Food: It Shouldn’t Be a
Mystery
Alan M. Tart
Regional Retail Food Specialist
U.S. Food and Drug Administration
Atlanta, GA
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Objectives



Name several examples of chemical,
physical, and biological hazards found in
food
Review principles of microbiological
growth & survival
Discuss how to prevent, eliminate, or
reduce hazards/risks of concern
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Foodborne Illness in the U.S.
3
The Problem – Foodborne Illness

Estimated 76 million illnesses

325,000 hospitalizations annually;
hospital stays estimated at more than
$3 billion

and 5,000 deaths!
Mead et al., Emerg. Infect. Dis. 5:607-625
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Factors Affecting Foodborne
Illness in the U.S.
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Globalization of the food
supply
Food consumption patterns
Methods/Surveillance/
Awareness
Changing production and
processing practices
Evolution of new strains
Increased longevity
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Food Safety Hazards
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Hazard
A physical, chemical, or biological
property that may cause an
unacceptable consumer health risk.
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Physical Hazards

Poor handling
procedures in the
food flow

Examples: plastic,
bones, wood, glass,
metal fragments,
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Naturally Occurring Chemical Hazards

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Scombrotoxin
Ciguatera Toxin
Shellfish Toxins
Tetrodotoxin
Toxic Mushrooms
Allergens
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Biological Hazards

Includes bacterial, viral, and parasitic
organisms
Dennis Kunkel
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Percentage of Foodborne Illness
Attributable to Known Pathogens
Bacteria
30%
Protozoa
3%
Mead et al., 1999
Viruses
67%
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Bacteria, Viruses, and Parasites –
What’s the Difference?

Bacteria grow in food and in the body


Types of illnesses
 Bacterial Infection
 Intoxication
 Toxicoinfection (toxin-mediated infection)
Viruses and parasites cannot grow in food, only
in the body.
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Factors Affecting Bacterial
Growth
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Factors Needed for Bacterial Growth
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Food
Acidity
Time
Temperature
Oxygen
Moisture – Available Water
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Food (Nutrients)

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Protein
Carbohydrates (sugars)
Fats
Vitamins
Minerals
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Acidity (pH)
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pH is the measure of the hydronium ion (H+)
concentration of a product.
pH scale is 0-14
Below 7 is acidic, 7 is neutral, above 7 is basic
Most bacteria prefer to grow in a relatively neutral
environment.
Foods may be made shelf stable by adding acid.
At a pH of 4.1 or below, foodborne bacterial
pathogens do not grow but may survive.
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Approximate pH Values of Some Foods
ground beef
ham
chicken
fish
clams
oysters
butter
buttermilk
cheese
milk
vegetables
fruit
egg albumen
5.1-7.2
5.9-6.1
5.5-7.0
7.0-7.3
6.5
4.8-6.3
6.1-6.4
4.5
4.9-5.9
6.6-6.8
4.2-6.5
1.9-6.7
7.6
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Time and Temperature

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Basis for most food safety rules and
regulations.
Easily monitored and implemented.
Used to control almost all potential
biological hazards except viruses.
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Time and Temperature

Temperature Danger Zone
40°F – 140°F*
*Consumer guidance
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Logarithm10 of
viable cells
Time and Temperature
STATIONARY
PHASE
DEATH
PHASE
LOG PHASE
LAG PHASE
1
2
3
4
6
8
10 12 13 14 15 16
Time (in hours)
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Oxygen Requirements of Bacteria
L. monocytogenes
C. botulinum
E. coli
Aerobic
Facultative Anaerobic
Pseudomonas
Oxygen Dependent
Lactic acid bacteria
Oxygen Intolerant
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Moisture – Water Activity

Amount of water available for bacteria to
“live” or “grow”

Generally, the lower the water activity, the
lower the growth rate of organisms

The minimum water activity threshold for
bacterial pathogen growth in food is 0.87 or
less.
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Water Activity of Some Foods
Fresh Meat
Cakes
Cured Meat
Jam
Honey
Dried Milk
Crackers
0.95-1.00
0.90-0.94
0.87-0.95
0.75-0.80
0.54-0.75
0.2
0.1
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Other Factors

Interaction of pH and water activity

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Also called “hurdle technology”
Competitive microflora
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Comparing Vegetative, Sporeforming, & Toxin-producing Bacteria
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Vegetative Bacteria

Found on many raw animal foods (meat, fish, eggs,
milk), as well as processed foods

