1. Food Microbiology

2. Intrinsic Factors composition pH presence and availability of water
oxidation-reduction potential
altered by cooking
physical structure
presence of antimicrobial substances

3. Composition and pH putrefaction
proteolysis and anaerobic breakdown of proteins, yielding foul-smelling amine compounds
pH impacts make up of microbial community and therefore types of chemical reactions that occur when microbes grow in food

4. Extrinsic Factors temperature relative humidity atmosphere
lower temperatures retard microbial growth
relative humidity
higher levels promote microbial growth
atmosphere
oxygen promotes growth
modified atmosphere packaging (MAP)
use of shrink wrap and vacuum technologies to package food in controlled atmospheres

5. Microbial Growth and Food Spoilage
results from growth of microbes in food
alters food visibly and in other ways, make it unsuitable for consumption
involves predictable succession of microbes
different foods undergo different types of spoilage processes
toxins are sometimes produced
algal toxins may contaminate shellfish and finfish

6. Food Spoilage
Approximately 1/3rd of all food manufactured in world is lost to spoilage
Microbial content of foods (microbial load): qualitative and quantitative.
Shelf life
Non-perishable foods
Semiperishable foods
Perishable foods

7. General Principles Minimize contamination by:
Good management processes
Acceptable sanitary practices
Well-tested preservation procedures

8. Spoilage Meat Cutting board contamination Temperature
Failure to distribute quickly
Fecal bacteria from intestines
Fish
Polluted waters
Transportation boxes

9. Food-Borne Diseases two primary types food-borne infections
food intoxications

10. Preventing Foodborne Disease
Food infections (microbes are transferred to consumer)
Food poisoning (results from the toxin consumption)

11. Food-Borne Intoxications
ingestion of toxins in foods in which microbes have grown
include staphylococcal food poisoning, botulism, Clostridium perfringens food poisoning, and Bacillus cereus food poisoning

12. Toxins ergotism aflatoxins fumonisins
toxic condition caused by growth of a fungus in grains
aflatoxins
carcinogens produced in fungus-infected grains .
fumonisins
carcinogens produced in fungus-infected corn

13. Controlling Food Spoilage

14. Removal of Microorganisms
usually achieved by filtration
commonly used for water, juices, soft drinks, and other liquids

15. Low Temperature
refrigeration at 5°C retards but does not stop microbial growth
psychrophiles and psychrotrophs can still cause spoilage
growth at temperatures below -10°C has been observed

16. High Temperature
canning
pasteurization

17. Canning
food heated in special containers (retorts) to 115 °C for 25 to 100 minutes
kills spoilage microbes, but not necessarily all microbes in food

18. Spoilage of canned goods
spoilage prior to canning
underprocessing
leakage of contaminated water into cans during cooling process

19. Pasteurization
kills pathogens and substantially reduces number of spoilage organisms
different pasteurization procedures heat for different lengths of time
shorter heating times result in improved flavor

20. Water Availability

22. Radiation ultraviolet (UV) radiation Gamma radiation
used for surfaces of food-handling equipment
does not penetrate foods
Gamma radiation
use of ionizing radiation (gamma radiation) to extend shelf life or sterilize meat, seafoods, fruits, and vegetables

23. Detection of Food-Borne Pathogens
must be rapid and sensitive
methods include:
culture techniques – may be too slow
immunological techniques - very sensitive
molecular techniques
probes used to detect specific DNA or RNA
sensitive and specific

24. nucleic acid can be detected
even when plaque-forming
ability is lost

25. Helpful Suggestions
Refrigerate quickly
Wash hands
Clean cutting boards
Avoid home-canned foods

26. Microbiology of Fermented Foods
major fermentations used are lactic, propionic, and ethanolic fermentations

27. Fermentation
Any partial breakdown of carbohydrates taking place in the absence of oxygen.

29. Meat and Fish
sausages
hams
katsuobushi – tuna

30. Other Fermented Foods silages
fermented grass, corn, and other fresh animal feeds

31. Microorganisms as Foods and Food Amendments
variety of bacteria, yeasts, and other fungi are used as animal and human food sources
probiotics
microbial dietary adjuvants
microbes added to diet in order to provide health benefits beyond basic nutritive value

