fat and oil

Question 1

explain melting point of fats

Answer 1

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

Question 2

explain boiling point of fats

Answer 2

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

Question 3

explain smoke point of fats

Answer 3

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

Question 4

what is rendered fats

Answer 4

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.

Question 5

name and describe 3 types of animal fat

Answer 5

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.

Question 6

Oily fish are good sources of what

Answer 6

EPA & DHA.

Question 7

what should we think about when having marine oil supplements

Answer 7

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).

Question 8

how can we refine crude oils

Answer 8

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.

Question 9

what is rancidity

Answer 9

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

Question 10

what are the 3 rancidity pathways

Answer 10

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.

Question 11

what is the Most ‘vegetable’ oil in UK supermarkets

Answer 11

rapeseed oil

Question 12

explain fat content of rape seed oil

Answer 12

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

Question 13

why was rapeseed oil in the past discouraged

Answer 13

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.

Question 14

what is canola oil

Answer 14

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

Question 15

explain the oil content in sunflower oil

Answer 15

high oil content.

Question 16

whats sunflower oils used for

Answer 16

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.

Question 17

explain the fat content of sunflower oil

Answer 17

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.

Question 18

when are the most prized olive oils sold

Answer 18

sold unrefined, soon after harvest

Question 19

whats olive oils used as in cooking

Answer 19

as a flavouring versus as a medium to cook ingredients

Question 20

who are the largest producers and consumers of olive oil

Answer 20

Italy, Turkey, Tunisia, Greece and Spain.

Question 21

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

Answer 21

30%

Question 22

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

Answer 22

90%

Question 23

what are the EEC regulations for olive oil

Answer 23

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

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

Question 24

whats palm oil made from and where

Answer 24

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

Question 25

name and explain the 2 types of palm oil

Answer 25

Crude palm oil comes from squeezing the fleshy fruit.

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

Question 26

whats palm oil used in

Answer 26

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

Question 27

how do we feed the demand in palm oil

Answer 27

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

Question 28

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

Answer 28

Mild-tasting oil.

Available with a strong peanut flavour and aroma.

Often used in Chinese, S Asian & SE Asian cuisine

Question 29

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

Answer 29

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.

Question 30

what oils are good for frying

Answer 30

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).

Question 31

what oils are good for salad dressing

Answer 31

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

Question 32

how should oils be stored and why

Answer 32

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.

Question 33

what is the minimum percentage of fat in margarine

Answer 33

80%

Question 34

what percentage of fat do spreads contain

Answer 34

less than 80%

Question 35

what percentage of fat do reduced fat spreads have

Answer 35

60%

Question 36

what percentage of fat do low fat spreads have

Answer 36

40%

Question 37

what percentage of fat do very low fat spreads have

Answer 37

less than 25%

Question 38

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

Answer 38

Butter flavour and β-carotene

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

Question 39

whys salt added to margarine and spreads

Answer 39

to improve taste and prevent growth of micro-organisms.