CHAPTER ONE

Microorganisms & Food

 Learning objectives
 By the end of the chapter the student is
expected to:
 Describe the role and significance of
microorganisms in foods
 Identify some microorganisms common to foods
 Identify the growth requirements of microorganisms
 Discover the intrinsic and extrinsic parameters of
foods that affect microbial growth
 Learning objectives

 Explain the growth kinetics of microbes

 Illustrate the sources of microbial contamination of
food
 Spot the different stages and processes at which
food may be contaminated
Role and significance of microbes

 What are microorganisms?

 tiny organisms

 are ubiquitous

 cause food spoilage

 Food borne infections

 also play positive role (food processing)

 Cont’d
 Key role
 Decomposition of complex organic materials into
simple compounds by heterotrophs
All organic matter
(CHO, Proteins, lipids)

Energy + Inorganic compounds

(NO3, SO4……)
Microbes common to food
 Bacteria (cont’d)

 Some species produce spores

 Some may produce toxins

 Types according to their effect

1. Harmful - pathogenic bacteria
2. Undesirable - cause decomposition of food
3. Beneficial - used in the production of various foods
(yoghurt, cheese, cultured milk)
4. Benign – neither helpful nor harmful (most bacteria)
 Moulds

 Multi-cellular
 Mycelia(filamentous ) morphology
 30 -100 µm in diameter
 Characterized by their display of a variety of colours
and recognized by their cotton like appearance
 They greater variations of pH (2 – 8) & temperature.
 Oxygen is an absolute requirement for growth.
 Yeasts

 Unicellular organisms (size > bacteria)

 Grow in an acidic pH range (4.0-4.5).
 Reproduce by forming buds
 They are creamy white in appearance.
 Act on sugar to give alcohol and CO2.
 Viruses

 Are infective microbes with size of 20 - 300 nm

(electron microscope)
 Obligate parasites
 Unlike bacteria, viruses cannot reproduce in the food.
 Food only serves as a reservoir and a transporting
mechanism until it is ingested.
 Example – Infectious hepatitis A, Norovirus
What are the main sources of microbes for
food contamination?
 The different habitats of microbes which could serve
as sources for food contamination are:
 Soil
 Air
 Water
 Human and animal body
 Sewage
 Plants and plant products
 Food utensils
 Insects, vermin, birds and inanimate objects
Selected Infectious Agents and Their Main
Habitats
Selected Infectious Agents and Their Main
Habitats
Growth Requirements of Microorganisms

 The growth and reproduction of microbes in food can

be controlled by certain factors.
 These controlling factors can be internal or external.
Intrinsic factors
 relate to the characteristics of the substrates (food
stuffs) that support or affect growth of microbes.
 Moisture content

 pH

 Nutrients

 Antimicrobial constituents

 Biological structures
1. Moisture requirement

 Water requirement of micro organisms can be defined

in terms of Water activity(Aw)
Water Activity of Various Foods
Lowest Aw Values Permitting Growth of Microbes
2. pH

 Most microbes is near

neutral (6.6-7.5)
 Most pathogenic
microbes is around 6-8
 Yeasts - 4.0-4.5
 Moulds - 2.0-8.0 (but
growth is greater in acidic
range)
 Bacterial- near neutral pH
pH values of some popular foods & microbes
3. Nutrients

 Most microbes need external sources of nitrogen,

energy, minerals and vitamins to support their
growth
 They prefer organic group of foods
 They use carbohydrates and proteins to obtain
carbon and nitrogen
4. Antimicrobial constituents

 Is the presence of certain naturally occurring substances in

the food that have been shown to have anti-microbial
activity.
 Some spices are known to contain essential oils that
possess antimicrobial activity
 Example:
 Coumarins – fruits and vegetables
 Lysozyme – cow’s milk and eggs
 Aldehydic and Phenolic compounds – herbs and spices
 Allicin – garlic
 Polyphenols – green and black teas
 Citric acid in fruits
5. Biological structures

 Are natural coverings of some foods and provides

excellent protection against the entry and subsequent
damage by spoilage organisms.
 Example:
 Testa of seeds
 Outer covering of fruits
 The shell of nuts
 Hide of animals
 Shell of egg
Extrinsic factors
 related to environmental factors that affect the growth
rate of microbes.
 are those properties of the storage environment that
affect both the foods and their organisms.
 Temperature
 Oxygen
 Relative humidity
 Presence and concentration of gases in the environment
 Other factors (Osmotic pressure, light, chemicals….)
 1. Temperature

 T° outside the range for growth have a lethal or inhibitory action

 The optimum temperature for the proliferation of most microbes is
from 14 - 40 °C.
 Psychrophilic - <20 °C (10-20 °C)
• Pseudomonas, Moraxella acinetobacter
 Mesophilic – 20-45 °C
• Lactobacilli, Staphylococci

 Thermophile - >45 °C
• Bacillus stearothermophilus, Bacillus coagulans, Lactobacillus

thermophillus
Preferred temperature ranges for 3 types of Bacteria
 2. Oxygen

 The presence or absence of oxygen or other gases may

encourage or discourage the growth of a particular type of
organism.
 Aerobic - Pseudomonas, Moulds, Yeasts

 Anaerobic - Clostridium species

 Facultative - Lactobacillus species, Staphylococcus aureus

 3. Relative humidity

 Foods with low water activity placed at high humidity environment

take up water, increase their water activity and get spoiled easily.
 Bacteria require a higher moisture than do yeasts and moulds
 Optimum RH for :
 Bacteria - ≥ 92

 Yeasts - ≥ 90%

 Moulds - 85-90%
4. Concentration of Gases

 Presence of gases like:

 Oxygen

 Carbon dioxide

 Ozone in the environment may facilitate or inhibit

micro organisms growth and multiplication.

5. Presence of other factors

 Osmotic pressure
 Light
 UV light

 X - rays

 Chemicals and chemotherapeutic agents like:

 Acids

 Alkalis

 Alcohols

 Salts

 Heavy metals
Bacterial Growth Kinetics
 Increase in number not size
 Multiplication of bacteria - Binary fission
 Under favourable conditions - every 20 or 30 minutes
 The growth is exponential
 The growth pattern exhibits four distinct phases:
 Lag
 Logarithmic
 Stationary growth
 Decline
Bacterial growth curve
Bacterial growth curve
Bacterial growth curve
Bacterial growth curve
Bacterial growth curve
Stages of food contamination

 Contamination can occur at any point/stage along the

chain.
 Production
 Processing
 Distribution/transport
 Storage
 Preparation
 Serving
Hazards Stages Control measures

Night soil, Chemicals, Avoiding of food sources,

Poor PH, Irrigation practicing good PH
water, Natural toxins

FP sanitation, Poor PH, Validation of Processes T/T°,

additives controlling of additives

Dirty vehicles, T°,

breaking of equipment Sanitation of vehicles, T° control

Dirty storing Maintaining storing area/premises

area/premises, T° hygiene, T° control

T°, Poor PH, cross Good PH, T° control

contamination

Poor PH of FH & Good PH, hygiene of utensils

consumer, equipment
CHAPTER TWO

FOOD SPOILAGE
 Learning objectives

 At the end of the chapter the student will be

able to:
 Define food spoilage and its manifestations
 Identify main causes of food spoilage
 Differentiate the different categories of foods based
on ease of spoilage
 Know consequences of food spoilage and
preventive measures
 What is food spoilage?

 Undesirable deterioration of the physical and chemical

properties of food, making it unsuitable for
consumption.
 It leads to change in odour, colour, flavour or texture.
 Food Spoilage …

 Property changes of food may be exhibited as:

 Decomposition
 Decaying
 Fermentation
 Rotting
 Souring &
 Germination

 Changes not necessarily harmful - large number of

microbes responsible for food spoilage are non-
pathogenic to man
Spoilage signs
 Odor
 Breakdown of proteins –

putrefaction
e.g. “rotten egg” smell
 Sliminess/texture change
 Discoloration
 Mould on bread, blue and green

mould on citrus fruit and cheese

Spoilage signs…

 Souring
 Production of acid
 sour milk from production of
lactic acid

 Gas formation
 Meat becomes spongy
 Swollen or bubbling packages and
cans
Food Types: Based on rate of spoilage
1) Highly perishable
 Meat
 Fruit
 Milk

WET
 Vegetables
 Eggs
2) Semi perishable
 Potatoes
 Nuts
3) Stable

DRY
 Rice
 Flour
 Dry beans
Causes of Food Spoilage

1. Microbial
 Bacteria
 Yeasts
 Moulds
2. Non-microbial
 Enzymes
 Parasites
 Environmental factor
 Insects
Microbial Food Spoilage
 Each food unique microbial environment
 Unique spoilage agents for each
 Why do microorganisms spoil our food?
 Food composition ideal source of nutrients for
microbes
 Availability of water and oxygen
 Suitable pH
 Factors that affect spoilage:
 Oxygen, T°, pH, Moisture content, Humidity
 Spoilage by Enzymes

 Organic catalysts
 Speed up chemical reactions
 Lead to Autolysis
 Cause browning and ripening features in certain
foods
Food spoilage causes…

 Parasites
 Parasites like tape worms, flukes and viral infections
cause spoilage of meat and meat products
 Chemical changes
 Occurs when there is reaction between food and the
surrounding environment/oxygen
 Physical changes
 When spoilage occurs due to dehydration, freezing,
heating, drying
 Food spoilage causes…

 Spoilage by insects:
 Worms, bugs, weevils, fruit flies, moths cause

extensive damage to food and reduce its nutritional

value and make it unfit for human consumption.
 External contaminants:
 This includes harmful chemicals like pesticides,

insecticides, containers, additives etc.

