MICROBIOLOGY AND FOOD

SPOILAGE
1. Introduction

2. Different Groups of Food Spoilage Microorganisms

3. Dynamics of Microbial Growth in Food

3.1. Factors Affecting Growth of Microorganisms

3.2. Different Phases of Microbial Growth

4. Examples of Food Contamination :

the Microbiology of some Commodities
 INTRODUCTION

FOOD
Eatable Organic Matter

Living or Freshly Killed or Preserved

FRESH FOOD
Vegetal (Fruits and Vegetables)

Animal (Fish and Meat, Dairy, Eggs)

 INTRODUCTION

FOOD SPOILAGE

Is matter of

FOOD SAFETY
Sanitary Levels
Pathogenic Microorganisms
Foodborne Illnesses

FOOD QUALITY
Stability and Shelf Life
Sensory Quality
Commercial Value
 INTRODUCTION

FOOD SPOILAGE

Is related to both

INTRINSIC Properties of the Food

and

EXTRINSIC Factors Applied to the Food

 MICROBIAL FOOD SPOILAGE

FOOD CATEGORIES AND SUSCEPTIBILITY TO

SPOILAGE

1. Highly perishable foods (high water content)

meat, fish and seafood, poultry, eggs, milk,
some fruits and vegetables

2. Semiperishable foods
potatoes, apples, nuts

3. Nonperishable foods (low water content)

sugar, flour, rice, dry beans
 INTRODUCTION

FOOD SPOILAGE
can be one or combination of the following

MICROBIAL (Contamination with Microorganisms)

CHEMICAL and BIOCHEMICAL

(Enzyme Activities; Chemical Reactions)

PHYSICAL (Mishandling; Inadequate Processing)

Due to INFESTATION (Insects, Rodents, Parasites)

 FOOD SPOILAGE

FOOD SPOILAGE
Occurs when the Food Deteriorates and Becomes Unpalatable
with Undesirable Flavors, Odors, Appearances and Textures as
the Result of Microbial Growth and Action
(e.g. sour milk, slimy meat, stinky eggs or fish)

FOOD SPOILAGE
Damages Food Original Nutritional Value and Organoleptic
Features
Reduces Food Shelf Life
Food Becomes Unsuitable to Eat

All Foods are Subject to Spoilage BUT

Not All Foods can Cause Foodborne Illness
 FOODBORNE ILLNESS

FOODBORNE ILLNESS or FOODBORNE DISEASE

Occurrence of Disease or Injury or even Death as a Result of

Eating a Food Contaminated with Pathogenic Microorganisms
able to Produce Toxins.

Pathogens may Not Produce any Off-Odours, Off-Flavors

or Discoloration

All Foods are Subject to Spoilage BUT

Not All Foods can Cause Foodborne Illness
 TYPES OF FOODBORNE ILLNESS

FOOD INTOXICATION or FOOD POISONING

Illness Due to the Ingestion of a Food in which Pathogenic
Microorganisms have Grown and Produced Toxic Metabolites
(e.g. toxins of Staphylococcus aureus; Clostridium botulinum
and perfringens; Bacillus cereus; and mycotoxins produced by
molds)

FOOD INFECTION
Illness Due to the Ingestion of a Food Containing Living
Pathogenic Microorganisms
(e.g. Salmonella; Campylobacter; Listeria; and Escherichia coli
strain 0157:H7)

Some illnesses are caused by a combination of the two

(e.g. Clostridium perfringens)
 MICROBIAL FOOD SPOILAGE

FOOD SPOILAGE BY MICROORGANISMS

Microorganisms are Initially Present on Harvested Crops and
Slaughtered Animals BUT Usually Not Inside Healthy Tissues

Food Contamination Occurs when Commodities Move

Throughout the Food System
Contaminated Foods are Foods in which Microorganisms are
Present and will Grow, or Foods which merely Serve as a
Carrier for a Microbial agent, Virus or Toxin

