This chapter discusses biological hazards in food, which include harmful microorganisms like bacteria, viruses, parasites, molds, yeasts and prions. These microorganisms can cause foodborne illnesses through infection, intoxication or toxin-mediated infection. The key factors that influence microbial growth are food, temperature, acidity, time, oxygen, and moisture. Bacteria are particularly concerning and some important foodborne pathogens include Salmonella, E. coli, Listeria, Staphylococcus, Clostridium, Bacillus and others. Viruses and parasites can also cause foodborne illness. Proper food handling and storage is important to prevent the growth of harmful microorganisms.

1. Chapter 4
Biological Hazards

2. Biological Hazards
Acquired from disease-
causing microorganisms
and the poisonous
toxins they may
produce.
They are far the most dangerous
foodborne hazard in the food
service and food retail businesses.

3. • These include harmful microorganisms seen only under
the microscope such as:
– Bacteria
– Viruses
– Parasites
– Molds
– Yeast
– And the biological substance prion, a protein molecule
– Other living organisms such as:
• Insects
• Rodents
• Farm animals
• Domestic pets
• Birds
• Fish and plants
Biological Hazards

4. Foodborne illnesses:
• Generally classified as:
– Infection
– Intoxication
– Toxin-mediated infection

5. Infection
• Occurs when a living microorganism is ingested as a
part of food.
• After ingestion, the microorganisms attach themselves to
the gastrointestinal tract and begins to grow.
• An example of a bacterial infection is Salmonella spp.

6. • This can lead to common foodborne illness
symptoms like diarrhea.
• In some, instances, the microorganisms may be
carried by the bloodstream from the
gastrointestinal tract to the other parts of the
body.
• Foodborne viruses and parasites are
good examples of microorganisms that
can cause infection.

7. Intoxication
• Arises when a living microorganisms that grows in
food produces a toxin.
• The food is then ingested and the toxin itself causes the
illness.
• Some examples of bacteria that cause food intoxication
are Clostridium botulinum and Staphylococcus
aureus.
• An intoxication may also occur due to
consumption of a toxic chemical such as a
cleaning chemical.

8. Toxin-mediated infection
• Takes place when a living microorganism is
consumed and the ingested microorganisms
produces a toxin in the body that leads to
illness.
• An example of a microorganism that produces
toxin in the body is the Clostridium
perfringens.

9. Types of Microorganisms:
1. Beneficial Microorganisms
– Are found in food production. Examples of these
microbes are those used in making bread, beer,
yoghurt, and cheese.
2. Harmful Microorganisms
– Spoil food and cause diseases.

10. Microbial Forms:
1. Bacteria
2. Viruses
3. Parasites
4. Fungi
5. Molds
6. Yeast
7. Prions

11. Bacteria
• Of all microorganisms, bacteria provide
the most common threat to food safety.
• Bacteria are single-celled organisms and
can cause illnesses in two ways:
– Pathogenic (infectious; disease-causing) bacteria.
– Toxigenic (poisonous) bacteria produce harmful
toxins

12. • Most bacteria exist in a vegetative state, the
cells grow, reproduce , and produce waste just
like any other living organism.
• However, some bacteria are able to produce
protective, thick-walled structures called spores.
• Spores do not reproduce, but they enable
the bacteria to survive some cooking and
freezing temperatures and the destructive
effects of cleaning and sanitizing solutions.
• They even survive when there is not
enough food.

13. Classification of Bacteria:
• Spoilage bacteria – break down foods making them
look, taste, and smell bad. They reduce the quality of
food to unacceptable levels. When this happens, the
food will have to be thrown away.
• Pathogenic bacteria – are disease-causing
microorganisms that can make people ill if they or their
toxins are consumed through food.

14. Bacterial Growth:
• Bacteria reproduce when bacterial cell divides to form
two new cells.
• This process is called binary fission.
• The reproduction of bacteria and an increase in the
number of organisms are referred to as bacterial growth.
• This means that during each growth generation,
each cell gives rise to another cell.

