Sanitization of Chicken Frames by a Combination of Hydrogen Peroxide and UV Light To Reduce Contamination of Derived Edible Products.

Chicken carcass frames are used to obtain mechanically separated chicken (MSC) for use in other further processed food products. Previous foodborne disease outbreaks involving Salmonella-contaminated MSC have demonstrated the potential for the human pathogen to be transmitted to consumers via MSC. The current study evaluated the efficacy of multiple treatments applied to the surfaces of chicken carcass frames to reduce microbial loads on noninoculated frames and frames inoculated with a cocktail of Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium. Inoculated or noninoculated frames were left untreated (control) or were subjected to treatment using a prototype sanitization apparatus. Treatments consisted of (i) a sterile water rinse, (ii) a water rinse followed by 5 s of UV-C light application, or (iii) an advanced oxidation process (AOP) combining 5 or 7% (v/v) hydrogen peroxide (H2O2) with UV-C light. Treatment with 7% H2O2 and UV-C light reduced numbers of aerobic bacteria by up to 1.5 log CFU per frame (P < 0.05); reductions in aerobic bacteria subjected to other treatments did not statistically differ from one another (initial mean load on nontreated frames: 3.6 ± 0.1 log CFU per frame). Salmonella numbers (mean load on inoculated, nontreated control was 5.6 ± 0.2 log CFU per frame) were maximally reduced by AOP application in comparison with other treatments. No difference in Salmonella reductions obtained by 5% H2O2 (1.1 log CFU per frame) was detected compared with that obtained following 7% H2O2 use (1.0 log CFU per frame). The AOP treatment for sanitization of chicken carcass frames reduces microbial contamination on chicken carcass frames that are subsequently used for manufacture of MSC.

The synergistic effects of slightly acidic electrolyzed water and UV-C light on the inactivation of Salmonella enteritidis on contaminated eggshells.

Salmonella enteritidis (S. enteritidis) infection has been recognized as one of the most common bacterial causes of human gastroenteritis worldwide and is closely associated with eggs. Slightly acidic electrolyzed water (SAEW) is an emerging environmentally friendly technology for disinfecting eggshell surfaces to remove dirt and pathogenic microorganisms. However, the efficiency of SAEW could be affected by the presence of manure. UV-based advanced oxidation processes have been studied to improve the microorganism's inactivation effect of disinfection. Therefore, in this study, the synergistic bactericidal efficacy of SAEW and UV-C light (ultraviolet lamp, λ = 254 nm) for inactivation of S. enteritidis on artificially inoculated eggshells with or without manure was evaluated, and the bactericidal efficacy of different combination treatments of SAEW and UV-C light was compared. Without manure interference, complete inactivation (reduction of 6.54 log10 CFU/g) of S. enteritidis on the surface of eggshells was achieved following a 4-min treatment with SAEW+UV at an available chlorine concentration (ACC) of 20 mg/L. In the presence of manure, a 3.02 log reduction was achieved following a 4-min treatment with SAEW+UV at an ACC of 30 mg/L. Simultaneous treatment with SAEW and UV light exhibits higher bactericidal activity for eggshells than other combination process methods with UV and SAEW. The results suggest that the combined treatment of SAEW+UV is a novel method to enhance the microbial safety of eggshells.

Effect of Food Structure, Water Activity, and Long-Term Storage on X-Ray Irradiation for Inactivating Salmonella Enteritidis PT30 in Low-Moisture Foods.

