Food Spoilage - Enzyme Action

Question 1

What are enzymes?

Answer 1

Protein catalysts that speed up chemical reactions without being destroyed or changed

Question 2

Name one place where enzymes are naturally present?

Answer 2

Food

Question 3

What do enzymes in food bring about?

Answer 3

Ripening of food
Browning of food/enzymic browning
Enzymic deterioration

Question 4

What is spoilage caused by enzymes called?

Answer 4

Enzymic spoilage

Question 5

What happens to the taste of fruit or veg as enzymes bring about their ripening?

Answer 5

Sweetness improves as the high starch content converts into sugars such as fructose

Question 6

What happens to the colour of fruit or veg as enzymes bring about their ripening?

Answer 6

A colour change takes place such as tomatoes changing from green to red

Question 7

What happens to the texture of fruit or veg as enzymes bring about their ripening?

Answer 7

A texture change takes place such as bananas changing from hard to soft and easily digestible

Question 8

When do enzymes stop ripening fruit and veg?

Answer 8

Enzymes will continue to work even after the food has ripened

Question 9

What happens when enzymes continue to work after a fruit or veg has ripened?

Answer 9

The enzymes will bring about the overripening of the food and will bring about the decay and decomposition of food

Question 10

What happens to some fruit and vegetables when they are cut?

Answer 10

They will turn brown

Question 11

Why do fruits such as apples turn brown when cut?

Answer 11

An enzyme called oxidase is released from their cell walls which oxidises

Question 12

What happens to fruits and veg when their enzyme oxidase has oxidised?

Answer 12

They will turn brown and will eventually spoil

Question 13

The oxidisation of oxidase does what to the quantity of Vitamin C in fruits and veg?

Answer 13

Reduces the amount of Vitamin C available

Question 14

The oxidisation of oxidase reduces the quantity of what vitamin in fruit and veg?

Answer 14

Vitamin C

Question 15

What do fish naturally contain which speeds up the spoilage and deterioration of their flesh even at low temperatures?

Answer 15

Enzymes

Question 16

What do the enzymes naturally present in fish do even at low temperatures

Answer 16

They bring about the spoilage and deterioration of the fish’s flesh

Question 17

What is released when a fish’s flesh deteriorates by enzymes?

Answer 17

A putrid odour

Question 18

What five factors can control enzymic spoilage?

Answer 18

Acids
Heat
Additives (Preservatives) 
Cold Temperatures 
Blanching

Question 19

How do acids control enzymic spoilage?

Answer 19

Acids lower pH levels which inactivates enzymes which work best at neutral pHs

Question 20

How does heat control enzymic spoilage?

Answer 20

Enzymes are sensitive to high temperatures and are inactivated by cooking

Question 21

How do additives/preservatives control enzymic spoilage?

Answer 21

Sulfur dioxide is a preservative which inactivates enzymes and is used commercially to prevent enzymic spoilage

Question 22

How do cold temperatures control enzymic spoilage?

Answer 22

Low temperatures slow down enzyme activity in food, reducing the rate of spoilage and lengthening shelf life

Question 23

How does blanching control enzymic spoilage?

Answer 23

Blanching involves immersing vegetables in boiling water for five minutes and to destroy enzymes and then plunging them in ice cold water before freezing to prevent cooking