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Cleaning Honeycombs With Ozone


Worker bees remove the mummified remains of larvae infected by the chalkbrood fungus, Ascosphaera apis. ARS scientists have found that fumigating combs with ozone can destroy spores of this pathogen. 
Sometimes, even honey bees need help with “housekeeping”—especially when it comes to tidying up their combs once the honey’s been removed. Research by Agricultural Research Service scientists has shown that fumigating combs with ozone gas can eliminate pests and pathogens that threaten honey bee health and productivity. Recent results suggest that ozone fumigation may also help reduce pesticide levels in combs.
The findings stem from a two-part study led by Rosalind James, an entomologist in ARS’s Pollinating Insect—Biology, Management, and Systematics Research Unit in Logan, Utah. Results from the first part of her team’s study, published in 2011 in the Journal of Economic Entomology,demonstrated that fumigating combs with ozone gas at concentrations of 215 to 430 parts per million (ppm) killed all life stages of the greater wax moth, depending on length of exposure. Adult moths and their comb-damaging larvae were most susceptible, and eggs were more resistant, requiring greater exposure levels.
Ozone, a highly reactive state of oxygen, also destroyed spores of the chalkbrood fungus after 24 to 36 hours of exposure using 1,500 ppm. Another honey bee pathogen, however, proved tougher to kill: The American foulbrood bacterium required substantially longer exposure times, along with high humidity levels and an ozone concentration twice as high.
Both pathogens can persist for years on beekeeping equipment and in hives as dormant spores. They germinate when conditions are optimal, and they attack the colony’s most vulnerable members, the larvae or “brood.” Methyl oxide and gamma irradiation are among treatments that have proven effective for disinfecting comb, but these treatments can be costly and impractical. “Irradiation has to be done in a regulated facility,” says James, “whereas an ozone fumigation chamber is something beekeepers can set up on their own.”
In January 2013, the team published results from the second part of the study in the journal Agricultural Science. That paper details ozone’s breakdown of coumaphos, fluvalinate, and several other pesticides that can accumulate in hives. Honey bees are typically exposed to pesticides while visiting flowers that have been sprayed or when the bees are treated for parasitic mites, notes James. The study’s coauthors include James Ellis of the University of Florida in Gainesville, and Adrian Duehl, formerly with the ARS Center for Medical, Agricultural, and Veterinary Entomology, also in Gainesville.
The team was particularly interested in coumaphos and fluvalinate because of the chemicals’ use against Varroa mites. Considered a top threat of honey bees nationwide, the flat-bodied parasites can weaken and eventually kill bees by feeding on their bloodlike hemolymph. Severe Varroa infestations can decimate a hive within months if left unchecked.
In experiments with glass vials containing residues of these mite-killing pesticides, ozone exposures of 500 ppm for 10 to 20 hours degraded 93 to 100 percent of coumaphos and 75 to 98 percent of fluvalinate. Higher concentrations and longer exposure times were required to reduce pesticide concentrations in wax and comb samples, which were obtained from a Florida-based commercial apiary to reflect real-world exposure levels. The researchers observed that ozone treatments degraded the pesticides better in new combs (less than 3 years old) than in older ones (more than 10 years old).
“There’s something about the wax that can impede this breakdown, especially in a comb that’s been reused in hives for many years,” says James. “It may be that organic materials build up inside the wax, and these materials adsorb or break down the ozone before it can react with the pesticides.”

