleic fatty acids?

A

It is trying to imitate olive oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which oil is the most reactive? Why?

A
  • Soybean

- High linoleic, high linolenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why should the animal fat depot group be an oil rather than a solid?

A

Because they have 50-60% oleic and linoleic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the fatty acid profile of lard?

A
  • Saturated fatty acids (62.2%)

- MUFA (34.7%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the first step of the processing of oilseeds?

A
  • Crush the oilseed

- Give the crush a heat treatment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the heat treatment of a crush do?

A

Aids in knocking out the enzymes lipase and lipoxygenase, which can cause a deteriorative reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What deteriorative reactions do lipases cause? How? What are they present in?

A
  • Lipolysis
  • Hydrolysis of the ester linkage between glycerol and a fatty acid in the TG
  • Enzyme present in every living system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What deteriorative reactions do lipoxygenase cause? How?

A
  • Autoxidation

- Oxidation of polyunsaturated fatty acid chains that have a cis,cis-1,4-pentadiene group (e.g. linoleic and linolenic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which fatty acids have a cis,cis-1,4-pentadiene group?

A

Linoleic and linolenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the best way to inactivate an enzyme? What happens when you treat it?

A
  • By heat

- Treatment: oil is no longer virgin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the three ways in which oils are obtained from plant sources?

A

1) Hydraulic Pressing
2) Expelling
3) Solvent Extraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does hydraulic pressing form an oil from a crush?

A

Screw press applies pressure and crushes the seed to force the oil out of the crush

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the downsides to hydraulic pressing? (3)

A
  • Slow process
  • Not efficient: significant levels of residual oil are left in the meal
  • Oil quality is poor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Why is the oil quality poor in hydraulic pressing?

A

Due to the time factor, which allows enzymes (lipases and lipoxygenases) to act, leading to deteriorative reactions and development of flavours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Which oil has hydraulic pressing as its preferred method? Why?

A
  • Virgin olive oil

- Want the flavours to develop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is expelling? How does it compare to hydraulic pressing?

A
  • Mechanical version of hydraulic pressing; continuous process
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

An expeller is a simplified version of an ________. How does it work?

A
  • Extruder

- Archimedes screw in a barrel which tapers toward the end; pressure is increased and the oil is squeezed out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are the downsides of expelling?

A

Meal/press cake still contains significant levels of oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is expelling usually followed by?

A

Solvent extraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How does solvent extraction extract oil? Which solvent is usually used?

A

Organic solvent (usually hexane) is used to extract the residual oil from the oilseed cake produced by the expelling operation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are the advantages and disadvantages of solvent extraction?

A

Advantage: very efficient
Disadvantage: only economically advantageous when economies of scale are involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

In the case of fats and oils from animal and fish sources, what is the most common method of processing?

A

Rendering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Why is solvent extraction inefficient with animal/fish tissue?

A
  • Tissue contains high levels of moisture

- Extraction with HYDROPHOBIC solvents is inefficient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How does rendering work?

A
  • Ground meat/fish is placed into a large pressurized vessel and heated with steam under pressure
  • Lipids melt and are released from the tissue
  • The fat is skimmed off and then further processed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Following extraction of the oil by expelling/solvent extraction, what happens to the residual “press cake”? (2)

A
  • Desolventized (remove residual organic solvent) and is usually sold as animal feed (bulk)
  • Press cake may be further processed to obtain soybean protein for human consumption (minor amounts)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the dark brown colour of the extracted oil following expelling/solvent extraction due to? What does it smell like?

A
  • Lipid-soluble pigments (carotenoids and chlorophyll and pheophytin)
  • Smelly (paintlike to fishy)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What components are contained in the extracted oil following expelling/solvent extraction?

A
  • Cellular debris (protein and carbohydrates)
  • Free fatty acids (released from TG by lipases)
  • Oxidative breakdown products
  • Phospholipids (lecithins)
  • Free and complexed metal ions
  • Flavour components
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What are the four steps most oils go through following extraction?

A

1) Settling/degumming
2) Refining
3) Bleaching
4) Deodorizing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What happens in settling/degumming?

A

Vigorously mixing the oil with water and allowing it to stand in a conical tank for some time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the use of settling/degumming? What does it get rid of?

A
  • Carbs, proteins and phospholipids hydrate and associate themselves with the aqueous phase
  • Over time, aqueous phase separates from the oil, carrying with it the cellular debris, carbs and phospholipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Why is settling and degumming used rarely?

A

Because of the time factor involved and the capability of the oil to continue deteriorating during this time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is used instead of settling/degumming today?

A
  • Steam injection into the oil tank is used to accelerate the hydration process (higher temperature)
  • Oil is then continuously centrifuged to rapidly separate the aqueous phase from the oil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

In the settling/degumming phase of soybean oil, what is recovered from the aqueous layer? Why?