Agents of Foodborne illness may be present at all stages of

food chain (farm, processing, home preparation, storage,
marketing)
thus the importance of
Good Sanitation / Handling / Manufacture Practices
 MICROBIAL FOOD SPOILAGE

Microorganisms

Small Living Forms of Life Not Visible to Naked Eye

Exist Everywhere; Essential to many Planet Life Processes

Present in Air and Dust

Soil and Water
Humans
Animals
Plants
Surfaces and Utensils in Contact with Food
 MICROBIAL FOOD SPOILAGE

Microorganisms

Can be

DESIRABLE Assist in Palatable Food Manufacture

(Fermentations, Metabolite Production)

UNDESIRABLE Cause Food Spoilage and/or Foodborne

Illnesses
 GENERALITIES ON MICROORGANISMS

All Living Organisms (Large and Small)

Have one thing in common

The CELL

Complex Structure and Function

Nucleus Cytoplasm Cell Wall or Membrane

Unit of measurement = micrometer (1 m m = 0.001 millimeter)

 MICROBIAL FOOD SPOILAGE

FOOD SPOILAGE BY MICROORGANISMS

Major Microorganisms Involved in Food Spoilage

Bacteria

Molds

Yeasts
(Molds and Yeasts are known as Fungi)

Some Viruses and Parasites

 MICROBIAL FOOD SPOILAGE

MECHANISMS OF MICROBIAL FOOD SPOILAGE

Microorganisms Attack Basically All Food Constituents

Sugars
Starches
Cellulose
Fats
Proteins
 MICROBIAL FOOD SPOILAGE

MECHANISMS OF MICROBIAL FOOD SPOILAGE

Microorganisms Produce Different Metabolites

(Some Desirable and Some Not)

Acids (Sour Food)

Alcohol (Buzzy Beverages)
Gas (Foamy Food)
Pigments (Gives Color to Food)
Toxins (Cause Food Intoxication and Disease)
 FOOD SPOILAGE MICROORGANISMS

BACTERIA
Large Group of Single-Celled Microorganisms

Small Size : around 2 m m

Different Cell Shape

Round (Cocci)
Rod (Bacilli)
Spiral (Spirilla and Vibrios)

Different Cell Arrangement

e.g. cocci Grouped in Pairs (Diplococci)
Arranged in Bead-like Chains (Streptococci)
Bunched in Grape-like Clusters (Staphylococci)
 FOOD SPOILAGE MICROORGANISMS

BACTERIA
Bacterial System of Taxonomy = Classification System
Internationally Recognized
Family, Genera and Species Divisions Based on Genetics

Some Bacteria Form Resting Cells Known as Spores

Spore = Dormant Condition Resistant to Heat, Chemicals, UV
Light
Survival Strategy Against Environmental Stress

Spore Dormancy and Resuscitation are the Critical Rate

Limiting Steps in Food Processing and Spoilage

In Favourable environment, the Spore Germinates and Gives

Rise to a Single Vegetative Bacterial Cell
 FOOD SPOILAGE MICROORGANISMS

SOME BACTERIA INVOLVED IN FOOD PROCESSING

AND / OR SPOILAGE

In Food Processing
Lactic Acid Bacteria
(Lactobacillus spp. And Pediococcus spp.)

In Food Spoilage (Others than Pathogens)

Brochothrix Flavobacterium
Acinetobacter / Moraxella Serratia
Pseudomonas Micrococcus
Mesophilic Aerobic Bacteria
 FOOD SPOILAGE MICROORGANISMS

FUNGI

Microorganisms that Lack Chlorophyll

Differ from Bacteria by having Genetic Material Arranged on

Chromosomes, and a Membrane Surrounding the Nucleus

Includes Molds, Yeasts, Mushrooms and Rusts

Many Fungi are used in Food Industry

Brewing, Baking, Production of Antibiotics, Vitamins and
Food Proteins
 FOOD SPOILAGE MICROORGANISMS

