Sampling Strategy for Spinach

    Develop a simple and practical sampling strategy to detect Enterohemorrhagic Escherichia coli O157:H7 in spinach destined for bagged salad.  The strategy must be cost effective and easily implemented by the grower or processor into an existing system.  The focus of this task is to develop a sampling strategy (as opposed to a microbiological method).

Background

    Ensuring the safety of the food supply continues to be a top priority for the U.S. Food and Drug Administration (FDA).  Ready-to-eat fresh vegetables, fruits, and prepared salads have a high potential risk of microbial contamination because these foods are generally grown in a natural environment (for example, a field, or orchard) and are often consumed without cooking or other post-harvest treatments that could eliminate pathogens.  

In the Fall of 2006, an Escherichia.coli O157:H7 (E. coli O157:H7) outbreak was associated with bagged spinach.  The outbreak resulted in 205 confirmed illnesses and three deaths.  Investigators successfully identified the environmental risk factors and the areas that were most likely involved in the outbreak, but they were unable to definitely determine the origin of contamination.  E.coli O157:H7 can be transferred in many ways – including animals, humans, and water -- therefore the precise means by which the bacteria spread to the spinach remains unknown. 

    The number of illnesses associated with fresh produce is a continuing concern of the Agency, and we have worked on a number of initiatives to reduce the presence of pathogens in these foods.  FDA continues to work closely with it federal, state and local partners to keep produce safe from microbial contamination. 

    Growers and processors who wish to ensure confidence in the safety of their product, may choose to implement microbiological testing into their process.  In doing so, the grower/processor must decide when and where to sample the product, how to sample in an efficient manner to be able to divert product and to gain sufficient confidence with the least amount of spinach lost or other resources used.

Problem Statement

    Develop a simple and practical sampling strategy to detect Enterohemorrhagic Escherichia coli O157:H7 in spinach destined for bagged salad.  The strategy must be cost effective and easily implemented by the grower or processor into an existing system.  The focus of this task is to develop a sampling strategy (as opposed to a microbiological method).

Design Considerations

    Your proposed strategy should be easily evaluated on full scale level which equates to a minimum of 500 lbs of spinach.  The sampling strategy could take place prior to harvest, during harvest, as the product enters the fresh-cut processing facility, or at any point during production.  The solution must be capable of being used in a commercial setting and occur with enough rapidity to allow contaminated spinach to be diverted to a cooked product. The strategy must be easy to implement and maintain, cost effective, and take into account all aspects of clean-up, including any waste disposal.  The end product must be safe for human consumption.

The system must:

• be reasonably easy to use/maintain;

• be innovative;

• not cause new environmental problems;

• meet any applicable state and federal regulations;

• be cost effective;

• address safety considerations; and

• include a marketing strategy and outreach plan for small growers.

Evaluation Criteria

    Each team is advised to read the Participation Guide for a comprehensive understanding of the contest evaluation criteria.  Upon your registration, WERC will provide you with a copy of the Public Involvement Plan and Participation Guide.  Additionally, your proposed design will be evaluated on issues identified in the problem statement as well as others listed here.

• Ease of implementation;

• Ease of use/maintainability;

• Ability to rapidly and effectively detect contamination;

• Reliability;

• Energy and water use efficiency;

• Cost effective;

• Innovative design; and

• Consideration of waste products and disposal issues.

Bench-Scale Demonstration

    At the design contest, each team will receive multiple “lots” of spinach that may contain the surrogate bacteria. The exact amount of each lot as well as information on the surrogate bacteria will be provided at a later date.  Teams must demonstrate their proposed system and sampling strategy and be able to correctly identify and divert a contaminated lot.  As a part of your proposed solution, you must present a plan and demonstrate an appropriate clean up method to use after a contaminated lot is detected and be able to continue “processing”. 

    The bench scale construction should accurately represent a reduced scale simulation of the actual application to the conceptual site model.

Written Report Requirements

    The written report is the first presentation of your team’s proposed solution. The report should give the reader a full understanding of the magnitude of your team’s involvement with the problem details.  The report will be evaluated for clarity, logic, coherence and quality.  Standards appropriate for publications in technical journals apply.

    In addition to the listed requirements, the following must be discussed in your written report: 

• Describe selection process in detail including cost/benefit consideration, evaluation criteria, and screening protocol;

• Discuss advantages, disadvantages, and limitations of the selected method and other options considered;

• Include recent references and sources of information;

• Address any safety issues or considerations associated with the process;

• Include a marketing strategy and outreach plan for growers; and

• Discuss costs.

For More Information

Contact:
Barbara Valdez, Program Facilitator
(575) 646-7821
(800) 523-5996