Articles in this issue:
Irradiation has proven to be beneficial in controlling pathogens that could otherwise threaten meat products, but Food Safety Consortium researchers are careful to emphasize that it's not a stand-alone way of battling all potential problems. There is continued need for other controls, including production of healthy animals, sanitation throughout both production and processing and proper cooking. Irradiation can play an effective role in reduction of important pathogens as demonstrated in research by Consortium investigators at Iowa State University.
Producers and processors are looking for ways to accomplish long-term preservation of pork products and for ways to reduce possible contaminating pathogens to negligible levels. Irradiation can effectively inactivate harmful bacteria, yeasts, mold spores, parasite cysts, and parasite ova in and on meat. Researchers at ISU have also sought to measure the effects of irradiating meat to inactivate contaminating viruses. Researchers wanted to find out if acceptable dosage levels of irradiation would inactivate important types of viruses directly as well as whether irradiation would sensitize viruses on meat so that lesser amounts of heat would be needed to actually inactivate them.
"Our basic conclusions in the first study were that only large enveloped viruses like Herpes viruses were sufficiently affected by irradiation alone that contaminated meat would be make safe," said Dr. George W. Beran, ISU distinguished professor of microbiology, immunology, and preventive medicine. "In the second study we found that irradiation of virus contaminated meat only slightly increased the sensitivity of the viruses to low levels of heat, again with larger enveloped viruses being more susceptible. We found that in the range of viruses that the large viruses were more easily hit by the irradiation and inactivated than were the small viruses."
The herpes virus, a relatively large enveloped virus, was readily inactivated by irradiation and proved to be heat sensitive. "But as we turned to smaller viruses, the heat inactivation was only slightly increased in irradiated versus non-irradiated meat," Beran said.
The study showed, for example, that the pseudorabies virus (a model for Herpes viruses) in pork was completely inactivated at an irradiation dose of 5.27 kiloGrays or by 20 minutes of 50 degree Celsius heat. But studies of Echo viruses showed that although they were susceptible to being inactivated at slightly lower heating levels after irradiation, the question of whether irradiation could then be followed by lesser heating was not practically realized.
The study, conducted by Beran and ISU Food Safety Consortium investigators Terry Proescholdt and E.C. Pirtle, found that treatment programs for pork products, by a combination of irradiation and heat, reduce foodborne hazards by some of the most important contaminating viruses. But sanitary measures to prevent virus contamination and cooking of the meat to inactive contaminating viruses are still needed. Because most viruses which can cause human disease through meat occur through human contamination, protection of meat from viruses is important.
Although irradiation isn't a replacement for higher heating levels when reducing virus levels, irradiation is effective in inactivating both pathogenic and spoilage bacteria, and that extends the shelf life of pork products. "Viruses do not affect shelf life, because the viruses don't multiply.
They only stay viable," Beran said. "So from the standpoint of shelf life, which is essentially bacterial, the irradiation is definitely stronger."
The amount that pork products' shelf life is extended varies with levels of irradiation, sometimes lengthening the life span from one week to two weeks. But Beran cautioned that extended shelf life should be considered only a secondary result of a process that has safety as the main goal.
"It is more a consideration of having inactivated pathogenic bacteria that would be real foodborne hazards than it is extending shelf life," Beran said, adding that irradiation should not be considered as a "magic bullet but as an extremely valuable adjunct."
"We do not want to be accused of doing studies that would lead to irradiation being a cover-up for a dirty product," Beran said. "Dirty product can be bacteria, which are the easiest to measure. But dirty product can also mean contamination with viruses or also with agricultural and industrial chemicals or biological toxins which irradiation would not inactivate."
Beran said the sanitation of a product as it goes from production through processing is very important. Irradiation is valuable in eliminating pathogenic bacteria such as E. coli 0157:H7 in ground beef and Salmonella, Yersinia enterocolitica and Campylo
One of food scientists' major concerns about meat contamination is the reduction of pathogens acquired on the farm that animals take with them to the packing plant. "We are not going to eliminate them, but can we reduce them below the level that they are a hazard?" Beran said.
"So Salmonella is a major approach for us here. That's a major area of work right now and it is going to be increasing," Beran said. The question is if it is possible to raise swine in practical ways that will bring about a sufficient reduction of Salmonella and that will minimize the risk of Salmonella coming in to the packing plant with the hogs and contaminating their product.
"If there is one or two Salmonella per gram of meat on our plates, that's going to be an absolutely minimum risk," Beran said. "But if there are 1,000 to 10,000 per gram, then it's a major risk. Pathogens contaminate slaughter and processing equipment, cutting boards, knives, hands, and other foods that are not going to be cooked. We must pay attention to precautions at every stage from farm to fork to protect our meat from disease-causing hazards."
In the poultry processing plant of the future, the chicken carcasses will be moved down the line and a knife-wielding robot will cut out the meat in exactly the right place. This procedure will make it possible to bypass the evisceration, or disembowelment, of chicken carcasses and eliminate a source of contamination. It will also eliminate the need for running the carcasses through a chiller bath, another source for cross-contamination.