Recent outbreaks and recalls of low-moisture foods contaminated with Salmonella have been recognized as a major public health risk that demands the development of new Salmonella mitigation strategies and technologies. This study aimed to assess the efficacy of X-ray irradiation for inactivating Salmonella on or in almonds (kernels, meal, butter), dates (whole fruit, paste), and wheat (kernels, flour) at various water activities (aw) and storage periods. The raw materials were inoculated with Salmonella Enteritidis PT30, conditioned to 0.25, 0.45, and 0.65 aw in a humidity-controlled chamber, processed to various fabricated products, and reconditioned to the desired aw before treatment. In a storage study, inoculated almond kernels were stored in sealed tin cans for 7, 15, 27, and 103 weeks, irradiated with X ray (0.5 to 11 kGy, targeting up to a ∼2.5-log reduction) at the end of each storage period, and plated for Salmonella survivors to determine the efficacy of irradiation in terms of D10-value (dose required to reduce 90% of the population). Salmonella was least resistant (D10-value = 0.378 kGy) on the surface of almond kernels at 0.25 aw and most resistant (D10-value = 2.34 kGy) on the surface of dates at 0.45 aw. The Salmonella D10-value was 61% lower in date paste than on whole date fruit. Storage of almonds generally had no effect on the irradiation resistance of Salmonella over 103 weeks. Overall, these results indicate that product structure (whole, meals, powder, or paste), water activity (0.25 to 0.65 aw), and storage period (0 to 103 weeks) should be considered when determining the efficacy of X-ray irradiation for inactivating Salmonella in various low-water-activity foods.

Inactivation of Escherichia coli O157 and Salmonella Enteritidis in raw beef liver by gamma irradiation.

Irradiation of ground beef and beef liver inoculated with Escherichia coli O157 466 and DT66 and Salmonella Enteritidis 3313 were performed with gamma rays from cobalt-60 at refrigerated and frozen temperatures under air- and vacuum-packaged conditions. Results showed that D10 values for all pathogens in frozen beef liver were higher than those in frozen ground beef samples, with significant differences observed between the D10 values of E. coli O157 466 and S. Enteritidis 3313 under air-packaged conditions, as well as in E. coli O157 DT66 and S. Enteritidis 3313 under vacuum-packaged conditions. To verify effective bacterial inactivation under high bacterial-contamination levels (105-107 CFU/g), survival/death interfaces of E. coli O157 DT66 and S. Enteritidis 3313 inoculated in beef liver under vacuum-packaged and frozen conditions were constructed, with results suggesting that doses from 5.3 kGy to 5.5 kGy and 8.2 kGy-8.5 kGy would be sufficient to kill 105 CFU/g of E. coli O157 and S. Enteritidis 3313, respectively, at a 95%-99% predicted confidence interval. These results suggested that food matrixes containing high amounts of antioxidants (such as beef liver) and treated under frozen and vacuum-packaged conditions require additional consideration and evaluation for applications of irradiation treatment.

Evaluation of radio-frequency heating in controlling Salmonella enterica in raw shelled almonds.

This study was conducted to investigate the efficacy of radio-frequency (RF) heating to reduce Salmonella enterica serovars Enteritidis, Typhimurium, and Senftenberg in raw shelled almonds compared to conventional convective heating, and the effect of RF heating on quality by measuring changes in the color and degree of lipid oxidation. Agar-grown cells of three pathogens were inoculated onto the surface or inside of raw shelled almonds using surface inoculation or the vacuum perfusion method, respectively, and subjected to RF or conventional heating. RF heating for 40s achieved 3.7-, 6.0-, and 5.6-log reductions in surface-inoculated S. Enteritidis, S. Typhimurium, and S. Senftenberg, respectively, whereas the reduction of these pathogens following convective heating for 600s was 1.7, 2.5, and 3.7 log, respectively. RF heating reduced internally inoculated pathogens to below the detection limit (0.7 logCFU/g) after 30s. However, conventional convective heating did not attain comparable reductions even at the end of treatment (600s). Color values, peroxide values, and acid values of RF-treated (40-s treatment) almonds were not significantly (P>0.05) different from those of nontreated samples. These results suggest that RF heating can be applied to control internalized pathogens as well as surface-adhering pathogens in raw almonds without affecting product quality.

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature.