32. What is Food Poisoning
Food poisoning is an acute illness, usually of sudden onset, brought about by eating contaminated or poisonous food. The symptoms normally include abdominal pain, diarrhoea, nausea, vomiting and fever.
It may be caused by:-
bacteria or their toxins
chemicals including metals
viruses
Mycotoxins or by mushroom 1 1

33. Food Poisoning bacteria
Classified to
1-Food infections (microbes are transferred to consumer)
2-Food poisoning (results from the toxin consumption)
Other classification
1-accordind to symptomes & incubation period
2- according to pathogenesis

34. Most food poisoning is caused by?
Bacteria

35. Types of bacteria in the food
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

36. These cells are beginning to divide into two

37. Bacterial growth After 10 minutes After 20 minutes After 30 minutes

38. From 0 to 1,536,000 in only 80 minutes ! Time : 9.30 Bacteria : 0
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 bacteria
Time :
Bacteria : 48,000
Time :
Bacteria : 96,000
Time :
Bacteria : 192,000
Time :
Bacteria : 384,000
Time :
Bacteria : 768,000
Time :
Bacteria : 1.5 million
From 0 to 1,536,000 in only 80 minutes !

39. 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 cereus Found in soil, vegetation, cereals and spices

40. Campylobacter spp.
Escherichia Coli
0157

41. Staphylococcus aureus
Sources - nose, mouth, skin, hands, spots, boils, septic cuts etc
Common food vehicles – Dairy products. Cold cooked meat and poultry.
Onset period – 1 to 6 hours . (Toxic food poisoning)

42. 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.

43. Bacillus cereus
Sources - Cereals, especially rice, cornflour, spices, dust and soil
Common food vehicles – Reheated rice, cornflour and spices.
Onset period – 1 to 6 hours. Exotoxin produced in food. (Toxic food poisoning)

44. 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.

45. Clostridium perfingens
Sources - The intestines of humans and animals, faeces and sewage, soil food pests, raw meat and poultry
Common food vehicles – sauces and meat pies when cooking has removed oxygen
Onset period – 8 to 24 hours Enterotoxin in intestine. (infective food poisoning)

46. 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

47. 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 – (usually 12 to 36 hours). A heat sensitive neurotoxin produced in the food which affects the nervous system. (Toxic food poisoning)

48. 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 a toxin 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.

49. Escherichia coli Sources - water & food
Onset period hours & hours
symptoms– Sudden onset of watery diarrhea associated with nausea, vomiting, abdominal cramping and
bloating is commonly observed. This bacterium is responsible for majority of traveler’s diarrhea. The disease is
self-limiting and resolves in few days.

50. 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 – (usually 12 to 36) Endotoxin in intestine (infective food poisoning)

51. 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.

52. Campylobacter jejuni Source- Poultry (raw chicken),
unpasteurized milk and non-chlorinated water.
Onset-2-11days.
Symptoms-
Gastroenteritis inflammation of the lining membrane of the stomach and the intestines characterized especially by nausea, vomiting, diarrhea, and cramps

53. Staphylococcus aureus
Pathogenic Bacteria
Source
Symptoms
Average Onset Time
Raw meat
Poultry and eggs
Human and animal intestines
Dirt and refuse
Vomiting
Nausea
Diarrhoea
Abdominal pain
hours after eating
Salmonella
Human nose, throat, ears, skin
Septic wounds
Animals and raw milk
Vomiting
Abdominal pain
Low temperature
Staphylococcus aureus
1 – 6 hours after eating
Raw meat and poultry
Soil, dirt and refuse
Raw vegetables
Human and animal intestines
Clostridium perfingens
Diarrhoea
Abdominal pain
hours after eating
Soil
Marine sediment
Raw fish and meat
Animal intestines
Paralysis
Breathing and swallowing difficulty
Diarrhoea followed by constipation
Clostridium botulinum
12 – 36 hours after eating
Nausea
Vomiting
Abdominal pain
Diarrhoea
1 - 6 hours or –16 hours depending on the form of the food poisoning
Bacillus cereus
Dust and soil
Cereal, rice .