MOLDS

Multi-Celled Complex and Large Organisms (up to 40 m m)

Are often Filamentous due to Mycelium Production

All Produce Spores which often Give Spoilage Molds Distinctive

Colours (Molds on Bread are often Blue/Green due to Spore
Colour)

Spoil mainly Acidic Foods (Fruits, Jam, Pickles) and Low-

Moisture Foods (Wheat, Barley, Rye, Bread, Nuts, Cheese)
 FOOD SPOILAGE MICROORGANISMS

MOLDS
Some Molds (Aspergillus niger, Aspergillus flavus, Fusarium
species)
Produce Toxins called Mycotoxins
(Aflatoxins, Ochratoxins, Fumonisins, Tricothecenes)
which have Carcinogenic and Mutagenic Effects.
Found in Cereal Grains, Peanuts, Coffee

Ergotism is Caused by the Ingestion of the Reproductive

Bodies of the Mold Claviceps purpurea.
Symptoms are Hallucinations, Convulsions and Gangrene
Rye has been Associated with Ergotism
 FOOD SPOILAGE MICROORGANISMS

SOME MOLDS RESPONSIBLE FOR FOOD SPOILAGE

Species of

Penicillium

Aspergillus

Fusarium

Rhizopus

Geotrichum
 FOOD SPOILAGE MICROORGANISMS

YEASTS
Unicellular Fungi which Usually Reproduce and Grow by Budding

Around 20 m m Long. Some Produce Spores

Spherical, Ellipsoidal or Ovoid Shape

Commonly Associated with Fermentation Processes (Wine,

Beer, Bread) (Saccharomyces spp.)

Spoil Mainly Acidic Food and Beverage (with Low pH) and
Particularly Fruits and Vegetables, Jams, Honey, Tomato
Sauce)

Examples of Food Spoilage by Yeasts

 FOOD SPOILAGE MICROORGANISMS

YEASTS

The most recent authority on yeasts recognised some 600

yeast species, within 81 generic taxonomic groups

Currently, in depth, detailed studies have only been carried out

on some 12 of these yeast species

Over 110 species of yeasts from 30 genera are listed as

associated with foods

However, relatively few of these yeasts are recognised

as food spoilage microorganisms
 FOOD SPOILAGE MICROORGANISMS

SOME YEASTS RESPONSIBLE FOR FOOD SPOILAGE

A limited number of yeasts, about 10, are responsible for the
great majority of instances of food spoilage

Saccharomycodes ludwigii(Spoilage of Apple Cider)

Zygosaccharomyces spp. (Explosion of Juice Glass Bottles,

Presence in Wine)

Candida sorbosivorans (Contaminant of Sorbitol Oxidation

During Vitamin C Production)

Yarrowia lipolytica and (Isolated from Poultry Meat)

Candida zeylanoides
 FOOD SPOILAGE MICROORGANISMS

YEASTS

A Few Yeast Species are Known to be Pathogenic to Humans

Candida albicans and Cryptococcus neoformans

Current Studies in UK on :

Emerging Food Spoilage Yeasts

Pathogenic Species of the Genus Saccharomyces

 FOOD SPOILAGE MICROORGANISMS

VIRUSES
Sub-Microscopic Acellular Agents
Much Smaller than Bacteria

Core made of DNA or RNA Nucleic Acids Surrounded

by Protein Coat

Can Reproduce Themselves only with Living Tissues

and Usually Cause Damage or Disease to its Host

Can be Carried in Food from one Person to Another

Example: Hepatitis and Parainfluenza May be Transmitted

via Food Products
 FOOD SPOILAGE MICROORGANISMS

PARASITES
Some Parasites that may be Dangerous

Trichinella spiralis

Can be Found in some Foods

Trichinosis results from the consumption of pork
infested by a nematode

Viruses and Parasites

Cannot Multiply Other than in Specific, Living Host Cells
Cannot Multiply in Food (Do Not Produce Toxins)
 MICROBIAL FOOD SPOILAGE