The future is closing in. A Food Safety Consortium research team led by Joel Walker, a biological and agricultural engineering professor at the University of Arkansas, is programming a computer-driven robotic arm to make the precise movements for slicing into a carcass. The robot can currently be directed manually to perform functions down to movements of less than a millimeter. Translating those movements into a computer program is the time-consuming part of the project now under way.
A person who is manually directing the robot's movements can take whatever amount of time necessary to cut the meat out of the chicken. The computer program, however, must be developed so that the robot will be able to perform the functions repeatedly for a line of passing carcasses.
"One of the difficulties with this system is that as chickens come around on a normal shackle line at a processing plant, they would be moving continuously," Walker said. "Of course, we've got to have them stop for awhile so we can operate on them. ... Obviously, with a processing plant sometimes running 30 birds a minute, more or less, we're going to have to cut these birds up in a few seconds."
The first step toward creating the automated system was development of a holding platform that supports the carcass while the legs are suspended in shackles. Meat was cut from the chickens in experiments that measured the knife's manually guided linear and rotational movements.
One of the hazards of cutting into non-eviscerated chickens is the risk of cutting into the body cavity. "The closer you cut to the body cavity the more danger there is of breaking that body cavity and spilling the intestinal contents," Walker said. And the main point of using robotics is to avoid eviscerating the chicken before removing the meat.
"The object of this is to eliminate that contamination that comes from the intestinal contents," Walker explained. "Normally, when they eviscerate birds they drag the eviscera out of the bird. It hangs down over the skin for a short time before the inspection occurs. After the inspection it's removed and at that point may leave contamination on the surface of the skin.
"With this process leaving all that intact, we've reduced the likelihood that skin contamination will occur. But at the same time in doing that process we've got to be very careful not to cut into the body cavity and cause the same kind of spillage. Making the cuts in the precise location is important."
Experiments on the birds using manual operation of the robot resulted in varied sizes of body cavity openings. Walker said the use of precise robotics equipment would provide more consistent results and reduce the amount of the body cavity opening. Also, a higher level of harvest of breast meat is expected as the mechanical system is improved and more precise cutting is developed.
Mechanical meat stripping still has limitations. Experiments showed that thighs and wings were not always separated precisely at bone joints; tender meat was not readily separated from the rest of the breast meat, and some meat remained on the carcass, particularly on the back side. Measurement of the birds' size before cutting begins should allow better control of knife motions.
When chickens are placed on the shackle line in preparation for cutting, the robot program will have to be modified according to the size and classification of each bird. "We don't know how many classifications we'll need to make in order for that to work," Walker said. Cuts on large birds will need to be plotted into a computer program differently than those for a small bird.
The robot controller can weigh the birds, and that may make it possible to accommodate the various bird sizes. "The robot can collect that information and feed that onto the program," Walker said. "The program would automatically modify itself." So an approaching line of 3-pound birds would prompt the computer to program the robot to make incisions appropriate for a bird of that size.
Three computers combine to make this system work. The robot is operated on a portable hand-held computer attached to the main box from which the robot's motions are calculated. Another computer transmits that data and actually controls the robot's movements. A third computer collects data on force, temperature and other types of motion sensing, and that information can be transferred on disk to office computers where engineers measure and plot robot movements.
"We can actually write programs using simulation systems in the office and bring those (to the research lab), plug them in on disk and have the robot move according to those directions," Walker said.
The hand-held computer has a red panic button that will shut down the entire operation if necessary. It also has a key to control the robot's speed.
Other possibilities exist for the holding platform and shackle line. "We don't have that holding platform mechanized yet," Walker said. "This robot controller actually has the ability to control more things than the robot itself. We could put a motor with relays or whatever mechanism ... on that holding platform so that as those chickens come by we can use those mechanisms under the control of the robot's system to grab onto that chicken and hold it while we're cutting it up."
The primary benefit of this system remains food safety. Researchers are continuing to evaluate microbial contamination from the mechanical meat stripping. The goal is to establish a system in which automated meat stripping combined with carcass spraying will ensure that clean carcasses stay clean.
Elimination of the evisceration process would have other impacts, such as reduction of water and energy usage. And as is often the case with new technological developments, the use of labor will be affected.
The exact effect on the labor force is still uncertain without knowing how mechanizing of the holding platform will work, Walker said. Some jobs will be created as personnel will be required to monitor and operate the robots.
"It may work out that this can reduce some of the labor-intensive operation," Walker said. "It can reduce some of the work-related injuries from repetitive motions of cutting up. It could create more high-tech jobs."
As the Food Safety Consortium faces its eighth anniversary, I am proud of its accomplishments and proud to be associated with the organization as its coordinator and chairman of its steering committee. L.B. (Bernie) Daniels, who formerly held those positions, reurned to full-time faculty status in animal sciences on Jan. 1. In my role at the University of Arkansas as dean of the Dale Bumpers College of Agricultural, Food and Life Sciences and associate vice president for agriculture, I have agreed to succeed Dr. Daniels in his positions with the Consortium.
Dr. Daniels deserves our thanks for his tireless service to the Consortium. He has been a major player in the Consortium's operations since he worked on its founding with Sen. Dale Bumpers several years ago. His colleagues on the Consortium's Technical Executive Committee -- George Beran of Iowa State University, Curtis Kastner of Kansas State University and Frank Flora of the USDA Cooperative State Research, Education and Extension Service in Washington -- have offered their commendations to Dr. Daniels for a job well done.
