What are the symptoms and causes of food poisoning?
Food-borne illness affects very large numbers of people each year and can last from one day to several weeks, or much longer. Some people get an upset stomach, but some can suffer severe symptoms that can cause kidney failure and even death.
Everybody working with food therefore, has a duty to ensure that the food they prepare is safe.
Two kinds of food-borne illness
There are two kinds of food-borne illness:
- Food poisoning: caused by eating food that is contaminated by harmful substances, or harmful micro-organisms living in the food.
- Food-borne disease: caused by harmful micro-organisms being carried on food or in water. It usually only needs small numbers of these micro-organisms to be able to cause illness.
Food poisoning can be caused by:
- micro-organisms which include
- Bacteria in large numbers - such as Salmonella, Staphylococcus aureus and Clostridium perfringens (which we will look at in more detail later on in this module). They are able to grow in food under the right conditions.
- Viruses, which are micro-organisms that live on and in people, animals and other organisms.
- Certain kinds of moulds (which produce toxins on foods).
- poisonous plants and fish, such as some toadstools, berries, rhubarb leaves, red kidney beans and fish that has been poorly processed.
- chemicals and metals, which have got into food either from unsuitable containers or during the industrial, agricultural or cleaning process that the food has gone through before reaching the consumer.
Types of food bacteria
The types of bacteria that cause food poisoning come from several main sources.
- Raw foods (especially meat, poultry, eggs, shellfish and vegetables).
- Pests and domestic pets.
- People (from their hands, hair, nose, throat, infected cuts).
- Air and dust.
- Dirt and soil (unwashed vegetables and salads).
- Food waste.
What causes bacteria to develop?
All bacteria need to start reproducing are:
- food
- moisture
- warmth
- time.
Give bacteria the right combination of food, moisture, warmth and time and you have a problem.
Food
Bacteria are not fussy eaters and can live on a range of foods, but, like any living thing, they do have their favourite kinds of food. They prefer something that is moist and high in protein, such as meat, poultry, fish, eggs, milk and dairy products, and any combination of these foods. Even if food has been cooked and served cold later, bacteria can grow on it. Ready-to-eat foods like this are called HIGH-RISK foods.
Moisture
Like plants, bacteria need moisture to grow. If they find themselves in a dry environment, like powdered milk or dried eggs, they cannot multiply. Once water is added, however, the situation changes and you have the ideal conditions for bacteria to multiply.
Warmth
Bacteria can multiply at temperatures between 5oC and 63oC. Anything between these two temperatures is called the DANGER ZONE. If the temperature is colder than 5oC, pathogenic bacteria either multiply very slowly or not at all. If the temperature is higher than 63oC, pathogenic bacteria will not multiply. Multiplication will be greater in the middle of this temperature range. Their preferred temperature is 37oC (human body temperature).
Food, especially high-risk or perishable food, should be kept out of the danger zone as much as possible.
The temperature of food may enter the danger zone when:
- it is left to stand in a room
- it is left in sunlight
- it is heated slowly
- hot and cold foods are combined (eg hot sauce on cold food).
Time
Take the three previous elements (food, moisture and warmth) and leave the bacteria with them for long enough and they will start to multiply. All food poisoning bacteria need is about 10 or 20 minutes to double their numbers.
Food hygiene - basic rules
The basic rules to remember are:
- When hot food is cooled before refrigeration, it will pass through the danger zone during cooling. Hot food should be cooled within 11/2 hours of cooking.
- Keep cold foods really cold.
- Keep hot foods really hot.
High-risk foods
Given the right conditions, bacteria can affect most foods. However, there are certain types of food that are known as HIGH-RISK foods because they will be eaten without any more processing, such as cooking, that would destroy any bacteria present. These high-risk foods also provide bacteria with some ideal conditions for growth (food and moisture).
The main high-risk foods are:
- cooked meat and cooked poultry
- cooked meat products (eg stews, pies and pasties, gravy and soups made with meat or meat stock)
- meat or fish pâtés and spreads
- milk, cream, ice cream and cooked eggs
- uncooked and lightly cooked dishes made with milk and eggs (eg mayonnaise, hollandaise sauce, mousses)
- shellfish and seafood (eg oysters, prawns, shrimps, mussels, crab, lobster, scampi); cooked or, in some cases, raw
- cooked rice
- any combination of the above previous foods shown.
Food hygiene and Safety - online training course
This content is an extract from our Food Hygiene and Safety Course which is specifically designed for those who prepare and handle food, and is accredited by RoSPA.
The course has recently been updated to utilise latest e-learning technology and design. It covers the importance of preparing food that is safe to eat and details the importance of good hygiene practices and how to maintain hygienic premises and equipment.
This course delivers five CPD hours and as well as looking at how bacteria can cause food-borne illness also looks at:
- recognising
high risk foods and food allergies - contamination and food
spoilages and how to control it - effective hygiene
- the importance of storage
- HACCP and the law.
The course can be bought online or is included in our cost-effective training packages.
Get in touch to find out more
Related content:
Food Hygiene and Safety
This Food Hygiene & Safety course is specifically designed for those who prepare and handle food.
Read moreFood Hygiene and Safety
This four module course delivers five CPD hours and comprehensively covers:
- how bacteria can cause food-borne illness
- recognising high risk foods and food allergies
- contamination and food spoilages and how to control it
- effective hygiene
- the importance of storage
- HACCP and the law
Development updates to EduCare courses
As well as regularly updating the content of courses, EduCare also ensures the format of all courses remains up-to-date and utilises the latest e-learning technologies
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