Food Safety and Strawberries

Trevor Phister, PhDAssistant Professor

Department of Food ScienceTrevor_Phister@ncsu.edu

Why Should We Care?

Every year foodborne illnesses result in an estimated:

• 76 million cases of foodborne illness.

• 325,000 people hospitalized for foodborne illness.

• 5,200 needless deaths each year.

• Economic losses between 10-83 billion dollars.

Produce Associated Outbreaks Affect Business

• Strawberry industry lost an estimated $50 million in 1996 after mistakenly being indicated as the source of pathogens in an outbreak.

• Odwalla shareholder value dropped approximately 41% ($12.4 million) in six months after outbreak.

• Work against produce promotions campaigns.

• May result in unwanted legislation or regulation.

Microbes That Cause Foodborne Illness

• Bacteria – Single-celled organisms that live independently.

• Viruses - small particles that live and replicate in a host.

• Parasites - intestinal worms or protozoa that live in a host animal or human.

Parasites

Viruses

Bacteria

Number of Produce Associated Outbreaks by Decade, 1973 - 1997

3.7

6.5

10.5

0

2

4

6

8

10

12

1973-79 1980-89 1990-97

Decade

Outbreaks / year

Main produce items

• Leafy greens• Tomato• Sprouts• Berries• Melons

Harmful Microorganisms & Outbreaks Associated with Produce

Pathogen

Produce

E. coli O157:H7 Iceberg lettuce, radish sprouts, unpasteurized apple cider/juice

Salmonella spp. Tomatoes, bean sprouts, sliced watermelon, sliced cantaloupe, coleslaw & onions, alfalfa sprouts, root vegetables, dried seaweed

L monocytogenes Cabbage B. cereus Sprouts Hepatitis A virus Iceberg lettuce, raspberries, strawberries Cryptosporidium Apple cider Cyclospora Raspberries

Frequency of Pathogens on Produce

• Vegetables (from literature):– Salmonella 1- 8%

– L. monocytogenes 2- 30%

– Shigella 1%

– No difference was found between organic and conventional

• FDA Produce Surveillance Program– Imports - 4% positive rate (Salmonella &

Shigella)

– Domestic - currently being conducted

The Problem

Charles Dharapak/Associated Press

Strawberries

• 1992 Hepatitis A– 35 infected

• 1997– 2.6 million pounds frozen strawberries

recalled– Thousands of children exposed to

Hepatitis A– 262 children infected

What can we do?

Taken up through roots

JFP vol65 p18-23

Solutions

Washes and rinses

• Chlorine• Chlorine dioxide• Ozone• Acetic acid• Electrolized water

Good Agricultural Practices

Good agricultural practices

• Water• Fertilizer • Animal feces• Worker health and hygiene• Field sanitation• Packing facility• Transportation• Traceback

Good management practices

• Growers and packers who successfully pass will be listed on the USDA and NCDA web site

• Participation is voluntary• Program initiated by retailers asking for demonstration of

adherence to food safety practices• http://www.ncagr.com/markets/gradnreg/foodsafety/index.h

tm• Phone: (252)-792-1672

Good management practices

Good agricultural practices

• Water• Fertilizer and animal feces• Worker health and hygiene• Field sanitation• Packing facility• Transportation• Traceback

water

• Anytime water comes in contact with fresh produce, its quality determines the potential for pathogen contamination since water may be a carrier of a number of types of microorganisms:– Escherichia coli, Salmonella spp., Vibrio

cholerae, Shigella spp, Cryptosporidium parvum, Giardia lamblia, Cyclospora cayetanensis, Toxisplasma gondii, the Norwalk virus and hepatitis A

Courtesy of FDACourtesy University of Florida

• Usually, water for agricultural uses comes from:– Surface sources such as rivers, streams,

irrigation ditches and canals

– Reservoirs (open or capped)

– Municipal water systems

water

Courtesy of FDACourtesy University of Florida

Make sure you know your water system

Ground water may be contaminated by a variety of biological and chemical hazards,

which include:

• Bacteria and viruses• Domestic waste • Nitrate nitrogen • Synthetic organic chemicals • Heavy metals • Petroleum residues • Combustion products from roadways

Courtesy of FDA

Microbiological Testing

• Microbiological testing is used in the verification steps of a safety assurance program. • It is important to document the frequency and results of each water test for comparison purposes. • These records would become very important in the event of a microbiological outbreak investigation.

Courtesy of FDACourtesy University of Florida

Water Source Will Determine the Possible Frequency of Testing

Source Possible Water Testing Frequency*

Closed system, under the ground or covered tank

One annual test at the beginning of season

Uncovered well, open canal, water reservoir, collection pond

Beginning, middle and week before harvest

Municipal/District water system

Keep records from the municipality/district water system (monthly, quarterly or annual report)

* Obtained from California Strawberry Commission (1998) Quality Assurance Program

Courtesy of FDACourtesy University of Florida

Sampling criteria can differ greatly

Total coliforms(cfu/100 mL)

Thermotolerant coliformsCfu/100 mL)

E. coli (CFU/100mL)

Buyer 1 <100 <10 <10

Buyer 2 50%<1000 50%<100 50%<100

CLGMA NA NA <126 MPN for 5 samples<235 single

Frost protection

• Water should meet pre-harvest criteria– 126 E. coli per 100 mL

• If it is over this limit– Do not use water until

problem corrected– Examine water source– After actions taken

retest water at sampling point

– Test water for 5 days– sample the crop

• If crops positive do not use

Photo by Donnie Fulks, Belvedere Plantation,Fredricksburg, VA

Drip irrigation

• More efficient irrigation method– Less water lost to

evaporation

• Less transfer of pathogens to plant

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Conclusions

• GAPs best way to prevent foodborne illness

• Water quality for irrigation should be 126 MPN/5 samples (E.coli) although this may vary

• Drip irrigation safer than overhead

Acknowledgments

WaterWaterMark A. Ritenour, Ph.D.University of Florida, Indian River Research & Education Center, Fort Pierce

Elizabeth A. Bihn and Robert B. GravaniNational GAPs ProgramCornell University

Resources

http://www.ncagr.com/markets/gradnreg/foodsafety/index.htm

Trevor Phister Phone: 919-513-1644Email: tgphiste@ncsu.edu

www.extensionfoodsafety.org