16. • The generation time, or the time for cell numbers to
double is typically 20-30 minutes but can also be as
quick as 15 minutes.
• Under optimal conditions, this means that a single cell
can generate over 1 million cells in just five hours.
• Proper storage and food handling help
prevent bacterial growth.
Number
of cells
1 2 4 16 > 1000 >1
million
Time 0 15
minutes
30
minutes
1 hour 3 hours 5 hours

17. Phases of Bacterial Growth:
• Lag Phase
• Log Phase
• Stationary Phase
• Death Phase

18. Lag Phase
• Growth is slow at first, while the
microorganisms acclimate to the food and
nutrients in their new habitat.

19. Log Phase
• Once the metabolic machinery is running,
microbes start multiplying exponentially,
doubling in number every few minutes.

20. Stationary Phase
• As more and more microbes are
competing for dwelling food and nutrients,
the booming growth stops and the number
of bacteria stabilizes.

21. Death Phase
• Toxic waste products build up, food is
depleted and the microorganisms begin to
die.

23. Bacterial Growth Requirements
• Remember the acronym FATTOM:
• Food
• Acidity
• Time
• Temperature
• Oxygen
• Moisture

24. Food
• Microorganisms like all living things need food to grow.
• The presence of a suitable food supply is the most
important condition that affects bacterial growth.
• The food must contain the appropriate nutrients needed
for growth.
• Bacteria generally prefer foods that
are high in protein like meat and
dairy items.

25. Acidity
• Disease-causing bacteria grow best at acidity levels
equivalent to pH 4.6 to 7.5.
• The term pH is used as a symbol to designate the food’s
degree of acidity.
• The scale for measuring pH is from 0 to 14.
• A pH of 7.0 is neither acidic nor basic and is considered
neutral food.
• A pH less than 7.0 indicates that the food is acidic. A pH
range greater than 7.0 refers to basic food. (Examples of
alkaline foods are olives, egg whites, or soda crackers).

27. • Very acidic food (pH below 4.6), like lemons,
limes and tomatoes, cannot support the growth
of disease-causing bacteria.
• Pickling fruits and vegetables by adding acids,
such as vinegar, lowers the pH of the food and
slows down the rate of bacterial growth.
• High alkaline foods are also unfavorable for the
growth of microorganisms.

28. • Most bacterial growth is inhibited at an acidic
environment or at a pH of below 4.6.
• The optimum growth pH for yeast is from 4.5 to
6.0 while molds require a pH from 3.5 to 4.0.

29. Time
• Because bacteria grow
rapidly, it does not take
long before many cells are
produced.
• A rule of thumb in the food
industry is that the bacteria
need about four hours,
inclusive of the time food is
between 50C to 600C, to
grow to numbers high
enough to cause illness.

30. • Remember, a single bacterial cell can produce 1 million
cells in just five hours under ideal conditions.
• It is very important not to give bacteria an opportunity to
multiply.
• Proper storage and handling of foods help prevent
bacteria from multiplying.

31. Temperature
• Temperature is probably the most important factor that
affects growth of bacteria in food.
• Most disease-causing bacteria grow within a
temperature range of 50C to 600C.
• This is the range where microbial
growth and reproduction are at their
peak.
• This is commonly referred to as the
Temperature Danger Zone.

32. Classification of microorganisms
according to temperature requirements:
• Psychrophiles
• Mesophiles
• Thermophiles

33. Psychrophiles
• These cold-temperature loving microorganisms thrive in
a temperature range of 00C to 210C.
• They are especially troublesome because they are
capable of multiplying at both refrigerated and room
temperatures.
• Most psychophysics bacteria are spoilage organisms,
but some can also cause diseases.

34. Mesophiles
• These middle-range bacteria grow at
temperatures between 210C and 430C,
with the most rapid growth at human body
temperature.

35. Thermophiles
• Heat-loving microorganisms, they grow
best at temperatures above 430C.
• All thermophilic bacteria are spoilage
organisms

36. Oxygen
• Bacteria require different amounts of oxygen to
grow.
• Some require a lot of oxygen (aerobic), while
others cannot tolerate oxygen (anaerobic) at all.
• Those belonging to genus Clostridia
require the complete absence of free
oxygen to grow. Free oxygen is toxic
for this group of microorganisms.

