Food chemistry

Question 1

What are fats an esters of?

Answer 1

Fatty acids and glycerol.

Question 2

Two functions/ significance of fats?

Answer 2

-Forms part of cell membrane
- efficient way for body to store energy.

Question 3

Lipids are any classes of of organic compound that are?

Answer 3

Fatty acids, insoluble in water but soluble in organic solvents.

Question 4

What group does fatty acids have and how many carbons do their hydrocarbon chain contain?

Answer 4

They have a carboxyl (acid) group. Usually contain 16-18 carbons.

Question 5

What are triglycerides?

Answer 5

Are sets of 3 fatty acids bound together.

Question 6

What is triglycerides function in the human body?

Answer 6

It is the form in which fat is carried through the blood to the body tissues.

Question 7

When is triglyceride called a solid and when is it called a liquid ?

Answer 7

It is called a fat if it is solid at 25 degrees Celsius, or oil, if it is liquid at 25 degrees celsius.
Therefore, an oil is any triglyceride which is liquid at 25 degrees celsius.

Question 8

What determines the differences in melting point of fats and oils?

Answer 8

The degree of unsaturation and the number of carbons in the constituent fatty acids.

Question 9

What is the molecular formula of fatty acids?

Answer 9

C18H36O2

Question 10

What is the molecular formula of glycerol?

Answer 10

C3H8O3

Question 11

How is triglyceride(ester) formed?

Answer 11

When glycerol reacts with 3 fatty acids.

Question 12

List down some sources of fats and oils.

Answer 12

Sources of animal fats include liver oils, blubber oils and fish oils.
Sources of vegetable fats and oils are seeds and fruits.

Question 13

List some primary constituents of fat and oils.

Answer 13

Margarines, shortenings, oils, butter.

Question 14

List 3 three things in which fats and oils are found in higher quantity?

Answer 14

Dairy products, infant formulas, bakery goods and some sweets.

Question 15

What are the basic steps of fats and oils processing?

Answer 15

1. Extraction
2. Refining
3. Bleaching
4. Deodorization

Question 16

Explain the process of extraction of fats and oils for both animals and plants.

Answer 16

Vegetable oils are extracted by heating the seeds of the relevant plant with organic solids.
Animal fats are extracted when oil bearing tissues are chopped into small pieces and boiled in water. The oil floats to the surface of the water and is removed by skimming.

Question 16

Explain the process of extraction of fats and oils for both animals and plants.

Answer 16

Vegetable oils are extracted by heating the seeds of the relevant plant with organic solvents such as hexane or with pressure.
Animal fats are extracted when oil bearing tissues are chopped into small pieces and boiled in water. The oil floats to the surface of the water and is removed by skimming.

Question 17

Name a process that can be used for oil extracting from plants.

Answer 17

Steam distillation- is when high pressure steam is injected into the fats at temperatures between 180 to 250 degrees and a vacuum of about 1 KPa , removing the volatile products and leaving the fats almost tasteless.

Question 18

What impurities do extracted oils contain?

Answer 18

Fatty acids, pigments and waxes which can lead to undesirable properties in the final product.

Question 19

Explain the process of Refining.

Answer 19

Is a process to remove impurities such as pigments, fatty acids and waxes, which exist in the extracted oil. Many of these impurities are removed by treating fats at temperatures 40- 85 degrees celsius with caustic soda solution or sodium carbonate. The fatty acids react with alkali, forming a soap. The impurities settle at the bottom and are drawn off. The soap dissolves in water and the triglycerides (oils) float on the water. They are then separated by centrifuge and the oils are washed to remove any residual soap. Further purification is achieved by steam distillation.- (attach definition of steam distillation)

Question 20

Explain the process of Bleaching.

Answer 20

Is the major process conducted to remove undesired coloured materials in the oil. Heated oil can be treated with various bleaching agents such as fullers earth, activated clays and activated carbon. Impurities such as chlorophyll and pigments get absorbed by these onto these agents and are removed by filtering.

Question 21

Name and explain the last process of fats and oils processing.

Answer 21

Deodorization, It involves the use of steam distillation under reduced pressure. Volatile compounds with undesirable odors and tastes can be driven off, resulting in an odorless product.

Question 22

The final product produced at the last stage of fats and oil processing is known as?

Answer 22

‘refined oil’

Question 23

How can unsaturated fatty acids be converted to saturated fatty acids? (explain the process)

Answer 23

By the process of hydrogenation and using a nickel catalyst at temperatures at about 160- 220 and pressure of 2-10 atm. Hydrogenation is adding of hydrogen to the double bonds of the fatty acids, this increases its saturation and leads to hardening of the fat which also leads to increase in the melting point of fatty acids.

Question 24

Explain how fats are hardened?

Answer 24

Through the process of hydrogenation. Adding of hydrogen to the double bond of fatty acids increase its saturation and hardens the fat, increasing its melting point.

Question 25

Why is the hydrogenation process used to covert oils to fats?

Answer 25

1. it is easier to handle fats than oils.
2. Oils tend to be unstable due to their unsaturation, thus hydrogenation prevents rancidity of oils.

Question 26

List 3 differences between margarine and butter.

Answer 26

Butter is made from milk fat and water whereas margarine is made from vegetable oils.
Butter contains short chains of saturated fatty acids whereas margarine contain polyunsaturated fatty acids.

Question 27

What makes margarine hard?

Answer 27

Hydrogenation, the more trans- fat a margarine has, the more solid it is.

Question 28

List 3 physical properties of fats and oils.

Answer 28

1. melting point.
2. smoke point
3. solubility

Question 29

Explain the physical property, melting point of fats and oils.

Answer 29

The melting points of individual fatty acids depend on the chain length of the carbon atoms and the degree of unsaturation in the chain. The longer the chain of carbon atoms, the higher the melting point and the more saturated the chain of carbon atoms, the higher the melting point.

Question 30

Explain the physical property of, solubility of fats and oils. And what are some organic solvents in which fats are soluble?

Answer 30

As the length of the carbon chain increases, the solubility decreases and vice versa.
Fats are usually soluble in organic solvents such as petrol, chloroform, and alcohols. Otherwise they are generally insoluble in water.

Question 31

Explain the physical property, smoke point of fats and oils. And why is it important to take note of smoke points?

Answer 31

Smoke point is the temperature at which oil is decomposed or broken down.
It is important to take note of smoke points because a fat is no longer good for consumption after it has exceeded its smoke point and has begun to break down.

Question 32

What will happen if you consume oils past its smoke point?

Answer 32

It contains large quantities of chemical substances that contribute to risk of cancer and other diseases.

Question 33

What are the smoke point of these oils-
1. Ghee
2. Coconut oil
3. Butter
4. Soya bean oil
5. Canola oil

Answer 33

1. 252
2. 177
3. 177
4. 230
5. 205

Question 34

Describe carbohydrates.

Answer 34

They are the most important source of energy in our body and also is a main type of nutrients.

Question 35

Why does the digestive system change carbohydrate into glucose (blood sugar)?

Answer 35

It changes carbohydrates to glucose/ blood sugar for energy for the cells, tissues and organs.

Question 36

What is the general chemical formula of photosynthesis?

Answer 36

6CO2 + 6H2O —–reacting with light and chlorophyll—–C6H12O6 + 602

Question 37

Glucose and simple carbohydrates are converted to much complicated carbohydrates such as?

Answer 37

Starch and cellulose.