Antimicrobial Activity of Vanillin and Mixtures with Cinnamon and Clove Essential Oils in Controlling <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 in Milk

The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of vanillin against Listeria monocytogenes Scott A and Escherichia coli O157:H7 was determined in tripticase soy broth (TSB), pH 7 and 6, incubated at 35 °C/24 h and in semi-skim milk incubated at 35 °C/24 h and 7 °C/14 days. The influence of the fat content of milk on the antimicrobial activity of vanillin was tested in whole and skim milk incubated at 7 °C/14 days. Mixtures of clove and cinnamon with vanillin were also evaluated in semi skim milk incubated at 7 °C. The MICs for L. monocytogenes were 3,000 ppm in TSB (pH 7) and 2,800 ppm in TSB (pH 6). The MICs for E. coli O157:H7 were 2,800 ppm in TSB (pH 7) and 2,400 ppm in TSB (pH 6). The MBCs in TSB were 8,000 ppm for L. monocytogenes and 6,000 ppm for E. coli O157:H7. The pH values assayed did not influence significantly the MIC or MBC in TSB. The MICs in semi-skim milk for L. monocytogenes and E. coli O157:H7 were 4,000 and 3,000 ppm at 35 °C/24 h, and 2,500 and 1,000 ppm at 7 °C/7 days, respectively. The MBCs were 20,000 ppm for L. monocytogenes and 11,000 ppm for E. coli O157:H7. High incubation temperatures did not affect the MBC but increased the MIC of the vanillin in milk. This effect could be attributed to the increased membrane fluidity and to the membrane perturbing activity of vanillin at low temperatures. The fat in milk reduced significantly the antimicrobial activity of vanillin, probably due to effect protective of the fat molecules. Mixtures of clove and cinnamon leaves inhibited the growth of L. monocytogenes in a similar way that vanillin alone but had a synergistic effect on the E. coli O157:H7. Mixtures of cinnamon bark and vanillin had always a synergistic effect and some of the combination assayed showed bactericidal activity on the population of L. monocytogenes and E. coli O 157:H7.     

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes in milk by caprylic acid and monocaprylin

Listeria monocytogenes and Escherichia coli O157:H7 are major foodborne pathogens implicated in various outbreaks involving pasteurized or unpasteurized milk, and various dairy products. The objective of this study was to determine the antibacterial effect of caprylic acid (CA, C_8:0) and its monoglyceride, monocaprylin (MC) on L. monocytogenes and E. coli O157:H7 in whole milk. A five-strain mixture of E. coli O157:H7 or L. monocytogenes was inoculated in autoclaved milk (10⁶ CFU/ml) containing 0, 25, or 50 mM of CA or MC. At 37°C, all the treatments, excepting 25 mm CA, reduced the population of both pathogens by approximately 5.0 log CFU/ml in 6 h. At 24 h of storage at 8°C, MC at both levels and CA at 50 mM decreased L. monocytogenes and E. coli O157:H7, respectively by >5.0 log CFU/ml. At 48 h of 4°C storage, populations of L. monocytogenes and E. coli O157:H7 were decreased to below detection level (enrichment negative) by 50 mm of MC and CA, respectively. Results indicate that MC could potentially be used to inhibit L. monocytogenes and E. coli O157:H7 in milk and dairy products, but sensory studies need to be conducted before recommending their use.     

Predicting process lethality of Escherichia coli O157:H7, Salmonella,and Listeria monocytogenes in ground,formulated, and formed beef/turkey links cooked in an air impingement oven

The pathogen thermal lethality in ground and formulated beef/turkey was evaluated for a cocktail of E. coli O157:H7, Salmonella, and Listeria monocytogenes, respectively. At a temperature range of 55–70°C, the heat resistance of L. monocytogenes was not significantly (at α=0.05) different from those of Salmonella. The heat resistance of L. monocytogenes at 55–70°C was 45–81% higher than that of E. coli O157:H7. In this study, a practical approach was developed to predict log₁₀(CFU/g) reduction of E. coli O157:H7, Salmonella, or L. monocytogenes in ground, formulated, and formed beef/turkey links that were cooked in an air impingement oven. The predictions of pathogen thermal kills in the links were verified via the inoculation studies for at least a 7 log₁₀(CFU/g) reduction of E. coli O157:H7, Salmonella, and L. monocytogenes.     

Viability of multi-strain mixtures of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 inoculated into the batter or onto the surface of a soudjouk-style fermented semi-dry sausage

