Food Spoilage.

Question 1

What is food spoilage?

Answer 1

Deterioration of food is known as decay and leads to food spoilage.

Question 2

Food spoilage is caused by two main factors:

Answer 2

• Natural decay within the food itself.
• Contamination by microscopic forms of life (micro-organisms).

Question 3

What are perishable goods and what do they contain large amounts of?

Answer 3

Foods that spoil rapidly are known as perishable foods and contain large amounts of water and nutrients e.g. milk, fruit, and meat.

Question 4

What types of foods are susceptible to food spoilage once thawed, opened, or reconstituted?

Answer 4

Processed and cooked foods are also susceptible once thawed, opened, or reconstituted.

Question 5

What is natural decay in food a result of?

Answer 5

• Moisture loss.
• The action of enzymes.

Question 6

Moisture loss is best demonstrated in fruits and vegetables. Describe the loss of moisture from a fruit or vegetable.

Answer 6

After harvesting they continue to respire where moisture is lost through the leaves and skins and the lost water is not replaced which results in the fruit or vegetables shrinking, becoming limp and its skin becoming wrinkled and ‘leathery’.

Question 7

Where else does moisture loss occur that is not fruit or vegetables?

Answer 7

Moisture loss also occurs in other foods e.g. meat, fish, and, cheese because of evaporation from the surface.

Question 8

Once activated, what do enzymes do?

Answer 8

Once activated, such enzymes speed up the process of decay by breaking down the tissues and components of food in different ways.

Question 9

Name the three ways enzymes cause food spoilage.

Answer 9

• Oxidation.
• Browning.
• Ripening.

Question 10

Describe the action of enzymes that cause oxidation.

Answer 10

Oxidase enzymes cause the destruction of certain nutrients e.g. vitamin C, thiamine, and carotene.

Question 11

Describe the action of enzymes that cause browning.

Answer 11

If some foods are cut or bruised e.g. apples the damaged surface will discolor and turn brown.

Question 12

Describe the action of enzymes that cause ripening, particularly to do with bananas.

Answer 12

Enzymes are involved in the process that causes ripening in foods such as fruits and vegetables e.g. unripe bananas contain starch which is converted to sugars, until the bananas become very sweet and its skin colour changes from green to yellow and eventually dark brown.

Question 13

The main micro-organisms responsible for the contamination of food are:

Answer 13

• Bacteria.
• Moulds.
• Yeast.

Question 14

What do all three groups of food spoilage microorganisms need to grow and reproduce?

Answer 14

All three groups require a medium to grow and reproduce and food is ideal because it provides nutrients and moisture.

Question 15

How do food spoilage microorganisms contaminate food?

Answer 15

They contaminate the food by producing waste products or toxins (poisons) or simply make food inedible by their presence.

Question 16

What is the name given to microorganisms which cause food poisoning?

Answer 16

Microorganisms that cause food poisoning are called pathogenic (harmful) micro-organisms.

Question 17

However, not all food spoilage microorganisms are harmful. What are the non-harmful ones used for?

Answer 17

Some are used in the food industry to produce foods such as cheese, yogurt, and soy sauce.

Question 18

Under the suitable conditions of _________, ___________, ________, and _____ bacteria can multiply very rapidly.

Answer 18

Under suitable conditions of temperature, moisture, food supply, and time bacteria can multiply very rapidly.

Question 19

What happens when a large number of bacteria are present in one place? And is this visible to the naked eye?

Answer 19

When a large number of bacteria are present in one place they form a colony; which is usually not visible to the naked eye.

Question 20

What happens if the conditions for bacterial multiplication are unfavorable?

Answer 20

If the conditions for division are unfavorable, then bacteria are able to form spores that remain dormant until the right conditions return, when the spores will germinate.

Question 21

Are spores resistant to heat?

Answer 21

Spores are often very resistant to heat.

Question 22

What is the ideal temperature for bacterial multiplication?

Answer 22

30 to 37 degrees Celsius.

Question 23

What temperature are most bacteria destroyed at?

Answer 23

Most bacteria are destroyed at around 60°C.

Question 24

What substances are used for food preservation and why?

Answer 24

Many bacteria are affected by high concentrations of salt, acid, or sugar. They interfere with the normal life processes of bacteria cells, and either destroy them or prevent reproduction. Such substances are used for food preservation.

Question 25

What are the three causes of food contamination?

Answer 25

• Bacteria may be present in food.
• Bacteria may be carried and deposited onto food by vermin.
• Bacteria may be transmitted by man.

Question 26

Food Poisoning Bacteria can be transferred to food by several means, including: State the 11 ways this is done.

Answer 26

• Using the same utensils to serve contaminated food and other foods.
• Careless attention to personal hygiene while food handling.
• Leaving skin infections and cuts uncovered while preparing food.
• Coughing, sneezing, or spitting while preparing food.
• Incomplete cleaning of food utensils and serving dishes.
• Pests e.g. household flies.
• Rodents e.g. rats.
• Pets e.g. dogs.
• Infected or diseased cattle and dairy cows.
• Contaminated water supply.
• Soil and dust.

Question 27

Once bacteria have been transferred to food, they will grow and multiply under the following conditions: Name the four ways.

Answer 27

• Incomplete thawing and cooking of certain foods e.g. poultry, pork.
• Holding cooked food e.g. chicken, shellfish.
• Incomplete or repeated cooking of leftover food.
• Careless storage of food.

Question 28

Reasons for the increase in the number of cases of food poisoning: Give 4 reasons.

Answer 28

• Increase in communal feeding e.g. more people eating out at restaurants, take-outs
• More ready-prepared foods are eaten e.g. meat pies, pastries
• Increased importing of food from countries where food hygiene is not strict.
• Increased importing of animal feeds that could be contaminated.
• Insufficient training of staff who handle food.
• Failure by consumers to store food correctly and use it by the recommended date.

-Temperature too high in domestic freezer or refrigerator, leading to the growth of bacteria.

Question 29

Name 5 types of food poisoning-causing bacteria.

Answer 29

• Staphylococcus aureus.
• Salmonella.
• Clostrodium botulinum.
• Bacillius cereus.
• Listeria.