37. • Anaerobic bacteria grow well in vacuum
package foods or canned foods where oxygen is
not available.
• Anaerobic conditions also exist in the middle of
cooked food masses such as stock pots and
baked potatoes, or in the middle of a roast or
ham.

38. • Some bacteria only grow within a narrow oxygen range
(microaerophilic), usually three to six percent oxygen
levels. While others can grow with or without oxygen
(facultative anaerobes).
• Most foodborne-causing microorganisms are facultative
anaerobes.
• Controlling oxygen conditions may be
an effective way to prevent foodborne
illnesses. However, even without any
oxygen, some disease-causing
bacteria can still find the conditions
suitable for growth.

39. Moisture
• Just like most forms of life, moisture is an
important factor affecting bacterial growth, which
is why humans have been preserving food for
thousands of years by drying them.
• Scientists have determined that
bacterial growth is greatly
influenced by the amount of
available water which is
designated with the symbol aw

40. • Aw is water not bound to the food and is
available for bacterial growth.
• It is measured on a scale from 1 – 1.0.
• Disease-causing bacteria can only grow in foods
with an aw greater than .85

41. • In the Philippines, because of high relative
humidity, the top layer of some exposed food
can hydrate and make it moist enough for
microorganisms to grow.
• Good packaging and the control of
environmental relative humidity which can be
achieved with air-conditioning, dehumidifier, or
even adequate ventilation, can prevent this from
happening.

42. • There are many preservation process that can
be done to reduce the aw (below 0.85) of foods,
including sun drying and freeze drying.
• The addition of salt or sugar can also be used to
reduce available water. However, very high
amounts of these substances need to be used,
rendering this method impractical.

43. Bacterial, Viral, and Parasitic
Foodborne Hazards
• Biological hazards are of the greatest concern to
food service and food retail operators.
• The have been classified as:
• Spore-forming bacteria
• Nonspore-forming bacteria
• Viruses, and;
• Parasites

44. Foodborne Illnesses Caused
by Bacteria:

45. Spore-Forming Foodborne
Bacteria
• The following group of bacteria can produce a spore
structure that allows a cell to withstand environmental
stress such as cooking, freezing, salting, drying, and
pickling.
• Generally, bacterial spores are not harmful if
ingested. However, if conditions of the food are
changed, permitting the spore to turn into a
vegetative cell, the vegetative cell can grow in the
food and cause illness if eaten.

46. • Spore-forming bacteria are generally found in
ingredients grown near the soil like vegetables and
spices.
• They can be particularly troublesome in food retail-
type environments because they can survive on
foods.
• When conditions are improved, for instance, adding
dried spices to a beef stew mixture, spores can
become vegetative state.

48. • Spores are mostly likely to turn vegetative
when:
– Heat-shocked (heating causes spores to
change)
– Optimum conditions exist for growth (high
protein and high moisture)
– Temperatures are in the food temperature
danger zone or between 50C to 600C and
– The amount of time the food is in the danger
zone is four hours or more.

49. • To keep spore-forming bacteria from changing to the
dangerous vegetative state, it is critical that hot foods be
maintained at 600C or higher and cold foods be kept at
less than 50C.
• Cooking, reheating, and cooling of foods should also be
done as quickly as possible to limit bacterial growth.
• Important spore-forming pathogens in the food retail
industry include: Bacillus cereus, Clostridium
perfringens, and Clostridium botulinum.

50. Nonspore-Forming
Foodborne Bacteria
• The following groups of bacteria are not capable of producing a
spore structure; they are always in the vegetative state.
• Compared to spore-forming bacteria that are in the spore state,
vegetative cells are easily destroyed by proper cooking.
• There are numerous examples of nonspore-forming foodborne
bacteria that are important in the food retail industry.

