Pundit Special Science Report:
Part 1 — Food Safety Vulnerabilities In Yuma And Salinas
Jim Prevor’s Perishable Pundit, December 15, 2006
What do we really know about E. coli and the growing end of the business?
With everyone currently focused on green onions, it is worth noting that we do not fully understand the cause of the spinach/E. coli outbreak. There was a lot of attention paid to Salinas and possible problems with that growing area.
Now that production has shifted to Yuma, we wanted to assess the vulnerabilities in the region and visit with academic researchers in Yuma as well as Salinas working to understand the horticultural roots of foodborne illness outbreaks. To kick off the effort, Pundit Investigator and Special Projects Editor, Mira Slott, spoke to Jorge Fonseca of the Yuma Ag Extension Service:
Jorge Fonseca, Post-Harvest Specialist at the University of Arizona, Yuma Agriculture Extension Service. Learn more information here.
Q: Now that Salinas spinach production has transitioned to Yuma, will it be safer, less safe?
A: If we knew for sure the cause of the spinach/E.coli problem in Salinas, we’d all be much better off, but we don’t. The FDA discovery of a matching strain in samples from cattle feces, wild pigs and a nearby stream provide more pieces to the puzzle. But it still raises questions on the vector or vectors that transmitted the pathogens and on how the problem became so widespread.
There are still many unanswered questions. Regardless, we need to examine all possibilities and look at different areas where potential foodborne illness could occur in order to take effective actions. There are distinct differences in growing conditions between Salinas and Yuma that could play a role.
Q: Acknowledging that these differences may not be related to the problem, what would those be? And could they apply to leafy greens in general?
A: An overwhelmingly high percentage of the outbreaks associated with produce have occurred in July, August, September, and October, which happens to be the months when Salinas is harvesting leafy vegetables. We start harvesting in November. You won’t find a history of outbreaks with leafy vegetables in Arizona.
Q: Are you suggesting there could be a link based on weather conditions?
A: No one knows the cause of the outbreaks, but we need to examine all the possible reasons. In relation to this outbreak, I was in Salinas visiting suspected farms, and I went back and looked at weather conditions in those three or four different counties. The humidity in these areas is much greater than in Yuma, at least 15 to 20 percent higher.
Another thing… you always think Arizona is a very hot place, but if you want to compare harvest seasons in Salinas and Yuma, the Southwest part of Arizona, the temperature is much lower in Yuma. Sometimes it will be 10 to 20 degrees higher in Salinas. That may also be a factor. In Salinas, you have crops in higher humidity and soil in higher temps.
In fact, one problem we have in Yuma is ice on the leaves in December and January, which you normally wouldn’t have.
Q: Are there other contrasts between the two growing regions?
A: The water. Almost 100 percent of growers inYuma get their water from the Colorado river. In Salinas, most growers take water from wells. A practice of transferring that water to reservoirs is quite common because they need the pressure.
Q: What about irrigation techniques?
A: Irrigation in Salinas is basically with overhead sprinklers. In Arizona, 90 percent of growers use furrow irrigation for winter vegetable production. However, most of that furrow irrigation is used to grow head lettuce, as well as some Romaine and other small bed crop production. It is important to note that spinach grown here on large beds would also use overhead sprinklers similar to Salinas methods.
Q: Does the irrigation method play a part in food safety?
A: If there is a pathogen in the water, the food safety risk is higher if irrigating with overhead sprinklers, because it is easier for a bacteria to get attached to the leaves. The bacteria can hide in the stomata. It can attach to the pores in the leaves. If it’s too hot, the plant closes the stomata. If it gets colder in the evening, it opens up. Even during the day sprinklers stimulate the stomata to open, or bacteria could hide in cracks of leaves. If something goes wrong with the water, there is a much higher risk with overhead sprinkles.
Q: Are there advantages to overhead irrigation?
A: Yes. You can grow more plants per acre, for example. Ironically, some growers in Arizona are thinking of putting in overhead sprinklers. Another thing worth noting is that we have so much salt in Yuma that growers usually flood the field to wash it out before planting leafy vegetables.
Q: So the spinach outbreak problem may be unrelated to the differences in the weather conditions as well as the water and irrigation techniques?