MICROORGANISMS INVOLVED IN FOOD

PROCESSING AND SPOILAGE

Total Bacterial Count

Total Yeast and Mold Count

Mesophilic Sporeforming (Aerobic)

Mesophilic Sporeforming (Anaerobic)

Psychrotrophic Microorganisms

Thermophilic Flat Sour Sporeformers (Anaerobic)

Acidic and Thermophilic Flat Sour Sporeformers
 MICROBIAL FOOD SPOILAGE

MICROORGANISMS INVOLVED IN FOOD

PROCESSING AND SPOILAGE

Halophilic Microorganisms
Osmophilic Microorganisms

Lipolytic Microorganisms
Proteolytic Microorganisms

Pectinolytic Microorganisms

Acid Producing Microorganisms

Sulphide Spoilage Sporeformers
 MICROBIAL FOOD SPOILAGE

INDICATOR MICROORGANISMS AND PATHOGENS

Aeromonas hydrophila Bacillus cereus

Campylobacter species Enterococci

Clostridium botulinum Clostridium perfringens

Yersinia species Listeria species

Salmonella species Shigella species

Staphylococcus aureus Vibrio species

Coliforms – Escherichia coli (E. coli O157:H7)

and its enterotoxin
 MICROBIAL FOOD SPOILAGE

TOXINS AND MICROBIAL METABOLITES

Bacillus cereus Enterotoxin

Clostridium perfringens Toxin

E. coli O157:H7 Enterotoxin

Staphylococcal Enterotoxin

Molds Aflatoxins, Fumonisins and Mycotoxins

 GROWTH OF MICROORGANISMS

BACTERIA
Asexual Reproduction by Fission or Simple Division
of the Cell and its Contents

Generation Time or Doubling Time = Time for Cell

Reproduction

Growth in Cell Number not in Size

Bacterial Populations Expressed as Colony Forming

Units (CFU) per Gram or Millilitre
 GROWTH OF MICROORGANISMS

BACTERIA

Maximum Number of Bacteria Approximately

1 x 109 CFU / g or ml

Bacteria Grow Very Rapidly, Can Double in Number

Every 30 Minutes

Bacteria need about 4 Hours for Adaptation to a New

Environment Before Growth Starts
 GROWTH OF MICROORGANISMS

YEASTS

Reproduction Either by:

Budding Fungi Imperfecti or False Yeasts

Budding and Spore Formation

Ascomycetes or True Yeasts

Unlike Bacteria, Yeasts Form Spores as a Method of

Reproduction
 GROWTH OF MICROORGANISMS

MOLDS
Either Asexual or Sexual Reproduction

Asexual Reproduction
Fragmentation into Individual Cells
and Spore Formation

Sexual Reproduction
Production of Sexual Spores by Nuclear
Fission to Ensure Survival within
Unfavourable Conditions
 GROWTH OF MICROORGANISMS

DIFFERENT PHASES OF GROWTH

Growth Curve = Logarithm10 of Number of Viable
Colonies versus Time

Four Distinct Phases

Lag Phase

Exponential or Logarithmic Phase

Stationary Phase

Death Phase
 GROWTH OF MICROORGANISMS

Lag Phase
Time for Microorganisms to Acclimate to
New Environment
Little or no Growth during this Phase

Exponential (or Logarithmic) Phase

Growth Begins and Increases Exponentially
Rate of Multiplication Most Rapid and Constant
 GROWTH OF MICROORGANISMS

Stationary Phase
Rate of Multiplication Slows Down Because of
Lack of Nutrients and Secretion of Toxins

Number of Microorganisms Stabilizes

Death Phase
Growth Stops
Microorganisms Begin to Die Off
Cell Numbers Decrease
 BACTERIAL GROWTH