What happens when you eat spoiled food?

 Eating spoiled food caused by microbes can lead to

food borne illness: But not always!
 Food poisoning
 Food borne infections
 Most cases of food poisoning are due to common
bacteria such as:
 Staphylococcus
 Escherichia coli (E. coli)
 Clostridium botulinum
 Salmonella
 Campylobacter
Reasons for keeping foods from spoilage

 Deterioration may cause food to be wasted

 Approximately ⅓ of all food manufactured in world is

lost to spoilage
 Contaminated food can cause illness
 Money is saved when food commodities are kept from
spoilage
 When food is kept from spoilage, it maintains it
nutritive value
 It also ensures food is available for use even during
lean season
Control of Microbial Spoilage

 Cleaning and sanitation

 Processing environment
 Equipment
 Handling with minimal physical damage
 Washing (in some case)
 Proper storage temperature
 Rapid movement of food through processing
plant
 Food preservation
Food Preservation techniques
THANK YOU!
Learning Objectives

 At the end of the chapter you will be able to:

 Define food borne disease/illness
 Differentiate food borne infections and food borne
poisoning/intoxication
 Identify the causes, transmission method and
control measures of food borne illnesses
 Know what food borne outbreak is
 Know the measures taken to manage food borne
outbreaks
 Understand what HACCP is & its elements

57
What is Food Borne Illness?

 Is a disease which is caused by ingesting of food

which is contaminated by:
 Microbial cells

 Biological toxins

• Microbial toxins
• Poisonous plants
• Poisonous animals
 Harmful chemicals
• Intentional
• Accidental

58
Causes of Food Contamination

59
Common symptoms

Stomach Pain Diarrhea

Vomiting
Nausea
Headache

These are symptoms of a

FOODBORNE ILLNESS
60
Microbial food contamination

 The common microbes causing food borne illness

are:
 Bacteria  Viruses
 Salmonella
Hepatitis A
 Campylobacter
Norovirus
 Bacillus

 Staphylococcus

 Clostridium

 E-coli 0157:H7

61
Epidemiology

 2 million deaths/year due to contaminated food

worldwide (WHO, 2014)
 They have significant impact worldwide including
developed nation like the US.
 The Center for Disease Control and Prevention (CDC)
estimates for the US:
 76 million cases/year

 >300,000 hospitalization/year

 5000 deaths/year

 400-500 out breaks are reported each year

62
Epidemiology

Indeveloping countries like Ethiopia, the problem attains

great proportions due to many reasons:
 Poverty

 Lack of public health awareness

 Poor water supply

 Poor personal hygiene and

 Environmental sanitation

63
 According to the 2002-2003 Health and Health-related
Indicators MoH of Ethiopia:
 Dysentery and different parasitic infections were

among the ten top causes of illness

 Dysentery was among the leading causes of

hospital admissions and deaths

 The national average access to safe water was

28.4%
o 75.7% for urban &

o 19.9% for rural

64
Epidemiology

 National figure for safe excreta disposal was 11.5%

 49.7% for urban &

 3.9% for rural

 reported causes of outbreaks

 Typhoid fever

 acute diarrheal diseases

 bloody diarrhoea

 anthrax

65
Classification of Food Borne Diseases

 Depending on the causative agent they are grouped

into two:
1. Food-borne poisonings/intoxications &
2. Food-borne infections

66
67
1. Food Poisoning/Intoxication
 Caused by ingestion of microbial toxins, swallowing
of poisonous plants and animal tissues or due to the
consumption of food contaminated by chemical
poisonous.
 The main causes of food poisoning are:
 Staphylococcal food poisoning
 E. Coli food poisoning
 Gram positive spore forming bacteria
 Poisonous plants
 Poisonous animals
 Harmful Chemicals

68
I. Staphylococcal Food Poisoning

 Disease which occurs after eating food which has

been contaminated with staphylococcal organisms
like:
 S. aureus

 S. epidermides

 S. sapropyticus

69
Staphylococcus aureus

Toxin Enterotoxin (heat stable)

IP 1-7 hrs (usually 2-4hrs)
Foods involved Potato salad, Poultry, Sliced meat, Milk & Milk
products
Source Human & animal origin (human nose &
skin/wound)
Contributing Inadequate refrigeration & cooking or heat
factors processing of foods, practicing poor personal
hygiene, Keeping food at danger zone
Control Practicing good PH, Exclusion of infected
measures people from food handling, Proper handling of
high risk foods, Refrigeration of foods

70
 Haemorrhagic Colitis
Causative Escherichia coli O157:H7 (Shiga toxin)
agent
IP 2- 4 days
Symptoms Severe abdominal cramps, Bloody diarrhoea,
Nausea, Vomiting, Low-grade fever
Foods involved Ground beef, Unpasteurized apple cider,
Unpasteurized milk, Lettuce
Source Intestinal tracts of infected animals, Fecally
contaminated water
Control Thoroughly cook ground beef products,
measures Practicing good personal hygiene, Reheat
foods to 165°F for 15 seconds, Refrigerate
foods at 41°F or below.

71
II. Poisoning by Gram positive, Anaerobic
Spore forming bacteria

 Common food borne poisonings caused by gram

positive spore forming bacteria:
1. Botulism – caused by Clostridium botulinum, rod
shaped bacteria
2. Perfringens – Clostridium perfringens rod
shaped
3. Cereus – Bacillus cereus rod shaped bacteria

72
 Botulism
Toxin Neurotoxin (heat liable)
IP 12- 72 hours (average 1-2 days)
Symptoms Double vision, Difficulty speaking and
swallowing, Difficulty with breathing, Paralysis
Foods involved Home canned foods, Low acid (alkaline)
vegetables, Corn, Peas & other cereals
Source Soil, Plant crops, Intestine of animals
Control Heating suspected food to boiling temperature
measures for some time, Ensuring lower pH(<4.5),
Destruction of spores or inhibiting of their
growth, Creating aerobic conditions,
Refrigeration of foods to below 5°C,
Avoidance of home canned foods

73
Perfringens Food Poisoning

Toxin Enterotoxin
IP 8-24 hrs (8-12 hrs)
Symptoms Abdominal cramps, Watery diarrhoea, Nausea
Foods involved Meat dishes prepared one day and eaten the
next
Source Soil, Spices, Human & animal intestinal tract,
Sewage, Poultry, raw Meats
Control • Proper waste management
measures • Cold storage of foods
• Adequate cooking of foods
• Good personal hygiene of food handlers

74
Bacillus Cereus Food Poisoning

Toxin Enterotoxin
IP 10-16 hours
Symptoms • Abdominal cramps
• Watery diarrhoea
• Nausea
• Vomiting
Foods involved Meat pies, Rice, Starchy foods (potato, pasta)
Food mixtures (soups, sauces)
Source Soil, Dust and Water
Control • Thoroughly cook ground meat products.
measures • Cool cooked products to 41°F within 4hrs.
• Hold hot foods at or above 140°F.

75
III. Chemical Food Poisoning
 Caused by ingesting different chemicals with food
 It may occur in either of the following ways:
I. Accidental Poisoning
 Carelessly stored chemicals in food premises might
be mistaken for food ingredients and could be added
to food during preparation
II. Unauthorized additives
 Additives should be added with the right dose with
right person

76
Chemical Food Poisoning…

III. Residues of chemicals on raw food staffs

This refers to chemicals which have been applied to
control crops, vegetables and fruits during growing, storage
or processing and remaining as residues which finally may
reach mouth of consumers
Chemicals applied in food service establishments to
control rats, flies, cockroaches and other vermin may
contaminate carelessly exposed foods which finally may be
ingested with the food

77
Chemical Food Poisoning…

IV. Poisons resulting from containers

 From food utensils & equipment
 Toxic heavy metals (lead, cadmium, zinc, copper)
 Contamination from containers that are used to
store / hold chemicals
V. Radiation accident food contamination
 Radionuclide (Radium 226, Iodine 131, Strontium
90, Cesium 137) in the fallout from a nuclear test
explosion or a reactor accident can contaminate
foods

78
Chemical Food Poisoning…

VI. Food sources polluted by toxic/hazardous

chemicals such as pollution from industrial
effluents
 In areas where there is extensive industry and
mining, fish, vegetables and grains accumulate
concentrations of toxic substances such as lead
and mercury from industrial wastes/ discharges

79
 IV. Poisonous Animals
1. Paralytic shellfish poisoning
 By consumption of shellfish (mussels and clams)
 Ganyaulax Cantanella (poisonous sea weed)
2. Fish poisoning
 By eating of tetradon type of fishes

80
Poisonous Animals…

IP 5-30 minutes
Symptoms Trembling lips, Complete loss of power in
muscles of extremities and neck, Respiratory
paralysis
Control  Avoiding eating of shellfish when in doubt
measures and give enough caution for such foods as
to where they are harvested and whether
the poisonous weed grows in the area.
 Cooking has no effect on poison

81
 V. Poisonous Plants & Fungus
 Food poisoning due to the consumption of plants are
commonly related to the ingestion of certain toxic
fungi.
 The most common are:
 Mushroom
 Water hemlock
 Grass pea