Interior view of the ozone generator that supplies ozone to the fumigation chambers used in the studies.
One approach may be to start with new comb and treat it yearly to prevent pesticide residues from building up; another would be to replace comb more often than is commonly practiced. High-capacity ozone generators may be necessary for ridding comb of especially high pesticide concentrations—albeit at added cost.
During the study, participating beekeepers also reported an off-odor emanating from combs that had been treated for wax moths or small hive beetles and placed back into hive boxes. So, in a separate study, the team analyzed breakdown products from hives that had been treated with 2,000 ppm of ozone. They determined the primary source of the odor to be benign substances known as “carboxylic acids” and “straight-chain aldehydes.” Fortunately, the odors didn’t repel the bees and dissipated after a few months, according to the beekeepers. One also noted that bees accepted comb treated for wax moths better than untreated comb.
Besides coumaphos and fluvalinate, the ozone treatment reduced or eliminated eight other common agricultural pesticides found in Florida comb samples, including esfenvalerate (Conquer or Ortho Bug B Gon insecticides), thymol (a pesticide made from thyme extract), and chlorothalonil (Fung-onil or Daconil fungicides).
James envisions beekeepers fumigating combs after they’ve been removed from hive boxes and emptied of honey, but just before being placed in storage for the winter. Combs removed from storage aren’t necessarily placed in the original hive, but sometimes in a different one.
“This practice potentially transmits disease from one colony to the next, especially if the pathogen produces a spore that can stay dormant for long periods,” notes James.
Beekeepers may be reluctant to discard comb—even that which has become discolored from years of use—because of the considerable effort bees put into making comb. “It takes a bee time and energy to make wax, but it’s needed for making and storing honey, so creating new comb comes at a cost to honey production,” adds James.
Ozone offers an appealing solution for decontaminating combs before reuse because it’s a process that beekeepers can carry out using commercially available equipment. Although toxic at the concentrations that are used to kill pests and pathogens and degrade pesticides, ozone rapidly breaks down into water and oxygen, she notes.
Current uses of ozone, which is considered a “generally recognized as safe” substance by the U.S. Food and Drug Administration, include decontaminating pool and drinking water and safeguarding the postharvest quality of fruits and vegetables. Until James’s studies, there had been no published reports on using the gas to decontaminate honeycombs.
“In our next field trials, we are going to try using ozone on nesting boards for the alfalfa leaf-cutting bee, which is used for pollinating alfalfa crops intended for seed production,” says James. She also plans on collaborating with ARS’s Bee Research Laboratory in Beltsville, Maryland, to evaluate ozone’s effectiveness at reducing disease transmission and improving colony health.—By Jan Suszkiw, Agricultural Research Service Information Staff.
This research is part of Crop Production, an ARS national program (#305) described
Rosalind James is in the USDA-ARS Pollinating Insects—Biology, Management, and Systematics Research Unit, Utah State University, Logan, UT 84322-5310; (435) 797-0530.
"Cleaning Honeycombs With Ozone" was published in the March 2014 issue of Agricultural Research magazine.

Energy to protein ratio of several forage mixtures

The energy to protein ratio of forages affects ruminant N use efficiency but little is known on its variation among legume–grass complex mixtures. The objective of the research was to determine the variation in the ratio of forage readily-available energy to proteins along with the associated variation in yield and digestibility by mixing three or four grass species in combination with one of two legume species.
Four grass mixes [#1 – timothy (Phleum pratense L.), meadow fescue (Festuca elatior L.), and Kentucky bluegrass (Poa pratensis L.); #2 – timothy, meadow fescue, reed canarygrass (Phalaris arundinacea L.), and Kentucky bluegrass; #3 – tall fescue [Schedonorus phoenix (Scop.) Holub], meadow bromegrass (Bromus biebersteinii Roemer & J.A. Schultes), orchardgrass (Dactylis glomerata L.), and Kentucky bluegrass; #4 – tall fescue, meadow bromegrass, reed canarygrass, and Kentucky bluegrass] were grown with either alfalfa (Medicago sativa L.) or birdsfoot trefoil (Lotus corniculatus L.) at two sites with measurements taken on two simulated grazing events of the first post-establishment year.
The water soluble carbohydrate (WSC) to crude protein (CP) ratio among the eight legume–grass mixtures ranged from 0.64 to 1.04, while the ratio of readily fermentable carbohydrate fractions A and B1 to readily soluble protein fractions A and B1 [(CA + CB1)/(PA + PB1)], estimated using the Cornell net carbohydrate and protein system, ranged from 4.33 to 5.64.
This significant variation in the two ratios used to characterise the energy to protein balance was due to both legume species and grass mixes. Alfalfa-based complex mixtures had greater WSC/CP and (CA + CB1)/(PA + PB1) than birdsfoot trefoil-based mixtures (0.94 vs. 0.69; 5.42 vs. 4.47) but a lower in vitro true digestibility (IVTD; 902 vs. 913 g/kg dry matter, DM). The grass species mix #2 (timothy, meadow fescue, reed canarygrass, and Kentucky bluegrass) provided the best combination of high readily-available energy to protein ratio (WSC/CP = 0.87; (CA + CB1)/(PA + PB1) = 5.08), high DM yield, and average IVTD. The complex mixtures including alfalfa and meadow fescue had the best readily-available energy to protein ratio and DM yield.
Our results confirm the possibility of improving the balance between readily-available energy and proteins through the choice of species in complex mixtures made of one legume and three or four grass species.
To read more please visit the Science Direct website .
This has been taken from a paper issued in the Animal Feed Science and Technology Volume 188, February 2014.
Forage energy to protein ratio of several legume–grass complex mixtures 
Michele Simili da Silva, Gaëtan F. Tremblay, Gilles Bélanger, Julie Lajeunesse, Yousef A. Papadopoulos,  Sherry A.E. Fillmore, Clóves Cabreira Jobim