Generation Time is Determined in the Exponential

Growth Phase

Generation Time Dependent on

Medium Composition
Culture Conditions
Particular Microorganism Species

Bacteria Produce Slime, Toxins, Off Colours and

Odours in the Exponential Growth Phase
 BACTERIAL GROWTH

Growth Rate = Number of Cell Divisions per Hour

Growth Yield = Amount of Cells Produced per Mol of

Substrate Consumed

ATP Yield = Amount of Cells Generated per Mol of

ATP (Adenosine Triphosphate, Energy Source)
 GROWTH OF MICROORGANISMS

FACTORS AFFECTING MICROORGANISM GROWTH

INTRINSIC FACTORS
Related to the Food Properties

EXTRINSIC FACTORS
Environmental Conditions
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

pH or Food Acidity

Water Activity

Nutrient Content

Redox Potential

Antimicrobial Constituents

Biological Structure
 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

Temperature

Oxygen and Other Gases

Time

Relative Humidity

Osmotic Pressure

Competition of Other Present Microorganisms

 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

pH OR FOOD ACIDITY

Acidophiles Optimum pH Range 1 to 5.5

Neutrophiles 5.5 to 7.5
Alkalophiles 7.5 to 10.0 or Higher

Low Acid Foods pH > 5

Medium Acid Foods 4.5 < pH < 5.4
Acid Foods 3.7 < pH < 4.5
High Acid Foods pH < 3.7
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

WATER ACTIVITY (aw)

Amount of Water Available in Food

Available for Microbial, Enzymatic and Chemical Deteriorations

Expressed as Ratio of Vapor Pressure

aw of Pure Water = 1.0

All Microorganisms Require Water But Amount Necessary

for Growth Varies
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

WATER ACTIVITY (aw)

Microorganisms Growth Dependent on Water Activity of Food

Minimal Values for Growth

Most Spoilage Bacteria aw 0.90

Most Spoilage Fungi aw 0.88 – 0.80

Halophilic Bacteria aw 0.75

Xerophilic Molds aw 0.61

Osmophilic Yeasts aw 0.61

 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

NUTRIENT CONTENT

Microorganisms Need Food to Grow and Multiply

Requirements
Water Sulfur and Phosphorus
Carbon Vitamins
Nitrogen Micronutrients
Source of Energy Trace Elements

Food Nutrients are Broken Down by Microbial Enzymes;

Pass into the Cell where
They are Processed into Energy and New Cell Material
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

NUTRIENT CONTENT

Meats, Fish and Dairy Products are Ideal Environments for

Spoilage by Microorganisms

Because of

High Nutritional Value and

Presence of Easily Utilisable Carbohydrates, Fats and Proteins
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

REDOX POTENTIAL (Eh)

Oxidation – Reduction Potential (Measured in Millivolts)

Ease for Gaining or Loosing Electrons

Related to the Oxygen Amount Needed by Microorganisms

Also Related to pH Value

Aerobes Need Positive Redox Potential

Anaerobes Need Negative Redox Potential
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

REDOX POTENTIAL (Eh)

Depends on the Oxygen Tension of the Atmosphere

Surrounding Food

Oxygen Tension = Oxygen Availability to Microorganisms.

Can be Controlled by Packaging e.g. by Gas Flushing

Redox Potential Can be Lowered by Cooking Making Food

More Susceptible to Anaerobic Spoilage
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

ANTIMICROBIAL CONSTITUENTS

Some Foods Contain Natural Antimicrobial Components

Natural Protection

Spices e.g. Thymol in Sage and Allicin in Garlic

Milk Contains Several Nonimmunological Proteins:

Lactoperoxydase
Lactoferrin
Xanthine
Lysozyme (in eggs also)
 GROWTH OF MICROORGANISMS

INTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

BIOLOGICAL STRUCTURE OF FOOD

Physical Barriers
Skin and Rinds (Fruits)
Shells (Nuts, Eggs)
Testa (Seeds)
Protect Plants and Animals Against Microorganism Invasion

