Intermediate Food Safety Lesson objective - To understand the causes and effects of food poisoning and its relevance to food safety

Objectives By the end of the lesson you should be able to: 1.Describe the different types of food poisoning 2.Understand how bacteria cause food poisoning 3.Identify different pathogenic bacteria and their related symptoms

What is Food Hygiene? The science of preserving health It involves all measures necessary to ensure the safety and wholesomeness of food during it’s preparation and storage

What does it involve? Rejecting contaminated food Decontaminating food Protecting food from contamination through high standards of personal hygiene, cleaning and disinfection Preventing any organisms multiplying Destroying any harmful bacteria by thorough cooking Discarding unfit or contaminated food

Food Poisoning Normally associated with symptoms such as diarrhoea and vomiting May also include headache, stomach cramps and fever Bacteria are responsible for most cases Other causes include mycotoxins (poisonous chemicals produced by some moulds)

Food Poisoning (contd.) Physical contamination:- objects falling in to food – metal, glass, packaging materials etc. Chemical contamination:- Bleach, cleaning chemicals getting in to food Natural contamination: Poisonous plants and berries, undercooked red kidney beans

Poisonous mushrooms The deathcap – one bite can prove fatal And also…..The deadly Puffer fish!

Most food poisoning is caused by? Bacteria

Food poisoning is more likely to affect people with lowered resistance to disease than healthy people who might show mild symptoms or none at all. The following are particularly vulnerable to food poisoning: - Elderly or sick people Babies Young children Pregnant women Vulnerable Groups

Types of bacteria Spoilage: Not particularly harmful bacteria which cause food to go off Beneficial: “Good Bacteria” which are used to make yoghurt and cheese Pathogenic: Illness causing bacteria

In order to grow and multiply germs need: Warmth FoodMoisture Time Remember it like this TooManyFliesWaiting

In ideal conditions where there is Moisture, Food and Warmth (37degrees centigrade is ideal), bacteria can double every 10 to 20 minutes. They do this by dividing in to two. This is called Binary Fission

These cells are beginning to divide into two

After 10 minutes After 20 minutes After 30 minutes After 40 minutes

Time : 9.30Bacteria : 0 Time : 9.40 Time : 9.50 Time : Bacteria : 12,000 Bacteria : 24,000 Bacteria : 48,000 Time : Time : Time : Time : Time : Bacteria : 96,000 Bacteria : 192,000 Bacteria : 384,000 Bacteria : 768,000 Bacteria : 1.5 million From 0 to 1,536,000 in only 80 minutes !!!!!! Knife contaminated by blood cooking chicken to a core temperature of 75°C should kill most of the bacteria

Bacterial Growth Curve Time (hours) Numbers Of Bacteria Lag Phase Log Phase Stationary Phase Decline Phase no multiplication rapid multiplication Numbers of bacteria remain constant as the number produced is equal to the number dying Numbers of bacteria decrease

Spore A resting resistant phase of some bacteria (including Clostridium Perfingens and Botulinum and Bacillus Cereus). The bacterium produces a protective coat which helps it to survive high temperatures (up to 120°C) and lack of water. When favourable conditions return, the spores split open and release the bacteria which are then able to grow and multiply Bacterial cell Spore forming inside cell

Spore Formation This is what happens ………….. Cell

Spore forms in cell

Toxins Some bacteria release poisons known as toxins which cause food poisoning. Some toxins, known as exotoxins multiply in food. These toxins are not easily destroyed by cooking and may remain in food once they have developed. Other bacteria produce toxins inside the human body only after the food has been eaten. These are called endotoxins

Moulds and Yeasts Moulds are a type of fungi that will grow on most foods and at many temperatures. Some are used in food production such as cheese manufacture. Unwanted moulds usually spoil the food but do not cause food poisoning. Yeasts are another type of fungi that will grow in food. They are used in making food such as bread and beer but also spoil many foods including jam, fruit juice, yoghurts and meats

Food Poisoning bacteria Usually need millions of bacteria to cause illness.Usually need millions of bacteria to cause illness. The multiplication of bacteria within the food plays an important part in the diseaseThe multiplication of bacteria within the food plays an important part in the disease

Bacillus Cereus Found in soil, vegetation, cereals and spices Staphylococcus Aureus Found in human nose and throat (also skin) Clostridium Perfingens Found in animals and birds Salmonella Found in animals, raw poultry and birds Clostridium Botulinum Found in the soil and associated with vegetables and meats

Salmonella Sources - The intestines of ill people and carriers, animals and animal food, raw meat, raw poultry, raw milk, raw eggs, food pests Common food vehicles – Undercooked or contaminated cooked meat, raw milk and eggs Onset period – 6 to 72 hours (usually 12 to 36) Endotoxin in intestine (infective food poisoning)

Salmonella Symptoms - Abdominal pain, diarrhoea, vomiting and fever. Duration is usually one to seven days. Specific characteristics – Usually requires millions of bacteria to cause illness. Multiplies from 5°C to 47°C under aerobic or anaerobic conditions.

