Evaluating Factors Explaining U.S. Consumers' Behavioral Intentions toward Irradiated Ground Beef.

Although food irradiation is deemed safe and endorsed by health-related organizations worldwide, consumers are reluctant to accept the technology. Yet, consumer acceptance is critical as food irradiation has significant potential for increasing the safety and availability of food globally. To communicate about food irradiation, science communicators should understand the psychology behind consumers' decision making related to irradiated foods. Using empirical research, we developed a theoretical model and used structural equation modeling to determine how nine variables affect consumers' behavioral intentions toward irradiated ground beef. We purchased a national quota sample from Qualtrics and surveyed N = 1102 U.S. consumers. The model explained 60.3% of the variance in consumers' attitudes toward food irradiation and 55.4% of their behavioral intentions toward irradiated ground beef. Attitude had the largest positive, total effect on consumers' behavioral intentions, which was followed by subjective social norm and perceived benefit. Perceived risk had the largest negative, total effect on behavioral intentions. Attitude mediated the effect of subjective social norm, perceived benefit, perceived risk, objective knowledge, and food technology neophobia. Environmental concern and health consciousness did not significantly affect behavioral intention. Science communicators should develop messaging strategies that seek to improve consumer acceptance with these factors in mind.

Effect of post inoculation drying procedures on the reduction of Salmonella on almonds by thermal treatments.

Since two outbreaks of salmonellosis were linked to the consumption of almonds in 2001 and 2004, the study of pathogen inactivation kinetics in almonds has been encouraged, often by conducting inoculated challenge studies. The inoculation method could affect the results of such challenge studies, because of the possible increase of moisture on the almonds resulting from a wet inoculation procedure, which may result in a potential overestimation of the effectiveness of treatments used to pasteurize almonds in industrial settings. Salmonella enterica serotype Enteritidis phage type 30 (PT30) isolated from an almond-linked outbreak was inoculated on nonpareil almonds and dried by accelerated (drying the inoculated almonds at 37 °C for 12 h) and conventional (drying inoculated almonds overnight at room temperature) drying methods, before treating the almonds with hot water (blanching) at 88 °C or hot oil (oil roasting) at 127 °C. The Weibull model explained the death of this pathogen on almonds better than log-linear model for oil roasting, whereas both log-linear and Weibull models were similarly effective for blanching. For blanching, the D values for Salmonella Enteritidis PT30 were 12.7 and 10.7 s with accelerated and conventional drying, respectively. For oil roasting, the b-values were 4.59 and 4.18 s with accelerated and conventional drying, respectively. Based on the models, it was concluded that the accelerated drying process resulted in a significantly smaller reduction in Salmonella Enteritidis PT30 on almonds in comparison to conventional drying for both blanching and roasting. Although conventional drying led to significantly lower D or b - values (depending on the model), this difference is not likely to affect the current processing parameters used by the almond industry.

Determination of the occurrence of Arcobacter butzleri in beef and dairy cattle from Texas by various isolation methods.

Arcobacter butzleri is a pathogenic bacterium that has been found in dairy cattle, pigs, poultry, and humans. As of this writing, there are no data on the incidence of A. butzleri in beef cattle. Given the differences in rearing practices used for feedlot cattle and those used for dairy cattle, differences in the incidences of this organism in various types of cattle may also exist. Numerous culture methods have been used to isolate A. butzleri, but there are few data on the comparative efficacies of these methods. The objectives of this study were to determine the incidence of A. butzleri in cattle from Texas and to compare the effectiveness levels of the Johnson-Murano (JM) method (consisting of enrichment in JM broth followed by plating on JM agar) and the Collins method (consisting of enrichment in EMJH-P80 broth followed by plating on Cephalothin, Vancomycin, and Amphotericin B [CVA] agar) in the isolation of this organism. Fifty cattle each from two feedlots, a dairy, and a stocker yard were sampled. Fecal swabs were obtained from cattle, and each sample was cultured by the JM method, the Collins method, and combinations of the two methods with the broth of one method being used with the agar of the other. Polymerase chain reaction was used to identify the isolates for confirmation of A. butzleri. Samples from 18 of 200 cattle tested positive for A. butzleri. This organism was detected by the JM method in 4.5% of the samples and by the Collins method in 2.5% of the samples. An incidence of 4.0% was found when JM broth was used with CVA agar, while no samples tested positive for A. butzleri when EMJH-P80 broth was used with JM agar.

