Past Exam Questions

Question 1

Assess irradiation as a method of food preservation
(Advantages)
(4 points but you only need to know 2)

Answer 1

1. Extends the shelf life of food
2. Kills pests
3. Delays the ripening of fruit and the sprouting of vegetables
4. Retains sensory characteristics

Question 2

Assess irradiation as a method of food preservation
(Disadvantages)
(4 points but you only need to know 2)

Answer 2

1. Vitamin B1 and C are reduced or destroyed
2. The chemical composition of high fat foods may change e.g. lipids become rancid
3. May mislead consumers into believing the food is fresher
4. Can cause large numbers of free radicals which can increase the risk of cancer and coronary heart disease

Question 3

Explain quick freezing

4 main points

Answer 3

Food is quickly frozen at -25 degrees in the fast-freeze section of the freezer
Small ice crystals are formed inside the food which cause little damage to cell walls
Nutritional value, texture, colour and flavour are retained on thawing
Freezer should be turned to -25 degrees Celsius 6 hours prior to freezing

Question 4

Explain slow freezing

3 main points

Answer 4

Food is frozen slowly at 0 to -18 degrees Celsius in the ice box area of a fridge or storage area of freezer
Large ice crystals are formed which damage cell walls of food
There is a loss of nutritional value, texture, colour and flavour on thawing

Question 5

Name one method of home preservation that involves the application of heat

Answer 5

Jam making

Question 6

Explain the principle involved with jam making

4 main points

Answer 6

1. Fruit is boiled at 100 degrees Celsius to destroy microorganisms and inactivate enzymes
2. Boiling softens fruit by breaking down their cell walls
   65% sugar is added which creates a concentrated sugar solution which draws water out of microbial cells by osmosis which dehydrates and kill microorganisms
3. Pectin and acid is present which changes the watery fruit liquid into a set jam, pectin or acid can be added if there is not enough present naturally in the fruit
4. The jam is sealed at the end which prevents the re-entry of microorganisms

Question 7

Explain the principle involved with home freezing

3 main points

Answer 7

1. Uses freezing temperatures to inactivate microorganism growth and slow downs enzyme activity
2. Converts water into ice making it unavailable to microorganisms
3. Food is wrapped which prevents re-entry of microorganisms, prevents freezer burn and maintains colour, flavour, texture

Question 8

Explain the risk of food spoilage associated with jam making

Answer 8

1. Fermentation can occur which is the breakdown of jam by microbes which produces an off-flavour under the following conditions;
   If insufficient sugar is added
   If poor-quality fruit is used
   If the jam is not boiled for long enough

Question 9

Explain the risk of food spoilage associated with home freezing

Answer 9

1. Thaw food in the fridge to prevent growth of microorganisms and place thawing meat or fish on a plate in the bottom of the fridge to avoid drip contamination
2. Never refreeze thawed food unless it has been cooked as the food will contain higher levels of bacteria after being thawed which increases the risk of food poisoning
3. Freeze at -25 degrees Celsius to ensure quick freezing
4. Package well to avoid freezer burn which results in toughness, drying out and discolouration

Question 10

At what temperature does pasteurisation take place?

Answer 10

72 degrees Celsius

Question 11

For how long is milk heated at 72 degrees during pasteurisation?

Answer 11

15-20 seconds

Question 12

What is the effect of pasteurisation on milk?

Answer 12

Bacteria is destroyed

Vitamins such as thiamine and vitamin C are destroyed

Question 13

Why can there be a loss of vitamin C when peas are frozen?

Answer 13

Vitamin C is unstable at high temperatures and could have been destroyed during the blanching process

Question 14

Why may there be a loss of vitamin C when peas are canned?

Answer 14

Food is heated to extremely high temperatures during the canning process which destroys the Vitamin C as it is unstable at high temperatures

Question 15

Why may there be an increase in sodium when peas are canned?

Answer 15

Large amounts of salt are used during the canning process to prevent the growth of microorganisms as the high salt concentration dehydrates and kills microorganisms by osmosis

Question 16

Why may there be a loss of thiamine when peas are canned?

Answer 16

Thiamine is a B-group vitamin which is unstable at high temperatures and is therefore destroyed during the high temperatures involved in canning

Question 17

Describe how fresh vegetables should be frozen

8 main points

Answer 17

1. Boil 1L water in a saucepan
2. Wash, peel and chop 100g of carrots
3. Place carrots in water for 3 to 5 minutes
4. Drain carrots using a colander
5. Place carrots in 1L cold water with ice for three to five minutes
6. Drain carrots using a colander
7. Place carrots in freezer bag in usable portions and label with the food and date
8. Place in fast-freeze section of the freezer

Question 18

What are the main effects of freezing on fresh vegetables?

2 points

Answer 18

1. Shelf life is extended

2. Nutritional value and sensory characteristics are retained if frozen and thawed correctly

Question 19

What are the main effects of freezing on meat?

5 points

Answer 19

Slight loss of soluble nutrients e.g. vitamin B and C are lost through dripping during thawing
Fat can go rancid if frozen incorrectly
Freezer burn can occur if not packaged correctly
Nutrients are retained well
Slight loss of vitamin B and C

Question 20

Describe how pasteurisation is carried out

2 main steps

Answer 20

Milk is heated to 72 degrees Celsius for 15-20 seconds

Milk is then cooled rapidly to below 10 degrees Celsius

Question 21

Describe the effect of pasteurisation on the nutritive value of milk

Answer 21

Loss of vitamin B1 and Vitamin C

Question 22

Define fermentation

Answer 22

The breakdown of carbohydrates by microorganisms to produce carbon dioxide, alcohol and energy

Question 23

Name two by-products of fermentation

Answer 23

Carbon dioxide

Alcohol

Question 24

Write an informative note on irradiation

Answer 24

Food is exposed to low levels of gamma radiation which pass through the food and destroy microorganisms, kill pests and prevent the sprouting of vegetables or ripening of fruit
Results of irradiation: 
-Microorganisms are destroyed
-Pests are killed
-Sprouting of vegetables is prevented
-Ripening of fruit is prevented

Question 25

Name two commercial methods of freezing

2/4

Answer 25

Fluidised bed freezing
Cryogenic freezing
Blast freezing
Plate freezing

Question 26

Name a food suitable for fluidised bed freezing

Answer 26

Small foods such as peas or sweetcorn

Question 27

Name a food suitable for cryogenic freezing

Answer 27

Strawberries or prawns

Question 28

Name a food suitable for blast freezing

Answer 28

Fruit and vegetables (carrots)

Question 29

Name a food suitable for plate freezing

Answer 29

Thin pieces of meat