The aim of this study was to elucidate the antibacterial mechanism of 405 ± 5-nm light-emitting diode (LED) illumination against Salmonella at 4°C in phosphate-buffered saline (PBS) by determining endogenous coproporphyrin content, DNA oxidation, damage to membrane function, and morphological change. Gene expression levels, including of oxyR, recA, rpoS, sodA, and soxR, were also examined to understand the response of Salmonella to LED illumination. The results showed that Salmonella strains responded differently to LED illumination, revealing that S. enterica serovar Enteritidis (ATCC 13076) and S. enterica subsp. enterica serovar Saintpaul (ATCC 9712) were more susceptible and resistant, respectively, than the 16 other strains tested. There was no difference in the amounts of endogenous coproporphyrin in the two strains. Compared with that in nonilluminated cells, the DNA oxidation levels in illuminated cells increased. In illuminated cells, we observed a loss of efflux pump activity, damage to the glucose uptake system, and changes in membrane potential and integrity. Transmission electron microscopy revealed a disorganization of chromosomes and ribosomes due to LED illumination. The levels of the five genes measured in the nonilluminated and illuminated S Saintpaul cells were upregulated in PBS at a set temperature of 4°C, indicating that increased gene expression levels might be due to a temperature shift and nutrient deficiency rather than to LED illumination. In contrast, only oxyR in S Enteritidis cells was upregulated. Thus, different sensitivities of the two strains to LED illumination were attributed to differences in gene regulation.IMPORTANCE Bacterial inactivation using visible light has recently received attention as a safe and environmentally friendly technology, in contrast with UV light, which has detrimental effects on human health and the environment. This study was designed to understand how 405 ± 5-nm light-emitting diode (LED) illumination kills Salmonella strains at refrigeration temperature. The data clearly demonstrated that the effectiveness of LED illumination on Salmonella strains depended highly on the serotype and strain. Our findings also revealed that its antibacterial mechanism was mainly attributed to DNA oxidation and a loss of membrane functions rather than membrane lipid peroxidation, which has been proposed by other researchers who studied the antibacterial effect of LED illumination by adding exogenous photosensitizers, such as chlorophyllin and hypericin. Therefore, this study suggests that the detailed antibacterial mechanisms of 405-nm LED illumination without additional photosensitizers may differ from that by exogenous photosensitizers. Furthermore, a change in stress-related gene regulation may alter the susceptibility of Salmonella cells to LED illumination at refrigeration temperature. Thus, our study provides new insights into the antibacterial mechanism of 405 ± 5-nm LED illumination on Salmonella cells.

Efficacy of Traditional Almond Decontamination Treatments and Electron Beam Irradiation against Heat-Resistant Salmonella Strains.

Two outbreaks of salmonellosis were linked to the consumption of raw almonds from California in 2001 and 2004. As a result, federal regulations were developed, which mandate that all almonds grown in California must be treated with a process that results in a 4-log reduction of Salmonella. Because most of the technologies approved to treat almonds rely on the application of heat to control Salmonella, an evaluation of alternative technologies for inactivating heat-resistant Salmonella Enteritidis PT30 and Salmonella Senftenberg 775W was needed. In this study, almonds were inoculated with Salmonella Enteritidis PT30 and Salmonella Senftenberg 775W and then treated with an electron beam (e-beam) or by blanching or oil roasting. The irradiation D10-values for Salmonella Enteritidis PT30 and Salmonella Senftenberg 775W treated with e-beam were 0.90 and 0.72 kGy, respectively. For heat treatments, thermal D10-values for Salmonella Enteritidis PT30 and Salmonella Senftenberg 775W strains were 15.6 and 12.4 s, respectively, when subjected to blanching at 88°C and 13.2 and 10.9 s, respectively, when roasted in oil at 127 ± 2°C. No significant differences in irradiation and thermal treatment results were observed between Salmonella Enteritidis PT30 and Salmonella Senftenberg 775W (P > 0.05), indicating that e-beam irradiation may be a feasible technology for reducing Salmonella in almonds. However, the sensory changes resulting from irradiating at the doses used in this study must be evaluated before e-beam irradiation can be used as a nonthermal alternative for decontamination of almonds.

Electron-Beam-Inactivated Vaccine Against Salmonella Enteritidis Colonization in Molting Hens.

