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Food: It Shouldn’t Be a Mystery

Alan M. TartRegional Retail Food SpecialistU.S. Food and Drug AdministrationAtlanta, 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.

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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.

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

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

Viruses67%

Protozoa3%

Bacteria30%

Mead et al., 1999

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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

Food Acidity Time Temperature Oxygen Moisture – Available Water

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Food (Nutrients)

Protein Carbohydrates (sugars) Fats Vitamins Minerals

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Acidity (pH)

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 5.1-7.2

ham 5.9-6.1

chicken 5.5-7.0

fish 7.0-7.3

clams 6.5

oysters 4.8-6.3

butter 6.1-6.4

buttermilk 4.5

cheese 4.9-5.9

milk 6.6-6.8

vegetables 4.2-6.5

fruit 1.9-6.7

egg albumen 7.6

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Time and Temperature

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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Time and Temperature

1 2 3 4 6 8 10 12 13 14 15 16

Time (in hours)

Lo

ga

rith

m1

0 o

f v

iab

le c

ells

STATIONARY PHASE

LAG PHASE

LOG PHASE

DEATH PHASE

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Oxygen Requirements of Bacteria

Aerobic AnaerobicFacultative

Oxygen Dependent Oxygen Intolerant

C. botulinum

Lactic acid bacteria

L. monocytogenes

Pseudomonas

E. coli

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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 0.95-1.00Cakes 0.90-0.94Cured Meat 0.87-0.95Jam 0.75-0.80Honey 0.54-0.75Dried Milk 0.2Crackers 0.1

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Other Factors

Interaction of pH and water activity Also called “hurdle technology”

Competitive microflora

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Comparing Vegetative, Spore-forming, & 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 Salmonella E. coli O157:H7 Listeria monocytogenes Vibrio spp.

Control Measures Cooking No bare hand contact with RTE food Handwashing Not working when ill Temperature control

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Staphylococcus aureus 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 C. perfringens C. botulinum B. cereus

Control Measures 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 Most cases of botulism are due to home-

prepared 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 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 83,000 cases (5% foodborne)

Noroviruses (NoV) 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

F.P. Williams, U.S. EPA

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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*

*Teunis & Moe, 2008

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Control of Viruses

NoV survives heating at 140°F for 30 minutes Inactivated by boiling at 212°F

Hand sanitizers/antiseptics ineffective Important controls

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 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 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

C- Contamination FactorsP- Proliferation FactorsS- Survival Factors

Infected Person HandlingFood

Bare Hand Contact Holding

Food at Room Temperature

Insufficient Time/Temp. During Initial Cooking

Cross Contamination from Raw Animal Food

Raw Food Contaminated at Source

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Applying to the Classroom

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Applicability to the Classroom 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. TartRegional Retail Food Specialist

U.S. Food and Drug Administration60 8th Street, N.E.Atlanta, GA 30309

Alan.Tart@fda.hhs.gov(404) 253-1267