Reducing the Threat of Exotic Avian Diseases


ARS scientists have determined effective cooking times and temperatures for poultry meat and egg products to inactivate Newcastle disease and avian influenza viruses.
Before media headlines announced outbreaks of a new type of avian influenza virus in China in 2013, Agricultural Research Service scientists were already working day and night to pinpoint crucial information about the H7N9 virus that was affecting humans as well as poultry.
Inside the high-level, secure Southeast Poultry Research Laboratory (SEPRL) in Athens, Georgia, the scientists studied the virus sample received from the Centers for Disease Control and Prevention (CDC). They labored quickly to determine whether the existing genetic diagnostic assays, the real-time reverse transcriptase polymerase chain reaction (rRT-PCR), could identify the virus or needed to be modified first, and whether new ones needed to be developed. They examined the effectiveness of available avian influenza vaccines and began research to develop new vaccines to protect poultry against the virus. And they investigated the virus's origin to identify the poultry species potentially involved in transmission of the virus in humans and its continuation in China.
This is what the small team, led by David Suarez, research leader of the SEPRL's Exotic and Emerging Avian Viral Diseases Research Unit, does best. The group responds quickly to emergency needs in foreign or exotic animal diseases. The laboratory serves as an international collaborating center for avian influenza and Newcastle disease with global partners, industry, and U.S. governmental agencies, such as USDA's Animal and Plant Health Inspection Service and the CDC. Scientists focus on research to help prevent and control diseases such as avian influenza, sometimes called "bird flu," and Newcastle disease that threaten the poultry industry worldwide.
"Our lab looks at diseases from the poultry angle, but we're also very concerned about public health," Suarez says. "We work closely with CDC and the National Institutes of Health to share data and information for both animal and human health."

In an incubator room, veterinary medical officer David Suarez candles, or shines light through, embryonic chicken eggs to look for signs of life.
Embryo death may indicate viral infection.

Classifying Avian Influenza Viruses
Avian influenza virus strains, which infect poultry and other bird species, are characterized using two main proteins—hemagglutinin (H) and neuraminidase (N)—located on the surface of the virus, says David Swayne, SEPRL director.
Scientists sequence viruses or run serological tests for the 16 different hemagglutinins and 9 neuraminidases to determine the virus subtype. Some of these proteins are found in influenza viruses that grow in birds, and some are found in mammals and other species. Of the different H subtypes, only H5 and H7 have been found to be highly pathogenic for birds, which means they cause severe disease and kill more than 90 percent of infected birds, Swayne says.
"Highly pathogenic avian influenza viruses cause high poultry death losses, spread rapidly, and result in bans on international trade. They must be eradicated immediately. Low pathogenic viruses cause sick chickens and financial losses for farmers, but we can work with them through improved vaccines and other farm-management tools," Swayne says.
However, one exception makes research very essential, he adds.
"We want to know if the low pathogenicity virus can mutate to become highly pathogenic, which has happened multiple times," Swayne says. "That's the big question."

In a secure containment facility in Athens, Georgia, veterinary pathologist David Swayne and microbiologist Joan Beck (retired) determine the success of a new vaccine technology by taking throat swabs from chickens.

"Ducking" Bird Flu
A major concern is the H5N1 highly pathogenic avian influenza virus that continues to circulate in Asia, the Middle East, and Africa, causing great losses in poultry and disease in humans, says veterinary medical officer Mary Pantin-Jackwood.
Domestic ducks, which are common in Southeast Asia, have been implicated in the spread of the H5N1 virus. There, domestic ducks are raised in backyards and in rice paddies, where they can come into contact with wild ducks and other poultry.
"Because of these contacts, domestic ducks are a source of H5N1 and other influenza viruses. They're like a mixing vessel," Pantin-Jackwood says. "The influenza virus mutates a lot, but it can also pick up genes from other influenza viruses."
Ducks infected with H5N1 virus show a wide range of responses—from moderate-to-high mortality to no sickness at all—which makes it difficult to recognize and control H5N1 influenza in these birds. This helps explain why the virus remains endemic in countries like China, Vietnam, and Indonesia, where ducks are a large food industry.

A vaccine against Newcastle disease is administered to a baby chick by microbiologist Darrell Kapczynski.
In her studies, Pantin-Jackwood showed that young ducklings do not fight off H5N1infection as well as older ducks.
Successful control of the H5N1 virus in domestic ducks is important for the eradication of the disease in commercial poultry in Southeast Asia, she says. Duck species and husbandry practice should be considered when planning surveillance and control measures in countries with large domestic duck populations.
Pantin-Jackwood examined two commonly farmed domestic duck species, Muscovy and Pekin, and found a big difference in response to infection and vaccination against H5N1. Both species became infected with the virus, but Muscovy ducks developed a more severe disease.
"You need to vaccinate according to species of bird," she says. "In addition, domestic ducklings should be vaccinated before they are 1 month old and released into rice paddies, so they are well protected."

A new vaccine for turkeys, developed by ARS scientists, is effective against the H1N1 influenza virus.

Getting the Most Out of Vaccines
When a highly pathogenic H7N3 virus was reported in Mexico in 2012, microbiologist Darrell Kapczynski examined available vaccines to make sure they would be able to protect U.S. poultry against this virus. He analyzed two USDA-approved H7 isolates and developed inactivated vaccines.
"We demonstrated 100 percent protection in vaccinated birds against a lethal challenge of the virus, showing that the vaccine derived from these isolates could protect U.S. poultry," Kapczynski says.
Scientists also determined that the new virus was not the same H7N3 virus obtained from ducks in Mexico in 2006. The two viruses were related, but the 2012 virus was not a direct descendant of the 2006 virus, Kapczynski says.
"What is interesting about the 2012 virus is that the genetics that make it highly pathogenic come from the bird itself," he adds. "This virus mutated using the host's own nucleic acid—incorporating part of the chicken genome into the virus genome."
This unusual "genetic recombination" event underscores the need to make sure that poultry are also free of the low pathogenic forms of the virus, he says.
Kapczynski and his colleagues also demonstrated that the Mexican 2006 low pathogenic virus could be used as a vaccine. All birds vaccinated with the virus strain and challenged with the 2012 virus were protected.
"The economic impact of this newer virus is enormous," he says. "The affected region produces around 55 percent of the table eggs in Mexico. More than $720 million in losses were reported by the industry since the outbreak. Fortunately, the virus hasn't moved into the United States."

Diseases of chickens and other poultry are the focus of ARS's Southeast Poultry Research Laboratory in Athens, Georgia.

Keeping an Eye on Egg Production
The 2009 pandemic H1N1 influenza virus—known as "swine flu"—does not kill birds; it infects the reproductive tract of poultry, causing decreased egg production, Kapczynski says. First identified in Mexico, the virus spread quickly around the world. It was found in swine in Canada and in breeder turkeys in Chile, Canada, and the United States.
"This was a 'reassortant' virus, meaning it contains two or more pieces of nucleic acid from different parent viruses," Kapczynski says. "Typically, influenza viruses segregate based on species they can infect." This virus had gene segments of avian, human, and swine influenza viruses and was capable of infecting mammals as well as poultry.
The poultry industry wanted to know whether the vaccines in stock would protect turkeys against the 2009 H1N1 influenza virus. Kapczynski and his colleagues made a new vaccine from the pandemic H1N1 virus and tested it against commercial inactivated H1N1 vaccines. Birds were vaccinated either with the pandemic H1N1 vaccine or the commercial vaccines and then challenged in the laboratory. Scientists looked at egg production, serology, and shedding. The new vaccine protected against egg-production losses, whereas the commercial vaccines were not as effective.
"The take-home message was that the turkey industry needed to update the isolates in the vaccines to more closely match the field strains in order to protect their flocks against this virus," Kapczynski says.

Microbiologist Erica Spackman reviews results of a reverse transcription polymerase chain reaction test to determine whether there is virus in a sample and to generate material for gene sequencing.

Taking a "Swab" at Viruses
Before poultry is processed in the United States, the birds must be tested for avian influenza. Sample collection plays a key role in this process.
"In poultry, we test nearly 100 percent of all meat chicken and meat turkey flocks for the virus prior to processing. We also do a lot of surveillance in egg-laying chickens," says microbiologist Erica Spackman.
Identifying the best methods to collect avian influenza samples for optimal testing, and making sure the process is economically feasible, is important. Although the current method works well, Spackman found that improvements could be made.
"One of the most important variables is the number of swabs required—the sample size we take from inside the mouth of the chicken or turkey to see if the virus is there," Spackman says. "We need to collect a certain number of swab samples per flock to get a reasonable virus sample."
Swab samples are collected from the same flock and put into tubes for testing. Traditionally, each tube contains 1-5 swab samples. The idea was to determine whether more swab samples could be pooled together into a single tube without inhibiting or affecting the sensitivity of the test.
Spackman found that putting 1, 5, or 11 swab samples in the same tube did not affect testing. A similar experiment with Newcastle virus samples had the same results.
Industry groups are already using the new process, which saves money without comprising test performance, Spackman says.

Swabs are taken from inside the mouths of birds, placed in tubes, and then tested for the presence of avian influenza virus.

Investigating Newcastle Disease
Exotic Newcastle disease, an extremely virulent form of the virus, is not found in the United States, but it is widespread in Asia, Africa, South America, and Mexico. This contagious disease is costly, often fatal, and affects chickens and other bird species.
Like avian influenza, Newcastle disease threatens food security, particularly in countries like Africa, where poultry is the main source of meat protein, Suarez says. Most outbreaks are severe, killing about 80 to 90 percent of infected birds that have not been vaccinated or previously exposed to a less virulent form of the virus.
At SEPRL, microbiologist Claudio Afonso and veterinary medical officer Patti Miller study viruses from countries where the disease is endemic. They characterize the viruses, make sure existing tests and vaccines are effective against them, and develop strategies for better vaccines to control them. Recently, they proposed a new classification system for Newcastle disease isolates.
Newcastle disease virus comprises a diverse group of viruses. Historically, two systems have been used to classify isolates. The lineage system grouped isolates into six lineages and a host of sub-lineages. The genotype system grouped isolates into class I or class II.
Both systems were being used simultaneously, which generated confusion and sometimes the assignment of viruses to multiple genetic groups.
To produce reliable and consistent results, Afonso and his colleagues developed a single system to group viruses. They evaluated gene sequences of more than 700 Newcastle disease virus strains, comparing genomes to identify and classify specific groups of isolates.
"After our analysis, Newcastle disease virus isolates placed in class I had only a single genotype, while isolates in class II contained 15 genotypes," Afonso says. "Since we have developed guidelines to classify genotypes, three additional genotypes have been identified."
The new system can be used by any laboratory worldwide.

Avian influenza virus is harvested from a chicken egg as part of a diagnostic process.

Verifying Newcastle Vaccines
In collaboration with the poultry industry, the SEPRL team evaluates the capacity of current vaccines to protect against emerging isolates and tests improved vaccines.
"The genetics of Newcastle disease field strains differ from those of the vaccine strain," Suarez says. "As with avian influenza, the closer the 'seed'—the virus strain used to make the vaccine—is to the circulating virus, the more effective the vaccine."
Using this approach, scientists modified an existing Newcastle disease virus to include two key proteins in a new vaccine to provide optimal protection against other viruses or the field strain. The new vaccine reduced shedding and was more effective. Plans are being made to commercialize it.
In another study, Miller examined the role a bird's immunity plays in transmission of Newcastle disease virus, protection against it, and relationships among the genotypes. She determined the amount of antibodies produced by vaccinated animals and their capacity to transmit virulent challenge viruses.
"While there are multiple factors that affect the transmission of Newcastle disease, our findings suggest that, besides the level of antibodies induced after vaccination, decreasing the time to reach the peak antibody response should be a goal for future vaccines," Miller says.
Delivering Safe Egg Products
Scientists are taking their research a step further in a project that looks at how viruses can be rendered harmless when they are found in poultry products.
In past research, Swayne determined the times and temperatures needed to inactivate Newcastle disease and avian influenza viruses in poultry meat and egg products. "Those data sets are now included in the international regulations and used by the World Organization for Animal Health for cooking meat and eggs to make sure they are free of these disease-causing viruses," he says.
Because liquid egg products are normally pasteurized to eliminate Salmonella,Swayne and his colleagues investigated whether those pasteurization times and temperatures would also inactivate Newcastle disease and avian influenza viruses in egg products. They inoculated liquid egg products with both viruses and then heat-treated the eggs at various times and temperatures. The treatments were based on standard USDA pasteurization criteria for each specific product—homogenized whole egg and fortified, sugared, plain, and salted egg yolk.
Findings in one study suggested that one or more standard pasteurization processes killed the viruses in four of the five egg products, and the fifth required an extension of treatment for less than 1 minute.
Staying on Guard
Scientists at SEPRL continue to study existing Newcastle disease and avian influenza viruses and keep a vigilant watch on exotic poultry diseases as they emerge. They work to determine the origin of viruses, the best methods to detect them and to prevent them from spreading, and techniques to control and kill them. This research helps ensure that U.S. poultry is protected against these viruses if they happen to invade our country.—By Sandra Avant, Agricultural Research Service Information Staff.
This research is part of Animal Health, an ARS national program (#103) described
To reach scientists mentioned in this article, contact Sandra Avant, USDA-ARSInformation Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5128; (301) 504-1627.
"Reducing the Threat of Exotic Avian Diseases" was published in the March 2014 issue of Agricultural Research magazine.

Safer Eggs

New Technique Uses Radio Waves to Zap

Agricultural Research Service and Princeton University scientists have developed a better, faster way to pasteurize eggs.
If you’re a fan of classic Caesar salad or old-fashioned eggnog, you probably know that these foods contain raw eggs. For that matter, so do Béarnaise sauce, hollandaise sauce, conventionally made mayonnaise, some homemade ice cream, and, of course, eggs served sunny-side up or soft-boiled.
Problem is, about one out of every 20,000 chicken eggs produced in the United States has a high risk of being contaminated with Salmonella bacteria. Not all kinds of Salmonella are harmful to us, but some are, notably S. enteritidis, which has been associated with eating raw or undercooked eggs. This and other pathogenic Salmonella strains can cause diarrhea, stomach cramps, fever, and—in some instances—death.
Those most vulnerable to salmonellosis, as the disease caused by this microbe is known, are infants, preschoolers, pregnant women, the elderly, and anyone who has a compromised immune system.
Finding a Better Way To Kill the Bacteria
Properly cooking chicken eggs—such as by hard-boiling them—kills Salmonella.
So does pasteurizing them. Right now, a hot-water-immersion process is apparently the only technique used commercially in this country to pasteurize fresh “shell” eggs (eggs that are sold in-the-shell, instead of as a liquid product, for example). Many supermarkets offer these eggs as a specialty item in their dairy case.
But the hour-long immersion process may change qualities of these raw eggs, perhaps making them less satisfactory to discerning home cooks and restaurant chefs alike. Studies led by Agricultural Research Service chemical engineer Dave Geveke have resulted in a better, faster way to pasteurize raw shell eggs without ruining their taste, texture, color, or other important characteristics.
Geveke’s tests with some 4,000 fresh shell eggs indicate that heating them with the energy from radio waves, or what’s known as radiofrequency (RF) heating, followed by a comparatively brief hot-water bath, can kill harmful microbes without lessening the quality of the treated eggs.

