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From: Food Quality & Safety magazine, February/March 2008

It's Not Easy Bein' a Green

A collaborative, proactive approach is key to optimizing leafy green safety

by Linda L. Leake, MS

What can be a problem for an amphibian also pertains to produce. Consider this: The famous muppet Kermit the Frog appears to have it all—notoriety, popularity, and tremendous professional success. Yet, he sings, “It’s not easy bein’ green.”

Like Kermit, lettuce and spinach seem to have it all—nutritional notoriety, popularity, and booming sales. On average, according to the United Fresh Produce Association (UFPA; Washington, D.C.), 5 million bags of leafy greens are produced in the United States each day, and some 2 billion bags are sold annually. But in recent years, it hasn’t been easy to be a leafy green. The salad staples have gotten a bad rap on several occasions, and they’ve even been deadly, all because of a pathogen with killer capabilities.

Since 1995, some 22 outbreaks of foodborne illness caused by Escheria coli O157:H7 have been associated with consumption of fresh or fresh-cut lettuce and two with pre-washed spinach, according to the U.S. Food and Drug Administration (FDA). What was arguably the most widespread, dramatic, and highly publicized of these incidents occurred in 2006, when an outbreak of E. coli O157:H7 was linked to pre-washed spinach. Soon after, two outbreaks traced to the consumption of pre-washed iceberg lettuce at chain restaurants occurred.

Since the 2006 outbreaks, the leafy greens industry has developed and implemented extensive new food safety standards, metrics, and compliance programs, says David Gombas, PhD, UFPA’s senior vice president of food safety and technology. “In order to continue to improve the science that is the basis for these standards and programs, we must first identify the industry’s most acute research needs,” Dr. Gombas says. “That’s why, in September 2007, United Fresh hosted the first International Lettuce and Leafy Greens Food Safety Research Conference, which brought together U.S. and international academic scientists, state and federal regulators, and industry representatives to identify those essential research needs.”

These stakeholders were charged with developing a prioritized list of research needs to address the issue of E. coli O157:H7, Salmonella, and other human pathogens found in and on lettuce and leafy greens.

While some speculate that the 2006 crisis was attributable to water, cattle manure, and wildlife manure contaminated with E. coli O157:H7 in the vicinity of California spinach fields, the source of contamination was never definitively determined, according to the California Food Emergency Response Team, a collaboration of the California Department of Public Health (CDPH) and the FDA.

Farm to Fork Approach

“To minimize the risks associated with leafy greens, you have to scrutinize every step from farm to fork, and contaminants have to be controlled better than one in two billion bags per year,” Dr. Gombas says.

Under the authority of the California Department of Food and Agriculture (CDFA), a Leafy Green Products Handler Marketing Agreement (LGMA) was developed and implemented on April 2, 2007. The LGMA specifies that CDFA staff may conduct periodic inspections of leafy green handlers who are signatories to the LGMA to verify compliance with good agricultural practices (GAPs) developed by industry, reviewed by the CDPH and FDA, and referenced in the LGMA at

The proactive response to produce safety demonstrated by Natural Selection Foods (San Juan Bautista, Calif.), the firm implicated in the 2006 outbreak, is an example of management commitment, says Gale Prince, a food safety professional with 40 years experience in the retail food industry. He cites the company’s application of the latest science to the production of ready-to-eat produce as an example of produce safety programs of the future.

“Their program is built on rigorous field-by-field risk assessments of the growing environment and in further handling and processing,” Prince says. “The hold and test programs for raw materials and finished products at various points verify the efficacy of the upstream food safety measures put forth in” good agricultural practices and good manufacturing practices.

Expert Panel on Produce

Following the alarming events of 2006, Dr. Gombas served on a panel of 14 scientists with special expertise in the microbial safety of fresh produce, convened to review recently published research and current recommendations on the use and handling of packaged leafy green salads. Targeting three audiences—food service and restaurant operators, regulatory agencies with oversight over food facilities, and consumers—the panel developed guidelines for handling pre-washed bagged salads.