Aerobic and Anaerobic Bacteria which need oxygen to multiply are classed as aerobic Bacteria which only multiply without oxygen are called anaerobic Just to confuse you some bacteria including Salmonella, Staphylococcus aureus and Bacillus cereus are classed as facultative anaerobes which means they can multiply with or without oxygen!

Salmonella Specific controls Hygienic farm and abbatoir practices Avoid cross contamination Complete thawing of frozen poultry Thorough cooking to 75°C for one minute High standards of personal hygiene Effective cleaning Safe sewage disposal

Clostridium perfingens Sources - The intestines of humans and animals, faeces and sewage, soil food pests, raw meat and poultry Common food vehicles – Rolled joints, casseroles, stews, sauces and meat pies when cooking has removed oxygen Onset period – 8 to 22 hours (usually 12 to 18) Enterotoxin in intestine. (infective food poisoning)

Clostridium perfingens Symptoms - Abdominal pain, diarrhoea, (vomiting is rare) and fever. Duration is usually 12 to 48 hours. Specific characteristics – Usually requires millions of bacteria to cause illness. Multiplies from 10°C to 52°C under anaerobic conditions. At 46°C it can double every 10 minutes. Produces spores. Illness caused from consuming millions of organisms

Staphylococcus Aureus Sources - Human nose, mouth, skin, hands, spots, boils, septic cuts etc Common food vehicles – Dairy products. Cold cooked meat and poultry, peeled cooked prawns Onset period – 1 to 7 hours (usually 12 to 18) Exotoxin produced in food. (Toxic food poisoning)

Staphylococcus Aureus Symptoms - Abdominal pain, diarrhoea, vomiting. Occasionally subnormal temperatures. Duration between 6 and 24 hours. Specific characteristics – Usually requires millions of bacteria to cause illness. Toxin may survive boiling for up to 30 minutes. Multiplies from 7°C to 48°C under aerobic or anaerobic conditions. Can tolerate relatively high salt content.

Bacillus Cereus Sources - Cereals, especially rice, cornflour, spices, dust and soil Common food vehicles – Reheated rice, cornflour and spices. Onset period – 1 to 5 hours. Exotoxin produced in food. (Toxic food poisoning)

Bacillus Cereus Symptoms - Abdominal pain, diarrhoea, vomiting. Occasionally subnormal temperatures. Duration between 12 and 24 hours. Specific characteristics – Forms spores which produce an exotoxin under aerobic or anaerobic conditions. Both the spores and toxin will survive normal cooking temperatures. Millions required to cause illness. Bacteria multiply between 7°C and 48°C.spores

Clostridium Botulinum Sources - Fish intestine, soil and vegetables. Common food vehicles – Low acid processed food contaminated after canning or vacuum packing. Smoked fish, bottled vegetables. Onset period –2 hours to 5 days (usually 12 to 36 hours). A heat sensitive neurotoxin produced in the food which affects the nervous system. (Toxic food poisoning)

Clostridium Botulinum Symptoms - Difficulties in swallowing, talking and breathing. Double vision and paralysis. Diarrhoea followed by constipation. Fatalities are common and survivors may take several months to recover. Specific characteristics – Forms spores which produce an exotoxin under anaerobic conditions. Both the spores and toxin will survive normal cooking temperatures. Millions required to cause illness. Bacteria multiply between 3.3°C and 48°C.

Pathogenic Bacteria SourceSymptomsAverage Onset Time Salmonella Raw meat Poultry and eggs Pests and pets Human and animal intestines Dirt and refuse Vomiting Nausea Diarrhoea Abdominal pain hours after eating Staphylococcus aureus Clostridium perfingens Clostridium botulinum Bacillus cereus Human nose, throat, ears, skin Septic wounds Animals and raw milk Vomiting Abdominal pain Low temperature 1 – 7 hours after eating Raw meat and poultry Soil, dirt and refuse Raw vegetables Pests and pets Human and animal intestines Soil Marine sediment Raw fish and meat Animal intestines Dust and soil Cereal, rice and pasta Diarrhoea Abdominal pain hours after eating Paralysis Breathing and swallowing difficulty Diarrhoea followed by constipation 12 – 36 hours after eating hours or 8 – 16 hours depending on the form of the food poisoning Nausea Vomiting Abdominal pain Diarrhoea

Campylobacter enteritis Listeriosis Escherichia Coli 0157 Typhoid and paratyphoid fever Dysentery That’s the end of lesson 1! Coming next lesson: Foodborne diseases