52. Foodborne Illnesses Caused
by Viruses:

53. • Foodborne viruses differ from foodborne bacteria.
Viruses require a living host (animal, plant, or human) to
grow and reproduce.
• Unlike bacteria, they do not reproduce or grow in foods.
However, the consumption of even a few particles is
enough for a person to experience an infection.
• Viruses are usually transferred from one food to another,
e.g. from a food handler to a food, or from a water supply
to a food.
• A PHF is not needed by a virus to
survive.
• There are viruses common in food
retail preparation: Hepatitis A, Norwalk
virus, and rotavirus

54. Foodborne Illnesses Caused
by Parasites:

55. • Foodborne parasites are among the common
foodborne biological hazards.
• Parasites are microscopic creatures that need to
live on or inside a host to survive.
• Parasites can be found in irrigation water,
animal feces, muscle tissues of improperly fed
cattle and swine, and fish muscles.

56. • Human can become infected when undercooked
meat and fish are consumed.
• There are several examples of parasites that
can come in contact with food and cause
foodborne illnesses.
• Parasitic infection is far less common than
bacterial or viral foodborne illnesses.

57. Foodborne Illnesses Caused
by Fungi:

58. • A fungus is a eukaryotic organism that is a member of
the kingdom Fungi.
• Fungi are heterotropic organisms that possess a
chitinous cell wall.
• The majority of its species grow as multicellular filaments
called hyphae forming mycelium; some fungal species
also grow as single cells.
• Sexual and asexual reproduction occur
commonly through spores which are often
produced on specialized structures or in
fruiting bodies.

59. • Yeasts, molds, and mushrooms are all examples of
fungi.
• Occurring worldwide, most fungi are largely invisible to
the naked eye, living for the most part in soil, dead
matter, and as symbionts of plants, animals, or other
fungi.
• They perform as essential role in all ecosystems in
decomposing organic matters and indispensable in
nutrient cycling and exchange.
• Some fungi become noticeable when
fruiting, either as mushrooms or molds.

60. • Many fungal species have long been used as a direct
source of food, such as mushrooms and truffles, and in
the fermentation of various food products, such as wine,
beer, and soy sauce.
• More recently, fungi are being used as sources of
antibiotics used in medicine and various enzymes,
including cellulases, pectinases, and proteases, which
are important for industrial use or as active ingredients of
detergents.

61. • However, many fungi produce bioactive compounds
called mycotoxins that are toxic to animals and humans.
• Several species of fungi are significant pathogens of
human and other animals.
• They are also the causes of diseases of crops (e.g. rice
blast disease) and food spoilage, thereby proving that
they have a large impact on human food supply and
local economies.

62. Foodborne Illnesses Caused
by Prions:

63. • Prions refer to proteinaceous infectious particles (PrP).
• They are small glycosylated protein molecules found in
brain cell membranes.
• Prion disease, also called transmissible spongiform
encephalopathies (TSEs), create spongiform
pathological changes in the brain, resulting in
encephalopathy or brain damage.
• Prion diseases are fatal neuro-
degenerative disorders in humans and
other animals.

64. • Mad Cow Disease is the best known bovine spongiform
encephalopathy (BSE).
• An infected cow is observed to be disoriented, irritable
and unable to stand or walk properly.
• Most cases in Great Britain occur in dairy cow’s between
three to six years of age. Milk production decreases and
the animals show nervousness, aggression, abnormal
posture, poor coordination, and difficulty in rising.

65. • BSE is a chronic, degenerative disease that affects the
central nervous system of cattle.
• It also affects sheep, the disease being called scrapie.
• The incubation period takes months or years and the
illness is progressively debilitating.
• There is no treatment and the infected animal dies.
• BSE is believed to affect goats as well.
This is of no interest to consumers in the
Philippines who relish calderetang
kambing and other indigenous cooking of
goat meat.

66. • The first case of BSE in humans was observed in 1989
and was believed to have been transmitted from beef to
humans when contaminated bovine offal was used as
animal feed.
• Offal is made from the remains of butchered animals.
This practice is now banned.
• Creutzfeldt-jacob Disease (CJD) is a rare and fatal
neurodegenerative disease in humans.
• People affected are usually between 50 to
75 years old. The etiology is unknown.

67. • Typical clinical signs and symptoms include a rapidly
progressive dementia.
• A neuropathlogical examination reveals cortical
spongiform changes giving CJD another name –
spongiform encephalopathy.
• Majority of cases are sporadic (about 85%) while 10 –
15% are familial.
• An inherited abnormal gene causes the
latter.

