Brainscape's Knowledge GenomeTM

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


See full index

Food composition > Lipid > Flashcards

Lipid Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards
1
Q

oleic acid [c-x or t-x nomenclature]

A

18:1 c-9

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

elaidic acid [c-x or t-x nomenclature]

A

18:1 t-9

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

Linoleic acid [c-x or t-x nomenclature]

A

18:2 c-9, c- 12

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

stearic acid [c-x or t-x nomenclature]

A

18:0

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

α -linolenic acid [c-x or t-x nomenclature]

A

18: 3

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

lipids

A

Substances of biological origin that have the common properties:

  • soluble in non-polar solvents
  • poorly soluble in water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Lipid classification

A

Simple lipids / Complex lipids / Derived lipids

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

Derived lipids

A

non-hydrolysable, e.g. free fatty acids, sterols, tocopherol, vitamin A, etc

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

Complex lipids

A

yield 3 or more classes on hydrolysis, e.g. phospholipids are esters of alcohols, fatty acids and phosphoric acid

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

Simple lipids

A

yield 2 classes of product on hydrolysis, e.g. glycerides (acylglycerols) are esters of glycerol and fatty acids

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

14:0

A

myristic acid

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

palmitic acid

A

16:0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

4:0

A

butyric acid

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

lauric acid

A

12:0

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

Notable PUFAs

A

alpha- Linolenic acid (18:3 c-9, c-12, c-15)

gemma- Linolenic acid (18:3 c-6, c-9, c-12)

Arachidonic acid (20:4 c-5, c-8, c-11, c-14)

Eicosapentaenoic acid (20:5 c-5,c-8,c-11,c-14,c-17)

Docosahexaenoic acid (22:6 c-4,c-7,c-10,c-13,c-16, c-19)

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

Extraction of oils and fats

A

Mechanical pressing / Solvent extraction/ Rendering

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

Rendering

A

extraction of animal fats by combined action of water and heat

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

Solvent extraction

A

e.g. rapeseed oil

Seeds or nuts with higher oil content cannot be fully extracted by mechanical pressing

Petroleum ether or hexane can be used to further recover residual oil from pressed cake

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

Mechanical pressing

A

e.g. olive oil

De-shelled/de-hulled and coarsely ground plant material is heated and pressed in hydraulic or screw presses

Use no heating for cold-pressed or virgin oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Olive oil

A

Several grades available: Virgin olive oil is highest quality

> obtained by pressing the fruit by mechanical means under conditions where no change in the oil occur

> only washing, decanting, centrifuging, filtration allowed

> further classified by flavour and free acidity

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

Virgin olive oil Characteristics

A
  • pale green colour
  • good flavour
  • good stability: rich in phenolic antioxidants (secoiridoids) and low in linoleic acid (18:2)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Virgin olive oil Nutrition

A
  • diets rich in oleic acid (18:1 c-9) lead to low LDL cholesterol levels without reducing HDL cholesterol
  • antioxidants may be beneficial
  • 100 mg/kg α-tocopherol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Palm oil

A
  • Palm fruit also used as raw material for biodiesel fuel (600 USD per ton)
  • Tocopherol content 170 mg/kg
  • Tocotrienol content 570 mg/kg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Palm kernel oil

A
  • Tocopherol content 3 mg/kg
  • Commonly fractionated into palm kernel olein and palm kernel stearin
  • Palm kernel stearin used in chocolate flavoured coatings
25
Q

Soybean oil

A
  • Soybeans major crop of USA, Argentina, Brazil
  • Oil is extracted with hexane; soybean meal is good source of protein for animal feeds
  • Soy lecithin is good commercial source of phospholipids
  • Vitamin E 1500 mg/kg
26
Q

Rapeseed oil

A

Production 14 million tons in 2002-3

Produced from double-low rapeseed

  • low in glucosinolates, which allows meal to be used for animal feed
  • low in erucic acid (22:1), which allows oil to be used as human food
27
Q

Refining of edible oils

A

Neutralisation / Bleaching / Deodorisation / Antioxidant / Degumming

28
Q

Neutralisation

A

to remove free fatty acids (cause soapy/rancid off-flavours; smoke on heating)

29
Q

Bleaching

A

to remove pigments (stir with bleaching earth; adsorption removes soaps, oxidation products, some metal ions)

30
Q

Deodorisation

A

To remove off-odours (heat with steam under vacuum at 200 - 240°C)

31
Q

Antioxidant

A

may add primary antioxidants, e.g. BHA (butylated hydroxyanisole) or metal-chelating agents, e.g. citric acid

32
Q

Degumming

A
  • to remove phospholipids and polysaccharides (gums)

- add hot water or phosphoric acid or citric acid

33
Q

edible oils should avoid

A
  • carry-through of metal ions (which catalyse oxidation)
  • foaming in deodoriser
  • losses into aqueous phase
  • black specks on heating
34
Q

Requirements for fat in foods

A
  • Correct texture
    > Correct melting range
    > Crystal form/stability (in the case of solid fats)
  • Suitable crystallisation rate for processing (solid fats)
  • Acceptable flavour and flavour stability
  • Good price
35
Q

Factors that influence a higher melting points in fatty acid

A
  • Higher number of carbon atoms
  • Lower number of carbon-carbon double bonds
  • Trans rather than cis C=C
  • Straight chain rather than branched fatty acids
36
Q