82
 Mushroom Poisoning
 Certain species of mushroom, such as:
 Amanita phalloides &
 Amanita muscaria
 These fungi contain certain:
 Phalloidine & other alkaloids which are poisonous in
nature

Amanita phalloides Amanita muscaria

83
 Mushroom Poisoning…
 IP
 15 minutes to 15 hours
 Symptoms-
 Salivation
 Watery stools
 abdominal pain
 Excessive perspiration
 intense thirst
 Flow of tears &
 nausea
 Death in many instances
 Vomiting

 Cooking has no effect on the poison

84
 Fungal poisoning

 Ergot

 Ergot is produced by a group of parasitic fungus called

Claviseps purpurea
 These fungi produce the ergot poison in certain cereal
crops such as wheat, barely
 Ergotism is a crippling disease which affects different
areas of the body such as the extremities, legs, arms,
breasts

85
 Ergotism…
 IP
 Is very long as it is dependent on the consumption of
several meals containing the toxin
 Symptoms
 Gangrenous involvement of the limbs specially the
fingers, toes, occasionally ears and nose
 Weakness
 Headaches
 Painful cramps in limbs
 Itching of the skin

86
 Ergotism…
 Control measures
 Protecting the cereal grains from contamination by
ergot producing fungus during growing, storage and
processing of the cereals by application of
fungicides
 If possible, avoiding consumption of single cereal
grains such as barley & wheat for long period of
time
 Cooking or baking has no effect on the poison

87
 Other fungal toxins
 Aflatoxins
 Carcinogens produced in fungus-infected

grains and nut products

 Fumonisins
 Carcinogens produced in fungus-infected

corn
 Food borne Infections
 Caused by consuming foods or liquids contaminated
with:
 Bacteria
 Viruses
 Parasites
 These pathogens cause infection by:
 Invading and multiplying in the lining of the

intestines and/or other tissues.

 Mode of transmission – indirect

89
 Bacterial food borne infections
 The main causative agents of bacterial food borne
infections are:
 Salmonella
 Vibrio
 Shigella
 Camphylocter
 Listeria

90
Salmonellosis
Causative Salmonella sps.
agent
IP 6-72 hrs (12- 36 hrs)
Symptoms Diarrhea, stomach cramps, fever, loss of
appetite, headache, nausea & vomiting
Foods involved Milk, Egg, Poultry
Source Infected human & animal intestine
Control Hand washing, Thoroughly cooking of all
measures foods, Avoiding recontamination of cooked
foods, Do not use raw/cracked eggs
Use only pasteurized milk and milk products
Keep cold food below 5°C and hot food above
60°C, Educating FH on how to keep food safe

91
 Typhoid Fever
Causative Salmonella typhi
agent
IP 1-3 weeks
Symptoms Fever, headache, weakness, loss of appetite,
cough & rash, constipation (in adults)
Foods involved
Source Intestine of infected human, Water, Soil
Control • Practice good personal hygiene, Practice
measures basic food safety precautions, Avoid water
that might be contaminated, Do not drink
untreated surface water
• A vaccine for typhoid fever is available.

92
Shigellosis (Bacillary dysentery)
Causative Shigella spp.
agent
IP 1-7 days (1-3 days)
Symptoms mild to severe diarrhea, fever, nausea,
vomiting & cramps, Stools may contain blood,
mucus and pus
Foods involved
Source Intestines of infected persons, soil, food,
water
Control Practice good personal hygiene, Practice
measures basic food safety precautions, Avoid water
that might be contaminated

93
 Cholera
Causative Vibrio cholerae
agent
IP Few hrs to 5 days (2- 3 days)
Symptoms severe diarrhoea, vomiting, dehydration &
shock, death (if untreated)
Foods involved Seafood (fish, crab, shrimp, oysters), raw or
undercooked
Source Water, intestine of infected humans
Control • Thoroughly cook seafood
measures • Practice good personal hygiene
• Proper sanitation of food contact surfaces
and utensils
• Use a safe water supply

94
 Listeriosis
Cause Listeria sps. (Listeria monocytogenes)
IP 2-21 days
Symptoms Meningitis, Spontaneous abortions, Stillbirths,
Nausea, Fever, Diarrhoea, Encephalitis,
Vomiting
Foods involved Unpasteurized milk, Soft cheeses made from
unpasteurized milk, Raw fruits and vegetables
Ready to eat deli meats & salads, Hot dogs
Source Intestinal tracts of animals & humans, Soil,
Contaminated water, Manure
Control Thoroughly cook foods, Use pasteurized milk,
measures Proper sanitation of food contact surfaces and
utensils, Thoroughly wash fresh fruits and
vegetables, Prevent cross contamination.

95
 Campylobacterosis
Causative Campylobacter jejuni
agent
IP 2-3 days
Symptoms Abdominal cramps, Headache, Diarrhoea,
Fever, Watery and occasionally bloody stools
Foods involved Poultry, Unpasteurized milk, Raw meat (beef,
pork, mutton), Shellfish
Habitat Normal microflora of most animals & poultry,
Contaminated water, Infected pets
Control Thoroughly cook meat, poultry and fish,
measures Proper hand washing after handling raw meat,
poultry and seafood, Use pasteurized milk,
Use a safe water supply.

96
 Viral Food borne infections
 The main are:
 Norovirus

 Hepatitis A

 Rota virus

97
 Rotavirus gastroenteritis
Cause Rotavirus
IP 1–3 days
Symptoms Vomiting, watery diarrhoea, abdominal pains
and mild fever
Foods involved Ready-to-eat foods such as salads,
sandwiches, baked products, contaminated
water
Habitat Human faeces, faecal contaminated waters,
faecal contaminated food
Control Prevent ill food workers from working until
measures fully
Recovered, Ensure that food workers practice
good personal hygiene, Avoid cross
contamination, Clean and sanitize food
contact surfaces, Use potable water 98
 Hepatitis A

Causative Hepatitis A virus

agent
IP 10-50 days
Symptoms Loss of appetite, Nausea, Vomiting, Fever,
Jaundice
Foods involved Seafood, Any food handled by an infected
food handler
Habitat Intestinal tracts of infected humans,
Contaminated water
Control Thoroughly cook seafood including oysters,
measures Practice good personal hygiene

99
Parasitic food borne infections

 The main causative agents which lead to

parasitic food borne infections include:
 Giardia

 Amoeba

 Tania

 Trichinella

100
 Giardiasis
Causative Giardia lamblia
agent
IP 1-4 weeks
Symptoms Diarrhoea, Bloating
Foods involved Water, Any food handled by an infected food
handler
Habitat Intestinal tracts of infected animals & humans,
Water
Control Proper disposal waste, drinking of chlorinated
measures water, Cooking contaminated foods, Boiling
suspect water, practice good personal
hygiene

101
 Trichinosis
Causative Trichinella spiralis
agent
IP 1 day – 8 weeks
Symptoms Diarrhoea, Fever, Profuse sweating,
Weakness, Muscular pain, Swelling around
eyes
Foods involved Pork, Wild game (bear)
Habitat Muscle tissue of infected animals
Control • Thoroughly cook pork and wild game
measures • Storing infected meat in a freezer with a
temperature no higher than -13⁰F for 10
days will also destroy the parasite

102
What is food borne disease outbreak?

 Food borne disease outbreak:

 The occurrence of two or more cases of a similar

illness resulting from the ingestion of a common

food.
 An unexpected increase of a similar illness and

food is a likely source.

104
 These factors can be categorized into 3 groups:
1. Microbiological contamination of food
2. Improper time / temperature control
3. Other sources of contamination

105
1. Microbiological contamination of food

 Use of risky foods (raw, undercooked, unpasteurized)

 Cross-contamination(The process by which bacteria
are transferred from one area to another)
 Infected food handlers
 Poor personal hygiene
 Unsanitary dish ware & utensils
 Improper food handling procedures
 Unhygienic food preparation area
 Improper handling of leftovers

106
2. Improper time / temperature control

 Inadequate cooking
 Unsafe food holding
(danger zone) - 4°C
and 60°C
 Improper cooling
 Inadequate reheating

107
3. Other sources of contamination

 Insects and rodents

 Chemicals

108
How can we identify foodborne disease
outbreaks?

 Food borne illness complaints from private

citizens
 Medical evaluations of ill individuals from
healthcare professionals at hospitals, clinics, or
physician offices
 Routine surveillance and case investigation
of reportable diarrheal illnesses by
epidemiologists and public health nurses at state
and local health departments

109
How can we identify foodborne disease
outbreaks?
 Routine laboratory testing and techniques
conducted by microbiologists
 Information received through the media and
public information officers
 Reports from state and federal food safety
regulators and environmental health
specialists

110
Investigation of foodborne disease
outbreaks

 Food borne disease out breaks are among the

common occurrences everywhere.

 Why we do an investigation?

 To prevent reoccurrence of food borne disease

out breaks systematic investigations have to be
made.

