Food Spoilage. Flashcards
What is food spoilage?
Deterioration of food is known as decay and leads to food spoilage.
Food spoilage is caused by two main factors:
- Natural decay within the food itself.
- Contamination by microscopic forms of life (micro-organisms).
What are perishable goods and what do they contain large amounts of?
Foods that spoil rapidly are known as perishable foods and contain large amounts of water and nutrients e.g. milk, fruit, and meat.
What types of foods are susceptible to food spoilage once thawed, opened, or reconstituted?
Processed and cooked foods are also susceptible once thawed, opened, or reconstituted.
What is natural decay in food a result of?
- Moisture loss.
- The action of enzymes.
Moisture loss is best demonstrated in fruits and vegetables. Describe the loss of moisture from a fruit or vegetable.
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’.
Where else does moisture loss occur that is not fruit or vegetables?
Moisture loss also occurs in other foods e.g. meat, fish, and, cheese because of evaporation from the surface.
Once activated, what do enzymes do?
Once activated, such enzymes speed up the process of decay by breaking down the tissues and components of food in different ways.
Name the three ways enzymes cause food spoilage.
- Oxidation.
- Browning.
- Ripening.
Describe the action of enzymes that cause oxidation.
Oxidase enzymes cause the destruction of certain nutrients e.g. vitamin C, thiamine, and carotene.
Describe the action of enzymes that cause browning.
If some foods are cut or bruised e.g. apples the damaged surface will discolor and turn brown.
Describe the action of enzymes that cause ripening, particularly to do with bananas.
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.
The main micro-organisms responsible for the contamination of food are:
- Bacteria.
- Moulds.
- Yeast.
What do all three groups of food spoilage microorganisms need to grow and reproduce?
All three groups require a medium to grow and reproduce and food is ideal because it provides nutrients and moisture.
How do food spoilage microorganisms contaminate food?
They contaminate the food by producing waste products or toxins (poisons) or simply make food inedible by their presence.
What is the name given to microorganisms which cause food poisoning?
Microorganisms that cause food poisoning are called pathogenic (harmful) micro-organisms.
However, not all food spoilage microorganisms are harmful. What are the non-harmful ones used for?
Some are used in the food industry to produce foods such as cheese, yogurt, and soy sauce.
Under the suitable conditions of _________, ___________, ________, and _____ bacteria can multiply very rapidly.
Under suitable conditions of temperature, moisture, food supply, and time bacteria can multiply very rapidly.
What happens when a large number of bacteria are present in one place? And is this visible to the naked eye?
When a large number of bacteria are present in one place they form a colony; which is usually not visible to the naked eye.
What happens if the conditions for bacterial multiplication are unfavorable?
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.
Are spores resistant to heat?
Spores are often very resistant to heat.
What is the ideal temperature for bacterial multiplication?
30 to 37 degrees Celsius.
What temperature are most bacteria destroyed at?
Most bacteria are destroyed at around 60°C.
What substances are used for food preservation and why?
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.