The Food Safety Consortium has a track record of accomplishment and a level of recognition that few people likely expected it to achieve when it began. The credit goes to the people who have guided its progress as it set out to accomplish its congressionally mandated mission: to develop technology for rapid identification of infectious agents and toxins; to develop a statistical framework necessary to evaluate the potential health risks; to determine the most effective intervention points to control microbiological or chemical hazards, and to develop risk-monitoring techniques to detect potential hazards in the distribution chain.
The people who have shared the responsibilities for accomplishing these tasks over the years have been the principal investigators and their support personnel at the three universities who conduct the research that is the heart of the Consortium's activities. The steering committee -- comprised of representatives of the three universities, the USDA and the beef, pork and poultry industries -- has carefully reviewed the Consortium's overall activities to ensure that the congressional mandate is met each year.
We have reason to be very proud of our colleagues' fine work in food safety research. I am looking forward to working with them as the Consortium continues to build on its excellent record.
Disease-causing food pathogens must be found before they can be destroyed. Researchers at Kansas State University have found a way to stimulate the growth of pathogens and have obtained a U.S. government patent on the process.
Daniel Fung, a Food Safety Consortium investigator and professor of animal sciences and industry at KSU, developed the process called "Enzymatic Method for Acceleration of Comestible Products." It was patented in January.
Fung is an authority in microbiological rapid methods, the area of research that seeks to find pathogenic bacteria in food within several hours of testing so food processors can know the quality of their product and determine what to do if pathogens are found.
Fung's research team found that Oxyrase, a membrane fraction of the E. coli bacteria, can stimulate the growth of food pathogens such as Listeria monocytogenes, Campylobacter and E. coli 0157:H7 in liquid broths.
Kooranee Tuitemwong of the KSU research team showed that Oxyrase and food grade membrane fragments can stimulate the growth of starter cultures, resulting in faster production of yogurt, buttermilk, bread, wine, beer and summer sausage in laboratory scale experiments.
The process can save the amount of time food processors spend on fermentation. "If you ferment faster, you kill pathogens faster," Fung said.
"We started the research to find out how fast we can stimulate the growth of the pathogens to detect them," Fung said. "Now we find out that these starter cultures --- the 'good guys' --- with the help of enzymes grow faster so we can kill the 'bad guys' faster."
If it turns out there are no pathogens in the product, the use of Oxyrase and food grade membranes will make it possible for fermentation to take place faster, saving time and money for processors. "In large-scale fermentation --- talk about money for heating and cooling," Fung said.
Recent government approval of steam pasteurization as a way of removing bacterial contamination from beef carcasses came as welcome news to Food Safety Consortium researchers at Kansas State University. KSU investigators conducted several trials testing the procedure at the campus food microbiology and meat processing facilities and determined it was an effective decontamination treatment, especially when used with washing, trimming and hot water/steam vacuum spot cleaning to remove visible contamination.
The U.S. Department of Agriculture's Food Safety and Inspection Service approved the process in December. Steam pasteurization was jointly developed by Frigoscandia Food Process Systems Inc. of Bellevue, Wash., along with Cargill Meat Sector of Minneapolis and Excel Corp. of Wichita, Kan. KSU assisted in establishing proper operating parameters based on bacterial kills and carcass color followed by in-plant commercial trials. Excel already has a steam pasteurization unit installed for use at its meat packing unit in Sterling, Colo., and plans to place units in its remaining plants in the U.S., Canada and Australia this year. Other large meat packers have indicated that they will install pasteurization equipment shortly, with over 60 units reserved on a waiting list.
"Steam pasteurization is designed to be used only after carcasses have been trimmed or vacuum spot-cleaned to meet current USDA zero tolerance criteria for physical contamination," explained Dr. Randy Phebus, a Food Safety Consortium researcher and KSU assistant professor of food microbiology, who led the microbiological evaluations of the system.
"Steam pasteurization was not developed to replace current carcass decontamination methods, but to be used as a final whole carcass antimicrobial treatment immediately prior to carcasses entering the cooler," Phebus said.
USDA, as defined in a recent Federal Register notice, is going to open up other technologies, "such as rinsing technologies, steam pasteurization and vacuum spot cleaning in what's called a multiple hurdle approach so that you have a series of steps in the process that reduce microbiological contamination," said Dr. Jim Marsden, a Consortium researcher and KSU professor of animal sciences and industry. "So the carcass looks clean and it gets cleaner as it goes through each step in the process."
Once a carcass is cleaned of visible contamination, steam pasteurization comes into play for elimination of the invisible pathogenic bacteria. "It certainly works better when you present a clean carcass into the steam pasteurization system," Marsden said.
The E. coli 0157:H7 bacteria can enter meat products during the slaughter and evisceration process from intestinal contents, milk or filth from hide removal.
"Trimming and vacuum spot cleaning are effective in removing visible contamination from small localized areas of the carcass," Phebus said. "Steam pasteurization which utilizes a hot water vapor offers the advantage of uniformly condensing over every square millimeter of that carcass, thereby killing invisible bacteria even where the carcass appears visibly clean. Even washing and the organic acid sprays don't provide that type of coverage. We're eliminating almost all bacteria with the exception of a few sporeformers and using only environmentally friendly water vapor."