111
 Objectives
 To identify the cause, the risk factor(s), or source of
infection
 To determine how the food staff became contaminated
 To implement interventions or corrective actions to
prevent others from becoming ill
 To fulfill statutory obligations and respond to public and
political concern
 To evaluate existing recommendations or strategies for
preventing similar outbreaks
 To educate responsible people in the prevention of
similar occurrences

112
 Investigation procedures
1. Take prompt action whenever outbreaks occurred or
reported
2. Immediately visit and make a complete inspection of
the places where the suspected foods were consumed
and make a complete inspection
3. Interview as many persons as possible that partook of the
suspected food
4. Prepare a questionnaire suitable for the outbreak to be
completed for each person. It should contain pertinent
questions
5. If patients to be visited are hospitalized or being treated,
obtain information from the responsible physician

113
 Investigation procedures

6. Obtain specimens of stool/vomits from ill

persons
7. Collect and obtain for laboratory examinations
from the suspected food or beverage that was
served and appropriate specimen from the
victims or the food handlers
8. Arrange for the immediate laboratory
examination of the food samples and specimen
collected for conformed diagnosis

114
Personnel involved in investigation

 Epidemiologist (public health practitioner)

 Environmental health officer (food safety controller)
 Laboratory professional (microbiologist, toxicologist)
 Physician (clinician)
 Others (community leaders, press officer, Hospital
director, Secretarial and logistic support)

115
Env’t Health Investigator

The Env’tal Health Investigator focuses on

Contaminated food:
Receives foodborne illness complaints
Investigates suspected food and/or food establishment
• Interviews food workers and managers
• Examines food storage, handling, preparation
• Identifies factors that resulted in food contamination
• Collects environmental and food samples
• Collects paperwork
Implements control measures
 Epidemiologic Investigator

The epidemiologist investigator focuses

on cases:
 Analyzes data from pathogen- specific surveillance &
identifies clusters
 Characterizes cases by time & place
 Plans epidemiologic studies
 Interviews cases and healthy controls
 Analyzes and interprets results of epidemiologic studies
 Public Health Nurse

The public health nurse focuses on

patients:
 Interviews patients
 Collects clinical specimens from
patients
 Administers questionnaires for
epidemiologic studies
 Advises patients on how to prevent spread of
illness
 Provides public health education
 Laboratory Investigator

The laboratory investigator focuses on

specimens:
 Analyzes clinical, food, and
environmental specimens
 Interprets test results
 Advises team about tests and collection, handling,
storage, and transport of specimens
 Coordinates additional testing by partner laboratories
Prevention Measures

Trace back Investigations

Epidemiologic Environmental
Investigations Assessments

Laboratory
Investigations
FOOD BORNE OUTBREAK INVESTIGATION FLOW CHART

121
How we can prevent food borne disease?
Hazard Analysis and Critical Control Points
(HACCP)

 What is HACCP?
 Systematic preventive approach that identifies
specific hazards and measures for their control to
ensure the safety of food.
 A tool to assess hazards and establish control systems
from farm to table that focus on prevention rather than
relying mainly on end-product testing.
 Before doing HACCP Flow diagram should be
developed

123
 HACCP Principles

1. Assess the hazards and risks

2. Determine the CCP(s) required to control the identified
hazards
3. Establish the critical limits that must be met at each identified
CCP
4. Establish procedures to monitor the CCP(s)
5. Establish corrective actions
6. Establish procedures for verification that the HACCP system
is working correctly
7. Establish effective record-keeping systems that document
the HACCP plan

124
 1. Conduct a Hazard Analysis

 Assess the hazards and risks associated with the

growing, harvesting, raw materials, ingredients,
processing, manufacturing, distribution, marketing,
preparation, and consumption of the food in question.
 Hazard
 Biological
 Chemical
 Physical

125
 2. Determine Critical Control Points

 A CCP is an operation or step by which preventive or

control measures can be exercised that will eliminate,
prevent or minimize a hazard that has occurred prior to this
point.
 All hazards identified in step #1 (Hazard Analysis) must be
controlled at some point in the process
 2 types of CCPs:
 CCP1 – to control hazards
 CCP2 – to minimize hazards

126
3. Establish Critical Limits

 Critical limits
 One or more prescribed tolerances that must be met
to ensure that a CCP effectively controls a hazard.
 To prevent, reduce or eliminate hazards
 These limits can be obtained experimentally, from
regulatory sources, expert opinions and surveys
of the literature pertaining to a particular product.

127
 4. Establish Monitoring Procedures
 Monitoring is a scheduled observation of a CCP and its
limits
 Monitoring is essential because it:
 Tracks the operation of a process and predicts trends

that might eventually result in exceeding limits

previously set
 Determines if a critical limits being exceeded

 Provides confirmation or documentation of the HACCP

plan

128
 5. Establish Corrective Actions

 When there is deviation from an established CCP,

corrective actions must be taken to prevent a product
that may be unsafe from reaching consumers
 Corrective action must include:
 Correcting the problem and putting the process back in
control
 Placing the product on hold pending evaluation of safety

129
 6. Establish Verification Procedures

 Every HACCP plan should be examined to validate its

ability to control food safety hazards that are reasonably
likely to occur, and that the plan is being effectively
implemented
 Verification should include:
 Reassessment of the HACCP plan
 Review of CCP records
 Review of deviations
 Random sample collection and analysis
 Records review

130
7. Establish Record Keeping & Documentation
Procedures

 The HACCP plan must be on file at the facility

 It must include documentation relating to CCP’s and
any action on deviations and/or disposition of product
 Types of records could include:
 Processing

 Deviation

 Ingredients

 Product safety

 Storage and distribution

 Validation studies

131
Example of a flow diagram for the production of
frozen, cooked beef patties

132
 Limitations of HACCP
1. HACCP requires the education of non-professional food
handlers
2. To be effective, this concept must be accepted not only
by food processors but also by food inspectors and the
public.
3. Expert variability - experts will differ as to whether a
given step is a CCP and how best to monitor such steps
4. The adoption of HACCP by industry has the potential of
giving false assurance to consumers that a product is
safe, and, therefore, there is no need to exercise the
usual precautions between the purchase and
consumption of a product.

133
Merci!

134
Learning outcomes
 When you have studied this session, you should be able
to:
 Describe the categories of food and drink
establishments
 Explain the hygienic requirements that are applicable
in food and drink establishments
 Explain the hygienic behaviors required of food
handlers
 List the sanitary facilities required in food and drinking
establishments
 Describe the procedure for sanitary inspection in food
and drinking establishments

136
What is a food and drink establishment?

 Are places where food and drink is prepared in

large quantities for public consumption.
 Are also called food catering establishments.
 Food & drink establishments have a legal and
moral responsibility to provide safe food and
drink to the consumers.

137
 Types of food and drinking establishments
 According to USA FDA divided into 3:
1. Establishments open to public patronage
These are establishments open to the public at large all the time.
Commercial establishments (Restaurants, cafes, fast food outlets,
bars, hotels)
2. Establishments offering semi- public food service
1. These are food establishments that give service to persons to
whom other eating facilities are not available
2. Health institutions, educational institutions, prison institutions and
industrial plants
Establishments providing a limited type of food service
Private clubs, fraternal orders, various societies, churches and
religious affiliated organizations where service is provided to their
members only.
138
 Categories of FDEs
 There are several types of FDEs based on the service
they are providing.
 Restaurants
 Cafés
 Grocery
 Bakery
 Hotel
 Butcher shop
 Tea houses
 Tej bet
 Areki bet

139
Hygienic requirements of FDEs
1. Licensing
 There should be a system for licensing FDEs
 Woreda health office is responsible
2. Location
 The FDE should be:
1. Well away from any source of hazards (marshy areas,
waste disposal sites and flooding).
2. Conveniently accessible to staff and consumers.
 At a distance from public institutes such as schools and
health facilities.
 Access to clean air and natural lighting

140
 Hygienic requirements of FDEs

3. Sanitary facilities
I. Adequate & wholesome water supply from approved source
Hot and cold running water
Ice should be prepared from water of drinking quality

II. Adequate toilet and lavatory facilities for customers & workers
Conveniently located and accessible
Separate showers for males and females
Proper toilet seats which are easy to clean and urinals
Toilet not near and not opening to dining rooms or areas where

food is prepared
Proper wash hand basins with soaps
Toilets having self- closing doors (if possible)
Hand drying facility(preferably machine otherwise towel)

141
Hygienic requirements of FDEs
III. Proper waste collection and disposal systems
 Properly drained
 Washable, easy to clean and convenient to handle waste
containers(dust bins) with proper covers
 Wastes should be properly collected and disposed

IV. Proper plumbing connections(water & WW)

 Properly installed and maintained
 Proper types (non-corrosive or rusting types)
 No cross- connection of water and waste pipes
V. Proper insect & rodent proofing and control methods
VI. Keeping cleanliness of floors, walls and ceilings

142
Hygienic requirements of FDEs

VII. Adequate utensils of sanitary standard

VIII. Proper ventilation of all rooms
IX. Proper lighting of rooms, work areas, toilets
X. Dressing rooms together with lockers
XI. Properly trained, hygienic, and healthy food handlers

143
 Recommended equipment and utensils

 Food equipment and utensils should comply with

the following sanitary requirements:
 Should be of good repair and with no cracks
 No chips, pits or open seams that can hold

microorganisms
 Should be smooth and easily cleanable

 The equipment and utensils should be of approved

material
 Cause no corrosion or rusting

144
 Dish Washing in FDEs
 It has its own procedure and should be followed.
 Dish - plates, cups, glasses, spoons, forks and other
utensils.
 Significance of effective dish washing
1. Health aspect
 Health vs disease: dishes may serve to transmit many
diseases if they are not cleaned
 Aesthetic reason: people like to be served with clean
utensils
2. Economic aspect
 The consumer may refuse to eat or pay food served with
unclean dishes