Examples
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Salmonella
E. coli O157:H7
Listeria monocytogenes
Vibrio spp.
Control Measures
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Cooking
No bare hand contact with RTE food
Handwashing
Not working when ill
Temperature control
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Staphylococcus aureus

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High numbers of cells produce heat
stable toxin in ready-to-eat food
Caused by bare hand contact with
ready-to-eat food and temperature
abuse
Poor competitor on raw foods
Normal reheating will not destroy
toxin
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Bacterial Spore Formation

Spore – survival mechanism for certain bacteria

Heat resistance exceeds normal cooking
temperatures

Spore-forming organisms
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C. perfringens
C. botulinum
B. cereus
Control Measures

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Proper cooling
Hot and cold holding
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Clostridium botulinum



Proteolytic strains of Type A and B will
not grow below 10°C (50°F)
Non-proteolytic strains of type B and E
will not grow below 3.3°C (38°F)
C. botulinum will not grow at a water
activity of 0.94 or less
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Recent Botulism Outbreaks
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Most cases of botulism are due to homeprepared foods
Nearly all of the recent botulism outbreaks
due to commercial foods are the result of
extreme temperature abuse of refrigerated
foods (2 or more days at room temperature)
Outbreaks due to commercially processed low
acid canned foods are rare
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Recent Botulism Outbreaks
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Refrigerated pasta sauce in a plastic pouch
in a cardboard carton
Refrigerated bean dip in a 16 oz plastic tub
with a snap fit lid
Garlic in oil
Sautéed onions left in a warm skillet
overnight
Frozen shredded potato patty
Refrigerated carrot juice in a plastic bottle
Baked potato wrapped in foil
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Which would more likely have toxins in it if
temperature-abused?
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Which of following presents a
higher risk of causing botulism?
A.
B.
C.
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Viruses
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Foodborne Viruses

Hepatitis A


F.P. Williams, U.S. EPA
Noroviruses (NoV)

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83,000 cases (5% foodborne)
Formally known as Norwalk-like viruses
Responsible for >50% of all foodborne
gastroenteritis outbreaks in U.S.
Est. to be as frequent as Salmonella in causing
illness and death worldwide
Other viruses
Mead et al., 1999
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Why Viruses are Such a Problem

1,000,000,000,000 - # of viral particles you start
with in 1 ml of feces*
 10,000,000,000 - # of virus particles left after
properly washing your hands (2 log reduction)
(Ayliffe et al., 1978)
1,000,000,000 - # of virus particles transferred
from an ungloved hand to food (10%) (Montville, 2001)
In contrast, it takes 1-10 virus particles to make you
sick*
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*Teunis & Moe, 2008
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Control of Viruses
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NoV survives heating at 140°F for 30 minutes
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Inactivated by boiling at 212°F
Hand sanitizers/antiseptics ineffective
Important controls
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No bare hand contact with ready-to-eat food
Proper handwashing
Not preparing food when ill
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Parasites
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Parasites - Examples
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Anisakis
Giardia
Cryptosporidium
Cyclospora
Toxoplasma gondii
Trichinella spiralis
Taenia saginata/Taenia solium (Tapeworms)
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Behavioral Causes of Foodborne
Illness
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Foodborne Illness Risk Factors

Food from Unsafe Sources

Inadequate Cooking

Improper Holding Temperatures

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Contaminated Equipment/Cross
Contamination
Poor Personal Hygiene
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Food from Unapproved Source
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Food from Unapproved Source
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Food from Unapproved Source
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Unapproved Cheese Product
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CDC’s EHS NET OUTBREAK/ NONOUTBREAK STUDY Contributing Factors Identified in Outbreaks,
EHS-NET, 2002-2003
Infected Person Handling
Food
C- Contamination Factors
P- Proliferation Factors
S- Survival Factors
Bare Hand Contact
Cross Contamination from
Raw Animal Food
Raw Food Contaminated at
Source
Holding Food at
Room
Temperature
Insufficient
Time/Temp. During
Initial Cooking
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Applying to the Classroom
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Applicability to the Classroom
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The effect of water and temperature on
metabolic rates of living things
The use of acids and salts in real world
applications
Bacterial growth and the effect of
competition for available nutrients/food
Adaptation
Basic infection control
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Questions?
Alan M. Tart
Regional Retail Food Specialist
U.S. Food and Drug Administration
60 8th Street, N.E.
Atlanta, GA 30309
Alan.Tart@fda.hhs.gov
(404) 253-1267
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