Causes, Effects and Prevention of
Contamination of Foods
Lecture Three
HIGH RISK FOODS
• These are foods which have high potential for
contamination. These include
– All cooked meat and poultry
– Cooked meat products e.g. gravy and stock
– Milk, cream, artificial cream
– Custard and dairy produce
– Egg products e.g. mayonnaise
– Seafood
– Cooked rice.
2
Food Contamination Sources
• Both direct and indirect food-contact surfaces, water, air, and
personnel are primary areas of concern as contamination sources in
a food plant.
• Food products may transmit certain microorganisms, causing food
borne illness from infections or intoxications.
• Food borne infections can result in two ways:
1. The infecting microorganism is ingested and then multiplies, as is
true for Salmonella, Shigella, and some enteropathogenic
Escherichia coli.
2. Toxins are released as the microorganisms multiply, sporulate, or
lyse. Examples of such infections are C. Perfringens and some
strains of enteropathogenic E. coli.
3
FOOD CONTAMINATION
• These are 3 main types of contamination of
high-risk foods:
– Microbial contamination
– Physical contamination
– Chemical contamination
4
MICROBIAL CONTAMINATION
• If food that has been contaminated by certain harmful
bacteria (pathogenic bacteria) or their toxins (poisons
produced by some of these bacteria) is consumed, food
poisoning may result.
• Bacteria are responsible for most food poisoning cases.
• Symptoms of food poisoning may include vomiting, diarrhoea,
fever and abdominal pain.
• It is important to remember that foods contaminated with
pathogenic bacteria will look, taste and smell perfectly
normal.
5
SOURCES OF MICROBIAL
CONTAMINATION
•
•
•
•
•
•
•
Human Beings
Raw foods
Insects
Rodents
Dust
Refuse and waste food
Animals and birds
6
VEHICLES OF MICROBIAL
CONTAMINATION
•
•
•
•
•
Hands
Clothes
Equipment
Hand-contact surfaces
Food-contact surfaces
7
CHEMICAL CONTAMINATION
• Chemicals, including pesticides, bleach and
other cleaning materials can contaminate
food if not used carefully.
• For example, store cleaning fluids separate
from foods to prevent tainting and
contamination if there is a spillage.
8
SOURCES OF CHEMICAL CONTAMINATION
Meal preparation
Storage
Environment
FOOD
FOOD
Packaging
Agriculture
Animal
Husbandry
Processing
9
PHYSICAL CONTAMINATIONS
• These are “foreign bodies” which may find their
way into food and normally cause harm.
• Examples include:
– Bolts, nut, pieces of metal
– Cardboard pieces
– Hairs
– Droppings
– Glass
– Pieces of food(bones)
– Grease and oil
10
Control / Prevention of Contamination
• Keep food covered
(whenever possible)
• Do not use defective
equipment
• Do not use dirty wiping
cloths
• Handle foods with plates,
tongs and trays
• Always separate raw foods
from cooked foods
• Do not use the same
equipment for both raw &
processed food
• Prevent animals from food
rooms
• Remove waste food and
refuse from food
processing area
• Keep food & equipment
from the floor
• Use the right disinfectant
and cleansing technique
• Purchase food from
reputable sources
11
Good refrigeration practices
12
Bad refrigeration storage practices
13
Hygienic Kitchen Environment
14
Unhygienic Kitchen Environment
15
FOOD POISONING AND FOODBORNE DISEASES
• Food poisoning is illness resulting from
consuming contaminated or poisonous food
• Symptoms show within 1 to 36 hours and can
last from 1 to 7 days
• Symptoms include:
– Abdominal pains
– Diarrhoea
– Nausea and vomiting
– Fever
16
• In many illnesses, the disease-causing
microorganisms may remain with the person
after recovery. Even when evidence of illness
passes some of the causative microorganisms
may remain as a source of recontamination.
• A person with this condition is known as a
carrier.
• As a result great attention must be given to
areas such as our skin, fingernails, fingers, hair
eyes, mouth, nose and excretory organs in order
to prevent cross contamination
17
CAUSES OF FOOD POISONING
• Bacteria
• Viruses
• Chemicals e.g. Insecticides,
weedkillers
• Metals
• Poisonous plants
18
COMMON BACTERIA POISONING
• Salmonella poisoning
• Clostridium perfringens poisoning
• Staphylococcus aureus poisoning
19
FOOD PRESERVATION
• Preservation is the treatment of food to prevent
spoilage or unwholesomeness
• Methods of preservation include:
– High temperatures (pasteurization,
sterilization, cooking etc)
– Low temperatures (refrigeration)
– Dehydration (removal of moisture)
– Chemicals (salt, sugar, acids and SO2)
– Vacuum packing
– Physical methods (smoking)
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QUIZ ONE(1)
• Ama ate rice and gravy with eggs which had
been prepared earlier in the day. She run all
night amidst stomach ache and had to admitted
at the KNUST Hospital.
• What might be the cause for her illness?
• What is food poisoning?
• What is the difference between food infestation
and food intoxication?
21
Which of the following best describes sanitation as
applied to the food industry:
• Creation of healthy processed food
• The creation and maintenance of good health
• Creation and maintenance of hygienic conditions
• the application of a science to provide wholesome
food
Science of sanitaion relates to control of the following except
a. Biological
b. Chemical
c. and physical
hazards in a food
environment
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Term paper
• Write a five page literature review on current status
of food borne diseases (including Ghana) and their
impact on the economy and its development
• You are to defend the topic, poor hygiene is more
costly than maintaining good hygiene in a food
industry
• Critically examine how to manage pest and rodent in
a typical cereal processing facility.