145
 Dish Washing in FDEs
 Two methods of dish washing:
1. Manual - done by hands
2. Mechanical - done by machine
 Two accepted dish washing systems:
1. The three compartment
2. The two compartment

146
 Dish Washing in FDEs
 Essential steps in dish washing
1. Get ready wash materials and equipment
- Clean sinks or vats of 2 or 3 compartment
- Hot wash water(43°C to 49°C)
- Detergent or soap
- Scraper
- Garbage can
- Drying racks
- Sanitizing chemicals(disinfectants)

2. Scrap the dishes

3. Wash the dishes in compartment one
1. Wash each dish separately

147
 Dish Washing in FDEs
4. Rinse the dishes washed in compartment two
- This helps to remove soap or detergent retained while washing
at compartment one
- Rinsing is done by dipping repeatedly the dishes in warm clean
water

5. Sanitize the dishes in compartment three

 To ensure the dishes are free of pathogenic organisms and the
total bacteria count is also highly reduced
 The procedure is performed by immersing the articles in hot
water(77°C) or in a disinfectant solution such as Cl
Dry the sanitized articles in air
Store appropriately the sanitized dishes
Clean the vats

148
 Dish Washing in FDEs

Factors affecting cleaning performance

Time: contact time on the surface being cleaned

Action: physical force exerted on to the surface
Concentration: amount of cleaner used
Temperature: temperature of the cleaning water
Nature: composition of the dirt
Surface: nature of cleaned material

149
Food handlers’ health and hygiene

 Food handlers are a common source of food borne

diseases.
 The practice of good personal hygiene is essential for
anyone who handles food.
 A sick food handler with symptoms of diarrhoea, eye and
ear discharges, skin infections, open cuts and wounds,
or coughing should be excluded until full recovered.

150
Food handlers’ health and hygiene
Unhygienic practices by food handlers

Poor personal hygiene practice

Unguarded coughing or sneezing

The habit of licking the fingers

Nose picking or fingering the nose

Handling of handkerchiefs

Working in street clothing

Spitting in food-handling areas

Uncovered hair

Smoking in kitchens

151
 Sanitary Inspection of FDEs
 Is a set of activities concerned with the preservation of public health
and the investigation of environmental hazards in food
establishments.
Purpose of Inspection
 Sanitary inspection aims to investigate and detect:
→ Food spoilage and its sources

→ Food contamination and its sources

→ Provision for hygienic procedures (dish and hand washing, food

storage)
→ Provision of sanitary facilities (latrine, water, shower, hand
washing)
→ The proper location of the establishment

→ The hygienic practice of food handlers

→ Proper waste management (storage, collection and disposal)

→ The presence of vectors

152
 Sanitary Inspection of FDEs

Types of Inspection

1.Initial/complete inspection
 This is a detailed type of inspection, which should be
made when a property or establishment is first brought
under department control to determine compliance with
the law of the government that regulates food and drinking
establishments.
2.Routine inspection
 These are usually regular inspection of establishments
based on a field inspection form to determine compliance
with sanitary rules and regulations

153
 Sanitary Inspection of FDEs
3. Re-inspection
 A re-inspection would be made as a follow up on routine
inspection, particularly when significant violations are noted to
determine whether the needed correction have been made.

 Two forms of inspection:

I. The planned form: this is the programmed and routine
type
II. The unplanned form: this is incidental, occasional or
urgent type made based on call, information of an out
break

154
 Sanitary Inspection of FDEs
Preconditions for the inspection of FDEs
Inspection should be purposeful:
 To educate and persuade to monitor faults and to prevent the
occurrence of food borne diseases
It should be legal
 An inspector should be licensed and carries the proper
identification card and official letter of authorization
 Inspections should involve as a committee representatives of the
concerned legal authorities and offices such as the police, local
administration and the municipality in order to facilitate good
legal ground and backing
 Inspections initiated after the proper polite introduction with the
responsible management of the establishment
155
 Sanitary Inspection of FDEs

Preconditions for the inspection of FDEs

All establishments inspected with equal considerations

under the law
Inspections supported with a checklist besides to onsite
observations of situations
The presence of legal, original and timely work license
should be checked prior to starting inspection
 Unlicensed establishments should be reported to the
responsible authorities for action

156
 Sanitary Inspection of FDEs

Preconditions for the inspection of FDEs

Observations and findings recorded in duplicate, discussed
with the management of the establishment, signed by the
inspector, the responsible management and subordinate
observers present.
 The copy should be left at the establishment with the proper
recommendations and suggestions for correction and
improvement
Any actions of punishment should correspond to legal
procedures
All precautions considered when closing an establishment
157
 CHAPTER FIVE

FOOD SAFETY & PRESERVATION

Learning objectives

 After the completion of this chapter you will be able to:

 Identify the five keys for food safety

 Analyze quality control of food at different stages

 Define food protection and preservation

 Identify different food protection methods

 Analyze the difference between different food

preservation methods

159
Food safety

 Sanitary practice in food industries is the systematic control

of environmental conditions during at all stages of food
chain in such a manner that avoid food contaminating agents.
 Generally the protection of foods from deleterious effects
should begin at the source and should end when consumed.
Source
Processing
Transport
Storage
Distribution
Preparation
Serving

160
Five keys to Safer food

1. Keep Clean
 Wash hands before handling food and often during
preparation
 Wash hands after going to toilet
 Wash and sanitize all surfaces in equipment for food
preparation-protect kitchen from insects , pets
2. Separate raw and cooked food-
 Separate raw meat , poultry and seafood from other foods
 Use separate utensils for handling raw foods
 Store food in containers to avoid contact between raw and
cooked foods

161
Five keys to Safer food

3. Cook Thoroughly
 Meat, poultry , eggs and Seafood
 Bring soups in stews to boiling (ensure>70degree temp)
 Reheat cooked food thoroughly
4. Keep food at safe temperature
 Don't leave cooked food at room T° >2 hours
 Prompt refrigeration of cooked and perishable food
 Keep cooked food piping hot (>60 °C) prior to serving
 Don’t store food too long even in refrigerator
 Don’t thaw frozen food at room temperature

162
Five keys to safer food

5. Use safe water and raw materials

 Use safe water or treat to make it safe
 Select fresh and wholesome fruits
 Choose foods processed for safety - pasteurized milk
 Wash fruits and vegetables if eaten raw
 Don’t use food beyond expiry date

163
Food Preservation
 Food preservation is a technique by which foods are
kept for intended longer periods without altering their
natural state by applying different techniques.
 The main objective is to:
 Increase the storage life(shelf life) of foods and reduce wastage
 Prevent the development of infectious agents in the foods
 By
 Removing/inactivating of micro-organisms
 Inactivating enzymes
 Removal of insects, worms, rats and other vermin

164
What are the techniques?
 There are several techniques that may be applied to preserve
food.
1. Aseptic technique
 Is a technique of exclusion of contamination/contact with
spoilage agents
 Is by applying artificial covering for the food or consideration of
the natural protective covering of some foods
2. Removal of microorganisms
 This may involve techniques like the washing , trimming and
filtration techniques
3. Maintaining anaerobic conditions
 This is a technique of denial of access to oxygen for organisms
that are aerobic

165
What are the techniques?
4. Temperature control
 High temperature
 Low temperature

5. Reduced water availability

 Drying
 Freeze-drying (lyophilisation)
 Addition of high concentrations of solutes such as sugar or salt
6. Chemical-Based Preservation
 GRAS (Generally Recognized As Safe)

7. Radiation
 Ionizing
 Non-ionizing
8. Microbial Product-Based Inhibition
 Bacteriocins
 Fermentation

166
Food Preservation Principles
 Two general principles are employed in food
preservation.
1. Inhibition priciple
2. Killing principle
1. Inhibition principle
 Food preservation is achieved by inhibition of growth and
multiplication of microorganisms.
 Reduction of water activity (drying & salting)
 Reduction in pH (fermentation & addition of acids)
 Use of preservatives (Sodium benzoate)
 Use of low temperatures (Chilling & freezing)
 Smoking – which has a drying and preservative effect

167
Food Preservation Principles

2. Killing principle
 In this principle, spoilage microorganisms are destroyed

(Killed) in the food, and the food protected against

subsequent contamination by being enclosed in an air tight
container.
 Heat treatment (pasteurization or sterilization)
 Irradiation
 Use of gases (ethylene oxide or ozone)- The gases destroy
both vegetative cells and spores.

168
Food Preservation Methods
 Food can be preserved for extended periods as much in
its natural state with the application of different methods
on the basis of the preservation techniques
 The application of these methods may vary with the
different types of foods
 Preservation methods can work employing different
techniques

169
1. The use of high temperature
 Heat is one of the oldest methods of destroying
microorganisms in food processing and preservation.
 Destruction of microorganisms by heat can be measured by
three methods:
1. Thermal death-time(TDT) - time required at any specified
temperature to inactivate an arbitrary chosen proportion of the
spores
2. Decimal reduction time(D-value) - time in minutes required
to destroy 90% of the cells at a given temperature.
3. F-value - time taken to expose food to destroy spores and
vegetative cells of a particular organism using different
temperatures (time equivalent of sterilization process).