The steam condenses on the carcass at temperatures of about 200 degrees Fahrenheit since the pasteurization chamber is slightly over atmospheric pressure. "The meat surface almost instantaneously reaches this temperature, effectively kil,teria," Phebus said. "I haven't met too many food-related bacteria that can withstand these high temperatures."
Steam pasteurization is the final step in the process of cleaning carcasses that are first cleared of visible contamination. Marsden does not believe the procedure will become mandatory because of religious and ethnic concerns in the preparation of some foods. For example, steam is not permitted on carcasses of kosher products. But USDA's consideration of E. coli 0157:H7 as an adulterant in raw meats, along with consumer pressures for safe meat products, will probably drive the increasing popularity of steam pasteurization, Phebus said.
"If you come off the slaughter floor free of E. coli 0157:H7, because you've steam pasteurized it, it's very unlikely to recontaminate the carcass with that particular pathogen during further processing if proper sanitary procedures are in place and followed," Marsden said. "It's not one that's likely to be carried around by people or to be environmentally present in the fabrication area of the plant. So I think that once steam pasteurization, in conjunction with other decontamination processes, is implemented across the industry that the problem of E. coli 0157:H7 in ground beef are going to be tremendously reduced if not eliminated."
Arcobacter bacteria in swine and the susceptibility of piglets to it is emerging as a potential concern among scientists. Food Safety Consortium researchers at the National Animal Disease Center in Ames, Iowa, are looking for more information about the role of livestock as carriers of foodborne pathogens and are evaluating management practices to reduce the pathogens.
Elsa Murano, now a researcher at Texas A&M University; Cliff Collins, who was a graduate student at Iowa State University, and Irene Wesley, a principal investigator for the Consortium and a scientist at NADC, surveyed five ground pork plants for the presence of Arcobacter and found results testing positive in ranges from zero to 90 percent among recovered samples. Differences in plant hygiene or swine-rearing practices could account for the differences in the incidence rate, the research team conclude
Researchers examined neonatal piglets that had been experimentally infected and determined that Arcobacter butzleri species to be pathogenic. Earlier studies had shown that the pathogenic Campylobacter jejuni and Helicobacter pylori bacteria readily colonized neonatal piglets as did Arcobacter butzleri.
Scientists have been studying the advantages of protecting pigs from pathogenic infection soon after birth. Another aspect of the NADC effort at detecting potential foodborne pathogens in livestock is focusing on management practices with young pigs. This study is examining the practice of segregated early weaning of pigs.
"We wished to determine if the prevalence (Campylobacter jejuni, Campylobacter coli, Arcobacter and Listeria monocytogenes) was lower in pigs raised by segregated early weaning than with on-farm cohorts," Wesley said. At three weeks of age, the piglets entered the segregated nursery. They were sampled upon entering the nursery, upon exiting four or five weeks later, and when they reached market weight.
Preliminary data from the study indicated that the piglets were positive for Campylobacter even though they had been administered antibiotics as they entered the nursery and had received a diet of medicated feed. But the difference in incidence was slight between the segregated pigs, with 38 percent testing positive, and the pigs that remained on the farm, of which 41 percent tested positive.
Arcobacter, however, was more prevalent in this experiment among the segregated pigs. The segregated herds registered 84 percent testing positive while only 24 percent among the on farm pigs. No incidents of Listeria monocytogenes were found in either the segregated or on-farm herds.
The study showed that "a management system which reduces the prevalence of one pathogen may not guarantee a decline in all potential foodborne agents," Wesley said. The NADC study will continue with scientists conducting a second evaluation on the impact of segregation on reducing Campylobacter and Arcobacter in pigs. The researchers are also participating in a U.S. Department of Agriculture National Animal Health Monitoring Survey in which they will look for Campylobacter jejuni and Yersinia.
Karen Harmon, who is working at NADC while a postdoctoral fellow funded by the ISU Food Safety Consortium, developed a multiplex polymerase chain reaction (PCR) to distinguish potential zoonotic foodborne pathogens. Harmon designed a PCR test to differentiate Arcobacter from other closely related bacteria.
Listeria monocytogenes has caused major epidemics associated with consumption of cheese, coleslaw, French pate and pickled pork tongues. "Zero tolerance" regulations exist against allowing processing of foods with L. monocytogenes. A product can be recalled if L . monocytogenes is found in ready-to-eat foods. Imported products are banned if found positive for L. monocytogenes. Harmon has designed a PCR test to distinguish L. monocytogenes from other Listeria species.
The bacterium Campylobacter jejuni has been recently linked to Guillain-Barre syndrome. In collaboration with Food Safety Consortium researcher Debra Winters at the University of Arkansas, Harmon constructed a PCR test to differentiate Campylobacter jejuni from Campylobacter coli. These microbes are difficult to grow in the laboratory and there are few tests to separate them.
Researchers with the Food Safety Consortium assembled for their annual meeting recently in Kansas City and reviewed ways to reduce foodborne pathogens through improved methods of detection and elimination. The Consortium's members from the University of Arkansas, Iowa State University and Kansas State University met with representatives of industry and government.
