What is food poisoning? It is an acute illness, usually sudden, brought about by eating contaminated or poisonous food. The symptoms of food poisoning are:
1. nausea – a queasy feeling as if you were about to be sick
2. sickness – vomiting
3. Pains in the bowl – gripping pains in the area of the stomach
The main causes of food poisoning are:
1. Bacteria – the commonest
2. Viruses – which are smaller than bacteria, are normally found in water
3. Chemicals – Insecticides and weed-killers
4. Metals – lead pipes, copper pans
5. Poisonous plants – toadstools, red kidney beans (insufficiently cooked)
Bacteria is the most common form of food poisoning and so it is important that we know more about them. Bacteria are tiny bugs that live in the air, in water, in soil, on and in people, in and on food. Some bacteria causes illness. They are called PATHOGENIC bacteria. Some bacteria cause food to rot and decay, they are called SPOILAGE bacteria. There are four things that bacteria need in order to grow. These are:
Warmth. They love body temperature of 73 degrees but can happily grow at 15 degrees. They grow most readily between 5c and 63c. This is known as the DANGER ZONE
Time. Each bacteria grows by splitting in half. This takes time, on average every 20 minutes. This is known as BINARY FISSION. Imagine, one single bacterium by splitting in half every ten minutes can become more than a million in 3 and a half hours.
Food. They like high protein foods for example, poultry, cooked meat, dairy produce, shellfish, cooked rice, stews and gravies.
Moisture. They need water and most foods have enough water or moisture to let the bacteria thrive.
Some bacteria can form a hard protective case around themselves, this is called a SPORE. This happens when the ‘going gets tough’, when it gets too hot or too dry. So they are able to survive very hot or cold temperatures and can even be present in dried foods. Once the right conditions (5 – 63c) return, the spore comes out of its protective casing and becomes a growing, food poisoning bacteria again.
Bacteria and food poisoning
We have established that the presence of bacteria is one of the most common causes of food poisoning – the presence of poisonous chemicals can also cause food poisoning. There are a number of potentially toxic chemicals present in food. For example, potatoes which have turned green contain the toxic substance, Solanine, which is only dangerous when eaten in excess.
Rhubarb contains Oxalic Acid – the amounts present in the stems which are normally cooked are relatively harmless to humans, but the higher concentration in the leaves makes them very dangerous to eat.
A toxin is a poisonous substance that may be produced by the metabolism of a plant or animal, especially certain bacteria. Toxic food poisoning is mainly caused by Staphylococci in the uk and more rarely in this country, Clostridium Botulinum.
Foods most commonly affected by Staphylococci are:
• Meat pies
• Sliced meats
• Pies with gravy
• Synthetic cream
50-60% of people carry Staphylococci in their noses and throats and are present in nasal secretions following a cold. Staphylococci are also present in skin wounds and infections and find their way into foods via the the hands of an infected food handler. Hence the importance of keeping all wounds and skin conditions covered. Although staphylococci are themselves readily destroyed by thorough cooking or re-heating, the toxin which they produce is often much more heat-resistant and may need a higher temperature or longer cooking time for its complete destruction.
Food poisoning from Clostridium botulinum – known as botulism – is extremely serious. This produces a life-threatening toxin which is the most virulent poison known. Foods most commonly affected by clostridium botulinum are:
• Inadequately processed canned meat, vegetables and fish.
During the commercial canning process, every care is taken to ensure that each part of the food is heated to a high enough temperature to ensure complete destruction of any clostridium botulinum spores that may be present.
YEASTS & MOULDS – microscopic organisms some of which are desirable in food and contribute to its characteristics. For example, ripening of cheese, bread fermentation etc. They are simple plants which appear like whiskers on food. To grow they require warmth, moisture and air. They are killed by heat and sunlight. Moulds can grow where there is too little moisture for yeasts and bacteria to grow. Yeasts are single celled plants or organisms larger than bacterial, that grow on foods containing moisture and sugar. Foods containing a small percentage of sugar and a large amount of liquid such as fruit juices and syrups are liable to ferment because of yeasts. Yeasts are destroyed by heat.