170
Thermal profile of the heat treatment process

Bacterial destruction by heat is achieved due to the

function of time and temperature variation

171
1. The use of high temperature
I. Cooking/boiling
 Is the process of heat application to temperatures of

about 100°C for some time.

 Boiling of foods cannot completely destruct all

microorganisms but the vegetative cells of bacteria,

yeasts and moulds.
 Spore of some bacteria & heat resistant microbial toxins

cannot be affected at this temperature except inhibition

of their growth.

172
1. The use of high temperature
 Disadvantage of cooking
 It affects the nutritive value of food

 Gives cooked taste to food

II. Pasteurization
 Is a process of heat treatment of food with
sufficient holding time to assure the thermal
destruction of pathogens and organisms
responsible for fermentation and spoilage
without altering its nutritive value.
 Is a heat treatment process that kills part but
not all of the microorganisms present

173
1. The use of high temperature

 Three methods of pasteurization

 Low temperature long time (63°C for 30 minutes)
 High Temperature short time (72°C for 15 seconds)
 Flash method (88°C for 1-2 seconds)
III. Sterilization
 Is the use of physical or chemical means to eliminate all
microorganisms that are present in the food.
 Sterilization can be achieved by:
 Heating at high temperatures, e.g. 100-140°C
 Irradiation - kills bacteria, spores, and insects as well as
inactivates enzymes.

174
1. The use of high temperature
IV. Blanching
 Is a mild pre- cooking operation, which is often used to
reduce the bacterial load on vegetables by 90%
 It is the application of hot water or steam
 It wilts some bulky vegetables, prevents discolouring of
others, and removes some of the air from the tissue
V. Canning
 Is the application of a thermal sterilization procedure to
products packed in hermetically sealed containers
 It is one of the most widely used modern methods of
processing and preserving food
 It involves the careful preparation of food packed into a
sealed tin, glass or plastic container which is subjected to
definite elevated temperatures(above100°C) for the proper
period of holding time and then cooled
175
1. The use of high temperature
 Processes of canning
1. Preparation of the food - a variety of processes such as
grading, trimming, washing, blanching, precooking, etc are
employed
2. Filling of the container - this is accomplished mechanically or
by hand, requires to be carefully controlled
3. Exhausting – is the removal of air from the container before it
is sealed.
4. Sealing the container
5. Thermal processing- heating for an accurately predetermined
time and temperature
6. Cooling of the container and contents
7. Coding of cans

176
Drying
 Drying is a process by which removing of water content of
food through evaporation by using heat.
 Is most effective when combined with other methods of

controlling microbial growth such as salting

 Advantage  Disadvantage
 Dried foods have low weight  It is a slow operation
and reduced bulk therefore,  It is difficult to get uniform
easily stored and distributed application of heat
 End product may be stored at throughout the product
room temperature

177
2. The use of low temperature
 Low temperature preserve foods by retarding or preventing
the growth of spoilage organisms and by inhibiting the action
of natural autolytic
 Unlike high temperature, cold is not an effective means of
destroying pathogenic bacteria, viruses and toxins in foods
except retarding their multiplication and metabolic activities
 Preservation by low temperature could be achieved by:
 Chilling or
 Freezing temperatures

178
2. The use of low temperature
I. Chilling(refrigeration)
 Involves reducing food temperatures to below danger
zone, but above -1°C.
 Cold storage is normally used at 0°C to 8°C for
preservation of wide variety of food products.
 This temperature range is bacteriostatic and at the same
time slows the reaction rates of both enzymatic and
chemical processes which lead to deterioration and
spoilage.
 The temperatures for refrigeration are determined by the
kind of food, the condition of the food and the desired time
for keeping it.

179
2. The use of low temperature

II. Freezing
 Preservation by freezing is achieved by using temperatures
below 0°C(32°F)
 Is a dehydration method because the water in the food is
transformed to ice, thus making it unavailable for microbial
function.
 Freezing temperature depend on the kind of food and the
intended storage time
 Foods preserved for longer periods of time must be frozen to
below -18°C.
 A low temperature is important if prolonged storage life is
desired

180
4. Fermentation & Pickling
 Both methods work by lowering of the pH of foods.
 Fermentation
 The conversion of carbohydrates to carbon dioxide and
alcohol by yeast or bacteria (helpful).
 Pickling
 Is the immersion of certain food in concentrated natural
acid solution such as vinegar
 Fermented and pickled foods are semi perishable foods
and must be protected from moulds

181
5. Chemicals
 Mode of action:
 Decrease Aw (salt, sugar)
 Influence of ion balnce & pH (organic acids, salt)
 Antimicrobial effect (salt, nitrites)
I. Acid preservatives
 The effects of acids in the development of microorganisms
may be due to the hydrogen ion concentration or to the
toxicity of the un dissociated molecule or the anion
 The acid preservatives most widely used are:
 Benzoates (Sodium benzoate) – yeast & moulds
 Sorbates (Sordid acid or potassium sorbate) - moulds
 Propionates (Na or Ca propionate) - moulds
 Acetic acid - bacteria
 Lactic acid - bacteraia
182
Chemicals

II. Salting
 Salting is the addition of salt(mostly NaCl) to food
 The action of salt on microorganisms is osmotic effect
 The growth of micro organisms is inhibited by creating
hypertonic conditions
 Causes water to pass from bacterial cells to the medium thus
reduce available water for growth
Methods of operation in salting
 Rubbing - rubbing adequate quantity of dry salt into foods
 Immersion - food item is immersed into a concentrated salt
solution

183
Chemicals
III. Sugaring
 Action is similar to salt
 In concentrations of at least 65%, sugar inhibits the growth of
bacteria, yeasts and moulds
IV. Spices
 Spices have inhibitory and toxic effects on microorganisms
 The effect is due to the presence of essential oils
V. Smoking
 Oldest methods used to improve the quality of food

 It accomplishes preservation into two ways:

 Surface drying: removing moisture from the surface of the
food
 The deposition of a thick, brown, oily liquid containing the
bactericidal substance, which act as antiseptic on the surface
of the food
184
Chemicals
VI. Sulphur dioxide, carbon dioxide, benzoic acid
SO2: control carbohydrate deterioration
 is toxic to moulds and bacteria

CO2: inhibits the growth of bacterial

VII. Fumigation
Use gaseous chemicals like methyl bromide, hydrocyanic
acid and ethylene oxide
Used in the disinfecting of grain to destroy insect and
microbial infestations
Disadvantage: they can be absorbed readily by liquid or
greasy food products

185
Chemicals
VII. Quality improving agents
 Is the use of chemical compounds, which are used as

additives to protect the nutrient, flavour and physical

property of foods
 Antioxidant additives: maintain food freshness and

prevent spoilage
 Ascorbic acid: prevent or inhibit the activity of enzymes,

prevents the browning of fruits

 Poly-phosphates: control the growth of moulds

186
 Radiations
 Radiation - is the emission & propagation of energy through
space or material medium
 Radiations cause microbial death by inactivating cellular
components through energy absorbed within the cell
 Two forms of radiation energy:
 Ionizing energy(gamma rays, X- rays) and
 Non ionizing energy(UV)
 The type of radiation of primary interest in food preservation is
electromagnetic.

187
 Radiations
 The effect of preservation by radiation is affected by wave
length of radiation
 The shorter wave length being the most damaging to
microorganisms
 UV light
 is a powerful bactericidal agent, with the most effective
wavelength being 2600 A.
 It is non ionizing and is absorbed by proteins and nucleic acids,
which photochemical changes are produced that may lead to
cell death.
 The mechanism is due to the production of lethal mutations as a
result of action on cell nucleic acids.

188
 Radiations
 Gamma rays
 are EM radiations emitted from the excited nucleus of elements
such as Co and Cs, which are important in food preservation.
 This is the cheapest form of radiation since the source elements
are either by products of atomic fission or atomic waste
products.
 They have excellent penetration power
 Beta rays
 a stream of electrons emitted from radioactive substances.
 These rays posses poor penetration power
 X- rays
 are produced by the bombardment of heavy metals with high
velocity electrons(cathode rays ) within an evacuated tube.
 They are the same as gamma rays.

189
190
191
Microbial Product-Based Inhibition
 Bacteriocins
 Bactericidal proteins active against related species
 Some lead to DNA mutations
 Some inhibit protein or RNA synthesis
 Example
 Nisin - used in low-acid foods to inactivate Clostridium

botulinum during canning process

 Produced by some strains of Lactococcus lactis

192
Thank you!

193
Learning objectives

 At the end of the chapter, the students will able to:

 Define and identify potentially hazardous food
 Explain the sanitary practices and hygienic production of PHF
 Know the different methods to make these group of food safe
 Identify diseases associated with consumption of these foods if
contaminated
 Demonstrate different laboratory tests to check their quality

195
Potentially Hazardous Foods
 Are those foods that provide suitable conditions for rapid growth of
microorganisms.
 These include foods that are high in protein and high moisture
content.
 Need high care at all stages of food production chain.

 Milk & its products

 Meat
 Fish
 Poultry
 Egg
 Etc

196
197
Introduction

 Milk is the first natural food of all young

mammals immediately after birth.
 The lacteal secretion of the mammary glands of
a mammal, obtained by the complete milking of
one or more healthy cows The food value of milk
depends upon:
 milk fat
 milk solids-not-fat content
 If either of these contents is reduced its
composition also affected.

