3.1 Food spoilage

Question 1

What does a contaminated food mean?

Answer 1

-a food that contains harmful substances
-consumption can cause disease or injury

Question 2

what are the types of contamination?

Answer 2

biological contamination
chemical contamination
physical contamination

Question 3

what is food spoilage?

Answer 3

a process or change which renders a product undesirable or unacceptable for consumption

Question 4

why can food spoilage occur?

Answer 4

-microbial growth (bacteria, moulds and yeasts)
-enzymatic activity and enzymic browning
-chemical reactions - rancidity
-insects and pests
-physical changes

Question 5

What are the signs of food spoilage?

Answer 5

Unpleasant smell, appearance or taste

Question 6

what are examples of biological contamination?

Answer 6

• Foods contaminated with microorganisms and their waste products.
• Microorganisms include bacteria, moulds, yeasts, parasites and other toxins.

Question 7

what are examples of chemical contamination?

Answer 7

-contaminated with cleaning products and pesticides from throughout the food production chain.

Question 8

what are examples of physical contamination

Answer 8

Foods contaminated with physical items such as glass, metal, stones, hair.

Question 9

what can the microorganisms that cause food spoilage be classified into?

Answer 9

-Bacteria- have many useful functions, and only a few are pathogenic (harmful). Bacteria can also be categorized as to whether they can or cannot form spores.

-Moulds- can cause food spoilage by producing toxins, off flavours, discolouration and rotting. Moulds can grow on fruits, vegetables, cereals, meat, milk and fat.

-Yeasts- enable fermentation of produce wine, beer and bread, they can also cause spoilage of wine, fruit juices, meat, syrups and sauerkraut.

Question 10

Describe how microorganisms cause food spoilage?

Answer 10

-by bacteria, moulds and yeasts
-causes changes colour, texture and smell of the food, making it unfit for human consumption e.g. souring of milk, growth of mould on bread and rotting of fruit and vegetables.

Question 11

how does bacteria cause food poisoning?

Answer 11

are single cell organisms that can cause food poisoning either from ingesting the bacteria of from the bacteria producing toxins

Question 12

how do moulds cause food spoilage?

Answer 12

grow as filaments on food and reproduce by producing spores. -Moulds sometimes look “furry” and can be coloured e.g. blue coloured mould on bread

Question 13

how do yeast cause food spoilage?

Answer 13

are single celled and reproduce by budding and can also produce spores

Question 14

What is enzymic spoilage?

Answer 14

-Cells break down due to enzymes present in the food: this process is known as autolysis which means ‘self destruct’.

Question 15

how does enzymic activity cause food spoilage?

Answer 15

-ripening - continued ripening until the food becomes inedible
-browning - a brown colour on some fruits and vegetables caused by exposure to air
-oxidation - when food comes into contact with oxygen some nutrients are destroyed e.g. vitamins A and C, and thiamin

Question 16

Give an example of when enzymes can both help/cause food spoilage in food?

Answer 16

are important to the normal functioning of living cells but enzymatic activity also causes food spoilage e.g. enzymes in a tomato help it to ripen and cause it to decay.

Question 17

how does enzymic browning cause food spoilage?

Answer 17

-When some fruits and vegetables are cut and exposed to air, enzymes present in the cells caused an oxidation reaction.
-This causes colourless compounds to be converted into brown-coloured compounds causing a discoloration..

Question 18

What foods are sucseptible/ not susceptable to enzymic browning?

Answer 18

-Fruits and vegetables prone to discolouration are apples, pears, bananas, peaches and avocado are prone to enzymic browning.
-Enzymic browning does not happen in cooked fruits and vegetables because the enzymes are destroyed by heat.

Question 19

How can enzymic browning be prevented?

Answer 19

by either preventing the action of the enzyme of limiting the action of oxygen.
eg. adding Lemon juice (contains an acid which can stop enzymes working properly as enzymes often work best at a certain pH)
-water and sugar in jam- stops oxygen in the air getting to the enzymes and prevents the browning

Question 20

what are the 4 types of rancidity that cause food spoilage?