Prevalence of Salmonella and Campylobacter in beef cattle from transport to slaughter.

The objective of this study was to evaluate the effect of typical production practices during the transport of cattle on the resulting incidence of Salmonella and Campylobacter in the feces, on the hides, and on the carcasses of these cattle and in the environment (trucks, holding pens, and knock boxes). Various factors were evaluated, including the type of animal (feedlot cattle vs. adult pasture cattle), the breed of cattle, the body condition of the animal, the age of the animal, the time of feed and water withdrawal, the contamination level of the transport vehicle at the feedlot or farm, the transport time, the time cattle were held in the holding pen at the plant, and the contamination level of the holding pen. Four groups of each type of animal were sampled on different days. Samples were collected from cattle prior to transport and after transport (rectal and hide swabs) as well as from the carcasses of these cattle. Pre- and posttransit samples were also taken from the transport vehicle and from the holding pen and knock box at the slaughter facility. For feedlot cattle, fecal shedding stayed fairly constant for both organisms before and after transport (3 to 5% for Salmonella and 64 to 68% for Campylobacter). However, the shedding rate for adult cattle increased from 1 to 21% for Salmonella but stayed constant for Campylobacter (6 to 7%). Contamination of hides with Salmonella increased for both animal types from a level of 18 to 20% to a level 50 to 56%. For Campylobacter, the contamination level decreased from 25 to 13% for feedlot cattle but remained unchanged for adult animals (1 to 2%). Nineteen percent of feedlot cattle carcasses and 54% of adult cattle carcasses tested positive for Salmonella, while only2% of feedlot cattle carcasses and none of the adult cattle carcasses tested positive for Campylobacter. Thus, for feedlot cattle, the factors considered in this study did not affect the shedding of either organism but did affect the contamination of hides with both. For adult animals, the factors increased both shedding of and hide contamination with Salmonella only, not Campylobacter.

Serotyping and antibiotic resistance profiling of Salmonella in feedlot and nonfeedlot beef cattle.

As part of a larger study to assess risk factors associated with hide and carcass contamination of beef cattle during transport to slaughter, a total of 281 salmonellae were isolated from 1,050 rectal, hide, carcass, and environmental samples. For feedlot cattle, salmonellae were recovered from 4.0% of rectal samples, 37.5% of hide samples, 19.0% of carcass samples, and 47.4% of environmental samples. For nonfeedlot cattle, salmonellae were recovered from 10.9% of rectal samples, 37.5% of hide samples, 54.2% of carcass samples, and 50.0% of environmental samples. Overall, the five serotypes most commonly associated with feedlot cattle and their environment were Salmonella Anatum (18.3% of the isolates), Salmonella Kentucky (17.5%), Salmonella Montevideo (9.2%), Salmonella Senftenberg (8.3%), and Salmonella Mbandaka (7.5%). The five serotypes most commonly associated with nonfeedlot cattle and their environment were Salmonella Kentucky (35.4%), Salmonella Montevideo (21.7%). Salmonella Cerro (7.5%), Salmonella Anatum (6.8%), and Salmonella Mbandaka (5.0%). Antimicrobial susceptibility testing of all of the isolates associated with feedlot cattle revealed that 21.7% were resistant to tetracycline, compared with 11.2% of the isolates associated with nonfeedlot cattle. None of the other isolates from feedlot cattle were resistant to any of other antimicrobial agents tested, whereas 6.2% of nonfeedlot cattle isolates were resistant to more than four of the antimicrobial agents tested.

Prevalence of Listeria monocytogenes during production and postharvest processing of cabbage.