198
Composition of Milk
 Milk is most nearly perfect food.
 It doesn’t have Sufficient amount of Vitamin C & D and
Iron.
 The composition of milk is extremely complex.
 Water – principal constituent
 Proteins - Casein, Lacto albumin and Lacto globulin
 Sugar – Lactose
 Fats – 25 fatty acids (olein, palanitin and stearin)
 Highly variable
 Minerals - Ca, P, Na, K, Mg, Cl, SO4, Cu, Mn, I, Zn, Fe
 Vitamins- A, B2, B1, E, C, D
 Enzymes – Phosphatase, Lipase, Lactase
 Gases – CO2, O2, N2

199
Percentage composition of milk of different food animals

200
Physical Properties of Milk

 They are influenced by the composition of milk.

 They are also a great help in the processing and testing
of milk for adulteration.
 The major physical properties of milk are:
 Color

 Specific gravity- 1.027-1.035 (lactometer)

 Freezing point- -0.55°C (Cryoscopy)

 Boiling point- 100.17°C (thermometer)

 pH- 6.5 -6.8 (pH meter, pH colorimeter)

201
Milk Products
 Some of the common milk products that are made locally
or commercially from whole milk are:
 Cream

 Curd

 Whey

 Cheese

 Butter

 Ghee

 Margarine

202
What is milk hygiene?

 It is a study of all the methods necessary to ensure the

production, handling, and final delivery to the consumer
of clean, wholesome and unadulterated milk or milk
products.

 Purpose of milk hygiene

 Provision of safe and wholesome milk and its products
for the consumers.

 To prevent contamination of milk proper practices should

be followed from production to consumption.

203
Sanitary practices to be done during Production

Sources of contamination


1. Contamination from human discharge and wastes

 Construction of a proper waste disposal system
 Prevention of human discharge and wastes from
contacting animals and milk
 Practices of good personal hygiene
 Segregation of animals from human habitation
2. Contamination from air borne dust & droplets
1. Proper construction of the milking area
2. Sneezing or coughing away from milking containers during
milking
3. Provision of clean surroundings and avoidance of dusty
conditions during milking

204
Sanitary practices to be done during Production
3. Contamination from animal bodies, hides, udder and teats
Clipping, brushing, cleansing and sanitizing before milking
4. Milk containers (milking utensils & dirty water )
Proper washing and storing of milking containers
Using proper and easily cleanable utensils
Using only safe water for washing and cleaning
5. Milk handlers and milkers
Keeping the milker’s level of personal hygiene high
Washing of hands with detergents before milking
The milker should always wear clean garments while milking
6. Diseased cows
 Detecting and isolating affected animals
 Veterinary inspection and supervision of animals
 Treatment and vaccination of animals.
205
Sanitary Requirements for Dairy Farms

 In addition, the cleanliness of the following places should

be kept clean:
 Animals shelter (Barn, cowshed)

 Milking place

 Milk storing place

206
Milk-borne diseases
 Milk is an excellent food for man but it is an ideal medium for
the growth of micro-organisms.
 From the time milk leaves the udder of the animal, unless
adequate safeguards are maintained, it may receive bacteria
and other micro-organisms from the surroundings.

 Diseases resulting from  Diseases transmitted from

infected carriers infected cows
Typhoid & paratyphoid Tuberculosis (bovine)
fever Undulant fever (Brucellosis)
Tuberculosis (human) Anthrax
Diphtheria Q-fever
Scarlet fever Mastitis (bovine)
Foot & mouth disease

207
Methods of making milk safe

 The most common method of treating raw milk

is by regulating the temperature.
 There are at least five methods of treating
milk.
Boiling
Sterilization
Drying
Cooling &
Pasteurization

208
Boiling

 This is the easiest and most practicable method of

making milk safe in every home.
 It is raising the T° of the milk to boiling point and
maintaining the milk at this temperature for a few
minutes.
 Then the milk should be immediately cooled.
 If it has to be stored the temperature should be
maintained below 40°F.
 Disadvantages

It affects the nutritive value of milk, its flavour and palatability

and appearance.

209
Sterilization

 In this process milk is heated to destroy all micro-

organisms including spore forming.
 It can only be done by keeping the milk at a temperature
above normal boiling point for at least 20 minutes.

 Disadvantages
Change in the taste of the milk
Affects nutritive value of the milk

210
Drying
 This is a method by which the entire water constituent is
removed from the milk by evaporation.
 The solids remaining form milk powder (dry milk).
 Milk powder can then be made into liquid milk by adding a
proper amount of water.
 There are two known methods of drying:
1. Roller drying
2. Spray drying
 Drawbacks
Not a simple operation (untouchable at home)
Needs special equipment and arrangement

211
Cooling

 Is the process by which keeping the milk at 40°F or below

starting immediately after milking.
 This temperature range is essentially needed to arrest the
growth of micro-organisms specially Brucella organisms.
 However milk should not be allowed to freeze.
 This is very important especially if milk is going to be
delivered raw to consumers.

 Drawback
Doesn’t kill microbes

212
Pasteurization

 The process of heating every particle of milk and milk

products to a predetermined temperature and holding
this temperature for a predetermined time.
 Pasteurization:
 Destructs:
All pathogenic micro-organisms
A good number of other non-pathogenic and non-spore
forming bacteria and certain undesirable enzymes
 Keeps the nutritive value of the milk

213
Pasteurization

 Objectives of Pasteurization

 It has three objectives:

to ensure that all pathogenic micro-organisms
commonly found in milk are completely destroyed.
to safeguard the food value of milk
to ensure that other non-pathogenic bacteria and
certain undesirable enzymes, which may cause
spoilage, are inactivated or reduced to optimal levels

214
Pasteurization
 Basically pasteurization of milk involves three essential
steps:
 Heating raw milk to a predetermined temperature
 Holding at this temperature for a predetermined time
 Immediately cooling down to at least below 40°F

 two most important variables are:

 Pasteurization temperature &
 Exposure or holding time

215
 Methods of Pasteurization of Milk

1. The holding or vat method

 Is a method of holding the milk in a vat (container) to a
temperature of 63°C (145°F) for 30 minutes.
2. The high temperature-short time method
 Milk is rapidly brought to a temperature of 71°C (161°F) and
heated continuously for 15 seconds.
3. The ultra-high temperature (UHT) method
1. In this method the milk is heated to at least 88°C (191°F) for at
1-2 seconds.

216
Pasteurization

 Milk is said to be properly pasteurized it must satisfy

the following three conditions:
The milk must be cooled adequately (50°F or less)
before pasteurization so as to prevent the formation of
heat resistant staphylococcal enterotoxin.
The pasteurization equipment should function properly
and adequately.
Precautions should be taken to prevent any post
pasteurization contamination.

217
Pasteurization

 Limitations
It can only be effectively done on a commercial basis
It requires special and expensive equipment and budget
It requires skilled technicians to operate

218
Milk Testing

 The laboratory examination of milk is one of the most

valuable and necessary aids to the overall milk quality
control program.
 The laboratory tests are used to:
 Know the chemical composition
 Determine the bacteriological quality
 Check the presence of extraneous substances
 Check the effectiveness of pasteurization of a sample milk

219
Microbial milk testing

 There are four methods of determination of

microorganisms in food.
1. Standard plate counts for viable cells

2. The most probable numbers method as a statically

determination of viable cells
3. Dye reduction techniques to estimate numbers of
viable cells that posses reducing capacities
4. Direct microscopic counts for both viable and non
viable cells

220
Common Tests of Milk Quality
1. The alcohol- alizarin test
 This test is used to know the acidity of milk
 Procedure:
 Take about 5 ml of milk in a test tube
 Add equal amount of alcohol alizarin solution (0.2%)
 Mix the contents well
 Observe for presence of flakes and color of the contents

Parameter Normal milk Slightly acid Acid milk Alkaline milk

milk
pH 6.6 – 6.7 6.4 – 6.6 ≤ 6.3 ≥ 6.8
Color Red brown Yellowish Yellow Lilac
brown
Appearance No No Coagulation No
of milk coagulation coagulation coagulation
221
Common Tests of Milk Quality
2. Methylene-blue reduction test
Is used to determine the bacterial quality of raw milk.
It involves determination of time required for the disappearance
of color when methylene blue thiocynate solution is added to raw
milk
 Procedure
 In a test tube add 10 ml of milk
 Add 1 ml of standard methylene blue solution
 The sample is mixed and placed either in a hot water bath or in
an incubator at 35-37°C
 Observations are made at intervals of 15 – 20 minutes for an 8
hour period

222
Common Tests of Milk Quality

 Milk with a high bacterial content will decolorize the dye quite
rapidly whereas milk with low bacterial content retains the
blue color for several hours.
 Based on this test, milk can be graded as follows:
 Excellent: very low bacterial count
- Its decolorized time is about 8 hours
 Good: low bacterial count
- Decolourization time is 6 – 8 hours
 Fair: high bacterial count.
- Decolourization time is 2 – 6 hours
 Poor: very high bacterial count
- Decolourization time is below 2 hours

223
Common Tests of Milk Quality

3. Resazurin test
Is the most widely used test for hygiene and the potential
keeping quality of raw milk.
Resazurin can be carried out in different time ranges:

1. The 10 min resazurin test

 Is useful and rapid, screening test used at the milk
platform
2. The 1 hr & 3 hr tests
 Provide more accurate information about the milk
quality, but after a fairly long time.
 They usually carried out in the laboratory

224
Common Tests of Milk Quality
 Procedures
 Add 10 mls of milk into a sterile test tube
 Add 1 ml resazurin solution
 Stopper with a sterile stopper and mix gently the dye into the
milk
 Mark the test tube and incubate it
 Interpretation
Color Grade of milk Remark
Blue Excellent Accept
Light blue Very good Accept
Purple Good Accept
Purple pink Fair Separate
Light pink Poor Separate
Pink Bad Reject
White Very bad Reject 225
Common Tests of Milk Quality

4. Lactometer test and Freezing point determination

Both tests are used to detect adulteration of milk.
The lactometer test is designed to detect the changes in
density.
Cryoscopy is used to measure the freezing point of milk which
is -0.55°C for normal milk.