A
  • The phospholipids since soybeans contain 5-8% phospholipids (mainly lecithin)
  • They have commercial value as emulsifiers
46
Q

What does refining remove?

A

Removes the free fatty acids from the oil

47
Q

How does refining work?

A
  • Treatment of the oil with dilute alkali
  • Convert the fatty acids into soap
  • Soap formed is removed with the aqueous phase
48
Q

Why does the alkali have to be carefully measured in refining? It requires accurate measurement of the ___________ content of the oil

A
  • To avoid saponification of the oil

- Free fatty acid content

49
Q

How does modern processing systems combine settling, degumming and refining into one operation?

A

Using steam injection of dilute base combined with centrifugation

50
Q

What removes 99.9% of the moisture and particulates from the oil?

A

Centrifugation and filtration

51
Q

What does bleaching remove?

A

Designed to remove the coloured material from the oil (carotenoids, chlorophyll, and pheophytin)

52
Q

Why are colour compounds slightly more polar than triglycerides?

A
  • Hydrophobic in character

- But, they tend to contain many double bonds (are oxygenated to some extent)

53
Q

After centrifugation in the refining step, the oils are essentially _______-free

A

water-free

54
Q

What compound is capable of absorbing slightly polar compounds in the ABSENCE OF MOISTURE?

A

Dry bentonite (bleaching clay) or charcoal

55
Q

How does bleaching work?

A

Passing the dry centrifuged oil through a bed of bentonite or activated charcoal to absorb the colored compounds

56
Q

Bleaching is also often used as a secondary filtration process to remove what? What colour oil does it produce?

A
  • Residual colloidal material or hydrogenation catalyst from oils
  • Produce a clear pale yellow oil
57
Q

What does deodorization remove?

A

Removes the volatile compounds that give the oil off-flavours

58
Q

How does deodorization work?

A
  • By steam stripping, which involves spraying the oil into an evacuated chamber containing steam flowing counter-current to the oil droplets
  • Volatiles are carried away with the steam
59
Q

In olive oil, what compounds are not removed for the best quality? Which steps are not used?

A
  • Flavour and colour compounds

- Only pressed; bleaching and deodorization are not used

60
Q

What does virgin mean?

A

Means the oil was produced by the use of physical means and no chemical treatment

61
Q

Are refined oils or virgin oils of higher quality?

A

Virgin oils are of higher quality (paying more for less processing)

62
Q

What does a refined oil mean?

A

Means that the oil has been chemically treated to neutralize strong tastes (characterized as defects) and neutralize the acid content (free fatty acids).

63
Q

What is olive pomace oil?

A

Means oil extracted from the pomace using solvents, mostly hexane, and by heat.

64
Q

What is the most sought-after olive oil?

A

Cold-press

65
Q

What is winterization used for?

A

Used to produce salad oils from oils not suitable for this purpose

66
Q

What is the problem with winterization?

A

Clouding of an oil under refrigeration conditions

67
Q

What can crystallization break? In what process?

A
  • Breaks emulsions

- Winterization

68
Q

In what conditions does oil cloud in winterization?

A

Clouding of an oil under refrigeration conditions may occur due to fractional crystallization of the more saturated triglycerides at refrigerator temperatures (~4oC)

69
Q

Which oil helped develop winterization? Why?

A
  • Cottonseed oil

- Stored in the winter, the more saturated triglycerides precipitated out

70
Q

How is winterization carried out nowadays?

A
  • Heat exchanger

- Same result, more efficient manner

71
Q

What does winterization separate?

A

One fraction highly saturated, the other is unsaturated

72
Q

What is large-scale fractional crystallization carried out with? What does it produce?

A

Carried out with palm oil to produce palm stearin or palm fat, a useful source of natural hard vegetable fat for food applications.

73
Q

What is hydrogenation used for?

A
  • Hydrogenation is a process used to change the physical and chemical properties
    of fats and oils by reducing their overall degree of unsaturation.
  • Used to convert an oil into a fat or to reduce the susceptibility of an oil to oxidative rancidity.
74
Q

How is hydrogenation achieved?

A

Achieved by treating oil with H2 at high temperatures/pressures in the presence of a nickel catalyst

75
Q

What is the hydrogenation a function of? (3)

A

(a) Form and concentration of the catalyst
(Ni catalyst must be in a finely divided state)
(b) Temperature and H2(g) pressure
(c) Amount of agitation of the oil

76
Q

What is the significant reaction in hydrogenation?

A

Isomerization of the natural cis form to the trans form

77
Q

The solidification achieved by catalytic hydrogenation processes is caused by a combination of what?

A

combination of hydrogenation and formation of trans isomers.