VIRUS – microscopic particles transmitted by food which may cause illness. For example, Hepatitis A (jaundice). Unlike bacteria, viruses cannot multiply or grow in food.
PROTOZOA – single celled organisms which live in water and are responsible for serious diseases such as malaria, usually spread by infected mosquitoes and dysentery. These food-borne infections are mostly caught abroad.
ESCHERICHIA COLI – E Coli is a normal part of the intestines of man and animals. It is found in human excreta and raw meat. E Coli causes abdominal pain, fever, diarrhea and vomiting. High standards of hygiene and through cooking of foods must be applied. Raw and cooked meat must be stored at correct temperature and cross contamination must be avoided.
SALMONELLA – is present in the intestines of animals and human beings. Foods affected include poultry, meat, eggs and shellfish. Prevention should include:
• good standards of personal hygiene
• elimination of insects and rodents.
• washing hands and equipment and surfaces after handling raw poultry
• not allowing carriers of the disease to handle food.
Control of Bacteria
There are three methods of controlling bacteria:
1. Protect food from bacteria in the air by keeping foods covered. To prevent cross contamination, use separate boards and knives for cooked and uncooked foods Use different coloured boards for particular foods. For example, red for meat, blue for fish, yellow for poultry etc. Store cooked and uncooked foods separately. Wash your hands frequently.
2. Do not keep foods in the danger zone of between 5c and 63c for longer than absolutely necessary.
3. To kill bacteria, subject bacteria to a temperature of 77c for 30 seconds or a higher temperature for less time. Certain bacteria develop into spores and can withstand higher temperatures for longer periods of time. Certain chemicals also kill bacteria and can be used for cleaning equipment and utensils.
The main food hygiene regulations of importance to the caterer are: Food Safety (General Food Hygiene) Regulations 1995 and Food Safety (Temperature Control) Regulations 1995. These implemented the EC Food Hygiene directive (93/43 EEC). They replaced a number of different regulations including the Food Safety (General) Regulations of 1970. The 1995 Regulations are similar in many respects to earlier regulations. However, as with the Health & Safety legislation, these regulations place a strong emphasis on owners and managers to identify the safety risks, to design and implement appropriate systems to prevent contamination, these systems and procedures are covered by Hazard Analysis Critical Control Points (HACCP) and/or Assured Safe Catering. The regulations place two general requirements on owners of food businesses:
• To ensure that all food handling operations are carried out hygienically and according to the ‘Rules of Hygiene’.
• To identify and control all potential food safety hazards, using a systems approach either HACCP or Assured Safe Catering.
• In addition, there is an obligation on any food handler who may be suffering from or carrying a disease which could be transmitted through food to report this to the employer who may be obliged to prevent the person concerned from handling food. Catering establishments have a general obligation to supervise and instruct and provide training in food safety & hygiene commensurate with their employees’ responsibilities. Details with regard to how much training is required, are not specified in the regulations. However, HMSO Industry Guide to Catering provides guidance on training which can be taken as a general standard to comply with legislation.
Prevention of food poisoning
Almost all food poisoning can be prevented by:
• complying with the rules of hygiene
taking care and thinking head
• ensuring that high standards of cleanliness are applied to premises and equipment
• preventing accidents
• high standards of personal hygiene
• physical fitness
• maintaining good working conditions
• maintaining equipment in good repair and clean condition
• using separate equipment and knives for cooked and uncooked foods
• ample provision of cleaning facilities and equipment
• storing foods at the right temperature
• safe reheating of foods
• quick cooling of foods prior to storage
• protection of foods from vermin and insects;
• hygienic washing-up procedures;
• Knowing how food poison is caused
• carrying out procedures to prevent food poisoning.
This has been just a brief overview of food safety. If you are in the catering trade or are planning do become a cook or chef, it is essential that you learn all there is to know about the subject. The following links should help to fill the gaps.