From November 1999 to May 2000, analyses of 425 cabbage, 205 water, and 225 environmental sponge samples from four cabbage farms with packing sheds and from two packing sheds in the Rio Grande Valley and Uvalde, Tex., were conducted to determine whether Listeria monocytogenes was present. Samples were tested by the Food and Drug Administration method for the isolation of Listeria spp., and confirmed isolates were DNA fingerprinted by repetitive-element sequence-based polymerase chain reaction (rep-PCR). L monocytogenes was isolated from 3% (26 of 855) of the samples. Twenty of these isolates were obtained from cabbage (7 isolates from farms and 13 from packing sheds). Three isolates were from water samples(two from farms and one from a packing shed), and three were from environmental sponge samples of packing shed surfaces. Rep-PCR-generated fingerprints of 21 of the isolates revealed 18 distinctive banding patterns. Four isolates from environmental sponge samples of conveyor belts and from cabbage samples shared identical banding patterns, suggesting common sources of contamination. These identical environmental isolates suggest that contact with packing shed surfaces may be a source of contamination of cabbage. However, the cabbage samples could have arrived contaminated, since they were not washed.

Sensitivity of three methods used in the isolation of Arcobacter spp. in raw ground pork.

Arcobacter, an aerotolerant Campylobacter-like organism, has been designated an emerging pathogen because of its newly recognized ability to cause diarrheal illness in both humans and animals and its presence in the human food supply. Because there is no standard isolation method for its detection, the true occurrence of this pathogen is largely unknown. In addition, the lack of a standardized isolation protocol limits the ability of investigators to compare field data. Arcobacter has been detected in whole muscle and ground pork at various levels by two different isolation methods (those of deBoer and Collins). In this study, these methods were tested along with the Johnson-Murano (JM) method, developed in our laboratory. The sensitivity of each method was tested for ground pork inoculated with Arcobacter butzleri and Arcobacter cryaerophilus IA at levels of 10(4), 10(3), 10(2), and 10(1) CFU/g. Controls included tubes with uninoculated pork and broth tubes without pork. All samples that were morphologically similar to Arcobacter were analyzed by Gram staining and by catalase and oxidasereactions. Presumptive positive samples were confirmed by the polymerase chain reaction. The JM method was determined to be the most sensitive, detecting A. butzleri down to a level of 10(1) CFU/g in 100% of the samples and detecting A. cryaerophilus IA at a level of 10(1) CFU/g in 75% of samples. In a pure buffer system, the Collins method was as effective as the JM method in isolating both organisms to levels of 10(1) cells per g.

Lack of a cytolethal distending toxin among Arcobacter isolates from various sources.

Arcobacter has been shown to be present in numerous different sources, including poultry, water, and humans exhibiting gastroenteritis. The production of a cytolethal distending toxin (CDT) has been documented in Campylobacter, Helicobacter, and other species. The polymerase chain reaction was used to screen Arcobacter isolates from poultry, cattle, irrigation water, and human diarrhea for the presence of CDT genes. Cell filtrates and sonic extracts were also tested for CDT-like activity on Chinese Hamster Ovary, HeLa, and Intestinal 407 (INT407) cells in culture. No CDT amplimers were observed in any of the Arcobacter isolates investigated. However, toxicity to HeLa and INT407 cells was observed and was subsequently analyzed for cell cycle arrest in the presence of the Arcobacter extracts with flow cytometry. Cells treated with Arcobacter sonic extracts and filtrates exhibited normal cell cycles, suggesting that CDT is not expressed by Arcobacter. Thus, Arcobacter was shown to produce an entity that was toxic to some cells in culture, but this entity was toxic in a manner different from that of Campylobacter CDT.

Antimicrobial resistance of Listeria monocytogenes isolated from various cabbage farms and packing sheds in Texas.

Twenty-one isolates of Listeria monocytogenes from cabbage, environmental, and water samples were evaluated for antimicrobial resistance by the disk diffusion method. Ninety-five percent (20 of 21) of the isolates tested were resistant to two or more antimicrobial agents. This finding is significant, since multiresistant strains of Listeria spp. are not commonly found in nature. Eighty-five percent (17 of 20) of the multiresistant strains were resistant to penicillin, and the remaining multiresistant isolates were somewhat sensitive to penicillin. A multiresistant strain showing intermediate sensitivity to penicillin was resistant to gentamicin. One isolate was susceptible to all antimicrobial agents except penicillin. Penicillin- and gentamicin-resistant L. monocytogenes have not previously been reported from human, food, or environmental samples. This study provides evidence of the emergence of multiresistant L. monocytogenes strains, pointing to an increase in the potential threat to human health posed by this pathogen.