Milk = Fluid Product

No Barriers for Microorganism Expansion

Viscera, Belly in Fish and Meat = Source of Microorganisms

 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

TEMPERATURE

Psychrophiles Very Low Temperatures –5°C to 15°C

Psychrotrophs Low Temperatures 5°C to 25°C

Mesophiles Moderate Temperatures 20°C to 45°C

Thermophiles High Temperatures 45°C to 80°C

Hyperthermophiles Very High Temperatures 65°C to 110°C

 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

OXYGEN

Obligate Aerobes Presence of Oxygen Essential for Growth

Some Bacteria, All Molds

Obligate Anaerobes Absence of Oxygen Essential for Growth

Some Bacteria, Most Yeasts

Facultative Growth in Either Presence OR Absence of

Oxygen Yeasts
 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

OXYGEN

Microaerophiles Require Low Oxygen Levels for Growth

(2 to 10%)

Aerotolerant Anaerobes
Oxygen not Required for Growth but Not Harmful if Present

OTHER GASES
Carbon Dioxide ; Ozone
 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

TIME

Time Needed for the Microorganism to Grow and Reach

Maturity

Corresponds to Time of Food Exposure to Conditions that

Promote Growth

Some Microorganisms Grow Faster than Others

Under Ideal Conditions, Certain Bacterial Populations Can

Double in as Short as 9 Minutes, Others Require Hours

Bacteria that Reproduce Most Quickly will Dominate

 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

RELATIVE HUMIDITY

Relative Humidity of the Environment Surrounding Food is

Closely Related to Food Water Activity (aw) (Equilibrium)

Lower is Relative Humidity for Food Storage

Lower is Food Water Activity
Longer is ProductShelf Life
 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

OSMOTIC PRESSURE

Microrganism Growth can be Affected by Solute

Concentration Outside Microbial Cell

Some Microorganisms can Withstand High External

Solute Concentrations (Yeasts, Molds)

Halophiles Grow in High Salt Concentrations

Osmophiles Require High Osmotic Pressure (Sugar)

 GROWTH OF MICROORGANISMS

EXTRINSIC FACTORS AFFECTING MICROBIAL GROWTH

COMPETITION OF OTHER MICROORGANISMS

Competition for Access to Food Nutrients

Competitive Inhibition through Waste Excretion

Symbiosis =
Share of Food Supply and
Excretion of Mutual Beneficial Wastes
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

Spoilage Microorganisms in Raw Milk

Bacteria
Coliforms Alcaligenes
Pseudomonas Flavobacterium

Molds
Aspergillus Penicillium
Fusarium

Yeasts
Candida
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

Spoilage Microorganisms in Raw Milk

Pseudomonas are Destroyed by Pasteurisation

However

Some like Pseudomonas fluorescens and Pseudomonas fragi

can Produce Proteolytic and Lipolytic Extracellular Enzymes
Heat Stable and Able to Cause Spoilage.
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

Spoilage Microorganisms in Pasteurised Milk

Some species and strains of

Bacillus Lactobacillus
Microbacterium Clostridium
Micrococcus Cornebacterium
Streptococcus Arthrobacter

Can Survive Pasteurisation and Grow at Refrigeration

Temperatures which can Cause Spoilage Problems
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

Spoilage Microorganisms in Butter

Bacteria
Pseudomonas Serratia

Yeasts
Candida Torula

Molds
Geotrichum Cladosporium
Penicillium Alternaria
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

Pathogenic Microorganisms in Milk and Dairy Products

Bacillus cereus (Raw Milk, Dairy Products)

Listeria monocytogenes (Milk Powder,Cheese)
Salmonella species (Raw Milk, Cream, Custard)
Escherichia coli 0157:H7 (Cheese)
Campylobacter jejuni (Raw Milk)
some Clostridia (Raw Milk)
Staphylococcus aureus (Raw Milk, Milk Powder)
Yersinia enterolitica (Raw Milk)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MEAT AND MEAT PRODUCTS