Electron-beam (eBeam) irradiation technology has a variety of applications in modern society. The underlying hypothesis was that eBeam-inactivated Salmonella enterica serovar Enteritidis (SE) cells can serve as a vaccine to control SE colonization and shedding in poultry birds. An eBeam dose of 2.5 kGy (kilograys) was used to inactivate a high-titer (10(8) colony-forming units [CFU]) preparation of SE cells. Microscopic studies revealed that the irradiation did not damage the bacterial cell membranes. The vaccine efficacy was evaluated by administering the eBeam-killed SE cells intramuscularly (1 x 10(6) CFU/bird) into 50-wk-old single comb white leghorn hens. On day 14 postvaccination, the hens were challenged orally with live SE cells (1 x 10(9) CFU) and SE colonization of liver, spleen, ceca, and ovaries determined on day 23. Blood samples were collected on days 0, 14, and 23 postvaccination and the sera were analyzed to quantify SE-specific IgG titers. The vaccinated chickens exhibited significantly (P < 0.0001) higher SE-specific IgG antibody responses and reduced SE ceca colonization (1.46 ± 0.39 logi10 CFU/g) compared to nonvaccinated birds (5.32 ± 0.32 log10 CFU/g). They also exhibited significantly lower SE colonization of the ovaries (1/30), spleen (3/30), liver (4/30), and ceca (7/30) compared to nonvaccinated birds. These results provide empirical evidence that eBeam-based SE vaccines are immunogenic and are capable of protecting chickens against SE colonization. The advantages of eBeam-based vaccine technology are that it is nonthermal, avoids the use of formalin, and can be used to generate inactivated vaccines rapidly to address strain-specific infections in farms or flocks.

Combining Lactic Acid Spray with Near-Infrared Radiation Heating To Inactivate Salmonella enterica Serovar Enteritidis on Almond and Pine Nut Kernels.

The aim of this study was to investigate the efficacy of near-infrared radiation (NIR) heating combined with lactic acid (LA) sprays for inactivating Salmonella enterica serovar Enteritidis on almond and pine nut kernels and to elucidate the mechanisms of the lethal effect of the NIR-LA combined treatment. Also, the effect of the combination treatment on product quality was determined. Separately prepared S. Enteritidis phage type (PT) 30 and non-PT 30 S. Enteritidis cocktails were inoculated onto almond and pine nut kernels, respectively, followed by treatments with NIR or 2% LA spray alone, NIR with distilled water spray (NIR-DW), and NIR with 2% LA spray (NIR-LA). Although surface temperatures of nuts treated with NIR were higher than those subjected to NIR-DW or NIR-LA treatment, more S. Enteritidis survived after NIR treatment alone. The effectiveness of NIR-DW and NIR-LA was similar, but significantly more sublethally injured cells were recovered from NIR-DW-treated samples. We confirmed that the enhanced bactericidal effect of the NIR-LA combination may not be attributable to cell membrane damage per se. NIR heat treatment might allow S. Enteritidis cells to become permeable to applied LA solution. The NIR-LA treatment (5 min) did not significantly (P > 0.05) cause changes in the lipid peroxidation parameters, total phenolic contents, color values, moisture contents, and sensory attributes of nut kernels. Given the results of the present study, NIR-LA treatment may be a potential intervention for controlling food-borne pathogens on nut kernel products.

Inactivation kinetics of foodborne pathogens by UV-C radiation and its subsequent growth in fresh-cut kailan-hybrid broccoli.