Answer 20

Hydrolytic rancidity
Oxidative rancidity
Microbial rancidity
Absorption rancidity

Question 21

What is hydroylitic rancidity?

Answer 21

-caused by the splitting of triglycerides into glycerol and fatty acids due to the presence of enzymes (lipases), water and heat. -Some of these fatty acids have unpleasant flavours and odours.
-Milk and butter can make an unpleasant taste if stored for too long.

Question 22

what is oxidative rancidity?

Answer 22

-oxygen from the air can oxidize unsaturated fats producing unpleasant flavours.
-A process called autoxidation occurs where acylglycerols which occur in the air, are oxidised without the presence of enzymes,
-As a result of autoxidation, hydroperoxides are produced which have no taste, but they decompose easily to form aldehydes, ketones and acids, which give oxidised fats and oils their rancid flavours.

Question 23

what is microbial rancidity?

Answer 23

the process where microorganisms cause rancidity causing deterioration of fats which leads to undesirable flavours and odours.

Question 24

what is absorption rancidity?

Answer 24

-when oils and fats are stored next to strong smelling foods or products and the food absorbs the smell, therefore making it unpleasant to eat.
-For examples fats and oils absorbing the smell of onions, garlic, paints, detergents, or disinfectants.

Question 25

How do physical changes cause food spoilage?

Answer 25

-Physical damage during harvesting, processing or distribution can increase the risk contamination by microorganisms or by chemical or microbial spoilage.
-Physical spoilage can also occur due to moisture lost or moisture gain.

Question 26

How can insects and pests cause food spoilage?

Answer 26

-infestations of insects and pests occur in a number of ways eg. tunnelling into stems and roots of food plants, or boring into and feeding on the insides of grains
- Some pests and insects carry pathogenic bacteria.

Question 27

What are the categories of how perishable food is to spoilage?

Answer 27

-perishable, semi-perishable and non-perishable

Question 28

What does it mean if a food is perishable?

Answer 28

-spoil quickly and have a short shelf life and include: meat, milk, poultry, eggs, some fruits and vegetables.
- need to refrigerated or frozen to slow down bacterial growth,

Question 29

what does it mean if a food is semi-perishable?

Answer 29

-can have a long shelf life if handled and stored correctly. E.g apples and potatoes.
-These foods may have undergone some mild preservation process e.g. pickled vegetables, smoked meat.

Question 30

what does it mean if a food is non-perishable?

Answer 30

do not spoil unless they are handled carelessly e.g. flour, sugar, dried pasta, rice, canned foods.

Question 31

how does water activity relate to food spoilage?

Answer 31

-Water is required for most microorganisms to grow.
-The amount of water available in a food can be described in terms of water activity (aw). Pure water has (aw) of 1.0.
-Foods have a (aw) range of 0.2 for very dry foods to 0.99 for moist foods.
-Removal of water does not destroy microorganisms, however it will prevent their growth. A water activity (aw) of 0.6 is required to prevent the growth of microorganisms.

Question 32

Give some examples of the water activity in common foods

Answer 32

Fresh meat and fish 0.99
Bread 0.95
Dried fruit 0.6
Biscuits 0.6
Milk powder 0.2

Question 33

What does use-by date mean?

Answer 33

-Food can be eaten up until the use by date but not after this date. -Use by dates are on foods that deteriorate quickly such as meat and meat products, ready prepared salads.

Question 34

What are best-before dates?

Answer 34

-are about food quality rather than food safety.
-Food can be eaten after a best before date but after this date freshness, taste or nutritional value, or may be affected.

Question 35

how can food spoilage/ bacteria growth be monitored?

Answer 35

-monitoring systems
-predictive models

Question 36

Describe how monitoring systems can be used to monitor food spoilage?

Answer 36

-use various methods:
Food regulations
Staff training
Management systems such as HACCP
-Record keeping enables food producers to establish monitoring procedures with the aim of preventing food contamination and spoilage.

Question 37

How can predictive models monitor food spoilage?

Answer 37

-used to create shelf life dates to ensure food is safe to eat. This involves examining preservative effects as well as the spoilage process