68. • In the United Kingdom, with a population of about 58
million, there are only a few death a year caused by
genetic CJD.
• The sporadic type occurs all over the world at a rate of
about one case per million per year.
• The cause of sporadic CJD remains uncertain.
• However, the most favored theory
suggests that the normal prion protein in
the brain undergoes a spontaneous
change to an abnormal form that results in
disease.

69. How to Control Microbial
Growth?

70. • Any method to slow down the pathogenic organism, or
totally kill them, based on the application of the principles
of FATTOM will prevent/reduce the incidence of
foodborne illnesses.
• Food preservation techniques, whatever
traditional or newer ones, are effective means of
prolonging the shelf life of foods, and improving
palatability qualities in some cases because of
their effects on microbial life and growth.

71. Methods on How to Control
Microbial Growth
• Application of Heat
• Application of Low Temperatures
• Controlling pH Conditions
• Reduction of Free Oxygen
• Reduction of Available Water
• Role of other Chemicals
• Safe and Sanitary Food Handling

72. Application of Heat
• Adequate heat (proper temperature and period of
exposure) kills microorganisms by changing the physical
and chemical properties of their proteins.
• As structural proteins and enzymes are altered, the
organisms will die.
• Blanching and canning are examples of applying heat.
• Modern commercial canning processes
are complex and include a sterilization
process designed to eliminate the most
resistant bacterial spores, especially those
of the genera Clostridium and Bacillus.

73. • Boiling destroys nonspore-forming microorganisms
rapidly.
• To ensure safe drinking water, bring the water to a boil
and continue boiling it for a few minutes.
• In cooking meat, fish, poultry, eggs and other foods,
follow their suggested time and temperature for cooking
and use a reliable thermometer to measure
recommended internal temperatures.

74. Application of Low
Temperatures
• This category includes refrigerating and freezing.
• Modern refrigeration at 400F will stop or slow down the
growth of most microorganisms, although they can still
survive at refrigeration temperatures.
• Storage periods in refrigerated conditions for specific
kinds of foods have to be monitored to prevent food
spoilage.

75. • It is best to use refrigerated foods as soon as possible
and not to wait for the maximum storage time.
• Keep foods covered to avoid cross-contamination and
drying.
• Label and date foods, especially leftovers.
• Defrost regularly and do not crowd the food containers to
allow air to circulate.
• Check the temperature with a refrigerator
thermometer.

76. • Freezing halts the growth of all microorganisms.
Frozen foods should be kept solidly frozen.
• Check your freezer with an accurate thermometer.
• One way to detect if your home freezer is working
well is to check the ice cubes and a brick of ice
cream. These should be completely frozen, attaining
a temperature of - 180C or 00F throughout the
product.
• Avoid temperatures higher that 50F or
– 150C.
• Be sure to date food packages and use
moisture and vapor-proof packaging
materials.

77. Controlling of pH Conditions
• Lowering the pH of a food to a level where most
microorganisms cannot survive (<4.6) can be
accomplished by fermentation or acidification with
ingredients like vinegar, lemon juice or citric acid.
• Fermentation refers to the anaerobic and aerobic
metabolism of carbohydrates by microorganisms.

78. Reduction of Free Oxygen
• Some pathogenic microorganisms require free oxygen
for growth.
• Particle or complete removal of available oxygen will
therefore retard their growth and their metabolic activities
which are harmful to humans.
• Examples of processes that reduce free
oxygen include vacuum-packaging,
modern canning with hermetic seals, and
modified atmospheric packaging (MAP).

79. • Another method to reduce the amount of available
oxygen for bacterial growth is to coat the foods with wax
or other edible coatings, as done with fresh fruits and
vegetables in the US.
• Consumers should be aware that some of these coatings
are regarded as food additives.

80. Reduction of Available Water
• Drying is one of the oldest methods of food preservation.
• Modern techniques of dehydration still apply the same
principle of depriving the microorganisms of free or
available water for growth.
• The amount of free water or water activity needed by
molds, yeasts, and bacteria varies.