Spoilage Microorganisms in Raw and Cured Meat

Bacteria
Pseudomonas fluorescens (Raw Meat)
Pseudomonas species (Cured Meat)
Proteus vulgaris (Raw Meat)
Micrococcus (Raw and Cured Meat)
Brochothrix thermosphacta (Raw Meat)
Lactobacillus (Raw and Vacuum Packaged
Meat)
Leuconostoc (Cured Meat)
Acinetobacter (Carcass Meat)
Alcaligenes (Raw Meat)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MEAT AND MEAT PRODUCTS

Spoilage Microorganisms in Raw and Cured Meat

Molds
Aspergillus (Cured Meat)
Rhizopus (Cured Meat)
Penicillium (Cured Meat)

Yeasts
Saccharomyces rouxii (Salami)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF MEAT AND MEAT PRODUCTS

Pathogenic Microorganisms in Raw and Cured Meat

Salmonella (Raw Meat, Ham)

Clostridium botulinum (Vacuum Packaged Meat)
Clostridium perfringens (Meat Stews, Gravies, Pies)
Staphylococcus aureus (Raw Beef and Veal)
Campylobacter (Meat and Meat Products)
Listeria monocytogenes (Raw Meat, Bacon,
Ham)
Yersinia enterocolitica (Pork Mince and
Tongue) Aeromonas hydrophila (Packaged Fresh
Meat)
Vibrio (Bacon, Ham)
Escherichia coli (Raw Meat)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF POULTRY AND EGGS

Spoilage Microorganisms in Raw and Processed Poultry

Bacteria
Pseudomonas
Alcaligenes

Yeasts
Yarrowia lipolytica
Candida zeylanoides
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF POULTRY AND EGGS

Spoilage Microorganisms in Eggs

Bacteria
Pseudomonas
Proteus
Aeromonas
Proteus

Molds
Penicillium Cladosporium
Mucor Sporotrichum
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF POULTRY AND EGGS

Pathogenic Microorganisms in Raw and Processed Poultry

Clostridium perfringens (Poultry Stews, Gravies, Pies)
Salmonella
Campylobacter jejuni (Poultry Products)
Listeria
Staphylococcus aureus
Escherichia coli (Raw Poultry)

Pathogenic Microorganisms in Eggs

Salmonella enteritidis Aeromonas
Shigella Staphylococcus aureus
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF FISH AND SEAFOOD

Spoilage Microorganisms in Raw and Cured Fish

Bacteria
Pseudomonas (Raw Fish)
Alteromonas putrefaciens (Raw Fish)
Alcaligenes (Raw Fish)
Acinetobacter (Raw Fish)
Moraxella (Raw Fish)
Serratia (Raw Fish)
Flavobacterium
Halobacterium (Salted Cured Fish)
Halococcus (Salted Cured Fish)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF FISH AND SEAFOOD

Pathogenic Microorganisms in Raw and Cured Fish

Salmonella (Raw Fish)

Staphylococcus aureus (Cooked Fishery Products)
Clostridium botulinum (Canned Fish and Seafood)
Listeria monocytogenes (Lightly Preserved
Seafood) Bacillus spp. (Seafood)
Vibrio parahaemolyticus (Raw Fish and Seafood)
Enteropathogenic E. coli
Aeromonas hydrophila (Raw Fish and Seafood)
Viruses (Hepatitis A and Norwalk) (Shellfish)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF FRUITS AND VEGETABLES

Spoilage Microorganisms

Bacteria
Acetobacter (Fruits and Concentrated Orange Juice)
Erwinia (Fresh Fruits and Vegetables)
Lactobacillus (Concentrated Orange Juice)
Leuconostoc (Concentrated Orange Juice, Carrots)
Pseudomonas (Vegetables)
Coliforms (Raw Fruits and Vegetables)