Thirty papers were presented by researchers reporting on the progress of their projects. University of Arkansas researcher Amy Waldroup reported on the results of using trisodium phosphate (TSP) to reduce microorganisms in commercial poultry processing plants. Only one U.S. processor has adopted the use of TSP for routine treatment of its products. Waldroup's report revealed that three retail surveys suggested that turkey carcasses or leg quarters treated with TSP did not provide the consumer with a microbiologically safer product, and recovery of Listeria was actually enhanced by TSP treatment. Waldroup noted that poultry companies should not rely solely on TSP to control Salmonella or any other pathogen.
An Arkansas research team led by Michael F. Slavik and Debra K. Winters has developed a polymerase chain reaction (PCR) for Campylobacter jejuni, a bacterium that is a major cause of human acute gastroenteritis. The assay can be used to detect C. jejuni on chicken carcasses. This immunoassay, which is specific for C. jejuni, could be used for reliable identification and diagnosis of C. jejuni gastroenteritis.
"Rapid detection of low numbers of C. jejuni directly from contaminated foods would be beneficial not only in reducing the time in which appropriate measures could be taken to remove such food from consumers, but also in reducing the time of diagnosis and treatment," Winters said.
A study by another team led by Slavik and J.W. Kim found that eggs washed in processing plants with alkaline chemicals were 30 to 70 times more porous than eggs washed with other chemicals. The team found that chemicals added in washwater could cause damage to the egg shell, which could allow bacterial penetration. The results showed that commercial detergents based on strong alkaline chemicals removed most of the cuticle layer, making the eggs more porous and possibly more susceptible to post-wash bacterial penetration. The team suggested that egg processing plants might consider the use of washes other than high alkaline detergents in egg washing.
Joel Walker of Arkansas reported on his team's work on a robotic system to remove meat from noneviscerated chicken carcasses. The system, which is still under development, would eliminate or reduce contamination of chicken from spilled contents of the body cavity. The project is focusing on development of methods to hold the carcass in place, the knife motions required to remove the meat and the measure of benefits in reducing microbial contamination.
Walker's team is also examining the results of tests conducted with a research oven to study how the cooking process affects the destruction of microbes, heat transfer and the effects of air impingement and moisture within the oven.
Iowa State researchers found that treatment of pork products with heat after irradiation may reduce contamination and extend their shelf life. George W. Beran told the annual meeting about experiments in which ground 80-percent lean pork was contaminated with four viruses and treated with different levels and times of heat after being exposed to measured doses of irradiation. The question was whether the absorbed irradiation would sensitize a virus so that a lesser amount of heat would be necessary to inactivate the virus.
Beran also reported on progress being made in reducing pathogens in meat. Pathogenic bacterial contaminants "must be prevented or removed during slaughter operations," Beran said. "The HACCP (Hazard Analysis and Critical Control Points) approach will be different from the traditional inspection system."
Essential components of prevention programs, Beran said, include the following: keeping all feeds free of Salmonella and protected from contamination, sanitation in production units, control of personnel working in the production units, prevention of contact between production units or animals with dogs, cats, rodents, birds and insects; prevention of animals from exposure to infectious and parasitic diseases, and maximum control of stress.
"A limited number of studies evaluating costs and benefits of approaches to prevent hazards at production level have been reported, particularly in Salmonella control programs in Europe, and studies in progress at Iowa State University are assessing effectivity of multisite, age-segregated rearing in breaking endemic cycles of Salmonella infections," Beran said.
Michael Grant of Iowa State reported on development of a new membrane filtration medium (in ColiBlue) for simultaneous detection and differentiation of total coliforms and Escherichia coli . Evaluated so far for application in water testing, further studies are identifying sensitivity in cultures on pork. This is important in consideration of monitoring meat for E. coli contamination.
Kansas State researchers discussed their work in steam pasteurization as a way of decontaminating freshly slaughtered beef tissue. The process has been shown to be effective in reducing high pathogenic bacterial populations. "We are on the verge of a revolution in improving the microbiological safety and quality of meats," KSU researcher Randy Phebus said.
Research showed that the most effective treatments would involve trimming and/or spot steam vacuuming of visible contamination followed by application of steam to the meat surface. Phebus said that in addition to improving the efficiency of pathogen removal, the steam pasteurization process would likely enhance the shelf life of further processed meat portions.
Melvin Hunt of Kansas State explained the results of another study of the effects of supplementing the diets of cattle with Vitamin E. The vitamin is administered to give ground beef patties up to a five-day extension of retail display life. Hunt said Vitamin E does not affect the internal cooked color or expressible juice of patties nor does it prevent premature browning of patties or cause persistent redness. Premature browning can create a potential safety hazard because it gives patties the appearance of having been cooked thoroughly when in fact any pathogens in the patty might still be viable.
Irradiation of boneless pork chops was found to have no effects or very limited effects on quality, Don Kropf of Kansas State said. He presented the results of a study of the effects of irradiation at three low-dose levels on flavor, aroma, color and product life of chilled and frozen pork chops in vacuum and aerobic packaging.
