fat and oil Flashcards

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1
Q

explain melting point of fats

A

Most fats do not have sharply defined melting points, but soften gradually over a broad temperature range.

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2
Q

explain boiling point of fats

A

Melted fats eventually change from a liquid to a gas - only at very high temperatures: 260oC to 400oC.

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3
Q

explain smoke point of fats

A

Temperature at which a fat breaks down into visible gaseous products.

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4
Q

what is rendered fats

A

Pure fat is rendered from fat tissue by cutting the tissue into small pieces and heating it by steaming, boiling or dry heat.

Some fat melts out of the tissue and more is squeezed out by applying pressure.

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5
Q

name and describe 3 types of animal fat

A

Suet: Solid white fat of beef or mutton from
around the kidneys.

Tallow: Beef or mutton fat prepared from parts
other than the kidney.

Lard: Semi-soft white fat from a pig.

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6
Q

Oily fish are good sources of what

A

EPA & DHA.

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7
Q

what should we think about when having marine oil supplements

A

Choose omega-3 oil rather than fish liver oil.

Check vitamin A content - SACN advises no more than 1.5mg (1500ug) a day from food & supplements combined.

Do not take supplements containing vitamin A if pregnant or planning a baby.

Check labels for DHA & EPA content - stick to the daily amount provided by eating 1-2 portions of fish per week (~ 450mg/day).

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8
Q

how can we refine crude oils

A

Degumming:
Impurities are removed by adding hot water to warm oil and separating the gum particles from the oil.

Neutralizing
Free fatty acids are removed by neutralising the oil with caustic soda which converts the fatty acid into insoluble soap which is removed.

Washing and drying
Oil is washed with warm water to remove last of the soap, and dried. Oil is clear, but usually yellowish and with a distinct odour.

Bleaching
Fuller’s earth and activated carbon are added to adsorb the coloured matter, The oil-earth mixture is passed through a filter process and the oil emerges as clear, colourless liquid.

Deodorizing
Oil is heated under a vacuum in a small tank and steam injected so the liquid is violently agitated.
The volatile odoriferous substances and remaining free fatty acids are stripped from the oil.

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9
Q

what is rancidity

A

complete or incomplete oxidation or hydrolysis of fats & oils when exposed to air, light, or moisture or by bacterial action, resulting in unpleasant taste and odour

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10
Q

what are the 3 rancidity pathways

A

Hydrolytic rancidity - refers to the odour that develops when triglycerides are hydrolyzed and free fatty acids are released.

Oxidative rancidity - degradation by oxygen in the air.

Microbial rancidity - a water-dependent process in which micro-organisms use their enzymes such as lipases to break down fat.

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11
Q

what is the Most ‘vegetable’ oil in UK supermarkets

A

rapeseed oil

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12
Q

explain fat content of rape seed oil

A

Lower in SFA than other oils, high in MUFAs, and high in ALA.

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13
Q

why was rapeseed oil in the past discouraged

A

because it contained naturally high levels of erucic acid (c22:1).

No confirmed reports of erucic acid causing health problems in humans, but animal and lab studies suggest regular consumption of high levels may increase CHD risk.

Levels of erucic acid in foods are strictly controlled. All rapeseed oil the market contains extremely low levels so no risk to health.

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14
Q

what is canola oil

A

a GM variety of rapeseed oil – low in erucic acid.

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15
Q

explain the oil content in sunflower oil

A

high oil content.

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16
Q

whats sunflower oils used for

A

high oil content. They can be eaten as a snack or pressed to make cooking oil.

The oil is used in the manufacture of spreads, in cooking and for dressing salads.

17
Q

explain the fat content of sunflower oil

A

very high in PUFAs and low in SFAs.

Sunflower oil contains a high proportion of the n-6 PUFAs which help to reduce blood cholesterol levels if eaten as part of a heart healthy diet.

18
Q

when are the most prized olive oils sold

A

sold unrefined, soon after harvest

19
Q

whats olive oils used as in cooking

A

as a flavouring versus as a medium to cook ingredients

20
Q

who are the largest producers and consumers of olive oil

A

Italy, Turkey, Tunisia, Greece and Spain.

21
Q

Pulp layer surrounding the olive seed can be up to what percentage in oil

A

30%

22
Q

how much of the worlds olives produced go towards making olive oil

A

90%

23
Q

what are the EEC regulations for olive oil

A

Extra virgin olive oil must contain <0.8% free fatty acids.

Virgin olive oil must contact <2% free fatty acids.

24
Q

whats palm oil made from and where

A

Made from fruits of African oil palm trees - mainly grown on plantations in Indonesia and Malaysia.

25
Q

name and explain the 2 types of palm oil

A

Crude palm oil comes from squeezing the fleshy fruit.

Palm kernel oil comes from crushing the kernel (stone) in the middle of the fruit.

26
Q

whats palm oil used in

A

Found in chocolate to oven chips to cosmetics. Also used in biofuels across Europe (not UK).

27
Q

how do we feed the demand in palm oil

A

tropical rainforests and peat lands in Indonesia and other countries are torn down to make way for palm oil plantations.

28
Q

explain groundnut/ peanut oil in terms of taste and where used

A

Mild-tasting oil.

Available with a strong peanut flavour and aroma.

Often used in Chinese, S Asian & SE Asian cuisine

29
Q

explain soyabean oil in terms of flavour, who the leading producers are and cooking mechanism problems

A

Has a neutral, light flavour.

China and the US are leading producers.

Doesn’t withstand high temperatures well, so not good for roasting or frying.

30
Q

what oils are good for frying

A

For frying at high temperatures, choose rapeseed, peanut or sunflower oil – with a high smoke point (temperature at which the oil starts to burn and smoke).

31
Q

what oils are good for salad dressing

A

use extra virgin olive oil, nut oils or flavoured oils.

32
Q

how should oils be stored and why

A

Store in a dark, cool, dry place:

  • Sunlight can destroy vitamin E in oil.
  • Very cool temperatures cause oil to become cloudy and thicken.
  • Replace cap tightly to delay development of rancid flavours.
33
Q

what is the minimum percentage of fat in margarine

A

80%

34
Q

what percentage of fat do spreads contain

A

less than 80%

35
Q

what percentage of fat do reduced fat spreads have

A

60%

36
Q

what percentage of fat do low fat spreads have

A

40%

37
Q

what percentage of fat do very low fat spreads have

A

less than 25%

38
Q

whats added to achieve products which taste and look like butter.

A

Butter flavour and β-carotene

also
Whey powder, skimmed milk powder or other milk types can be added.

39
Q

whys salt added to margarine and spreads

A

to improve taste and prevent growth of micro-organisms.