Factors that influence a higher melting points in Triacylglycerols

A
  • Asymmetric vs. symmetric: PPO > POP
  • Polymorphism (crystalline structure):
    β (beta) > β’ (beta prime) > α (alpha)
    most stable least stable
    slow cooling rapid cooling
37
Q

Polymorphism

A

the occurrence of several different crystal forms for the same compound

38
Q

Fat Bloom

A

the appearance of rough and/or white crystals on surface

> caused by uncontrolled recrystallization of triglycerides into an undesirable crystal form
melting and migration of triglycerides can occur during storage

39
Q

Packing of polymorphs in solid state

A

α - hexagonal 90*
β’ - orthorhombic 68-70*
β - triclinic 59*

40
Q

Polymorphism in chocolate

A

Tempering
> avoids bloom and good contraction from moulds
> allows fat to crystallise into form V (polymorph β) (with higher melting point)

41
Q

Tempering Plain chocolate:

A
  • melt at 50°C

> cool in scraped surface heat exchanger (tempering unit) to 27 - 28°C (1-2% fat crystallises into mixture of α and β’ crystals)
heat to 30-32°C to melt β’ crystals (0.1-1.0% solid remains)
fill mould or use for enrobing
cool product in cooling tunnel at 0-15°C - β crystals grow on existing crystal surfaces

42
Q

Polymorphism in margarine

A

In order to have a glossy surface, the fat in margarine should be stable in the β’ form

Some fats (e.g. palm oil) convert to α  crystals on storage
this causes large fat crystals to grow, and the surface becomes dull (graininess or sandiness)

Avoid graininess by selecting suitable fat blends, especially interesterified fats

43
Q

Modification of edible fats

A

Hydrogenation / Transesterification / Fractionation / Blending

44
Q

Blending

A

mixing 2 or more fats changes the melting range and composition

Blending of a semi-solid fat with a liquid oil will generally lead to a softening of the product

Unexpected softening or hardening effects may occur when blending two fats if eutectic or compound phase behaviour is observed

45
Q

Fractionation

A

physical separation

Dry fractionation/ Solvent fractionation

46
Q

Transesterification or interesterification

A

chemical reaction or lipase-catalysed transesterification

> Stir fat (or fat blend) with sodium methoxide or sodium at 90°C
Random rearrangement of fatty acids between triacylglycerol molecules to produce a fat with a wide melting range, which is stable in the β’ polymorph

47
Q

Hydrogenation

A

chemical reaction

Produces a semi-solid fat from a liquid oil
> raises melting point of triacylglycerols
> improves flavour stability

Only partial hydrogenation used

48
Q

Solvent fractionation

A
  • most efficient

> dissolve semi-solid fat in warm solvent
stir as reduce temperature until fat crystals appear
filter off fat crystals from liquid oil solution
evaporate solvent

49
Q

Dry fractionation

A

> semi-solid fat stirred at moderate temperature after melting
separate higher melting fat and liquid oil

50
Q

The liquid fraction is called

The solid fraction is called

A

The liquid fraction is called the olein fraction

The solid fraction is called the stearin fraction

51
Q

Hydrogenation conditions

A

neutralised, bleached oil stirred with hydrogen at 150-180°C, 1-6 bar, nickel catalyst (0.1-0.5%), stirring (1000 rpm)

52
Q

Side reaction of Hydrogenation

A

isomerisation
> increased melting point
> loss of nutritional quality

double bond migration
> change of ratio of PUFA

53
Q

Oleic acid

A

cis unsaturated fatty acid making up 55–80% of olive oil

54
Q

Elaidic acid

A

trans unsaturated fatty acid side reaction product found in partially hydrogenated vegetable oils

55
Q

Stearic acid

A

intended product, saturated fatty acid found in animal fats

56
Q

Nutritional effects of trans unsaturated fatty acids

A

Increase:

  1. total plasma cholesterol
  2. LDL cholesterol
  3. HDL cholesterol
  4. lipoprotein a

Effects 1 & 2 similar to saturated fatty acids
Effects 3 & 4 are undesirable

57
Q

Mechanism of hydrogenation

A
  • Hydrogenation occurs at the surface of the nickel catalyst, where hydrogen, and unsaturated fatty acids (in triacylgycerols) are bound

> Increase hydrogen supply to catalyst surface (increased H pressure; faster stirring) to favour addition of hydrogen

58
Q

Effect of conditions on hydrogenation selectivity

A

Conditions that favour addition of H cause:

  • increased consumption of linoleic and linolenic acids in TAGs
  • increased formation of saturated fatty acids (with less monounsaturates)
  • reduction of trans formation

Increase hydrogen demand at metal surface*

  • increased linoleic acid selectivity, i.e. 18:2 reduced to 18:1 with less 18:0 formed
  • increased trans formation
59
Q

Advantages and disadvantages of fat modification techniques

A

Blending
+ cheap and normally produces products with properties in between those of 2 fats

Interesterification
+ chemical reaction but nutritional quality more or less same as blend of fats

Fractionation
- physical separation of triacylglycerols

Hydrogenation
- formation of trans fatty acids, loss of PUFA
+ can use a wide range of raw materials, e.g. fish oil

Food composition (2 decks)

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