226
Common Tests of Milk Quality

5. Inhibitor test
Used to check the presence of chemicals in milk.
Milk collected from producers may contain drugs or pesticide
residues.
These when present in significant amounts in milk may inhibit
the growth of lactic acid bacteria used in the manufacture of milk
products like cheese, besides being a health hazard.
The suspected milk sample is subjected to a fermentation test
with starter culture and the acidity checked after three hours.
The value of the acidity obtained is compared with acidity of a
similarity treated sample, which is free from any inhibitory
substance.

227
 Common Tests of Milk Quality
 Procedure
 Three test tubes are filled with 10 ml of sample to be tested and
three test tubes filled with normal milk
 All tubes are heated to 90°C by putting them in boiling water for
3-5 minutes
 After cooling to optimum temperature of the starter culture, 1 ml
of starter culture is added to each test tube, mixed and
incubated for 3 hours.
 After each hour, one test tube from the test sample and the
control sample is determined
 If acid production in suspected sample is the same as the
normal sample, then the suspected sample does not contain
any inhibitory substances
 If acid production in suspected sample is less than in the
normal milk sample, then the suspected sample contains
antibiotics or other inhibitory substance
228
 Common Tests of Milk Quality

6. Phosphatase test
This test is used to determine the efficiency of
pasteurization.
The test depends up on the hydrolysis of a disodium
phenyl phosphate to form phenol and phosphate.
The addition of BQC(Dibromo Quimone Chloramines)
causes a blue colour reaction to occur with the phenol.
The presence of Phosphatase is demonstrated by a blue
reaction while the destruction of Phosphatase by proper
pasteurization fails to produce a blue colour.

229
 Common Tests of Milk Quality

 The intensity of colour is measured by a colorimeter.

 If no Phosphatase, it indicates that the milk was
adequately heated
 But if is present, it means that pasteurization was
incomplete or that raw milk has been added to
pasteurized milk.

230
Introduction
 Egg - is a body consists of an ovum surrounded by layers of
membranes and an outer casing of some type, which acts to
nourish and protect a developing embryo.
 Every part of egg is edible except the egg shell.
 Nutritionally eggs are a good source of protein and choline.

Components of Egg
 An egg consists of:
 Shell
 Membrane
 Albumin
 Yolk
 Chalazae
 Nutritional value of eggs

 Protein - 12.85%
 Fat - 11.15%
 Water - 73.80%
 Mineral salts - 1.60%
 Vitamins – A, B2, D & E
 Eggs are deficient in carbohydrates
Microbial spoilage of eggs

 Although most freshly laid eggs are sterile inside, the

shells soon become contaminated by fecal matter
from the hen and the lining of the nest.
 The main cause of contamination is washing of eggs
 An egg shell has a natural protective coating called
cuticle or bloom that resists the entrance of bacteria
and retains moisture inside
Microbial spoilage of eggs

 So when the eggs are washed this cuticle removes from

the shell and makes MOs to penetrate the shell easily
and multiply inside
 This causes egg spoilage
 Common symptoms of spoiled egg are green, black and
red rots, mustiness and sourness
 Washed eggs should be eaten as soon as possible
Quality maintenance
 Maintaining fresh egg quality from producer to consumer
is one of the major problems facing those engaged in
marketing eggs.
 Proper attention to production, distribution and point of
sale phases are vital importance in maintaining egg
quality
 The main production factors that affect the quality of
egg are the following:
 Breed of hen
 Age
 Feed
 Disease
 Handling/collecting eggs
 Housing conditions
Egg Storage

 Some of the traditional egg storage methods used

are:
 Clay pot

 Oil coating

 Water glass paste

 Water glass solution

 Lime water solution

 Refrigeration
Egg Storage

 All egg storage systems must meet the following

requirements:
 Minimize water loss by evaporation

 Mould and bacteria growth to be minimized

 Interior quality to be maintained

 The first two requirements can be met by ( 3-5 months)

 Coating eggs with oil or water glass

 Immersing eggs in lime water or water glass solution

 But all the three requirements can only met by:

 Refrigeration is best storage method
Packaging of Eggs
 Packaging is an important component in delivering
quality eggs to buyers.
 Packaging protects the eggs from:
 Micro organisms

 Natural predators

 Loss of moisture

 Tainting

 Temperature

 Crushing
Transport of Eggs

 For the successful transport of shell eggs three essential

requirements must be met.
 The containers and packing materials must be

protect the eggs against mechanical damage

 Care should be taken at all stages of handling and

transport
 The eggs must be protected at all times against

exposure to temperature that cause deterioration in

quality as well as contamination.
Egg Inspection Methods

 Eggs should first be inspected for cracks, leaks,

stains or dirt on the exterior and general bloodiness
or translucent spots in the yolk when candled.
 The most accurate test of interior quality is the
break- out method.
 In this test, around 10 eggs out of 100 are taken
randomly and checked for spoilage by breaking
them open to see what is inside.
Egg Inspection Methods

 In marketing, however, the above method can only be

used on a sample basis.
 It is not cost-effective
 There are three types of egg inspection methods:
 Candling

 Shaking using hand

 Brine test or immersing in water

Egg Inspection Methods
1. Candling/natural light
 Is the only method of testing eggs both internally and
externally, without breaking them.
 It is projecting of light through eggs that makes the
interior quality visible
 Fresh egg – translucent

- Yolk is faintly yellow in color

 Stale egg – dark or red(blood) spot seen

Fresh egg Stale egg

 Egg Inspection Methods

2. Shaking using hands

 Fresh egg – gives no sound when shaken

 Stale(bad) – makes sound

3. Brine test or immersing in water

 Fresh egg – will sink in water or 10% salt

solution
 Stale(bad) – floats
Poultry Hygiene

 Due to poor hygiene, poultry and poultry products are

responsible for a number of food borne illnesses
including salmonellosis, staphylococcal food poisoning
and botulism.
 The production of healthy poultry depends on the
maintenance of health and hygiene throughout the
entire production system.
 Contaminations from external sources should be
prevented, reduced or controlled.
Poultry Hygiene

 External contamination of live birds can come from

different sources like:
 Transport vehicles
 Poultry crates or modules
 Visitors or from the staffs
 Both ante mortem and postmortem inspection should be
applied for safety.
 Otherwise the poultry may be contaminated by
pathogenic microbes.
 Microbial Spoilage of Poultry

 There are many types of spoilage organisms, but

pseudomonas is the most important.
 They are found in large numbers on feathers but
rarely in the alimentary tract.
 There are also other species like:
 Salmonella

 Clostridia &

 Staphylococcus

 Pathogenic organisms in poultry are responsible for

gastro intestinal disturbances in humans.
Introduction

 Fish are cold blooded aquatic vertebrates covered

with scales and with gills
 It provides prime source of high quality protein and
vitamin D
 There are 27,000 species of fish (see foods)
 However, only a small number of the total species
are commonly eaten
 Some of these are: Cod, Tuna, Carp, Trout,
Mackerel, Snapper, Tilapia, Crab, Shrimps &
Haddock, Catch fish, Nile perch
Spoilage of fish

 The factors which principally contribute to the spoilage

are:
 Autolysis

 Self- degradation of protein with a subsequent

formation of various products by the action of

some undesirable enzymes
 Microbiological actions

 Are the main and fastest cause of spoilage

 Bacillus group of bacteria are the main causes

Signs of fresh & decomposed fish

Body parts Fresh Stale

Eyes Full and bright Gray and sunken

Flesh Firm, solid & elastic when Soft

pressed
Scales Full & firm Easily rubbed off

Abdominal Clean, not discolored Smell with reddish

cavity discoloration
Gills Clean, bright, not swollen Gray, brownish slimy,
swollen
Fresh fish Will sink if placed in water Floats in water
Fresh Stale
Inspection of Fish

 Check the condition of the eyes, scales and flesh of the

fish
 Check if gills are firm and elastic, test with fingers if any
doubt exists
 Split the fish and examine backbone for decomposition.
 If bone is pink or red from end of the tail towards the
head condemn it
 Test the blood of the fish with the fingers, if the fish is
stale there is a faint smell on the fingers
 The abdominal cavity shows discoloration when the
fish are stale.
Methods of Preservation of Fish

1. Salting
 Is a traditional processing method in most countries of
the world
 It is used in combination with drying and smoking
2. Canning – Promotes international trade
3. Refrigeration
Methods of Preservation of Fish

4. Drying
 Is the removal of water from fish by evaporation
 Factors which affect the rate of drying are:
 Relative humidity of the air
 Air velocity
 Air temperature
 Surface area of fish

5. Smoking
 Combines 3 effects:
 Antimicrobial effect

 Drying

 Cooking