Food spoilage and preservation

Question 1

What are the signs of food spoilage

Answer 1

Appearance change eg colour or shape
Smell
Change in texture
Change in flavour

Question 2

What organisms cause food contamination?

Answer 2

Yeast
Moulds
Bacteria
Enzyme activity

Question 3

What are enzymes?

Answer 3

Proteins found in living things
They are a biological catalyst so speed up chemical reactions

Question 4

What do enzymes do?

Answer 4

Speed up chemical reactions
Cause harvested fruit and veg to ripen and eventually breaks down their cells + tissues
Causes tissue of meat and fish (animal foods) to break down once the animal is dead

Question 5

What is enzymic browning?

Answer 5

When the cell of a fruit or vegetable is broken the enzymes mix with oxygen and substances in the vacuole. OXIDATION.

Question 6

How to delay enzymic browning with ACID?

Answer 6

Adding an acid eg lemon juice, denatures the enzyme protein, breaking its chemical bonds. As is it no longer at its optimum pH

Question 7

How to delay enzymic browning with HEAT?

Answer 7

heat will denature the enzyme proteins by going above the optimum temp

Question 8

How to delay enzymic browning with WATER?

Answer 8

water will stop the enzymes mixing with the oxygen
You can also do BLANCHING where you plunge the veg/ fruit in boiling water for a short time before freezing. This will denature the enzymes

Question 9

Ideal Conditions for YEAST SPOILAGE

Answer 9

acidic moist foods
Warm conditions (25-29c) (although can grow at 0c)
high sugar conc
Liquid to reproduce

Question 10

What temp is YEAST killed at to avoid spoilage?

Answer 10

100 degrees c

Question 11

What is the scientific name of black bread mold?

Answer 11

Rhizopus stolonifer

Question 12

Are moulds Tiny fungi that produce thread like filaments?

Answer 12

Yes

Question 13

What conditions do moulds like?

Answer 13

Acidic, alkaline, high sugar or salt
20c-30c
Humid
Moisture

Question 14

What are the three groups of bacteria?

Answer 14

Harmless
Pathogenic (cause food poisoning)
Food spoilage

Question 15

Where are bacteria found?

Answer 15

Raw food, our skin, soil, in water, in air

Question 16

What foods use microorganisms?

Answer 16

Cheese
Yogurts
Bread
Sausages
Soya sauce

Question 17

Microorganisms is CHEESE production

Answer 17

Bacteria and Moulds are used in blue cheeses.
Bacteria ONLY is used in cheddar

Question 18

3 examples of CHEESES THAT USE MOULD?

Answer 18

Stilton
Danish blue
Gorgonzola

Question 19

How is mould used on BRIE AND CAMBERBERT?

Answer 19

special mould spores are sprayed onto the cheese
Or can be dipped into a liquid containing them.
This causes them to develop a white surface mould ONLY

Question 20

microorganisms IN YOGURT

Answer 20

milk is boiled
harmless bacteria is added to the previously boiled milk
Left to multiply for several hours in warm conditions
Becomes tangy as lactose turns to lactic acid
LACTIC ACID DENATURES and COAGULATES the milk to thicken into a yogurt

Question 21

What is preservation

Answer 21

extending the shelf life of food by killing or slowing the growth of bacteria

Question 22

How does chilling preserve food?

Answer 22

Slows the growth of bacteria as low temp of 1-5c so out of danger zone

Question 23

What is modified atmosphere packaging

Answer 23

Extends shelf life as delays bacterial growth by changing or modifying the air that surrounds the food. Eg O2, CO2 or nitrogen. Sealed into the packaging

Question 24

How does freezing preserve food?

Answer 24

STOPS the growth, long term investment preservation. Bacteria become DORMANT until defrosted.

Question 25

What are the different types of freezing

Answer 25

Plate freezing = flat products eg fish frozen between two plates Blast freezing = freezing air blasted over irregular shaped foods eg prawns Immersion freezing = immersed in liquid nitrogen. expensive so only used for delicate foods eg raspberries