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 Moisture Food Time Remember it like this Too Many Flies Waiting
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
After 10 minutes After 20 minutes Bacterial growth After 30 minutes After 40 minutes
cooking chicken to a core temperature of 75°C should kill most of the bacteria Time : 9.30 Bacteria : 0 Time : 9.40 Bacteria : 12,000 Time : 9.50 Bacteria : 24,000 Knife contaminated by blood Bacteria : 48,000 Time : 10.00 Bacteria : 96,000 Time : 10.10 Time : 10.20 Bacteria : 192,000 Time : 10.30 Bacteria : 384,000 Time : 10.40 Bacteria : 768,000 Time : 10.50 Bacteria : 1.5 million From 0 to 1,536,000 in only 80 minutes !!!!!!
Spore Formation This is what happens ………….. Cell
Now see as, in suitable conditions, the cell begins to divide (binary fission)………………………….
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
Food Poisoning bacteria Usually need millions of bacteria to cause illness. The multiplication of bacteria within the food plays an important part in the disease
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 Bacillus CereusFound in soil, vegetation, cereals and spices
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.
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. 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.
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 survive under normal cooking conditions. Millions required to cause illness. Bacteria multiply between 7°C and 48°C.
Clostridium Botulinum • Sources - Fish intestine, soil and vegetables. • Common food vehicles –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 will survive normal cooking temperatures. Millions required to cause illness. Bacteria multiply between 3.3°C and 48°C.