81. • Molds require the least water, which is why they can still
grow on dried fruit, jam, and jelly whereas bacteria
cannot.
• Most dry foods are relatively stable. However, they
should still contain over 20% water so kitchen shelves
should not be close to a stove or any source of heat.

82. Role of Other Chemicals
• Besides the chemical additives mentioned in lowering
the pH of food, other agents that may retard microbial
growth are nitrates, nitrites, salt, and sugar.
• Antioxidants and antibiotics also affect microorganisms
or reduce microbial growth.

83. Safe and Sanitary Food
Handling
• Bacteria and other microorganisms cannot move by
themselves.
• They need carriers to be transmitted to other places,
which could be living and nonliving habitats.
• The most common carriers of foodborne illnesses are
food handlers.

84. • Kitchen personnel are given an orientation that includes
personal hygiene, grooming, physical safety, etc.
• The food handler must likewise undergo an extensive
training on food safety and sanitation which includes
food preparation, storage, service, and other job-related
sanitary practices.

85. • Animals and insect-borne diseases are transmitted to
humans by exposure to the infected animal or insect.
• These include farm animals, domestic pets, marine
organisms, and household pests.
• How each group transmits pathogenic organisms and
how their transfer and conditions for growth should be
controlled.

86. Prevention of Foodborne
Illnesses:

87. • Most cases of foodborne illnesses can be
prevented through proper cooking or processing
of the food.
• In addition, because bacteria multiply rapidly
between 400F and 1400F, food must be kept out
of this temperature range.

88. Follow these tips to prevent harmful
bacteria from growing in food:
• Food Preparation Stage
– Refrigerate food promptly. If prepared food
stands at room temperature for more than two
hours, it may not be safe to eat anymore. Set
your refrigerator at 400F or lower and your
freezer at 00F.

89. – Prevent cross-contamination. Bacteria can
spread from one food product to another
throughout the kitchen and can get onto
cutting boards, knives, sponges, and counter
tops. Keep raw meat, poultry, seafood, and
their juices away from ready-to-eat foods.

90. – Handle food properly. Always wash your
hands for ate least 20 seconds with warm,
soapy water before and after handling raw
meat, poultry, fish, shellfish, or eggs. Wash
your hands after using the bathroom,
changing diapers, or touching animals.

91. – Wash utensils and surfaces before and after
use with hot, soapy water. Better still, sanitize
them with diluted bleach – one teaspoon of
bleach to one quart of hot water.

92. – Wash sponges and dish towels weekly in hot
water in the washing machine.

93. • Food Processing Stage (Cooking)
– Cook food with the appropriate internal temperature:
1450F for roasts, steaks, and chops of beef, veal, and
lamb. 1600F for pork, ground veal, and ground beef;
1650F for ground poultry; and 1800F for whole poultry.
Use a heat thermometer to be sure. Foods are
properly cooked only when they are heated long
enough and at a high enough temperature to kill the
harmful bacteria that causes illnesses.

94. • Food Storage Stage
– Keep cold food cold and hot food hot.
– Maintain hot, cooked food at 1400F or higher.
– Reheat cooked food to at least 1650F.
– Refrigerate or freeze perishables, produce,
prepared food, and leftovers within two hours.
– Never defrost food on the counter. Use the
refrigerator; cold running water; or the
microwave oven.

95. – Never let food marinate at room temperature,
refrigerate it.
– Divide large amount of leftovers to small,
shallow containers for quick cooling in the
refrigerator.
– Remove the stuffing from poultry and other
meat immediately and refrigerate it in a
separate container.

96. – Wash all unpackaged, and packaged and not
marked “pre-washed,” fruits and vegetables,
under running water just before eating,
cutting, or cooking. Scrub firm produce, such
as melons and cucumber, with a clean
produce brush. Dry all produce with a paper
towel to further reduce any possible bacterial
growth.
– Do not overcrowd the refrigerator. Cool air
must circulate to keep food safe.

97. Acknowledgment:

98. Textbook:
Food Safety and
Sanitation
By:
Mary Jean C. Ang
And
Hannah A. Balanon
C & E Publishing, inc., 2010
edition

99. End of Presentation