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Sustainable Agriculture, Food & Nutrition > Lipids 1 > Flashcards

Lipids 1 Flashcards

Oil Extraction & Refining

1
Q

What makes up over 90% of oils and fats?

A

Triacylglycerols (TAGs).

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2
Q

Other than triacylglycerols, what other constituents can oils and fats have?

A

Phospholipids, pigments, antioxidants, vitamins, waxes, free fatty acids, non-esterified fatty acids and sterols.

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3
Q

What are the food uses of oils and fats?

A

Flavour, heat transfer (frying), sensory qualities, emulsifiers and staling inhibitors (baked goods).

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4
Q

Name some of the non-food uses of oils and fats.

A

Soap, paints, resins, lubricants and fuels (e.g.biodiesel).

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5
Q

Approximately what % of commercially extracted TAG oils are used in food applications globally?

A

70%.

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6
Q

Globally, is the % calorie intake from fat above or below the FAO recommendation?

A

Below, although it is rising.

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7
Q

Around 30% of oils and fats produced worldwide end up as what? Why might this be controversial?

A

Biodiesel. Should oils and fats be used for fuel when the global population is at a deficit?

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8
Q

The prices of fats and oils fluctuates, following which model?

A

Supply and demand.

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9
Q

Which two plant oils make up over 50% of worldwide consumption (2015)?

A

Palm oil and soybean oil.

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10
Q

Name the fatty acids:

C8:0
C10:0
C12:0
C14:0
C16:0
C18:0
C20:0
C22:0

Are they saturated or unsaturated?

A

C8:0 - caprylic acid
C10:0 - decanoic acid
C12:0 - lauric acid
C14:0 - myristic acid
C16:0 - palmitic acid
C18:0 - stearic acid
C20:0 - arachidic acid
C22:0 - behenic acid

They are all saturated fatty acids.

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11
Q

Name the fatty acids:

C18:1
C18:2
C18:3
Are they saturated or unsaturated?

A

C18:1 -C18:1 - oleic acid
C18:2 - linoleic acid
C18:3 - alpha-linolenic acid
C22:1- erucic acid.

They are unsaturated fatty acids.

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12
Q

Which are the main fatty acids in palm oil?

A

Palmitic acid, oleic acid and linoleic acid.

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13
Q

What are the main fatty acids in palm kernel oil?

A

Lauric acid, myristic acid, oleic acid.

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14
Q

What are the main fatty acids in olive oil?

A

Majority oleic acid, some palmitic acid and linoleic acid.

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15
Q

What are the main fatty acids in oilseed rape oil?

A

Mostly oleic acid, some linoleic acid and alpha-linoleic acid.

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16
Q

What are the main fatty acids in sunflower oil?

A

Mostly linoleic acid, some oleic acid.

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17
Q

What are the main fatty acids in soya oil?

A

Linoleic acid, oleic acid, palmitic acid and alpha-linoleic acid.

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18
Q

What is the difference between a saturated fatty acid and an unsaturated fatty acid?

A

A saturated fatty acid has NO double bonds.

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19
Q

How much lipid do seeds store by weight?

A

20%-50%.

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20
Q

Do sunflower seeds, soya beans or rapeseed have a higher % of oil by dry weight?

A

Sunflower seeds and rapeseend both have an oil content of 50% by dry weight, soya beans are only 20% oil by dry weight (so soya bean oil is usually a by-product of soya protein production.

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21
Q

Is there any use for the residual meal left over after seeds have been processed for oil?

A

Yes, it can be used for animal feed because it is protein-rich.

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22
Q

‘Double zero’ varieties of oilseed rape have been cultivated to remove erucic acid and glucosinolates…why?

A

Erucic acid (22:1) is esterified in rape and has been linked to heart disease since the 1970s.

Glucosinolates convert to isothiocyanate and taste like wasabi!

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23
Q

Is palm oil a seed oil?

A

No - palms are a fruit, the oil comes from the orange flesh (mescotic tissue).

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24
Q

Palm oil produces how much more oil than soya beans, rapeseed or sunflower per unit area?

A

Palm oil produces 4x more oil per unit area than soya beansm sunflower seeds or oilseed rape.

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25
Q

Outline the basic supply chain model of rapeseed oil.

A

Pre-treatment and processing - solvent extraction - refinery plant.

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26
Q

Name some of the processes at the pre-treatment and processing stage of oilseed rape production.

A

Cleaning, crushing, softening, flaking, cooking, pressing and filtration.

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27
Q

Name some of the systems at the solvent extraction stage of oilseed rape production.

A

Solvent extraction system, DTDC system, mixed oil evaporation system, condenser and recovery system.

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28
Q

Name some of the processes at the pressing and filtration stage of oilseed rape production.

A

Degumming, deacidification, decolourisation and deodourisation.

