Fats

Question 1

What is rancidity?

Answer 1

Chemical change in fats and oils by oxidation or hydrolysis leading to production of flavours and odours. These are caused by aldehydes and ketones as fat deteriorates

Question 2

What is hydrolytic rancidity

Answer 2

Fats in the presence of water break down to release fatty acids from the glycerol in their triglycerides. The process is accelerated by lipases and microorganisms

Question 3

What is oxidative rancidity?

Answer 3

This occurs in unsaturated fats and oils and starts adjacent to the double bonds. The reaction is initiated by the presence of metals, ultra violent light and high temperatures. Free radicals which are highly reactive are involved in the reactions

Question 4

How many double bonds does a saturated fatty acid chain have?

Answer 4

0

Question 5

How many double bonds does a monounsaturated fat have?

Answer 5

1

Question 6

Are fatty acids on a triglyceride the same?

Answer 6

They can be this is the simplest form of triglyceride they usually have a mixture of 2 or 3

Question 7

How many fatty acid chains to a glycerol molecule?

Answer 7

3

Question 8

Give an example of a monounsaturated fat

Answer 8

Oleic acid

Question 9

Give an example of a polyunsaturated fat

Answer 9

Linoleic acid

Question 10

What is hydrogenation of fat?

Answer 10

The conversion of oil into fat by heating the oil with hydrogen gas at 60C breaking the double bonds and creating single bonds. Unsaturated to saturated

Question 11

Are fats and oils soluble in water?

Answer 11

No they are insoluble. However with an emulsifying agent it is possible to form a stable mixture of fat and water.
Fat and water emulsion = milk
Water in fat emulsion = butter

Question 12

What is the melting point?

Answer 12

The temperature at which a fat begins to melt. The triglycerides affect the melting point and mean the melting temperature is a range because they

Question 13

What is the slip point?

Answer 13

The point at which fats begin to melt usually around 30-40C

Question 14

What is the smoke point?

Answer 14

When a fat or oil starts to decompose it produces a blue haze or smoke and acrid smell. Most around 200 degrees. Veg oils usually higher smoke point. This is considered when assessing suitability for frying

Question 15

What is the flash point?

Answer 15

When a fat is heated to a high enough temperature the vapours given off will spontaneously ignite.

Question 16

What is the plasticity of a fat?

Answer 16

Substances which possess plasticity will change shape when pressure is applied but remain in final shape when pressure is removed. Fats are plastic at certain temperatures. Margarines are manufacturerd to

Question 17

What is saponification?

Answer 17

When triglycerides react with alkalis forming a soap and glycerol. Sodium hydroxide is most commonly used in the manufacturing of soap

Question 18

Describe the 2 different arrangements of atoms in a trans fat

Answer 18

Cis arrangement is when both hydrogen are the same side as the double bond

Trans fatty acids have the hydrogen atoms on geometrically opposite sides of the double bond

Question 19

How can products containing fat be made healthier?

Answer 19

Changing method of cooking
Using monounsaturated instead of saturated
Trimming off fat
Exercise animals for slaughter
Using other ingredients for flavour colour texture
Using fat replacers
Reducing total fat content
More effective ways of draining excess fat