Their peer-reviewed document, “Recommendations for Handling Fresh-cut Leafy Green Salads by Consumers and Retail Foodservice Operators,” appeared in the November 2007 issue of Food Protection Trends, published by the International Association for Food Protection (Des Moines, Iowa).

“The expert panel achieved its goal,” says Larry Kohl, senior director of food safety for the Food Marketing Institute. “Their review of current science led to viable recommendations that are needed by consumers and the retail and food service industries.”

The National Restaurant Association (NRA; Washington, D.C.) has already implemented the recommendations in its ServSafe educational programs for food service workers, according to Donna Garren, PhD, NRA’s vice president of health and safety regulatory affairs. “We have expanded our references on how to handle produce in the back of the house,” Dr. Garren explains. “We stay vigilant with educating all restaurant employees about personal hygiene and cross contamination issues. We also encourage all our members to ask their produce distributors what food safety, audit, and incident management programs they have in place with the growers. Our goal is for all our members to be able to serve leafy greens with confidence.”

Take-Home Message

There are several key take-home messages from the current research, says Christine Bruhn, PhD, director of the Center for Consumer Research at the University of California, Davis, who served on the expert panel.

“Pre-washed salad is probably safer than greens that have not gone through a washing process,” Dr. Bruhn says. “The pre-washing process is so thorough and controlled that if bacteria are where they can be reached by water, they will be washed off. The greens are as clean as anyone can make them due to the process.”

There’s more risk associated with washing pre-washed leafy greens at home or in food service venues than there is with just opening the bag and dispensing them directly onto plates or bowls, says panel member Larry Beuchat, PhD, distinguished research professor with the Center for Food Safety at the University of Georgia in Athens.

“Handling bagged salads provides many opportunities for cross contamination in the kitchen,” Dr. Beuchat adds. “For example, the colander or the water or the hands of the person doing the washing could be contaminated with pathogenic bacteria.”

The second take-home message from current research, Dr. Bruhn says, is that the washing process is not perfect. There can be bacteria in the stem end of the leaves and on the cut surfaces, so washing is not the most foolproof safety step in and of itself. Moreover, in a vat, bacteria can be washed off one leaf and onto another. “The world has bacteria,” Dr. Bruhn says. “Those bugs are going to get into the leafy greens, and sometimes the bacteria are where they can’t be reached. If you want the safest possible product, you need a kill step.”

But a commercially viable kill step is years away, Dr. Gombas says. Irradiation of leafy greens is promising, but it will take time for the FDA to approve a suitable protocol. The FDA has a petition under review to permit the irradiation of multi-ingredient foods, including prepackaged (bagged) fresh produce, for the purpose of controlling microbial contamination. This petition, if approved, would permit the irradiation of prepackaged fresh spinach at specified doses. “But we can’t wait for all that,” Dr. Gombas emphasizes. “It’s critical that research proceeds now in search of a meaningful intervention.”

The third take-home message Dr. Bruhn offers is the importance of proper refrigeration. “Research has demonstrated that E. coli O157:H7 will grow under refrigeration temperatures as low as 50°F,” she says. “Just two or three E. coli cells, multiplying in transportation and storage, can make a susceptible person sick. As few as 10 cells can send them to the hospital. So the retail and food service sectors and their transportation partners need to be extremely careful to maintain proper temperatures during transport and storage, 41°F or less, according to the U.S. Food Code. And consumers need to be mindful of temperature issues once they leave the grocery store with purchased greens.”

“If leafy greens are kept cold, they can be considered safe,” Dr. Bruhn says. “And cooking to 160°F for 15 seconds adds an extra measure of safety to spinach.”

Leake is a food safety consultant and writer based in Wilmington, N.C. Reach her at or (910) 799-4881.



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