An investigation of how children under 4 years old acquire Salmonella infections showed that environmental contamination from a common unidentified source is likely to be an important factor contributing to children's acquisition of the infection. According to the study by Gordon Schutze and Russell Kirby of Arkansas Children's Hospital in Little Rock, food did not appear to play a major role in development of the infections. The study was conducted over two years on 90 children to identify the risk factors that led to the infections.
Ever since a strain of bacteria was linked to several cases
of food poisoning in the Northwest in 1993, food safety has been
of increasing concern to consumers. But detecting this bacteria,
E. coli 0157:H7, is difficult.
Scientists at Iowa State University and two other land grant universities have turned to biotechnology in the search for a way to detect this dangerous bacteria.
A grant from the USDA is funding the research at ISU. One of the projects in the grant is being conducted by Loren Will, along with Greg Phillips, both in the Department of Microbiology, Immunology and Preventive Medicine.
The researchers use a molecular probe to find E. coli 0157:H7 genetic material. Then with a process called polymerase chain reaction (PCR), these genetic markers are multiplied for easier detection.
Will said the PCR technique allows the scientists to generate enough DNA material to identify E. coli. "We're not actually coming up with live cells," he said. "Instead, we're able to simply identify the bacteria by a pattern that forms as the material is drawn across a gel."
Before the use of PCR, the only way for researchers to identify bacteria was to grow them in a culture dish, run biochemical tests on isolated colonies, and view them under a microscope. Will said the PCR technique is a more precise method, and the next step is to "speed up the process and make sure it works accurately every time."
The ISU research has only been done on ground pork. Will's team will continue to use the PCR technique to look for E. coli markers in a variety of places.
"We'll be testing samples of soil, water, and slaughtered animals from both farms and processors," he said. "We're essentially trying to detect this bacteria anywhere it could be, from the farm to the fork."
The USDA is working on a new system of meat inspection called Hazard Analysis and Critical Control Points (HACCP). The idea is to prevent bacterial contamination at all points in the food chain. It would be incorporated with the current system of using sight, smell and touch to
Will said he believes using PCR to detect the E. coli bacteria could work in concert with HACCP. "This process could take about four hours to see if the bacteria is present," he said. "Using a culturing method, it can take 36 to 48 hours to do the same thing." With that kind of lag time between slaughter and detection, Will said the meat would already be moving from the processor to the consumer before any problems could be found.
As part of the three-state Food Safety Consortium, research on PCR to detect E. coli bacteria is also under way at Kansas State University on beef and at the University of Arkansas on poultry.
"What we're doing is meaningful," Will said. "But this is only one of many tools being looked at to improve food safety. We're one cog in the wheel of science in this effort."
When poultry reaches the processing plant, some birds are condemned
during the inspections for a variety of reasons. By determining
what factors contribute to those condemnations, poultry processors
can reduce the number of carcasses condemned and improve the overall
quality of the processed product.
A Food Safety Consortium research project helped one poultry company take advantage of readily available statistics to improve its condemnation record. Dr. Amy Waldroup, a University of Arkansas poultry science professor, reviewed the material in agricultural survey data and showed the company where its weak spots affected the health of its flock. Since then, the company has significantly reduced the percentage of carcasses condemned at the plant.
Poultry companies regularly obtain data from agricultural survey companies that monitor the efficiency of the companies' live production and the quality of their processed carcasses. Statistical reports on the companies are prepared and distributed to them, ranking them according to their performance. A particular company can see what its numbers are and can see how its competitors are doing, although the statistics don't identify the competitors by name. So a poultry company's executives would know how its statistics compare to the top company on the list, although they wouldn't know who has the top ranking.
The statistics provide data on the number of condemnations experienced by poultry companies, but they don't tell why the numbers are at a certain level. "Is it because you have an inspector who's more strict than others?" Waldroup said. "Do you have poor bird health? Do you have poor nutrition?"
The poultry company that the UA researchers investigated is a small one. Its level of condemnations was higher than several of its competitors. "We wanted to try to help them look at this data in a new way to see if they could determine why they were falling short all the time," Waldroup said.
Researchers conducted a case study to determine whether any live production factors were related to the percentage of condemnations in the company's processing plants over two years. The client company's figures were compared to the corresponding numbers for the top-ranked companies. Then the production factors were correlated to the condemnation figures. For example, did the calorie content of the birds' diet correlate with the condemnation levels among the companies? Other factors evaluated were the number of days a chicken house sat empty between flocks, the rate of early mortality, overall mortality and stocking density.
"What we determined was that a lot of these factors in the processing plant had to do with bird health," Waldroup said. "Nutrition wasn't a factor. All the factors that had to do with bird health correlated with processing plant problems."
With that information, the company made changes to improve flock health and carcass quality. The changes included improved hatchery sanitation, increasing the number of days between flocks occupying the chicken houses, and a reduction in stocking density.
Poultry companies have generally not correlated agricultural survey data figures to determine the source of their problems. Industry representatives who listened to a presentation on the Arkansas research process at the annual Poultry Science Association meeting in Canada expressed interest in the procedure, Waldroup said. They wanted to know how to implement it so they could evaluate their companies' performance.
The chemical compound trisodium phosphate (TSP), although approved
by the government for use as a processing aid for poultry, doesn't
provide consumers with a safer product, a Food Safety Consortium
research team has found. The researchers, based at the University
of Arkansas, concluded that poultry companies should not rely
solely on TSP treatments to control pathogens.