Yeasts
Torulopsis species (Concentrated Fruit Juice)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF FRUITS AND VEGETABLES

Spoilage Microorganisms in Fruits and Vegetables

Molds
Penicillium
Aspergillus niger (Fresh Fruits and Vegetables)
Rhizopus (Fresh Fruits and Vegetables)
Botrytis (Fresh Fruits and Vegetables)

Pathogenic Microorganisms in Fruits and Vegetables

Salmonella (Salads)
Listeria monocytogenes (Raw Vegetables)
Bacillus (Vegetables and Fruit Juice)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF CEREAL PRODUCTS

Spoilage Microorganisms

Bacteria
Sarcina Serratia
Achromobacter Bacillus spores (Wheat Flour)
Flavobacterium Coliforms
Alcaligenes

Molds
Xeromyces bisporus (Cereals)
Alternaria Cladosporium (Wheat Flour)
Aspergillus Penicillium (Wheat Flour)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF CANNED FOODS

Spoilage Microorganisms in Canned Foods

Bacteria
Mainly thermophiles and Anaerobes

Bacillus stearothermophilus (Thermophile)

Bacillus subtilis (Facultative thermophile)

Clostridium thermosaccharolyticum
(Anaerobe Not Producing H2S)

Desulfotomaculum nigrificans (Anaerobe H2S

Producer)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF CANNED FOODS

Spoilage Microorganisms in Canned Foods

Canned Foods are a Low-Oxygen Environment

Important to Destroy all Clostridium botulinum Spores

by Heat Treatment

Especially for Canned Low-Acid Content Foods

 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF DRIED FOODS

Spoilage Microorganisms of Various Dried Foods

Bacteria
Lactobacillus (Spices and Condiments)
Butyric Anaerobes (Dried Fruits)

Molds
Aspergillus echinulatas (Xerophilic) (Flour)
Xeromyces bisporus (Candy)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF DRIED FOODS

Spoilage Microorganisms of Various Dried Foods

Yeasts
Saccharomyces (Spices and Condiments)
Saccharomyces bisporus (Dried fruits)
(Osmophilic)

Pathogenic Microorganisms in Various Dried Foods

Bacillus (Spices and Condiments, Dried Fruits)
Clostridium (Spices and Condiments, Dried Fruits)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF SWEET PRODUCTS

Spoilage Microorganisms in Various High Sugar Content Products

Bacteria
Enterobacter aerogenes (Maple Syrup)
Micrococcus roseus (Maple Syrup)

Molds
Aspergillus flavus (Jams and Jellies)
Wallemia sebi (Honey)
Penicillium (Maple Syrup, Jams)
Xeromyces bisporus (Candy)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF SWEET PRODUCTS

Spoilage Microorganisms in Various High Sugar Content Products

Yeasts
Saccharomyces (Maple Syrup)
Zygosaccharomyces (Maple Syrup)
Saccharomyces bailii (Jams, Fruit Cake)
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF BREAD
Spoilage Microorganisms in Bread

Bacteria
Bacillus subtilis

Molds
Rhizopus nigricans
Penicillium
Aspergillus niger
Mucor
 EXAMPLES ON FOOD CONTAMINATION

MICROBIOLOGY OF PICKLES
Spoilage Microorganisms in Pickles

Bacteria
Coliforms (Cucumber Pickle)
Bacillus (Cucumber and Vegetable Pickles)

Yeasts
Rhodotorula (Pickles, Sauerkraut)
Saccharomyces (Sour Vegetable Preserves)
Pichia (Sour Vegetable Preserves)

Molds
Pectinolytic Species (Cucumber Pickles)
 CONCLUSION

FOOD SAFETY

Good Handling / Manufacture / Storage Practices

Quality Management System on the Whole Food Chain

HACCP Method

Different Food Preservation Techniques

Heat, Refrigeration and Freezing, Ionisation, Fermentation,
Canning, Pickling, Candying