Sensitivity of Listeria monocytogenes to Sanitizers after Exposure to a Chemical Shock.

We tested the hypothesis that exposure of Listeria monocytogenes to sublethal levels of sanitizers (chemical shock) could affect survival to a subsequent exposure to lethal levels and the ability of the cells to attach to stainless steel surfaces. L. monocytogenes was exposed to an acidic anionic sanitizer, a chlorine-based sanitizer, an iodophor, and a quaternary ammonium compound, as well as to citric, lactic, and propionic acids. The cells were exposed to sublethal levels of each sanitizer for up to 60 min (chemical shock), followed by exposure to either the minimum inhibitory concentration (MIC) for 48 h, to the lethal level for 48 h, or to the MIC for 40 min followed by the lethal level for 48 h. No significant difference in survival was observed with most of the sanitizers used. However, exposure to a chemical shock with the acid anionic sanitizer for at least 10 min resulted in survival of the cells in the MIC of this sanitizer, as well as in the lethal level, but only when the cells were first exposed to the MIC for 40 min. Deliberate dissociation of citric acid by pH adjustment also resulted in survival of chemically shocked cells to lethal levels of this acid, suggesting that exposure to the dissociated form somehow enabled cells to survive exposure to lethal levels of the acid. Chemical shock did not affect attachment of the cells to stainless-steel chips.

Effect of Storage Conditions on Growth of Heat-Stressed Yersinia Enterocolitica in Ground Pork.

Ground pork was inoculated with either heat-shocked or non-heat-shocked (control) Yersinia enterocolitica . After thorough mixing, the meat was divided into 25-g portions in plastic pouches and sealed under air, vacuum, or modified atmosphere (50% CO2 and 50% N2). All the samples were heat-treated at 55°C for 15 min and then stored at either 25 or 4°C. Samples were plated at regular intervals after storage and the growth of Y. enterocolitica was determined. Survivors were also examined for pathogenicity by performing certain biochemical assays. The growth of Y. enterocolitica , both heat-shocked and control, was observed under all atmospheres and both temperatures. There was no significant difference in growth rates between the heat-shocked and control samples under all the storage atmospheres and temperatures. Also, in both heat-shocked and control samples, Y. enterocolitica grew rapidly under all atmospheres, and the survivors remained pathogenic. The results indicated that storage of meat at 4°C, whether under vacuum or modified atmosphere, was insufficient to inhibit growth of Y. enterocolitica and that prior heat shock had no effect on growth rate or pathogenicity of survivors.

Effect of Heat Shock on the Thermotolerance and Protein Composition of Yersinia enterocolitica in Brain Heart Infusion Broth and Ground Pork.

The optimum conditions required to induce a heat-shock response in Yersinia enterocolitica in brain heart infusion (BHI) broth were determined. The production of heat-shock proteins and the increased thermotolerance of heat-shocked Yersinia cells in ground pork when exposed to higher temperatures was also examined. Heat shocking Y. enterocolitica cells at 45°C for 60 min consistently resulted in an increased number of survivors to a subsequent treatment of 55 or 60°C in BHI broth when compared with non-heat-shocked controls. D values at 55°C were calculated as 7.7 and 2.0 min and at 60°C as 1.6 and 1.2 min for heat-shocked and control cells, respectively. After examination of heat-shocked cells by sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE), two distinct heat-shock proteins with molecular masses of 70.5 and 58.0 kDa were observed that were not present in the control. Evaluation of heat-shocked and control cell survival in ground pork revealed D55 values of 15.6 and 6.5 min and D60 values of 6.7 and 1.7 min, respectively. The results indicate that prior heat shock can induce increased resistance in Y. enterocolitica in ground pork to higher heat treatments. Survival of Yersinia enterocolitica in cooked meat due to the phenomenon of the heat-shock response can become a cause of concern regarding microbiological food safety.