TSP is a substance also used in detergents and in making water softeners and paper. A process for treating turkeys with TSP has been patented. The Arkansas researchers analyzed commercial turkey carcasses that had been treated with TSP and compared them with untreated carcasses. Pathogens were not virtually eliminated, the researchers determined.
"Some could argue that TSP treatment is just one hurdle or step in a HACCP-based program," the team's research report said. "However, if a hurdle is not effective, why include it?" (HACCP programs are science-based approaches to identifying and controlling critical points in food production that can affect food safety. The system is being implemented in meat and poultry plants in addition to the current inspection system to provide more check points to prevent microbiological contamination.)
Dr. Amy Waldroup, a poultry science professor at Arkansas and a principal investigator for the Consortium, said the research showed there wasn't any benefit in using TSP in poultry processing.
Waldroup objected to any characterization of the process as virtually eliminating pathogens. "It makes the consumer think (pathogens) are almost all gone, and they're not," she said. It would be more accurate if a TSP marketer claimed that the ingredient was being used in an effort to control pathogenic organisms, she said.
Currently, only one poultry processor has adopted TSP for routine treatment of its products although several companies have experimented with its use. "If this new technology significantly improves the safety of raw poultry, why hasn't the practice been adopted by a major portion of the industry?" the team's report asked.
In three separate trials, the research team analyzed whole turkey carcasses. In two trials the turkeys were purchased at retail with those in one trial fresh and those in the other trial frozen. In the third trial, the carcasses were obtained directly from the processor. In each trial, carcasses had been treated with TSP or were untreated. In the fourth trial, TSP-treated and untreated turkey leg quarters were examined.
The trials showed mixed results as to the prevalence of pathogens on the carcasses, but pathogens were present at various levels in all cases.
The first trial showed that 65 percent of the untreated turkeys and 10 percent of the TSP treated turkeys were contaminated with Salmonella. Seventy-five percent of the TSP-treated carcasses contained Listeria bacteria, although not the pathogenic Listeria monocytogenes species.
In the second trial, 56 percent of the TSP-treated turkeys tested positive for Salmonella contamination while 31 percent of the untreated turkeys were contaminated. Eighty-eight percent of the TSP-treated carcasses tested positive for Listeria; of the Listeria isolates from the TSP-treated carcasses, 64 percent were identified as the pathogenic Listeria monocytogenes.
Results of the third trial --- using the turkey carcasses provided by the processor --- were different than those in the first two trials. The TSP treatment appeared to work. Only 5 percent of TSP-treated carcasses were positive for Salmonella while 30 percent of the untreated carcasses were positive. Twenty percent of the TSP-treated carcasses tested positive for Listeria although none of the isolates were identified as Listeria monocytogenes. Levels of the pathogens E. coli and Campylobacter jejuni were reduced in these cases, although by very small amounts.
The researchers noted that it might appear that the carcasses purchased at retail may have had higher levels of these pathogens because retail storage allowed for the growth of the organisms. But the scientists saidthat temperature abuse of the carcasses could have occurred during transportation, distribution or retail storage. That could account for the growth of E. coli, they said, but it is unlikely that Campylobacter jejuni would grow under those conditions.
Also, the TSP-treated carcasses in the third trial did not contain necks or giblet but the untreated carcasses did contain these items. The necks and giblets are usually more contaminated on the surface, which could account for the reduced pathogen count on the TSP-treated carcasses.
The fourth trial used turkey leg quarters because this was the only TSP-treated product available at the retail location where the products were purchased. The goal in this test was to determine whether the first two trials offered results representative of TSP-treated products, so only TSP-treated leg quarters were purchased. These results showed the levels of aerobic plate count and the pathogenic Staphylococcus aureus and Campylobacter jejuni were higher than in the other three trials. Aerobic plate counts indicated that the leg quarters would have been considered spoiled. Thirty percent of the samples tested positive for Salmonella.
A contributing factor to these higher rates of contamination may be the additional handling required. "They had to go through a cut-up where they may have stayed longer at room temperature so organisms like E. coli could have had a chance to grow," Waldroup said.
Reviewing the overall results, the team determined that recovery of Listeria may be enhanced by treating poultry with TSP and that levels of Staphylococcus aureus do not appear to be affected by TSP.
Daniel Y.C. Fung of Kansas State received a grant from
the Organization for Economic Cooperation and Development based
in France to participate in research work on safety of meat, milk
and other animal products. Fung traveled throughout Europe and
presented papers at the Technical Institute of Olsztynie, Poland;
Agricultural University of Wroclaw, Poland; Ninth World Congress
of Food Science and Technology in Budapest, Hungary, and the Public
Health Department of the city of Budapest. He was also an invited
speaker at the Pasteur Institute in Paris. He presented a paper
on "Rapid Methods and Automation in Microbiology."
George W. Beran of Iowa State attended the United States Animal Health Association meeting Oct. 30-Nov. 2 in Reno, Nev. He is vice chair of the USAHA pseudorabies committee and a member of the food safety, animal production food safety, feed safety and pseudorabies program standards committees.
Beran also represented the American Veterinary Medical Association in Washington in November at a USDA Food Safety and Inspection Service meeting to finalize a new inspection system.