78
Q

What are the double bonds in hydrogenated oils capable of?

A

“wandering” (positional isomerism)

79
Q

What does positional isomerism result in?

A

Conversion of unconjugated double bonds to CONJUGATED double bonds or MIXED bonding systems.

80
Q

Define selectivity. It is a property of what?

A
  • Preferentially hydrogenating more highly unsaturated fatty acids
  • Property of the catalyst
81
Q

What does the selectivity ratio to produce C18:0 imply?

sr = C18:2/C18:1 = 12.2

A

Implies that stearic acid is produced 12x faster from linoleic acid than from oleic acid (presumably because the catalyst has a higher affinity for highly unsaturated fatty acids)

82
Q

What is the effect of selectivity? What accumulates?

A

Accumulation of more monounsaturates

83
Q

How can selectivity vary?

A

By selecting specific reaction conditions (varying catalysts/operating conditions)

84
Q

What is proprietary?

A

Knowledge of conditions and selectivity characteristics provides control

85
Q

What is the method that compensates for hydrogenation?

A

Interesterification

86
Q

The properties of a fat are a function of what? (2)

A
  • Fatty acid composition

- Fatty acid distribution

87
Q

What fat explains the process behind interesterification?

A

Lard has a similar fatty acid composition to vegetable oils but is a solid due to the high levels of fatty acids present in a specific configuration - GS3 (3%) and GS2U (27%).

88
Q

What causes lard to be “grainy”?

A

In lard, the GS2U component is largely made up of oleopalmitostearin, which has a propensity to form large crystals.

89
Q

What can overcome the grainy texture of lard?

A

By randomizing the fatty acid distribution by interesterification.

90
Q

Define interesterification.

A

Exchange of fatty acids on the glycerol backbone, using heat and a catalyst such as tin, lead, zinc or alkali earth metals

91
Q

If interesterification is carried to completion, there will be complete _________”

A

randomization of the fatty acid on the glyceride; changes the physical properties of the fat/oil

92
Q

What catalyst can be used for interesterification?

A

Carbonyl anion of diacylglycerol

93
Q

What happens when interesterification is carried out at lower temperatures?

A
  • The more saturated long-chain glycerides will FRACTIONALLY crystallize out
  • The oil portion becomes more unsaturated, while the fat portion becomes more saturated.
94
Q

What are the two uses of interesterification?

A
  • Used extensively to remove the graininess from lard

- Change the characteristics of other fats and oils to give properties other than those naturally present.

95
Q

Which technique produces randomization?

A

Chemical interesterification produces fats which have a random distribution of fatty acids in TAGs molecules

96
Q

How can the structure of lipids in human milk be reproduced artificially?

A

Enzymatic interesterification reaction using sn-1,3 specific lipase as a catalyst.

97
Q

Which method is better suited when the aim is to produce lipids with highly specific compositions for functional and medical applications?

A

Enzymatic interesterification

98
Q

Why is cocoa fat/butter expensive?

A

Has the property of having a sharp melting point at body temperature; unique melting point

99
Q

How can cocoa fat/butter be imitated?

A

proper modification of other fats and oils, so that they can be used as extenders – reduce the amount of more expensive cocoa butter needed

100
Q

What is used for the manufactore of mono and di-glycerides for emulsification? (2)

A
  • Interesterification

- Enzymatic reaction employing lipase

101
Q

Do fats have a sharp melting point? Why or why not?

A
  • No

- A fat is a complex mixture of triglycerides, each of which has its own melting point; leads to a broad melting range

102
Q

Fat appears to be “solid” at room temperature, what does it consist of really?

A

Consist of oil trapped in a crystalline matrix.

103
Q

There can be as little as ___% solids in a fat that still retain a solid character

A

10

104
Q

Why can fat have plasticity or spreadability?

A

Because a fat is made up of a liquid in a crystalline matrix

105
Q

The crystalline matrix of fat forms a 3-D network that holds the system together by what force? How does it explain plasticity?

A
  • Van der Waals forces

- Because they are weak forces, they can be broken and readily re-formed again

106
Q

The plasticity of a fat is a function of the __________ ratio, which in turn is a function of _________.

A

Solid-to-liquid, temperature

107
Q

When a fat can be deformed readily, it is said to be in what range?

A

Plastic range

108
Q

What is the plastic range a function of?

A

Function of the fatty acid composition of the triglycerides and the distribution of the fatty acids on their glycerol backbones.

109
Q

Which ingredient has a wide plastic range? Why?

A
  • Soft margarine

- To be plastic at refrigerator temperatures but not melt at room temperature.

110
Q

How is butter the opposite of margarine?

A

Solid at refrigerator temperatures, but melts at body temperature

2) Food Chemistry I (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions