New Guidelines Focus on Microbial Hazards in Fresh Produce

This article by Les Bourquin, Michigan State University Department of Food Science and Human Nutrition, appeared in "The Vegetable Growers News," November 1999.

Over the past several years, food-borne illness outbreaks associated with both domestic and imported produce have increased significantly. During 1973-1987, fresh produce accounted for less the 2 percent of all outbreaks. However, this has increased to more than 5 outbreaks since 1987. Currently, approximately 15 to 20 food-borne illness outbreaks reported to the U. S. Center for Disease Control and Prevention each year have been associated with consumption of fresh produce.

The "Initiative to Ensure the Safety of Imported and Domestic Fruits and Vegetables" (produce safety initiative) began in October 1997 as part of President Clinton's food safety initiative. The President directed the Secretary of Health and Human Services, in partnership with the Secretary of Agriculture and the agricultural community, to issue guidance on good agricultural practices (GAPs) and good manufacturing practices (GMPs) for fruits and vegetables as part of the produce safety initiative. In response, the FDA and USDA issued the document "guidance for Industry - Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables" (The Produce Guide) in October 1998. The Produce Guide is not a regulation, and does not carry the force of law; however, adherence to the principles outlined in the Guide may be required for growers and handlers.

Use of the Produce Guide as a set of 'de facto' standards in some parts of the industry is already apparent, and likely will increase over the coming years. The Produce Guide focuses on microbial hazards (e.g., pathogenic bacteria, protozoa, and viruses) associated with fresh produce. It does not specifically address other potential hazards such as pesticide residues or chemical contaminants. The Guide also focuses on risk reduction, not elimination, as current technologies cannot eliminate all potential microbial hazards associated with produce that will be eaten raw. The guidance is broad in scope and does not refer to production and processing practices specific to any particular commodity. Hence, producers and processors should use the general guidelines in the Produce Guide to assess microbial hazards that may apply to their own operation.

Although discussion of the full range of guidance in the Produce Guide is not possible in this article, certain basic principles of microbial food safety are identified for the fresh produce industry. These are:

Principle 1: Prevention of microbial contamination of fresh produce is favored over reliance on corrective actions, once contamination has occurred.

Principle 2: To minimize microbial food safety hazards in fresh produce, growers, packers, or shippers should use good agricultural management practices in those areas over which they have control.

Principle 3: Fresh produce can become micro biologically contaminated at any point along the farm-to-table food chain. The major source of microbial contamination with fresh produce is associated with human or animal feces.

Principle 4: Whenever water comes in contact with produce, its quality dictates the potential for contamination. Minimize the potential of microbial contamination from water used with fresh fruits and vegetables.

Principle 5: Practices using animal manure or municipal bio-solid wastes should be managed closely to minimize the potential for microbial contamination of fresh produce.

Principle 6: Worker hygiene and sanitation practices during production, harvesting, sorting, packing, and transport play a critical role in minimizing the potential for microbial contamination of fresh produce.

Principle 7: Follow all applicable local, state, and federal laws and regulations, or corresponding or similar laws, regulations or standards for operators outside the U. S. for agricultural practices.

Principle 8: Accountability at all levels of the agricultural environment is important to a successful food safety program. There must be qualified personnel and effective monitoring to ensure that all elements of the program function correctly, and to help track produce back through the distribution channels to the producer.

Michigan State University Extension staff currently are developing food-safety educational programs on the guidelines covered in the Produce Guide. These programs will likely be offered in Michigan in the winter and spring of 2000.

Copies of the Produce Guide are available from the FDA through its web site at: <>

or by mail at: Food Safety Initiative Staff, HFS-32, U. S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 200 C Street SW, Washington, DC 20204.

Alfalfa Sprouts and Salmonella

This report from "IFT Science Communicators Newsletter" (1/13/99) appeared in the "Texas Food Processor," February/March 1999.

Due to ineffective pathogen control in seeds, alfalfa sprouts are a high-risk source of Salmonella, concluded researchers investigating the cause of a 1995 North American outbreak of Salmonella enterica serotype Newport. "The fundamental problem is that the sprouting process contains no 'kill step' that would eliminate pathogens [harboring in sprout seeds] without compromising a seed's germination potential," the researchers wrote in the January 13 Journal of the American Medical Association. "Consumers are left with little protection other than chance." Investigators uncovered a direct association between the distribution of a seed lot shipped to multiple growers and the distribution of cases. They noted unique epidemiological features, including:

1. A prevalence of adult women with illness, perhaps highlighting the difference in eating habits between men and women;

2. A medium incubation period for cases longer than the normal three or fewer days cited as the maximum in a standard communicable disease reference; and

3. Recall of eating alfalfa sprouts by only a minority (41 percent) of cases, pointing to the likelihood of cross-contamination during salad or sandwich preparation or of sprouts' concealment in other food.

The Food and Drug Administration on August 31, 1998, warned consumers at high risk for food-borne illness not to eat alfalfa sprouts.

Organics and E. coli

This article by Jim Prevor appeared in the October 1999 issue of Produce Business.

The Center for Disease Control data for 1996 - the most current year available - indicates that of all confirmed E. coli 0157:H7 cases that have been traced to food, over one-third of these cases (36 percent) were traced to organic and natural foods. Organic lettuce and non-pasteurized juices were the prime sources of contamination. Organic and natural products constitute only between .5 and 1.5 percent of the food supply, so this level of contamination is wildly disproportionate.

The produce trade is particularly vulnerable to food safety problems because of the parity nature of the product. Put another way, if one brand of soup has a problem, consumers can easily identify that brand from the labels, easily remember it because it is a well-known consumer brand, and easily select an alternative brand. In produce, the commodity orientation means all of that particular information tends to be lumped together in the mind of any individual consumer. So, if one farmer - say, of watermelon - has a problem, it is highly likely that all vendors of watermelon will suffer from the publicity given to the problem.

This 'we're-all-in-it-together' attitude is what leads food safety to be an industry concern, and it is why trade associations are always coming up with handbooks and manuals to help industry members do a good job with HACCP (Hazard Analysis Critical Control Points) and other procedures that contribute to safe food.

The conventional produce industry has always treated the organic community with a high of 'hand-off' approach. This is partly because conventional agriculture didn't want to be seen as the 'bully' trying to snuff out this incipient industry; it also is partly because (at around one percent of total fresh produce sales) the organic industry isn't all that significant; and finally, it is partly because most conventional growers and handlers don't know enough about organics to be giving advice or making demands.

Conventional growers may not like the yields that organic farming produces, and wholesalers and retailers may question their appearance, availability, or price, but the 'cottage industry' reputation and favorable media image have protected organic producers from many food safety inquiries.

That really must change. It is not easy to get good statistics, and one year's statistics should never be taken as meaning anything with certainty. Nonetheless, the numbers are a serious cause for concern. After all, consumers who purchase these products (often paying a premium to do so) are not expecting to run any risk of E. coli contamination, and certainly not a higher risk than with conventional product.

The concern traces itself back to one problem to which attention has to be paid: the use of manure in the raising of organic food products. It is commonly accepted that farmers should never use raw manure. Instead, the manure must be properly composted to insure that potentially harmful bacteria, including E. coli 0157:H7, does not get on the food.

But there are problems. Traditional composting has not been rigorously tested to ensure that it is sufficient to kill all relevant bacteria. At the University of California, Davis, Dr. Dean Claver, who is studying manure composting and its relationship to bacterial risks, has said that typical composting methods are simply not sufficient to kill E. coli 0157:H7. Besides, there are no laws or regulations dictating composting practices, so there is no assurance that organic farmers follow the customary procedures to begin with. Sadly, this issue is so 'politically correct' that it is difficult to get knowledgeable people to speak out. Robert V. Tauxe, M.D., Chief of the Foodborne and Diarrheal Disease branch of the Center for Disease Control, was quoted in an article in the Journal of the American Medical Association: "Experts say that increased consumption of organically grown, unprocessed foods . . . may be contributing to the problem." Unfortunately, those who make the most mild and unobjectionable of observations on this subject are so vilified that most decide to be quiet. Dr. Tauxe has since refrained from comment on the subject, and now claims he has no opinion about the relative dangers of conventional and organically produced foods.

The produce industry cannot stay quiet. Every time someone gets sick from organically grown lettuce, it is another news article disparaging lettuce. And who can say how many consumers have shied away, or will shy away in the future, from all lettuce because of news articles like this?

This solution is very clear: all compost used in agriculture must come from a certified source. Farmers could have their own facilities certified, or purchase compost from an outside certified facility. Whichever, the organic community must withhold organic certification from anyone not following this procedure. This will not happen easily. But it is important, and pressure must be brought to bear. Supermarkets must establish that their buying offices will not recognize an organic certification without this requirement as a legitimate prospect for purchase. This means trade associations need to begin an education process. If the organic community won't cooperate, legislative action will have to be pursued to regulate the use of animal wastes in food production.

This industry has worked hard to maintain and enhance a wholesome, healthy image. It must take preemptive action to stop a terribly dangerous practice in the organic community that could hurt innocent people and sully the consumer's image of fresh produce in the process.

Prevention is the Only Policy for Producers

This article by Devon Zagory of Davis Fresh Technologies appeared in The Packer, November 29, 1999.

Why all the excitement about food safety all of a sudden? Is foodborne illness from produce new? Is it worse than it used to be? What are we supposed to do about it?

These and other questions about food safety are often asked when produce professionals gather. And answers tend to be in short supply. However, there sometimes seems to be plenty of blame to go around. It is the fault of the newspapers, television, the government, consumers, big agriculture, genetic engineering, and so on. The truth is both less sinister and more difficult than many believe.

Foodborne illness associated with produce is not new, but our awareness of it may be. People have been getting sick from eating food for a long time, but we, perhaps, didn't realize it until recently. When, in the past, we have said we have the stomach flu, we really had foodborne illness. The flu is a viral disease that causes fever. Headache, and achy muscles. Vomiting and diarrhea are not common symptoms of the flu, but they are common symptoms of foodborne illness. Although foodborne illness from eating produce was and is a rare event, it does happen, sometimes with dire consequences.

Although we may prefer to believe produce is not a vector for human pathogens, science and public health agencies have become much more sophisticated in tracking down the causes of foodborne illness, and they are increasingly looking at fruits and vegetables as likely suspects. So, if we admit that produce has, at times, been the culprit and that it is likely to be again in the future, then we must ask ourselves what we can reasonably do to reduce the likelihood that our products are to blame.

Many believe they have programs that prevent their products from carrying pathogens and making anyone sick. Chlorinated water, ozone, ultraviolet light, 'antibacterial' packaging materials, irradiation, organic acid washes, and microbiological testing all have their place in produce sanitation. But the simple fact is once fruits and vegetables have been contaminated with bacterial pathogens or parasites, none of these methods will assure the safety of the product. It is possible to reduce the numbers of pathogens on produce by washing in sanitized water, but it is not possible to eliminate them through any of the above means. And if a few bacterial cells remain on the surface, it only takes a few hours at warm temperatures for those cells to multiply. The only treatment we have available that will eliminate pathogens from fruits and vegetables is thorough cooking. And most people prefer their salads raw.

If we can't remove pathogens from produce, what can be done? The answer is simple: prevention. Prevent fruits and vegetables from getting contaminated in the first place. In produce food safety, prevention isn't just the best policy, it's the only policy. This is the reason for the focus on good agricultural practices, good manufacturing practices, and Hazard Analysis and Critical Control Points programs. They are all preventive programs to keep pathogens off fresh produce. The difficulty comes because pathogens can get on produce from many paths and at any time during growing, harvesting, packing, processing, distributing, or handling. So preventive programs cannot start and stop at your doors. There must be a continuous chain of prevention throughout all the steps involved in getting fruits and vegetables to America's tables.

Before we can prevent pathogens from getting onto our products, we have to understand how they get there. Most of the pathogens of potential concern on fresh produce come from one of four sources: contaminated water, animals and their manure, infected workers, or soil. If we are aware of these sources, and manage them in all phases of our operations, we can effectively prevent produce from becoming contaminated. Good sanitation practices should focus on those places and practices where contamination of food is most likely. Contamination of fruits and vegetables with pathogens is most likely to occur from:

Prevention programs start with identifying specific places in an operation where risks of contamination from the above sources could occur. For each identified risk there should be a program that addresses and minimizes that risk. For vegetable production areas, berms and ditches can be constructed to divert runoff away from the growing vegetables. In this way the risk has been identified and minimized.

As another example, if workers touch product with their hands in a harvest operation, packing shed, or processing facility, there is a risk of contamination of the product from infected workers. Several steps may be taken to address these kinds of risks. A company policy should be articulated in writing and through worker training that workers who are ill may not handle product. The training materials should make it clear to the workers shy this policy is important. Where possible, temporarily divert recently sick workers to jobs that do not involve contact with product. Establish and enforce policies regarding hand washing after using the toilet, before working with product, and after touching anything that may be a source of cross-contamination, such as garbage or plant material on the floor. Such policies should be enforced through oversight by supervisors and worker training sessions, and those sessions should be documented. The importance of hand washing and instruction in proper hand washing should be a central part of worker training. Ensure bathrooms are clean, well stocked, and accessible. If bathrooms are unpleasant to enter or use, workers are less likely to use them.

As can be seen from the above examples, in some cases there may be no single, simply remedy for an identified risk. It may be that many small things must be done to address a risk. This is why risk reduction can be difficult and require substantial commitment, attention, resources, and multiple programs. In many cases no single program - neither HACCP nor GMPs nor GAPs - will fully and effectively address all risks. Risk assessment and mitigation require systematic analysis, careful planning, creative solutions, and commitment at all levels of a company.

The time has come when ignoring the risks of foodborne illness or making believe they are not serious has passed. The responsibility to provide even safer, more wholesome food rests with each of us, and the reward will be the continuing trust of our customers that we are providing them with the best, safest products possible.