In October, Beran visited Premium Standard Farms in Princeton, Mo., for collaborative research in swine Salmonellosis with ISU graduate student Dave Baum.
Dermot Hayes, Jason Shogren and James Kliebenstein of Iowa State published "Valuing Food Safety in Experimental Auction Markets" in the February 1995 issue of the American Journal of Agricultural Economics; "A Comparison of Preferences for Pork Sandwiches Produced From Animals With and Without Somatotropin Administration" in the Journal of Animal Science, and "Consumer Response to Milk Produced by Cows Provided Bovine Somatotropin" in the 1995 Dairy Report produced by Iowa State University Extension. Kliebenstein was also interviewed on "Consumer Response to Improved Food Safety" on KICD Radio in Spencer, Iowa.
Dong Ahn of Iowa State, who recently joined the Food Safety Consortium as a principal investigator, reported he has had 24 publications in refereed journals and 11 presentations in conferences from 1987 to 1995.
Paula J. Fedorka-Cray of the National Animal Disease Center in Ames, Iowa, co chaired the HACCP Symposium at the Conference of Research Workers in Animal Diseases meeting in November.
Yanbin Li, Joel Walker, Michael Slavik and Hong Wang of Arkansas published "Electrical Treatment of Poultry Chiller Water to Destroy Campylobacter jejuni" in the Journal of Food Protection.
H.M. Stahr of Iowa State has been issued a patent, "Volatilization of Antimicrobial Drugs." The purpose is the elimination of antimicrobials in feed to eliminate residues in tissues. The process is for reusing chill water with ozonolysis sanitation with the American Water Purification Co. The process has been accepted by the USDA Food Safety and Inspection Service and the Food and Drug Administration. Stahr has also been invited to present a paper on "Reduction of Aflatoxin in Milk From Cows in China" at the Rocky Mountain American Chemical Society meeting in Denver in June. The Journal of Veterinary Diagnostic Investigation has accepted Stahr's article on "The Improved Method for Rumensin Analysis."
Nancy Brown of Iowa State published "Evaluation of Microbial Hazards of Pork Products in Institutional Food Service Settings" in two segments in successive issues of Dairy, Food and Environmental Sanitation.
The U.S. Department of Agriculture has taken the first major
step toward implementing a rule on Hazard Analysis and Critical
Control Points (HACCP) inspection systems in meat and poultry
plants. The USDA Food Safety and Inspection Service in January
released regulatory reforms that are designed to lead to adoption
of a final rule on HACCP plans later this year.
HACCP programs are science-based preventive systems of food safety controls implemented at key points in food processing.
"The changes are part of our comprehensive overhaul of the nation's meat and poultry inspection system," said Michael R. Taylor, USDA acting undersecretary for food safety. "The reforms are intended to support the new food safety measures USDA plans to adopt for all federally inspected meat and poultry plants."
As part of the regulatory reform effort, FSIS conducted a page-by-page review of its existing rules. FSIS said it identified more than 400 pages of regulations, about three-fourths of the total, "as candidates for elimination or change to make them simpler, less burdensome or more performance-based."
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The work of Food Safety Consortium researchers at the National Animal Disease Center in Ames, Iowa, was featured in the February edition of Agricultural Research, the monthly magazine published by the USDA Agricultural Research Service. The article, entitled "Keeping 'em Off the Farm," examined NADC's efforts to combat foodborne diseases spread by pathogenic microorganisms. The article covered NADC's work on several projects: weaning piglets in a sanitized environment to prevent Salmonella outbreaks; studying the relationship between stress and the presence of Salmonella in pigs' feces; developing a polymerase chain reaction to quickly detect Campylobacter, Listeria and Arcobacter; learning about the link between dietary stress in cattle and incidence of E. coli 0157:H7; detection of Listeria monocytogenes in cattle; pasteurization methods for killing Mycobacterium paratuberculosis in livestock, and development of a polymerase chain reaction to detect Brucella in cattle.
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The state of New York is beginning a public education campaign this spring to prevent illness from the pathogenic E. coli 0157:H7 bacteria. The campaign will be aimed at the highest risk groups: young children, the elderly and those with weakened immune systems. Media events and public and private organizations will be used to reach the public.
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Three federal agencies that deal with food safety are working together to collect data about diarrheal diseases, particularly those caused by E. coli 0157:H7 bacteria. The USDA Food Safety and Inspection Service, the Food and Drug Administration and the Centers for Disease Control are gathering information in northern California, Oregon, Minnesota, Connecticut and Atlanta. The project will review the risk factors for diarrheal diseases related to meat, poultry, dairy products, fruits, vegetables and seafood.
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The Food Safety Consortium now has a 3-by-6-foot color poster with photos depicting research highlights at its three universities. Three copies of the poster exist, one for each campus to display as it wishes. The poster has been displayed at the USDA Food Safety Conference in Washington and the American Farm Bureau Federation convention in Reno, Nev. We hope to show it at other events as they are held.
If you have comments or questions, contact us by U.S. mail at the Food Safety Consortium, 110 Agriculture Building, University of Arkansas, Fayetteville, AR 72701; by fax at 501-575-7531, or by e-mail at firstname.lastname@example.org.