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29
Q

What part of a TAG molecule can be affected by hydrolytic rancidity. What happens and why is it undesirable?

A

Hydrolytic rancidity happens in short/medium chain fatty acids.

When free fatty acids are hydrolysed from the TAG backbone, an ‘off’ flavour can be produced. This flavour is undesirable, except in blue cheeses!

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30
Q

Oxidative rancidity and polymerisation are caused when what part of a TAG molecule is oxygenated?

A

Unsaturated fatty acids.

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31
Q

What causes oxidative rancidity? Why is this undesirable?

A

Oxidative rancidity is caused by a chemical change in oil when fatty acids are oxidised. This process is promoted by PUFAs, oxygen and often a transition metal ion.

It leads to an ‘off’ flavour.

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32
Q

What causes polymerisation in a TAG molecule? Why is this undesirable?

A

When an unsaturated fatty acid is hydrolysed, it can be polymerised which makes it viscous. An example of this is frying oil which is reheated multiple times and becomes thicker and thicker.

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33
Q

Phospholipids are found at interactions between ………… and ………… , so they tend to be ‘brought over’ in oil refining as they are attracted to the ………. component.

A

Oil, water, fat.

34
Q

Why do phospholipids need to be removed from edible oil during refining?

A

They can decrease the quality of the oil. Phospholipids are surface active so they can cause foaming during cooking or draw water into the bulk oil which leads to hydrolysis of TAG molecules, causing rancidity or polymerisation.

35
Q

How are phospholipids removed in the oil refining process?

A

In degumming.

The oil is exposed to water and the phospholipids are therefore hydrated. Centrifugation is then used to separate the oil and water phases.

36
Q

What is phosphatidylcholine (lecithin)? Where does it come from and what can it be used for?

A

Phosphatidylcholine is a hydratable phosphatide and a by-product of degumming. They can be recovered and sold into the food and pharma industries.

37
Q

The presence of ……-…………… phosphatides make degumming more difficult. They are formed by naturally occuring selective enzymes called …………………. and ……….. ………………….. .

A

Non-hydratable, phospholipases, acyl hydrolases.

38
Q

What CANNOT be removed in the degumming process?

A

Non-hydratable phosphatides.

39
Q

What contaminants can be present in crude oil and therefore need to be removed during refining?

A

Pesticides, smoke and industrial chemicals (e.g. dioxins).

40
Q

What are the objectives of oil and fat processing?

A

Eating quality, appearance, oxidative shelf life stability (considering rancidity), consistency of quality, safety (e.g. maximum residue limit of pesticides.

41
Q

Give some examples of factors that can affect oil quality.

A

Lipase enzymes - can hydrolyse TAG molecules into FFAs, causing oxidative rancidity.

Exposure to air - oxidation.

Exposure to moisture - promotes hydrolysis.

Transition metals - promote oxidation.

42
Q

Name FIVE methods of oil extraction.

A
  1. Rendering - fish oils and animal fats.
  2. Wet screw processing - palm oil, olive.
  3. High pressure screw processing (cold-pressed) - copra, palm kernel oil, groundnut oil, soya bean oil.
  4. Pre-pressing then solvent extraction - sunflower oil, rapeseed oil, cottonseed oil, copra, palm kernel oil, groundnut oil, soya bean oil.
  5. Direct solvent extraction - soya bean oil, rice bran oil.
43
Q

Which extraction method is used for palm oil?

A

Wet screw processing.

44
Q

Why is palm oil orange?

A

It is high in carotenoids.

45
Q

What is formed when phosphatidic acid joins to a divalent cation, e.g. Mg2+ or Ca2+? Why are these a problem in oil refining?

A

Non-hydratable phosphatides, which cannot be removed by deguumming with water.

46
Q

Approximately how much crude palm oil is made from 1,000kg palm fruit? What other product is a result of this process?

A

225kg. 67kg of palm kernels are also yielded, which can be used to make palm kernel oil.

47
Q

Typically, which extraction method is used for soya bean oil?

A

Direct solvent extraction, although extrusion followed by mechanical oil extraction is gaining popularity.

48
Q

Why is direct solvent extraction the most common method of soya bean oil production?

A

It gives a high yield of oil.

49
Q

Approximately how much crude soya bean oil is made from 1,000kg of raw beans? What is a by-product of this process?

A

184kg. 715kg of high-protein meal is a by-product which can be used as animal feed.

50
Q

Direct solvent extraction gets the highest yield from soya beans - what % of this would cold-pressing the beans yield?

A

70%.

51
Q

Name the three things that need to be prevented when storing crude oil and why.

A
  1. Leakage.
  2. Oils mixing - contamination with different types of oils.
  3. Moisture - can cause lipolysis and rust of metal containers (if iron leaches into the oil it can promote oxidation).
52
Q

What are the two benefits of the sterilisation of palm fruit with steam at 132c?