The inactivation of Escherichia coli, S. Enteritidis and Listeria monocytogenes after UV-C radiation with 0, 2.5, 5, 7.5, 10 and 15 kJ UV-C m(-2) on fresh-cut kailan-hybrid broccoli was explored. Inactivation did not follow linear kinetics. Hence, it was modelled by using the Weibull distribution function, obtaining adjusted R(2) values higher than 94%, indicative of the accuracy of the model to the experimental data. The UV-C doses needed to reduce 1 log cycle the E. coli, S. Enteritidis and L. monocytogenes counts were 1.07, 0.02 and 9.26 kJ m(-2), respectively, being S. Enteritidis the most sensitive microorganism to UV-C radiation while L. monocytogenes was the most resistant. According to experimental data, UV-C doses higher than 2.5 kJ m(-2) did not achieve great microbial reductions. No differences in the growth behaviour of these microorganisms was observed in the treated samples stored under air conditions at 5, 10 and 15 °C, compared to the control. Conclusively, low UV-C doses are effective to reduce E. coli, S. Enteritidis and L. monocytogenes populations in fresh-cut kailan-hybrid broccoli keeping such counts stable during shelf life at 5-10 °C. The current study provides inactivation models for these foodborne pathogens that can be used in microbial risk assessment.

Inactivation of Salmonella enterica by UV-C light alone and in combination with mild temperatures.

The aim of this investigation was to study the efficacy of the combined processes of UV light and mild temperatures for the inactivation of Salmonella enterica subsp. enterica and to explore the mechanism of inactivation. The doses to inactivate the 99.99% (4D) of the initial population ranged from 18.03 (Salmonella enterica serovar Typhimurium STCC 878) to 12.75 J ml(-1) (Salmonella enterica serovar Enteritidis ATCC 13076). The pH and water activity of the treatment medium did not change the UV tolerance, but it decreased exponentially by increasing the absorption coefficient. An inactivating synergistic effect was observed by applying simultaneous UV light and heat treatment (UV-H). A less synergistic effect was observed by applying UV light first and heat subsequently. UV did not damage cell envelopes, but the number of injured cells was higher after a UV-H treatment than after heating. The synergistic effect observed by combining simultaneous UV and heat treatment opens the possibility to design combined treatments for pasteurization of liquid food with high UV absorptivity, such as fruit juices.

High-intensity 405 nm light inactivation of Listeria monocytogenes.

The antimicrobial properties of light is an area of increasing interest. This study investigates the sensitivity of the significant foodborne pathogen Listeria monocytogenes to selected wavelengths of visible light. Results demonstrate that exposure to wavelength region 400-450 nm, at sufficiently high dose levels (750 J cm(-2)), induced complete inactivation of a 5 log(10) population. Exposure to wavelengths longer than 450 nm did not cause significant inactivation. Analysis of 10 nm bandwidths between 400 and 450 nm confirmed 405(± 5) nm light to be most effective for the inactivation of L. monocytogenes, with a lesser bactericidal effect also evident at other wavelengths between 400 and 440 nm. Identification of the optimum bactericidal wavelength enabled the comparison of inactivation using 405(± 5) nm filtered light and a 405 nm light-emitting diode (LED) array (14 nm FWHM). Results demonstrate similar inactivation kinetics, indicating that the applied dose of 405 nm light is the important factor. Use of the 405 nm LED array for the inactivation of L. monocytogenes and other Listeria species resulted in similar kinetics, with up to 5 log(10) reductions with a dose of 185 J cm(-2). Comparative data for the 405 nm light inactivation of L. monocytogenes and other important foodborne pathogens, Escherichia coli, Salmonella enteritidis and Shigella sonnei, are also presented, with L. monocytogenes showing higher susceptibility to inactivation through 405 nm light exposure.

Effects of irradiation dose and O(2) and CO(2) concentrations in packages on foodborne pathogenic bacteria and quality of ready-to-cook seasoned ground beef product (meatball) during refrigerated storage.

Combined effects of gamma irradiation and concentrations of O(2) (0, 5, 21%) and CO(2) (0, 50%) on survival of Escherichia coli O157:H7, Salmonella enteritidis, Listeria monocytogenes, lipid oxidation, and color changes in ready-to-cook seasoned ground beef (meatball) during refrigerated storage were investigated. Ground beef seasoned with mixed spices was packaged in varying O(2) and CO(2) levels and irradiated at 2 and 4 kGy. Irradiation (4 kGy) caused about 6 Log inactivation of the inoculated pathogens. Inactivation of Salmonella was 0.9- and 0.4-Log lower in 0 and 5% O(2), respectively, compared to 21% O(2). Irradiation at 2 and 4 kGy increased thiobarbituric acid reactive substances in meatballs by 0.12 and 0.28 mg malondialdehyde kg(-1), respectively, compared to control. In reduced-O(2) packages, radiation-induced oxidation was lower, and the initial color of an irradiated sample was maintained. Packaging with 0% + 50% CO(2) or 5% O(2) + 50% CO(2) maintained the oxidative and the color quality of irradiated meatballs during 14-day refrigerated storage. MAP with 5%O(2) + 50% CO(2) combined with irradiation up to 4 kGy is suggested for refrigerated meatballs to reduce the foodborne pathogen risk and to maintain the quality.