A: That’s true. Many times it’s cross contamination from meat, or somewhere in the handling. An important discussion to bring to the table is related to the fresh-cut industry. I do research with the fresh-cut industry, which is the fastest growing food segment, and we definitely need to have all the companies sampling product daily to know microbial quality is OK.
Q: Do you know of any companies that have done such testing?
A: On the east coast, there are some smaller companies, like McEntire Produce in Columbia, South Carolina, that test daily for bacterial indicators, exploring the product and waiting to ship when they don’t see anything wrong. McEntire Produce was a pioneer in more comprehensive food safety testing. I know, because in 1998 as a graduate student, I was involved in taking product samples out of the packing line to test for pathogens.
I don’t think this is happening in some of larger companies. It’s hard for a company sourcing from nine farms to sample from all those farms daily. But to alleviate food safety risks, they have to implement a solution where they actually sample product before they ship it out. Issues do arise with sampling because you have to test a huge number of products for the tests to be statistically valid. And of course, you can never be sure that contaminated product doesn’t slip through the system.
Q: What about differences in topography between Salinas and Yuma?
A: One very important contrast: you see in some places in Salinas leafy vegetables in the valley, and another crop right next to it on a foothill, then a buffer area where you don’t grow anything, and then at the top of the hill, there is sometimes a cattle farm.
Q: And there is no scenario in Arizona where such proximity exists between vegetable production and livestock?
A: Nowhere to that extent. There is only one place in Arizona I can think of where you can find cattle and produce in the same area, and it’s still not that close in proximity. But I’m not saying that’s the reason why Arizona spinach production has been free of the outbreaks that Salinas has faced. We still don’t know the causes, and that’s why we need to continue researching.
Q: Do you have research projects underway to help uncover the underlying causes?
A: We are undertaking an irrigation study funded by a grant from the Arizona Iceberg Lettuce Research Council. We will be monitoring irrigation water in the Yuma Valley for three years. At the same time, we will be taking samples in different areas, counting birds, insects, and other animals, keeping track of wind, rain, relative humidity and temperature, to see if and how any of these factors correlate with peaks in microbials. We don’t know what is causing the outbreaks, but research studies like these will help us get closer to finding out.
So Jorge Fonseca believes in product testing and reassures us that Yuma doesn’t have the history of problems that the Salinas Valley has when it comes to food safety. What he can’t tell us is why. He lays out a few hypotheses:
Humidity during growing season in Salinas is 15 to 20% higher than what it is during growing season in Yuma.
The temperature is cooler in Yuma, growing season to growing season.
Water comes from the Colorado River in Yuma versus wells in Salinas. And an implication that transferring water to reservoirs might be an issue.
Irrigation is done mostly with overhead sprinklers in Salinas versus mostly furrow irrigation in Yuma.
Topography is such that cattle operations are closer to vegetable growing areas in Salinas than in Yuma.
Pundit Special Science Report:
Part 2 — The Science Of Waterborne Bacteria
Jim Prevor’s Perishable Pundit, December 15, 2006
In addition to exploring the differences in environmental conditions and growing practices between Salinas and Yuma, we still wanted to know more about Yuma and particularly water issues there, so Mira Slott, Pundit Investigator and Special Projects Editor, spoke with Charles Sanchez of the Yuma Ag Extension Service:
Charles Sanchez, University of Arizona, Yuma Ag Extension Service, Director and Professor of Soil, Water and Environmental Sciences
Q: Wasn’t there an issue several years ago in Yuma regarding potentially dangerous perchlorate levels in water used for production of leafy greens?
A: There had been a lot of speculation about toxic levels of perchlorate in the leafy vegetables, but research has shown they are perfectly safe to eat. Essentially, perchlorate isn’t a viable food safety issue.
Q: Could you explain the science behind that?
A: There are trace levels of perchlorate in the Colorado River, but the levels in lettuce are a small fraction of the reference dose considered safe as recommended by the National Academy of Science. I’ve measured spinach as well. The levels are a little higher, but certainly less than 10 percent of the reference dose.
Q: How did perchlorate become an issue in the first place?
A: There had been plants at a site near Las Vegas in Henderson, where perchlorate had leaked out through Lake Mead to the Colorado River. The contamination could have been there a long time, but we only had the technology a few years ago to detect it at the parts per billion level. In fact, due to bio remediation near the site of the contamination, the levels of perchlorate in the river have dropped substantially over the last few years.
Q: Has the water used for production been chemically treated?
A: Growers are rigorously testing water for pathogens, but to my knowledge, water is not being chemically treated in Yuma. In any case, it would be challenging to do so based on the production system here. Growers do spray with hyperchorloide in the field, but that’s not related to chemically treating water.
Q: Why would it be difficult?
A: The water is diverted from the river to canals on to the fields. We do furrow irrigation here. Logistically, it would be very difficult to chemically treat the volumes of water we use. We’re talking about approximately 5 billion cubic meters of water in the Yuma and Imperial Valley area that are used. Growers will use 40 inches of water for a lettuce crop. The water is let out of canals on to the field by gravity. You can’t treat those volumes of water. Well, it would be extremely challenging. Obviously if there was a need, we’d figure out a solution, but beyond that there hasn’t been a need to chemically treat it.
Q: Can you elaborate on that?
A: The pathogen testing hasn’t shown a need to chemically treat. During the production times starting in November through late March, the counts and surface water are extremely low, and there’s no evidence of harmful pathogens in leafy greens. Jorge Fonseca can attest to that.
So perchlorate is an old issue we don’t have to worry about. But what should we worry about? We went back to Salinas and Pundit Investigator and Special Projects Editor Mira Slott talked to Trevor Suslow of UC Davis:
Trevor Suslow: Extension Research Specialist at University of California, Davis. Learn more here.
Q: What was the impetus behind your in-depth studies of the water used for vegetable production in the Salinas, California area?
A: The California Lettuce Research Board in Salinas commissioned us about 4½ years ago to study water used for production, particularly looking to assess the safety of the reservoirs and identification of risks, analyze what kind of testing is appropriate, what the results mean, and what needs to be done to improve food safety. We had started doing work funded by the Board before then, examining livestock, manure issues, and moving to other areas including irrigation concerns predominantly around Romaine.
Q: Why the emphasis on water?
A: Nothing is black and white. In essence, obviously the water and water quality has always been a primary concern and point of control as it relates to fruit and vegetable production, disease control and food safety. Our primary focus was E. coli. In other areas of study, our primary concern was salmonella.
Most of the water testing has been focused on the Salinas Valley and the Central Coast, but we’ve extended it to other areas for comparative reasons.
Q: Could you bullet point the key findings for us?
A: In the reservoir study, we did comprehensive testing of 19 different reservoirs and found the water to be extremely safe. The majority of water at the times we were taking samples throughout the seasons contained very, very low populations of non-pathogenic E. coli. The amounts tend to fluctuate from sample date to sample date, and there is some variability based on a number of issues such as location and time, but by sampling over a couple of years, we established a base line for comparison.
We extended our research to capture water coming out of sprinklers at the farm level when irrigating. Typically, we found the background non-pathogenic bacteria lower in that water than from grab samples at the same reservoir from the shore line area. We simulated the way a grower would be testing the water from the reservoir for more meaningful numbers.
The final step was to look at populations of the same non-pathogenic bacteria on the plants themselves, a series of snapshots from the irrigated field, and the majority of plants showed very low or non-detectable E. coli.
We never found E. coli 0157:H7 in the samples taken from an irrigation reservoir. We have been taking samples over the last three and a half years, still continuing to do studies, but more narrowly focused based on our findings.
Q: Are you conducting studies to help in discovering answers to the spinach/E. coli outbreak?
A: That’s a tough question. Obviously, we at UC Davis and within our lab are more than willing to provide diagnostic testing and analysis if asked by the industry, the public, or the government. At this point, I don’t believe anyone here has been involved in the trace-back investigation. But we have been involved in the follow-up understanding of what led to the outbreak. Obviously we are paying very much attention to what is going on and want to use our experience and expertise to provide options for better implementation of food safety.
Q: What are some of the areas that need more research?
A: There are similarities and differences in production regions. None of these environmental connections are as straight forward as one tends to think. We need to go into more depth to understand what leads to pathogens’ survival and growth.
Local climates and micro climates in the Salinas region could play an important role. Temperature is a cause of bacteria multiplying on lettuce. Temperature, moisture and the method of delivery of irrigation are important factors.
We have studied differences between furrow and overhead irrigation as it relates to the presence of bacteria on the leaf. Expect slightly higher populations with overhead irrigation. If contamination does occur, we need to understand the likely outcomes of survival and growth, and the potential of plant internalization. We need to do these studies to protect the public. What I don’t like is speculation or increased testing for the sake of testing that gives everyone a false sense of security.
Q: Has this outbreak created hyper sensitivity to the dangers of eating produce?
A: An outcome of this very tragic situation is that consumers who had a lack of awareness are looking at food safety in a way they haven’t done before. The general public is confronting the world around them with the realities of the microbial world, questioning what they’re exposed to. That’s what we’ve been working on for 11 years at UC Davis, food safety concerns and challenges. Unfortunately, there’s only so much people will do until a catastrophe.
Q: But hasn’t the produce industry put food safety as a top priority long before this outbreak?
A: The thing that needs to have a bright spot put on it is that people and sectors in the produce industry have been working hard to develop the highest food safety standards. But there are still too many non-compliances and the industry needs to ferret out some of those lapses. With minimal participation, everyone falls down together.
I worked within the fresh produce industry before I came back to the University. Even with the best intentions, mistakes happen. You can have the best plan, but if you don’t have 100 percent buy-in from the top down throughout the organization, you can have very serious consequences.
Q: Will this involve extensive testing from the field to the processing operation to the finished product before it leaves the plant?
A: Testing and monitoring has a role in the right place and with the right frequency. It is not enough to just extend a lot of resources. In fact excessive testing can give a false sense of safety. First, there are not enough resources to go around, even for all the research that’s needed. You have to pick priorities and target areas where the information will be effective. Testing has a role and can be a great guide. But the best use of testing is where control points are used with strategies to minimize change, using the dollars to monitor those areas and make necessary adjustments.
Q: But wouldn’t more testing throughout the supply chain reduce the chance of food outbreaks?
A: The problem with product testing is that you can never do enough sampling. It’s just like me saying I never found a pathogen in a reservoir. The testing is only as good as the number of samples at that time on that date. You can identify some changes in what’s normal, establish a two-year baseline on 19 reservoirs and know what is in and out of range.
So we need to guard against false security from product testing and we need 100% buy-in from top down as to the priority of food safety.
Additionally, we sent Pundit Investigator and Special Projects Editor, Mira Slott, to talk to Richard Smith of the Cooperative Extension in Monterey County, California:
Richard Smith, Vegetable Crop and Weed Science Advisor, University of California Coop Extension in Monterey County. Learn more here.
Q: What can Salinas County do at this point to alleviate concerns about spinach production?
A: We are left looking at a plethora of possibilities that exist for E. coli contamination from the field to the harvest operation to the processing and packing plants. At any of those places, there is the potential for something to happen.
The reality is that growers take extensive measures. There is example after example of quite extraordinary efforts in the Salinas Valley and in general with the vegetable industry to make food safe. Part of the problem is that everybody has a theory. We’ve dealt with so many calls. Without all the data, it’s anyone’s guess, and there may be factors not even being considered.
Q: There have been concerns that if water were to be contaminated, Salinas irrigation systems could exacerbate the problem. Could you comment on this?
A: My colleague Steve Koike has worked with Trevor Suslow [see above] at U.C. Davis conducting an extensive 2 1/2-year evaluation of the water in Salinas County, looking at the most likely source of contamination; the piece of the puzzle where water is pumped out of the ground and goes into reservoirs. That’s a pretty solid piece of research that I don’t think people are giving enough credence to. The reality is you can find generic E. coli, but not necessarily the strain that’s the problem.
Q: Could you discuss how irrigation systems work in Salinas?
A: We do use overhead irrigation sprinklers here, and that is something we have to deal with if water turns out to be the issue. If the grower was using contaminated water, overhead irrigation could create a greater possibility of it getting on the plant. There is potential for that to spread the problem. With furrow irrigation, the water is at the base of the plant, so you wouldn’t be splashing water on the foliage.
Q: Would it make sense for growers to change irrigation strategies?
A: It would be very huge to make a change in our irrigation methods. First of all, the way spinach is produced in Salinas, it grows on 80-inch wide beds, so they don’t lend themselves to furrow irrigation. Furrow is not an option for that wide of a bed, so the other option would be drip irrigation. That would be a dramatic and costly change, because currently I don’t think there is even one acre of that.
Growers use a lot of drip irrigation on 40 inch beds. But high density spinach plantings would be a radical modification of our agricultural practices. Not that we can’t or wouldn’t make the change. It could be done, but we’re at the very bottom of the learning curve on that.
Q: Another issue being examined is the proximity of vegetable fields to livestock and other wild animals.
A: Growers started last year putting up plastic fencing in spinach fields within close proximity of ranches and to keep out rodents, coyotes and other wildlife. If growers don’t take heightened precautions to minimize food safety risks, they’ll lose their market.
Q: When an outbreak occurs, everyone loses, even growers with the most stringent standards…
A: We all feel terrible about the outbreak and the very serious illnesses and deaths. The problem is that all through this thing, I’ve been hearing off the cuff conjecture and assumptions from so many people. They may mean well, but when we have something this serious with illness and death, and millions and millions of dollars lost, we need to be prudent in researching and evaluating theories before making determinations.
The problem is the world is not going to wait for the research to fully understand the problem. We have to act on the best available information, even while redoubling our efforts to learn more.
Pundit Special Science Report:
Part 3 — Product Testing At Natural Selection Foods & McEntire Produce
Jim Prevor’s Perishable Pundit, December 15, 2006
A lot of coverage in the first two parts of this report was on the subject of product testing, so we asked Pundit Investigator and Special Projects Editor Mira Slott to get “real world” application of product testing from the folks at the epicenter of the spinach/E. coli crisis, Natural Selection Foods, which now tests product as it comes in from the farm:
Samantha Cabaluna, Senior Manager of Communications, Natural Selection Foods, San Juan Bautista, California
Q: What new food safety initiatives have you put in place?
A: We hired top food safety experts that did work in the beef industry to develop an even more aggressive three-pronged plan: field, firewall, and facility.
Q: Does the food safety plan emulate regulatory mechanisms created for the beef industry?
A: The program is based on the recommendations of the International Commission for Microbiological Specifications in Food. These are the same testing requirements the meat industry is using.
Q: Can you outline the key components in the field?
A: On the field side, we are testing every lot of seed for pathogenic E. coli and Salmonella. Every soil input requires a certified analysis from the supplier. Water sources will be tested aggressively. At first we are conducting weekly tests to assess the risk, and then a minimum monthly and as often as weekly based on the water source risk. For example, deeper water has less risk and surface water more.
We are increasing field inspection staff and frequency of inspections based on risk factors. We were visiting fields weekly before the outbreak. Heightened sanitation is being implemented at all points during harvest, from equipment to bins, to trailers, etc.
Q: What safety mechanisms are you implementing once product reaches the processing plant?
A: We are creating a firewall. We will break loads of 24 pallets leafy greens into six lots, four pallets each. We will pull 60 samples from each of the four pallet lots and send the product for testing of E. coli pathogens and Salmonella. Those samples are taken to a lab truck. The test takes 12 to 18 hours. During that time we will hold product in our warehouse. Once the test results are back, if they are clear , we will release the product for processing. If the test comes back positive, we will dump and destroy the product and go back and trace to the field.
Q: What about after processing?
A: Our facility had top notch food safety manufacturing procedures in place before the outbreak. We are adding to that, increasing agitation in the wash line, boosting filtration in the water and the water testing. We also put in a different type of chlorine that may be stronger at killing pathogens.
Q: Have you considered testing finished product before it is shipped out to retail?
A: We’re looking at testing product at the end of the line as a way to validate our new food safety protocols.
Q: Since Natural Selection was at the core of the outbreak and of the media onslaught, do you face more challenges in turning around consumer perceptions about food safety in your products?
A: More of the attention has been on Natural Selection and Dole. The Earthbound Farm brand definitely got associated with the outbreak. But we’ve received so many positive consumer comments about how we’re driving food safety forward and finding solutions. We are turning this tragedy into a catalyst for positive industry change, and trying to take a leadership role in these efforts.
One of the criteria the public will be looking for in any new food safety protocols is a test step for the product. We don’t have a kill step, so the public will demand a test step.