• Discuss the role of 10 microbes associated with food
spoilage and / or food related illnesses.
Submission last Friday before Mid-Semester Exams.
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Sources of food contamination,
Effects and Prevention
Lecture Three
• What are the sources of contamination?
• How do we get food contamination?
Food Contamination Sources
• Generally from the environment-hence
emphasis on hygiene and sanitation
• Primary areas of concern as contamination
sources in a food plant:
Direct and indirect food-contact surfaces
Water
 Air
Personnel are
FOOD CONTAMINATION
These are 3 main types of contamination:
– Microbial contamination
– Physical contamination
– Chemical contamination
MICROBIAL CONTAMINATION
• If food that has been contaminated by certain harmful
bacteria (pathogenic bacteria) or their toxins (poisons
produced by some of these bacteria) is consumed, food
poisoning may result
• Bacteria are responsible for most food poisoning cases.
• Symptoms of food poisoning may include vomiting, diarrhoea,
fever and abdominal pain.
It is important to remember that foods contaminated with
pathogenic bacteria may look, taste and smell perfectly
normal
Food borne Infection
Food borne infections can result in two ways:
1. Food products may transmit certain microorganisms,
causing food borne illness from infections or intoxications
2. The infecting microorganism is ingested and then
multiplies, as is true for Salmonella, Shigella, and some
enteropathogenic Escherichia coli
3. Toxins are released as the microorganisms multiply,
sporulate, or lyse. Examples of such infections are C.
Perfringens and some strains of enteropathogenic E. coli
FOOD POISONING AND FOOD-BORNE
DISEASES
• Food poisoning is illness resulting from consuming
contaminated or poisonous food
• Can be caused by eating food contaminated with
bacteria, viruses, chemicals or poisonous metals
such as lead or cadmium. Most food poisoning,
however, is caused by bacteria
• Symptoms show within 1 to 36 hours and can last
from 1 to 7 days
• Symptoms include:
– Abdominal pains, Diarrhoea, Nausea and
vomiting, Fever
Food poisoning
• In many illnesses, the disease-causing microorganisms
may remain with the person after recovery. Even when
evidence of illness passes some of the causative
microorganisms may remain as a source of
recontamination.
• A person with this condition is known as a carrier.
• As a result great attention must be given to areas such
as our skin, fingernails, fingers, hair eyes, mouth, nose
and excretory organs in order to prevent cross
contamination
CAUSES OF FOOD POISONING
• Bacteria
• Viruses
• Chemicals e.g. Insecticides,
weedkillers
• Metals
• Poisonous plants
COMMON BACTERIA POISONING
• Salmonella poisoning
• Clostridium perfringens poisoning
• Staphylococcus aureus poisoning
SOURCES OF MICROBIAL
CONTAMINATION
•
•
•
•
•
•
•
Human Beings
Raw foods
Insects
Rodents
Dust
Refuse and waste food
Animals and birds
VEHICLES OF MICROBIAL
CONTAMINATION
•
•
•
•
•
Body/hands
Clothes
Equipment
Hand-contact surfaces
Food-contact surfaces
HIGH RISK FOODS
Foods which have high potential for
contamination
– All cooked meat and poultry
– Cooked meat products e.g. gravy and stock
– Milk, cream, artificial cream
– Custard and dairy produce
– Egg products e.g. mayonnaise
– Seafood
– Cooked rice.
CHEMICAL CONTAMINATION
• Chemicals, including pesticides, bleach and
other cleaning materials can contaminate
food if not used carefully
• For example, store cleaning fluids separate
from foods to prevent tainting and
contamination if there is a spillage
SOURCES OF CHEMICAL CONTAMINATION
Meal preparation
Storage
Environment
FOOD
FOOD
Packaging
Agriculture
Animal
Husbandry
Processing
PHYSICAL CONTAMINATIONS
• These are “foreign bodies” which may find their
way into food and normally cause harm eg:
– Bolts, nut, pieces of metal
– Cardboard pieces
– Hairs
– Droppings
– Glass
– Pieces of food(bones)
– Grease and oil
– Any other from your experience?
Prevention of contamination
• Practice general good hygiene
• Use controlled practices
• Use standard methods to preserve food
Control / Prevention of Contamination
• Keep food covered
•
Do not use the same equipment
for both raw & processed food
•
Prevent animals from food rooms
•
Remove waste food and refuse
from food processing area
•
Keep food & equipment from the
floor
•
Use the right disinfectant and
cleansing technique
•
Purchase food from reputable
sources
(whenever possible)
• Do not use defective
equipment
• Do not use dirty wiping
cloths
• Handle foods with plates,
tongs and trays
• Always separate raw foods
from cooked foods
Good refrigeration practices
Bad refrigeration storage practices
Hygienic Kitchen Environment
Unhygienic Kitchen Environment
Preservation
Methods of Food Preservation
• Preservation is the treatment of food to prevent
spoilage or unwholesomeness
• Methods of preservation include:
– High temperatures (pasteurization, sterilization,
cooking etc)
– Low temperatures (refrigeration)
– Dehydration (removal of moisture)
– Chemicals (salt, sugar, acids and SO2)
– Vacuum packing
– Physical methods (smoking)
Current status of food poisoning in
Ghana
• Reading and discussion (statistics/references)
• Each group will give 6 points
48