Modeling the inactivation of Salmonella Typhimurium, Listeria monocytogenes, and Salmonella Enteritidis on poultry products exposed to pulsed UV light.

Pulsed UV light inactivation of Salmonella Typhimurium on unpackaged and vacuum-packaged chicken breast, Listeria monocytogenes on unpackaged and vacuum-packaged chicken frankfurters, and Salmonella Enteritidis on shell eggs was explained by log-linear and Weibull models using inactivation data from previous studies. This study demonstrated that the survival curves of Salmonella Typhimurium and L. monocytogenes were nonlinear exhibiting concavity. The Weibull model was more successful than the log-linear model in estimating the inactivations for all poultry products evaluated, except for Salmonella Enteritidis on shell eggs, for which the survival curve was sigmoidal rather than concave, and the use of the Weibull model resulted in slightly better fit than the log-linear model. The analyses for the goodness of fit and performance of the Weibull model produced root mean square errors of 0.059 to 0.824, percent root mean square errors of 3.105 to 21.182, determination coefficients of 0.747 to 0.989, slopes of 0.842 to 1.042, bias factor values of 0.505 to 1.309, and accuracy factor values of 1.263 to 6.874. Overall, this study suggests that the survival curves of pathogens on poultry products exposed to pulsed UV light are nonlinear and that the Weibull model may generally be a useful tool to describe the inactivation patterns for pathogenic microorganisms affiliated with poultry products.

The effect of X-ray irradiation on Salmonella inactivation and sensory quality of almonds and walnuts as a function of water activity.

The overall goal of this study was to develop a set of process design principles for low-energy X-ray irradiation of tree nuts. Almonds and walnuts were inoculated with Salmonella Enteritidis PT30 and Salmonella Tennessee, and conditioned to four different water activities (0.23, 0.45, 0.64, and 0.84 a(w)). Thereafter, the inoculated/conditioned samples were irradiated to achieve up to a 5-log reduction in Salmonella using a pilot scale low-energy X-ray food irradiator. Greater efficacy (D(10)-value: the dose required to eliminate 90% of the microbial population) for inactivating SE PT30 and S. Tennessee was seen on the surface of almonds (0.226-0.431 kGy) than on walnuts (0.474-0.930 kGy) at all water activities. Also, the efficacy did not change monotonically with water activity. Overall, no significant difference (P>0.05) in sensory characteristics was seen between non-irradiated almonds and those irradiated to achieve a 5 log reduction in Salmonella. However, irradiating walnuts to the dose corresponding to a 5 log reduction caused a perceivable change in flavor. Post-irradiation storage tests revealed that surviving bacterial counts did not change over 120 days, regardless of nut type, Salmonella serovar, and a(w). Therefore, low-energy X-ray irradiation technology appears to be a promising non-thermal pasteurization strategy for certain types of nuts.

Effects of gamma irradiation on the viability and phenotypic characteristics of Salmonella Enteritidis inoculated into specific-pathogen-free eggs.