Finally, we finish our Pundit Special Science Report with insights into another processor’s program for product testing. In the first part of our Special Report, Yuma Post-Harvest Specialist Jorge Fonseca referenced a long-established program at McEntire Produce, Columbia, South Carolina.
Pundit Investigator and Special Projects Editor, Mira Slott, touched base with R.C. “Buddy” McEntire, Jr., and got him to give us a little background on his food safety efforts:
R.C. “Buddy” McEntire, Jr., President and Owner of McEntire Produce, Columbia, South Carolina.
R.C. McEntire began the company in 1938 as a tomato re-packer. Buddy bought the company from his father in 1975 with one employee, three ripening rooms and a delivery truck. Today, McEntire Produce employs 450 people and recently opened a new 163,000 square-foot, state-of-the-art food processing facility.
With more than 700 active products in its arsenal, R.C. McEntire distributes to both retail and foodservice clients throughout the Southeast on a daily basis. Main product categories are repacked tomatoes, fresh-cut lettuce, onions, cabbage, carrots and peppers as well as wholesale produce. McEntire was an early adapter of food safety methods such as product testing.
Pundit Investigator and Special Projects Editor Mira Slott caught up with Buddy while he was in the midst of moving into the company’s new processing facility. Buddy kindly took time out to share some of his thoughts on food safety and to reminisce about his personal journey to improve food safety within his own company:
The first day we cut lettuce and bagged it for restaurant use in the mid 70’s, I had a plan for sanitation and testing. There were no rules and no industry standards. However, I knew that I had a duty to do the best I could to protect public health. We used all stainless equipment, tables, etc., and when finished on the very first day, used sodium hypochlorite to sanitize surfaces after washing them.
I remember calling the dairy milk plant next door and discussing my sanitation product with the lab technician, and learning that it was the same product they were using, so I felt OK. That first year we bought some simple test kits for plate count and a small incubator to confirm our cleaning procedures were effective.
We originally did not wash iceberg lettuce, just pealed, trimmed, cored and shredded it on the slicing machine and bagged it with a twist tie. Then later on, we started using a vacuum system and metal clip. However, knowing that the metal could possibly end up in a sandwich, we decided to close the bag by heat sealing after evacuating the excess air. We built our own heat sealing machines.
We were one of the first to use a metal detector in the fresh-cut business, according to the companies that sold them. This was not my idea, but after seeing one in a bakery, I thought it would help make our cut lettuce and cabbage products safer.
Then we began washing cut lettuce and used chlorinated, chilled water and water extractors for drying after our first year. During the early years, I encouraged the other cut lettuce producers to institute a protocol that would protect our new industry. I was fearful of someone ruining our new fresh-cut, value-added industry by producing unsafe products. I was a founding member and board member of the National Association of Fresh Produce Processors (NAFPP), now part of United Fresh Produce.
Since the mid 70’s and even up until companies began using what is now called HACCP, we always controlled our production by the use of our black book, which basically had the same control steps with standards similar to today’s HACCP. We tested everything — hands, boots, surfaces, water temperatures, chlorine levels, PH levels, you name it. We have never been satisfied with the status quo when considering whether we were doing the right thing from a food safety standpoint.
We added oxide a couple of years ago and that really helped. Seems like very year we add a new method or machine to improve the safety of our products.
Once during our first five years, we received a load of carrots from the Midwest and checked the load for pathogens. We found the count too high. We put a hold on the raw product and I called the grower/packer to inform him of the problem. After quizzing him on his source of water, he told me he irrigated from a stream. I then asked him if any cattle farms existed nearby and he informed me there were some. I suggested he find a better source of water.
We rejected that load and took it to the city dump. I never bought from that company again. We have always tested product from day one. Today we continue to look for the 100 percent silver bullet that will further protect our customers, our industry, and most of all our publics’ health.
A lot of attention is always paid to the big Salinas-based processors, but in the early years of the NAFPP the industry was helped enormously by people like Buddy McEntire, who recognized early on that the whole industry could be destroyed a weak player. As Buddy said: During the early years, I encouraged the other cut lettuce producers to institute a protocol that would protect our new industry. I was fearful of someone ruining our new fresh-cut, value-added industry by producing unsafe products.
Lucky for the industry that he was fearful and that he had the vision to recognize that food safety knowledge was something to spread around, not hoard. Wonder what his Dad would say if he could see that new facility?