Food Safety Hazards Associated with Fresh Produce

William C. Hurst, Ph.D.Food Science and Technology

University of GeorgiaAthens, GA 30602

Sponsored by:USDA-CSREESCSREES Project Number 00-51110-9722National Integrated Food Safety Initiative

Types of Hazards

Microbiological Chemical Physical

Courtesy of W.C. Hurst

What is a “Pathogen”• Plant pathogen

– Microorganism known to cause diseases or lesions in plant tissues

• Human or animal pathogen– Microorganisms known to cause illness to animals or

humans

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• E. coli O157:H7• Salmonella spp• Listeria

monocytogenes • Shigella spp.• Vibrio cholera• B. cereus

• Hepatitis A virus• Cyclospora• Cryptosporidium

Microbial Pathogens of Concern in Fresh Produce

Bacteria Viruses and Parasites

Courtesy of Cornell University

Ecological Niches of Microbial Pathogens

• Normal inhabitants of soils– L. monocytogenes– B. cereus– C. botulinum

• Residents of human and animal intestinal tracts– Salmonella– E. coli O157:H7– Shigella– Campylobacter– Viruses

Courtesy of Cornell University

Published Outbreaks of Bacterial Foodborne Illness Associated

with Produce• Bacillus cereus – sprouts• Enterotoxigenic E. coli - carrots• E. coli 0157:H7 - unpasteurized apple

cider/juice, lettuce, alfalfa sprouts, radishes

Courtesy of W.C. Hurst

Published Outbreaks of Bacterial Foodborne Illness Associated

with Produce• L. monocytogenes – cabbage• Salmonella – sliced tomatoes, sliced

cantaloupe, sprouts, sliced watermelon, unpasteurized orange juice

• Shigella – lettuce, green onions• Vibrio cholerae – coconut milk

.

Courtesy of W.C. Hurst

Published Outbreaks of Viral/Parasitic Foodborne Illness

Associated with Produce

• Hepatitis A – Iceberg lettuce, raspberries, strawberries

• Cylcospora – raspberries• Crytosporidium – apple cider

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MICROBIOLOGICAL TESTING

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Microorganisms in Fresh Vegetables

Vegetable Population Recovered Reference

Bell Pepper 132,000 Golden et.al (1987)

Cabbage 500-100,000 Geeson (1979)Carrot 440-630,000 Splittstoesser (1970)

Collards 3.2x106-6.3x106 Senter et.al (1987)

Cucumbers 16,000 Splittstoesser (1970)

Lettuce 10,000-1x106 Riser et.al (1984)

Lima Beans 1-150 Splittstoesser (1970)

Tomatoes 10,000-501,000 Senter et.al (1985)Courtesy of W.C. Hurst

Types of Microbiological Testing on Produce

• Total plate count (TPC or APC)– Determine population of viable microorganisms present

• Yeast-mold count (YM)– Determine number of mold fragments and yeast cells

present• Lactic acid bacteria count

– Determine population of acid tolerant bacteria present• Presence of a specific pathogen

– e.g. Salmonella, E. coli 0157:H7

Courtesy of W.C. Hurst

Purpose of Microbiological Testing

• Compliance– Confirm that regulatory or contractual specifications are

being met– Quality control/assurance– Verify Hazard Analysis Critical Control (HAACP) system– Troubleshooting– Determine source of spoilage or safety problems

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MICROBIOLOGICAL SURVEY EQUIPMENT

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COLIFORM GROWTH

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CLEANING AND SANITIZING THE PACKING LINE

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VERIFYING SANITATION

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Water Testing• Research is needed relating to field irrigation water

quality and risks– Fecal coliform count less than 100 per ml is target

• Fecal coliform as indicator only partially useful, but best test available

• Remember that very low bacterial counts of E. coli O157:H7 will cause disease– 6 to 10 bacterial cells can cause illness– Very difficult to test for this organism

Courtesy of Cornell University

SIMPLE WATER TEST KIT

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PORTABLE INCUBATOR

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COLONY COUNTING MODEL

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Water Testing Frequency• Annually with municipal water• Quarterly with groundwater• Test surface water for quality assurance

– 3 times during season in temperate climates• at planting (high flow)• at peak use (low flow)• at harvest

– Quarterly in more southern climates• Maintain good records of results

Courtesy of Cornell University

HACCP

• Hazard Analysis Critical Control Point System– Basic concept is that of “prevention” rather

than “testing”– Only deals with Food safety issues– Procedures deal with continuous control of

identified risks in the Food handling chain

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7 Principles of HACCP

1. Conduct a Hazard Analysis2. Determine Critical Control Points (CCP’s)3. Establish Critical Limits4. Establish Monitoring Procedures5. Establish Corrective Action6. Establish Verification Procedures7. Establish Record Keeping and Documentation

ProceduresCourtesy of W.C. Hurst

Limitations of HACCP in Fresh Produce Production

• True controls don’t exist for hazards• There is no definitive “kill” step• Industry doesn’t have trained personnel to

run the program

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What are the Alternatives?

• Institute a HACCP-like program:– Hazard identification– Preventative steps– Documentation

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WASH WATER QUALITY

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CHLORINE TEST PAPER

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ON-FARM HAZARDPREVENTION PLAN

• Hazard identified: Human Pathogens

• Preventative measure: Water Chlorination

• Documentation step: Chlorine log

Courtesy of W.C. Hurst