The goal of this study was to determine the effects of various levels of gamma irradiation on the phenotypic characteristics of 20 strains of Salmonella Enteritidis inoculated separately into specific-pathogen-free shell eggs. Bacterial strains were inoculated into egg yolks and exposed to (60)Co radiation at doses of 0.49 to 5.0 kGy. The eggs were maintained at 25°C and analyzed for the presence of Salmonella on days 1, 2, 4, and 7, and the recovered Salmonella isolates were characterized biochemically. All strains were resistant to doses of 0.49, 0.54, 0.59, 0.8, and 1 kGy; colony counts were ≥10(5) CFU/ml of egg yolk except for one strain, which was detected at 96 h and at 7 days after irradiation at 1 kGy, with a population reduction of 2 log CFU/ml. For the other evaluated doses, 12 strains (60.0%) were resistant at 1.5 kGy and 7 strains (35.0%) were resistant at 3.0 kGy. Among all analyzed strains, 5.0 kGy was more effective for reducing and/or eliminating the inoculated bacteria; only two (10%) strains were resistant to this level of irradiation. Salmonella colony counts were significantly reduced (P < 0.01) with increasing doses from the day 1 to 7 of observation, when microbial growth peaked. Loss of mobility, lactose fermentation, citrate utilization, and hydrogen sulfide production occurred in some strains after irradiation independent of dose and postirradiation storage time. Increases in antibiotic susceptibility also occurred: seven strains became sensitive to ß-lactams, two strains became sensitive to antifolates, and one strain each became sensitive to fluoroquinolone, phenicol, nitrofurans, tetracyclines, and aminoglycosides. The results indicate that up to 5.0 kGy of radiation applied to shell eggs inoculated with Salmonella Enteritidis at 4 log CFU per egg is not sufficient for complete elimination of this pathogen from this food matrix.

Efficacy of UV light treatment for the microbiological decontamination of chicken, associated packaging, and contact surfaces.

UV light was investigated for the decontamination of raw chicken, associated packaging, and contact surfaces. The UV susceptibilities of a number of Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli ATCC 25922, and Salmonella enterica serovar Enteritidis ATCC 10376 in liquid media were also investigated. From an initial level of 7 log CFU/ml, no viable Campylobacter cells were detected following exposure to the most intense UV dose (0.192 J/cm(2)) in liquid media (skim milk subjected to ultrahigh-temperature treatment and diluted 1:4 with maximum recovery diluent). Maximum reductions of 4.8 and 6.2 log CFU/ml were achieved for E. coli and serovar Enteritidis, respectively, in liquid media. Considerable differences in susceptibilities were found between the Campylobacter isolates examined, with variations of up to 4 log CFU/ml being observed. UV treatment of raw chicken fillet (0.192 J/cm(2)) reduced C. jejuni, E. coli, serovar Enteritidis, total viable counts, and Enterobacteriaceae by 0.76, 0.98, 1.34, 1.76, and 1.29 log CFU/g, respectively. Following UV treatment of packaging and surface materials, reductions of up to 3.97, 4.50, and 4.20 log CFU/cm(2) were obtained for C. jejuni, E. coli, and serovar Enteritidis, respectively (P < 0.05). Overall, the color of UV-treated chicken was not significantly affected (P ≥ 0.05). The findings of this study indicate that Campylobacter is susceptible to UV technology and that differences in sensitivities exist between investigated isolates. Overall, UV could be used for improving the microbiological quality of raw chicken and for decontaminating associated packaging and surface materials.

Effect of E-beam treatment on the safety and shelf life of mayonnaise potato salad.

The radioresistance of Listeria monocytogenes, Salmonella enterica serovar Enteritidis, and S. enterica serovar Typhimurium has been studied in a complex matrix like mayonnaise potato salad. D(10)-values of 0.56, 0.32-0.35, and 0.41-0.42 kGy were calculated for each organism, respectively. Keeping in mind these values, the microbiological criteria, the characteristics of the microorganisms, and a shelf life of the products of 20 days stored at 4°C, an irradiation treatment of 1 kGy was calculated to reach the food safety objectives. A duplication of the shelf life is also achieved with a dose of 1 kGy. Mayonnaise potato salad radiated with doses of up to 2 kGy showed negligible off-sensory characteristics.

Maintenance of safety and quality of refrigerated ready-to-cook seasoned ground beef product (meatball) by combining gamma irradiation with modified atmosphere packaging.