Survival and Injury of Listeria monocytogenes , Listeria innocua and Listeria ivanovii in Ground Pork Following Electron Beam Irradiation †.

The sensitivity of five strains of Listeria to electron beam irradiation in ground pork as well as the extent of sublethal radiation injury exhibited by each were investigated. Ground pork was inoculated with one of five strains of Listeria and irradiated with from 0 to 1.25 kGy at 0.25 kGy intervals. Listeria innocua NADC 2841 was more radiation-resistant (D10 = 0.638 kGy) than L. monocytogenes NADC 2045 Scott A (D10 = 0.447 kGy), L. monocytogenes NADC 2783 (a hamburger isolate) (D10 = 0.424 kGy), L. monocytogenes ATCC 15313 (D10 = 0.445 kGy), and L. ivanovii NADC 3518 (D10 = 0.372 kGy), when recovered on tryptic soy agar supplemented with 0.6% yeast extract. D10 values for L. innocua , L. ivanovii , and L. monocytogenes ATCC 15313 were lower when cells were recovered on modified Oxford medium. These three strains were susceptible to radiation-induced sublethal injury, with the numbers of injured organisms increasing with irradiation dose. The two pathogenic strains of L. monocytogenes were not injured significantly at the dose levels used. The results show that the dose range currently being considered by the Food and Drug Administration for the irradiation of beef and pork (1.5 to 4.5 kGy) is adequate for the elimination of L. monocytogenes from pork.

Use of High Hydrostatic Pressure and Irradiation To Eliminate Clostridium sporogenes Spores in Chicken Breast.

High pressure has been studied for its usefulness in reducing microbial contaminants in foods. We sought to determine whether this technology could be used in combination with irradiation to develop shelf-stable products. We first determined the optimal pressure, temperature, and time conditions that would result in maximum reduction of Clostridium sporogenes spores in fresh chicken. At ambient temperature, a pressure of 6,800 atm for up to 60 min resulted in a 5-log-unit reduction. Heating the samples during pressurization at 80°C for 20 min resulted in the lowest number of survivors compared to samples that were heated and pressurized for only 1 and 10 min. Further, irradiation at a medium dose (3.0 kGy) before and after pressurization at 6,800 atm and 80°C for 1, 10, and 20 min revealed no significant differences in spore counts between samples that were pressurized and then irradiated or vice-versa. We then examined the effect of high pressure in lowering the irradiation dose necessary to eliminate all spores. The irradiation D value of C. sporogenes spores was calculated to be 4.1 kGy. Samples were then irradiated at various doses followed by pressurization at 6,800 atm at 80°C for 20 min. The irradiation D value was lowered to approximately 2 kGy, indicating that a combination of high hydrostatic pressure and irradiation can be used to produce chicken with an extended shelf life without the use of high irradiation doses.

Survival of Arcobacter butzleri and Campylobacter jejuni after Irradiation Treatment in Vacuum-Packaged Ground Pork.

The ability of Arcobacter butzleri to survive irradiation under vacuum in ground pork was determined and compared with that of Campylobacter jejuni . The D10 value for A. butzleri (0.27 kGy) was 1.4 × higher than that of C. jejuni (0.19 kGy). In addition, the D10 values for both organisms showed that an irradiation treatment of 1.5 kGy would yield a 5-log-unit reduction in the number of A. butzleri cells and a 7-log-unit reduction in the number of C. jejuni cells. This is sufficient to render meat products safe from these pathogens. These data indicate that A. butzleri is more tolerant to irradiation than C. jejuni .

Isolation and Purification of Enterocin EL1, a Bacteriocin Produced by a Strain of Enterococcus faecium †.

A meat isolate, identified as Enterococcus faecium L1, was found to produce a bacteriocin designated enterocin EL1 Enterocin EL1 was active against a narrow spectrum of microorganisms, inhibiting all tested strains of Listeria . Identification of the producer strain was determined phenotypically by biochemical and morphological tests. Enterocin EL1 was heat stable, sensitive to several proteolytic enzymes, and stable from pH 2 to 11. Adsorption of the bacteriocin to producer cells was dependent on ionic interaction of the bacteriocin and the cell surface at various pHs. By changing the pH of the extraction buffer, enterocin EL1 was extracted from E. faecium L1 cells in a concentrated form. Enterocin EL1 isolated by cell extraction was resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a protein with an approximate molecular weight of 2,300. Partially purified enterocin EL1 added to sensitive cells of Listeria ivanovii was bactericidal; however, the bacteriocin did not inhibit the producer strain L1.

