Food Technology
Hygiene
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Learning objectives
Learning objectives
To understand about good hygiene practices.
To understand the conditions in which bacteria grow.
To know about the different types of pathogenic bacteria.
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What is hygiene?
Hygiene is the practices which are
adopted in order to maintain
cleanliness and prevent disease.
We follow hygiene rules everyday
such as storing milk, meat and
cheese in the fridge, washing our
hands and cleaning the dishes in
hot water.
By following hygiene rules, it is
possible to ensure that equipment
and food is free from bacterial
contamination which can cause
food poisoning.
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Why is personal hygiene important?
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Washing hands
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What are bacteria?
Bacteria are micro-organisms that cannot be seen by the human
eye – thousands fit onto the top of a pin! They live on and in our
bodies and all around us. Not all bacteria are harmful; some do
useful jobs. Bacteria can be divided into three kinds. There are:
helpful bacteria which help digest the
food we eat, make foods such as
cheese and yoghurt, develop new
foods and treat sewage to make it
safe
spoilage bacteria which make food
perish, rot, spoil or go bad
pathogenic bacteria which cause
illness and food poisoning.
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Pathogenic bacteria
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How can bacteria be controlled?
If pathogenic bacteria are given the right
conditions (warmth, food, moisture and time)
in which to grow and multiply, they cause food
poisoning and in some cases, death. Some
bacteria also produce toxins which are
poisonous.
The young, old, pregnant and sick are the
most vulnerable. It is possible to prevent
bacteria multiplying to large numbers by
adopting good hygiene practices and
understanding the conditions which help
bacteria to grow.
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How does temperature affect bacteria?
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How do food and moisture affect bacteria?
Bacteria like foods which are moist and have a high protein
content such as red meat, poultry, fish and dairy products. They
are called high-risk foods as they are foods which bacteria are
most likely to grow on. They must be stored in a fridge at below
5ºC.
Dry foods such as gravy powder and custard powder can be
stored at room temperature because bacteria will not grow on
them. As soon as they are turned into gravy and custard by
adding liquid, they must be stored in a fridge.
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How does time affect bacteria?
In ideal conditions bacteria multiply very quickly – they divide into
two by binary fission. This means that within just a few hours,
one bacteria is able to increase in number to several thousands
or millions.
A cake has three bacteria on
it at 9am. If the bacteria can
multiply (divide in two) every
twenty minutes and the cake is
left out in a room until 1pm,
how many bacteria could there
be on it?
12, 288
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Food pests
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Cleaning
Correct cleaning prevents pest infestation and other bacterial
contamination. Cleaning is the process of making something free
from dirt and contamination.
Detergents help to dissolve grease and remove dirt. They may
kill some pathogenic bacteria.
Disinfection is the reduction of bacteria to a low and safe level.
It can be achieved by the use of very hot water (at 82°C or
hotter), steam or chemical disinfectants.
Sanitizers consist of a detergent and disinfectant so they can
remove grease and dirt at the same time as reducing the level
of bacteria.
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Do you know how to wash up correctly?
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Pathogenic bacteria quiz
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Hygiene quiz
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Key points
Key points
There are a number of different pathogenic bacteria
which cause food poisoning and are found in different
foods, on people and in soil.
Each bacteria has a variety of symptoms.
Bacteria need warmth, food, moisture and time to
grow; high-risk foods must be kept out of the danger
zone.
Food poisoning can be prevented with good hygiene
practices such as cooking food until very hot, washing
hands and storing food in cold places.
Pests such as rodents, birds and insects can
contaminate foods.
Cleaning with a sanitizer gets rid of grease and dirt and
reduces bacteria to a low and safe level.
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