food preservation

Question 1

What are the common causes of food spoilage?

Answer 1

Bacteria, mould, yeast

Question 2

2) What is the earliest form of long-term food preservation?

Answer 2

dehydration

Question 3

What is the range of the temperature danger zone for food? Why is it called this?

Answer 3

5°C-60°C is the
temperature range where most microorganism growth occurs

Question 4

Why does removing water inhibit microorganism growth?

Answer 4

The cells can no longer function, because
nutrient cannot move around without water.

Question 5

What are the requirements for bacterial growth?

Answer 5

food, optimal pH, warm/optimal temp., time to grow,
Oxygen, humid (FATTOM)

Question 6

How does our body help protect us from infection?

Answer 6

Skin, saliva, tears, mucus, stomach acid

Question 7

What is food preservation?

Answer 7

Action of treating foods such that they can be stored for a while and eaten
later.

Question 8

What are the 3 goals of food preservation?

Answer 8

Preventing spoilage, avoiding food borne illness, maintaining
freshness and nutritional content, denaturing enzymes which cause ripening.

Question 9

What do bacteria produce when they ferment ethanol?

Answer 9

Acetic acid

Question 9

What does yeast produce when it ferments glucose?

Answer 9

Ethanol and carbon dioxide (CO 2 )

Question 10

What do bacteria produce when they ferment glucose?

Answer 10

Lactic acid

Question 11

What are the downsides of canning?

Answer 11

Heating decreasing nutritional content, alter taste and texture,
chance of botulism

Question 12

How do jar lids let you know the food is safe to eat?

Answer 12

They pop when opened. This sound indicates the seal
has never been broken since the food was sealed in the sterile container, so little chance of food borne
illness.

Question 13

Why are cracked jars or badly dented cans associated with botulism?

Answer 13

Botulism spores can survive the
canning process. A crack or dent allows air in causing the botulism to multiply and increases the
chance of causing food poisoning.

Question 14

What type of food preservation make the food take up less space?

Answer 14

Dehydration

Question 15

What happens to food when it is frozen?

Answer 15

The water in the food turns to ice. This stops microbe growth.

Question 16

Why are freezers kept at -18°C when the freezing point of water is 0°C?

Answer 16

The water in foods usually has
other things dissolved in it (salt/sugar) and this lowers its freezing point. A low temperature ensures
the food is frozen solid (no liquid water which would promote microbe growth).

Question 17

Why would thawed tomatoes be better for cooking in a sauce than for slicing fresh in a salad?

Answer 17

Tomatoes have a high water content, so when frozen the ice crystals break open the cells. Later when they are thawed most of the water will not be in the fruit so better for making a sauce than eating whole.

Question 18

Can frozen food be kept indefinitely? Explain.

Answer 18

Yes. However, over time the ice in the food will sublime (slowly change to water vapour) leaving it dehydrated. This is freezer burn, the food is still edible but can have an off taste and/or very tough dry patches. It will not cause illness, but probably won’t be
enjoyable to eat.

Question 19

Why do foods generally lose more nutritional value during cooking and canning than from dehydration?

Answer 19

Dehydration happens at lower temperatures. The high temperatures can decompose vitamins and
phytochemicals reducing nutritional content.

Question 19

Are most fermentation reactions aerobic or anaerobic? What does that mean?

Answer 19

Anaerobic, meaning they
happen without oxygen.

Question 20

What type of acid is produced by cabbage when combined with salt to make sauerkraut?

Answer 20

Lactic acid

Question 21

How would you slice apples to dry them most effectively?

Answer 21

Thinly to maximise the contact with air so the water can evaporate quicker.

Question 22

Since drying temperatures are not high enough to kill bacteria, why does dehydration work to preserve food?

Answer 22

Bacteria need water to survive, if there is no water in the cells, they cannot function or reproduce.

Question 23

Should dried banana slices be stored in the refrigerator? Explain.

Answer 23

No, they need to be kept dry and
refrigerators are very humid.

Question 24

Dehydration Examples:

Answer 24

rice, sun-dried tomatoes, raisins, beef jerky…

Question 25

Freezing: pro and cons

Answer 25

 stops microbe growth
 long term freezing can lead to freezer burn, not good
for foods with high water content.

Question 25

Refrigeration: pro and cons

Answer 25

 slows spoilage by slowing microbe growth
 microbes can still grow, very
humid

Question 26

Canning: pro and cons

Answer 26

 long shelf-life and stored at room temp
 alters nutritional content, taste,
texture, can harbour botulism

Question 27

Fermenting

Answer 27

(bacteria & yeast)

Question 28

Dehydration: pros and cons

Answer 28

 long shelf-life, stored at room temp, takes up less space, concentrates nutrients
 any moisture and they can spoil

Question 29

Pasteurization: pro and cons

Answer 29

 kills harmful organisms
 kills useful microbes used in fermentation so
they need to be added back in, slight decrease in nutritional content

Question 30

Canning Examples:

Answer 30

vegetables, sauces, fruit, jam, pickles …

Question 31

Freezing Examples:

Answer 31

whole fruit, meat, vegetables, waffles…

Question 32

Fermentation Examples:

Answer 32

sauerkraut, wine, soy sauce, yogurt, sour cream…

Question 33

Pasteurization Examples:

Answer 33

milk, yogurt, juices, syrups, cheese, wine…