A

It kills any microorganisms, prevents rotting and denatures endogenous enzymes.

Fruit is loosened from the stalks.

53
Q

Why does palm fruit undergo a digestion stage with steam at 90c?

A

To help break down the cell walls which makes the oil come out more easily when the fruit is pressed.

54
Q

How is crude palm oil clarified?

A

Centrifuge.

55
Q

Outline the main steps in direct solvent extraction of soya bean oil.

A
  1. Tempering (7-10 days at 24c).
  2. Cleaning.
  3. Cracking / dehulling.
  4. Conditioning, flaking, solvent extraction.
56
Q

Why are soya beans cracked / dehulled?

A

To reduce impurities in the oil and wear on the screw press.

It increases the % of protein in the meal.

57
Q

Why are soya beans conditioned (softened)? How is this done?

A

The beans are kept for 30-60 minutes at 60c-80c.

This weakens the cell wall, reduces oil viscosity, coagulates proteins and ‘sterilises’ seeds.

58
Q

Outline the main steps in wet screw pressing of palm fruit.

A
  1. Sterilisation.
  2. Stripping.
  3. Digestion.
  4. Pressing.
59
Q

What is retained in the refining of crude oils?

A

Vitamin E (tocopherols. Approximately 50% is retained).

60
Q

Which substances are eliminated when refining crude oil?

A

Moisture
Free fatty acids
Pesticides
Phosphatides
Oxidation products
Dirt
Partial glycerides
Pigments and compounds with trace metals
Carbohydrates / pectins (removed in degumming).

61
Q

What is the difference between refining palm oil and soya bean oil?

A

Palm oil is refined in physical refining.

Soya bean oil is refined in chemical refining.

62
Q

Outline the steps of refining palm oil and what is removed at each step.

A

Pretreatment - degumming with phosphoric or citric acid. H2O added. Centrifuge. Removes carbohydrates, proteins and phospholipids.

Bleaching and filtration - uses fuller’s earth.

Deodorisation - steam at 270c removes fatty acids and volatiles.

63
Q

What is meant by ‘RBD’ palm oil?

A

Refined, Bleached, Deodorised.

64
Q

Outline the process used to refine 100kg of soya bean oil. How much refined oil is produced from 100kg of crude oil?

A

Degumming and deacidification - 2 litres of NaOH at 75c removes 2.5kg of gum which contains phosphatides, sterolglycosides and free fatty acids.

Decolourisation - 1kg of clay at 90c for 20 minutes removes carotenoids and chlorophylls. Sterols, tocopherols and tocotrienols are also removed in 0.5kg of distillate.

Deodorisation - 2kg of steam at 260c for 20 minutes.

Produces 97kg of refined oil.

65
Q

Why is soya bean oil refining a chemical process?

A

NaOH saponifies free fatty acids and phospholipids, making them into a soap which can be removed. The by-products can have other uses, e.g. as emulsifiers, in soap and cosmetics etc.

66
Q

What impurities are removed in the neutralisation of oils?

A

Neutralisation is treatment with an alkaline solution to reduce the acidity of the oil. This removes (or reduces) impurities such as fatty acids, phospholipids, pigments, trace metals, sulphur, oil insolubles and water solubles.

67
Q

How do fuller’s earth, activated charcoal or clay ‘bleach’ oil in the refining process?

A

They absorb pigments.

68
Q

What is removed in deodorising that might cause oils to have an unwanted flavour?

A

Short chain volatile fatty acids.

69
Q

What is the purpose of winterising oils? How is this done?

A

The oil is cooled which removes the most saturated TAG molecules.

This ensures that the oil remains clear at the range of temperatures that it might be stored at.

70
Q

Is the nutritional quality of the oil reduced when it is exposed to superheated steam in the deodorising process?

A

No.

71
Q

Which three fatty acids are present in ALL edible oils?

A

Palmitate, oleate and linoleate.

72
Q

Tropical oils tend to be low in ………….. and rich in ………….. .

A

Polyunsaturated fatty acids, saturated fatty acids.

73
Q

In chemical refining, FFAs are remove using …………….. . In physical refining FFAs are removed using ……… ………. ……….. .

A

NaOH, high pressure steam.

74
Q

C12:0

A

Laurate / lauric acid

75
Q

C14:0

A

Myristate / myristic acid

76
Q

C16:0

A

Palmitate / palmitic acid

77
Q

C18:0

A

Stearic acid

78
Q

C18:1

A

Oleate / oleic acid

79
Q

C18:2

A

Linoleic acid

80
Q

C18:3

A

Alpha-linolenic acid

Sustainable Agriculture, Food & Nutrition (8 decks)

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