Food is essential to life but if it is contaminated it can cause serious illness. Thankfully, only a minority of food poisoning cases lead to death but many cause unpleasant and debilitating illnesses. The cause is almost always human error. It is caused when food is prepared, stored or handled incorrectly.
Food poisoning can be prevented by following the basic rules of food hygiene. All food producers,whether in the work place or at home, have a responsibility to ensure that these rules are carried out.
IN THE BEGINNING.
The concern about which food to eat and which not too, has its origins way back in ancient times. In Biblical times, Moses made laws about which animals were fit for human consumption and cleanliness in general. These laws were based on experience and practical knowledge A lot of Religions have rules and laws, on which food to eat , if animals, how it should be killed, based on basic food hygiene practices. Food poisoning has been recognised for many centuries.
With the development of the microscope and then the work of men such as Pasteur and Robert Koch it was established that bacteria could cause disease. In 1888 a German doctor isolated bacteria from the organs of a man who had died in a food poisoning outbreak , he found identical bacteria in the left over meat that the man had eaten. It was also discovered that food that was contaminated with bacteria could still smell and taste the same as normal food, a very important discovery.
Bacteria, which cause food poisoning, grow best at a temperature of 37C, this is the normal temperature for the human body and are generally known as Pathogenic organisms. However they will continue to grow at temperature between 5C and 63C. This is known as the DANGER ZONE. Temperatures outside this zone are less suitable for bacterial growth. Most bacteria are killed at 75C when cooked between 10-30 minutes. This temperature must be reached at the centre of the food. Some bacteria require higher temperatures for a longer period of time to be killed.
In temperatures below 5C, the growth of bacteria ceases but is not destroyed. At very low temperatures, -18C (domestic deep freezer) or below some will die but many will survive and grow again in warm conditions. This is why defrosting must be carried out correctly.
Bacteria are living organisms that can only be seen with the aid of a microscope.
There are many different types but only a small number are responsible for food poisoning, a great many are very beneficial to us in our daily lives such as in the making of cheese and yoghurt.
HOW THEY GROW
As living organisms, bacteria require the four following conditions to live and grow.
Food Not all food is suitable for bacterial growth. Food that has a high content of sugar, salt or acid (vinegar) such as jams and pickles will discourage the growth of bacteria, hence the name Preserves.
Foods that encourage and allow bacteria to grow are known as high risk .
- meat and poultry. All meat and poultry products provide the conditions for bacterial growth. Raw meat and poultry may be soiled by the contents of the animals intestine. 80% of frozen chicken contain food poisoning bacteria.
- cooked meat, gravy,soups, stocks. These provide the nutrients that bacteria need to grow. Correct storage is essential to avoid bacterial growth.
- milk and eggs. High in protein and an ideal food for bacteria. Products containing milk and eggs such as cream, custard and mayonnaise are often involved in cases of food poisoning because of incorrect handling.
- raw shellfish and seafood. Prawns, mussels, crabs or lobsters may eat food that is contaminated by sewage polluted waters.
- cooked rice may contain bacteria that has survived the cooking process and will grow rapidly in warm conditions.
When bacteria have food, warmth and moisture they only need time to grow. The longer food is kept in the danger zone the more likely problems will occur. Each bacterial cell reproduces its self by splitting in 2. Each of these 2 will split and become 4 bacteria. They in turn will split in 2 and make 8 and so on. Bacteria will reproduce this way every 10-20 minutes when given the right conditions . This means that after only 24 hours one bacterium will have reproduced over 7000 million bacteria.
Bacteria will only grow in food that contains moisture and are less likely to survive in dried foods such as powdered milk. Some bacteria do survive in dried food and start to reproduce when fluid is added and so have to be treated and stored in the right conditions as for fresh food..