UNLABELLED: Meatballs were prepared by mixing ground beef and spices and inoculated with E. coli O157:H7, L. monocytogenes, and S. enteritidis before packaged in modified atmosphere (3% O2 + 50% CO2 + 47% N2) or aerobic conditions. The packaged samples were irradiated at 0.75, 1.5, and 3 kGy doses and stored at 4 °C for 21 d. Survival of the pathogens, total plate count, lipid oxidation, color change, and sensory quality were analyzed during storage. Irradiation at 3 kGy inactivated all the inoculated (approximately 106 CFU/g) S. enteritidis and L. monocytogenes cells in the samples. The inoculated (approximately 106 CFU/g) E. coli O157:H7 cells were totally inactivated by 1.5 kGy irradiation. D¹°-values for E. coli O157:H7, S. enteritidis, and L. monocytogenes were 0.24, 0.43, and 0.41 kGy in MAP and 0.22, 0.39, and 0.39 kGy in aerobic packages, respectively. Irradiation at 1.5 and 3 kGy resulted in 0.13 and 0.36 mg MDA/kg increase in 2-thiobarbituric acid-reactive substances (TBARS) reaching 1.02 and 1.49 MDA/kg, respectively, on day 1. Irradiation also caused significant loss of color and sensory quality in aerobic packages. However, MAP effectively inhibited the irradiation-induced quality degradations during 21-d storage. Thus, combining irradiation (3 kGy) and MAP (3% O2 + 50% CO2 + 47% N2) controlled the safety risk due to the potential pathogens and maintained qualities of meatballs during 21-d refrigerated storage. PRACTICAL APPLICATION: Combined use of gamma irradiation and modified atmosphere packaging (MAP) can maintain quality and safety of seasoned ground beef (meatball). Seasoned ground beef can be irradiated at 3 kGy and packaged in MAP with 3% O2 + 50% CO2 + 47% N2 gas mixture in a high barrier packaging materials. These treatments can significantly decrease risk due to potential pathogens including E. coli O157:H7, L. monocytogenes, and S. enteritidis in the product. The MAP would reduce the undesirable effects of irradiation on quality, and extend the shelf life of the product for up to 21 d at 3 °C.

Pulsed UV light inactivation of Salmonella enteritidis on eggshells and its effects on egg quality.

The majority of Salmonella Enteritidis outbreaks have been related to the consumption of raw or undercooked eggs or egg-containing foods. Therefore, the U.S. Department of Agriculture mandates egg washing for all graded eggs by use of a detergent solution and sanitizer. These agencies and the egg industry have been investigating alternative decontamination techniques, which could better serve the public, minimize costs, and benefit both the public and the industry. Pulsed UV light is an emerging technology that is used to inactivate microorganisms quickly. In this study, the effectiveness of pulsed UV light was evaluated for the decontamination of eggshells. Eggs inoculated with Salmonella Enteritidis on the top surface at the equator were treated with pulsed UV light 1 to 30 s, at a distance of 9.5 and 14.5 cm from the UV lamp in a laboratory-scale, pulsed UV light chamber. Three eggs were used per treatment in each repetition, except for quality measurements, which involved six eggs per treatment in each repetition. A maximum log reduction of 5.3 CFU/cm2 was obtained after a 20-s treatment at 9.5 cm below the UV lamp at a total dose of 23.6+/-0.1 J/cm2, without any visual damage to the egg. After a 30-s treatment at 9.5 and 14.5 cm, the temperature of eggshell surfaces increased by 16.3 and 13.3 degrees C, respectively. Energy usage increased up to 35.3+/-0.1 and 24.8+/-0.1 J/cm2, after 30-s treatments at 9.5 and 14.5 cm, respectively. The effect of pulsed UV light treatments on egg quality was also evaluated. Pulsed UV-light treatments for 3, 10, and 20s at either 9.5 or 14.5 cm did not change the albumen height, eggshell strength, or cuticle presence significantly (P<0.05). This study demonstrated that pulsed UV light has potential to decontaminate eggshell surfaces.