Contamination of Pork Carcasses during Slaughter, Fabrication, and Chilled Storage.

In an attempt to determine points of greatest pathogenic contamination of pork, the prevalence of five pathogens was determined on pork carcasses at specific points during slaughter, fabrication, and refrigerated storage. Pork carcass and loin surfaces were swabbed at three hog slaughtering plants. Carcasses were swabbed after singeing, after the final wash of the slaughter process, and after 24 h of chilled storage. Boneless loins were swabbed after trimming and deboning, but before packaging. Also, vacuum-packaged loins were sampled after 36 days of storage at 2°C. Staphylococcus aureus , Salmonella spp., and Listeria monocytogenes were the most prevalent. S. aureus isolates showed a significant linear increase (P = 0.0399) from slaughter to fabrication processes, with the highest numbers detected after 24 h of refrigerated storage. Trimming fat from surfaces of pork loins reduced the number of initial S. aureus counts, but there was no further reduction after 36 days of refrigerated storage. Salmonella were isolated primarily from pork before fabrication and refrigerated storage. A continuous reduction in the numbers of Salmonella isolates was detected from the point of singeing to the point of fabrication. No Salmonella were isolated from vacuum-packaged pork stored for 36 days at 2°C. The relatively higher prevalence of the psychrotrophic pathogenic bacteria L. monocytogenes and Yersinia enterocolitica in vacuum-packaged pork loins after 36 days of storage at 2°C indicates the need for proper cooking and handling of meats prior to human consumption.

Elimination of Pathogens of Significance in Food by Low-dose Irradiation: A Review.

Food irradiation is a processing technology that has been shown to be a wholesome process by many scientific studies conducted worldwide during the past 40 years. The research has been supported by the World Health Organization, the Food and Agricultural Organization, and govemmental agencies in many different countries. Industrial support also has been substantial. Some of the benefits ascribed to this technology include improved shelf life, reduced use of Chemicals as preservatives, and reduced levels of pathogens in foods. Pathogens such as Listeria monocytogenes , Yersinia enterocolitica , and Aeromonas hydrophila are capable of growing at temperatures as low as 0°C and are considered to pose a threat to the safety of refrigerated products. The number of cases of foodborne illness caused by contamination by Salmonella and Campylobacter spp. continues to increase. Researchers have been investigating ways in which food safety can be improved without sacrificing product quality and wholesomeness. The sensitivity of these pathogens to low-dose irradiation has been studied in several food products. Survival curves have been elucidated, and some studies on the effects of storage atmosphere, storage temperature, heating, and various treatments in combination with irradiation have been conducted. This review presents background information on this technology, with an emphasis on the radiation sensitivity of some pathogens of importance. Suggestions for future work in this area are also discussed.

Effect of Heat Shock and Incubation Atmosphere on Injury and Recovery of Escherichia coli O157:H7.

Escherichia coli serotype O157:H7 cells were grown at 30°C for 6 h and subjected to a heat stress, or heat shock, at 42°C for 5 min. Heat-shocked and nonheat-shocked controls were heat treated at 55°C for up to 60 min. The number of injured cells was significantly higher in heat-shocked cells than in controls, and the rate of release of cell components was higher in heat-shocked cells. Anaerobic plating resulted in higher recovery of injured cells, when compared with aerobic plating, regardless of whether the cells were heat shocked or not. In addition, heat shocking resulted in lower catalase and superoxide dismutase activities when compared with controls. It also resulted in greater survivability after exposure to hydrogen peroxide, suggesting that heat shocking somehow enables the cells to survive exposure to toxic substances in addition to heat. The heat-shock response, coupled with anaerobic conditions, increased the ability of E. coli O157:H7 cells to recover after a heat treatment. Thus, heat shock did not afford protection to the cells against injury, but rather enhanced their ability to recover during storage.