Chemical engineering technician Andy Bigley positions an egg as chemical engineer Dave Geveke prepares to inject it with Salmonella. Their research has produced a technique for killing Salmonella without affecting egg quality.
Two-Phase Process
Here’s how his technique works: Each raw egg is positioned between two electrodes that send radio waves back and forth through it. Meantime, the egg is slowly rotated, and its shell is cooled by spraying it with water—to offset some of the heat created by the radio waves.
Unlike conventional heating, RF heating warms the egg from the inside out. That’s critical to the success of the process. It means that the dense, heat-tolerant yolk, at the center of the egg, receives more heat than the delicate, heat-sensitive white (albumen).
The hot-water bath comes next. The warmth of the bath helps the yolk retain heat, to complete the pasteurization. The heat from the water also pasteurizes the white, without overprocessing it.
From start to finish, the treatment takes around 20 minutes, making it about three times faster than the hot-water-immersion technique. And in tests using a research strain of Salmonella, Geveke showed that the RF-based process killed 99.999 percent of the Salmonella cells.
Inoculating the Eggs
Before the treatment, Geveke’s team artificially infected the eggs by poking a small hole in the top of each, injecting the Salmonella into the egg via a glass syringe, then sealing the hole with a droplet of quick-setting epoxy glue. In nature, a hen’s eggs can become contaminated with Salmonella if her ovaries are infected with it.
The idea of using RF heating to kill pathogens in foods isn’t new. But using RF heating to kill pathogens in eggs is novel. And Geveke and his colleagues are evidently the first to pair RF heating with a hot-water bath to pasteurize raw shell eggs.
The new process is safe and effective and is expected to be cost-efficient, Geveke notes. Another plus: RF heating is already a familiar technology in the food industry: It’s used in cooking, baking, and defrosting, among other chores.
Right now, the research is at the prototype stage. Christopher Brunkhorst of the Princeton Plasma Physics Laboratory in Plainsboro, New Jersey, teamed with ARS chemical engineering technician Andy Bigley and Geveke to build the compact prototype that has been used in their Wyndmoor, Pennsylvania, laboratory for the past 2 years. Geveke, Brunkhorst, and Bigley have applied for a patent for the research. What’s more, several companies that process eggs have already expressed an interest in the technology.
A provision of the U.S. Food and Drug Administration’s Food Code may contribute to growth of the raw-pasteurized-egg market. Already adopted by some states, the code specifies use of raw pasteurized eggs, or other pasteurized egg product, in place of unpasteurized eggs when foods such as Caesar salad are served to at-risk populations or to people who receive meals through “custodial care-giving environments” such as nursing homes, hospitals, or eldercare centers.
Though the specialty market is an obvious application of the RF-heating process, it could of course be used to pasteurize all of the more than 221 million fresh shell eggs produced in the United States every day. This would undoubtedly add to processors’ costs, but might be a convenience for shoppers and would add an extra margin of safety to all fresh shell eggs—not just the specialty product, Geveke points out.
Commercial use of the RF-based method is at least a year or so away. Geveke expects to begin pilot-scale tests this year. After that, regulatory approval would be needed.
Those of us who remember being able to lick leftover cake batter off of the mixing spoon—without having to worry about Salmonella—can hardly wait.—ByMarcia Wood, Agricultural Research Service Information Staff.
This research is part of Food Safety, an ARS national program (#108) described
David J. Geveke is in the Food Safety and Intervention Technologies Research Unit, USDA-ARS Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038-8598; (215) 233-6507.
"Safer Eggs: New Technique Uses Radio Waves to Zap Salmonella" was published in the March 2014 issue of Agricultural Research magazine.

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