The fate of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on soudjouk. Fermentation and drying alone reduced numbers of L. monocytogenes by 0.07 and 0.74 log₁₀ CFU/g for sausages fermented to pH 5.3 and 4.8, respectively, whereas numbers of S. typhimurium and E. coli O157:H7 were reduced by 1.52 and 3.51 log₁₀ CFU/g and 0.03 and 1.11 log₁₀ CFU/g, respectively. When sausages fermented to pH 5.3 or 4.8 were stored at 4, 10, or 21 °C, numbers of L. monocytogenes, S. typhimurium, and E. coli O157:H7 decreased by an additional 0.08–1.80, 0.88–3.74, and 0.68–3.17 log₁₀ CFU/g, respectively, within 30 days. Storage for 90 days of commercially manufactured soudjouk that was sliced and then surface inoculated with L. monocytogenes, S. typhimurium, and E. coli O157:H7 generated average D-values of ca. 10.1, 7.6, and 5.9 days at 4 °C; 6.4, 4.3, and 2.9 days at 10 °C; 1.4, 0.9, and 1.6 days at 21 °C; and 0.9, 1.4, and 0.25 days at 30 °C. Overall, fermentation to pH 4.8 and storage at 21 °C was the most effective treatment for reducing numbers of L. monocytogenes (2.54 log₁₀ CFU/g reduction), S. typhimurium (5.23 log₁₀ CFU/g reduction), and E. coli O157:H7 (3.48 log₁₀ CFU/g reduction). In summary, soudjouk-style sausage does not provide a favorable environment for outgrowth/survival of these three pathogens.     

Antibacterial activity of oregano and thyme essential oils against Listeria monocytogenes and Escherichia coli O157:H7 in feta cheese packaged under modified atmosphere

The antibacterial activity of the essential oils (EO) of oregano and thyme added at doses of 0.1 or 0.2 and 0.1 ml/100 g, respectively, to feta cheese inoculated with Escherichia coli O157:H7 or Listeria monocytogenes was investigated during cheese storage under modified atmosphere packaging (MAP) of 50% CO₂ and 50% N₂ at 4 °C. Compositional analysis showed that the predominant phenols were carvacrol and thymol for both EO. In control feta inoculated with the pathogens and stored under MAP, results showed that E. coli O157:H7 and L. monocytogenes strains survived up to 32 and 28 days of storage. However, in feta cheese treated with oregano EO at the dose of 0.1 ml/100 g, E. coli O157:H7 or L. monocytogenes survived up to 22 and 18 days, respectively, whereas at the dose of 0.2 ml/100 g up to16 or 14 days, respectively. Feta cheese treated with thyme EO at 0.1 ml/100 g showed populations of E. coli O157:H7 or L. monocytogenes not significantly different (P > 0.05) than those of feta cheese treated with oregano at 0.1 ml/100 g. Although both essential oils exhibited equal antibacterial activity against both pathogens, the populations of L. monocytogenes decreased faster (P < 0.05) than those of E. coli O157:H7 during the refrigerated storage, indicating a stronger antibacterial activity of both essential oils against the former pathogen.     

Reductionin Listeria monocytogenes,Salmonella enterica and Escherichia coli O157:H7 in vitro and on tomato by sophorolipid and sanitiser as affected by temperature and storage time

Increased consumption of produce by consumers has been attributed to perceived health benefits of postharvest produce. Pathogen control is crucial because periodic occurrences and contamination of tomato and leafy greens have exacerbated food safety risks for consumers. We investigated the effects of temperatures (5 and 25 °C), storage time (30 min and 24 h) for inactivation of Listeria monocytogenes, Salmonella enterica and Escherichia coli O157:H7 by sophorolipid (SL‐p) produced fermentatively using palmitic acid as a co‐substrate at different concentrations in vitro. Reduction in pathogenic bacteria on grape tomato by SL‐p, sanitiser (Lovit) and combinations of SL‐p and sanitiser was determined. Temperature and storage time significantly (P < 0.05) affected pathogen inactivations by SL‐p as pathogen reductions were greater at 25 °C and 24 h than at 5 °C and 30 min of storage. L. monocytogenes was the most sensitive to SL‐p treatment as reductions of 5 log relative to untreated controls were attained at 0.12% of SL‐p. Significant reductions in S. enterica (1.91–3.85 logs) and E. coli O157:H7 (0.87–4.09 logs) were recorded at 2–5% of SL‐p. Lower populations of Salmonella and E. coli O157:H7 were inactivated than L. monocytogenes. On grape tomato, pathogen populations inactivated increased at higher SL‐p levels at 25 °C. Sanitiser and sanitiser + SL‐p reduced bacterial populations on tomato by 5.29–5.76 logs and 0.71–3.3.66 logs, respectively. These results imply the interactions of temperature, storage time and SL‐p significantly (P < 0.05) affected pathogen strain reductions. The combination of SL‐p with sanitiser led to synergistic effect on E. coli O157:H7, but not L. monocytogenes and S. enterica.     

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium,and Listeria monocytogenes on Stored Iceberg Lettuce by Aqueous Chlorine Dioxide Treatment

ABSTRACT: Inactivation of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes in iceberg lettuce by aqueous chlorine dioxide (ClO₂) treatment was evaluated. Iceberg lettuce samples were inoculated with approximately 7 log CFU/g of E. coli O157:H7, S. typhimurium, and L. monocytogenes. Iceberg lettuce samples were then treated with 0, 5, 10, or 50 ppm ClO₂ solution and stored at 4 °C. Aqueous ClO₂ treatment significantly decreased the populations of pathogenic bacteria on shredded lettuce (P < 0.05). In particular, 50 ppm ClO₂ treatment reduced E. coli O157:H7, S. typhimurium, and L. monocytogenes by 1.44, 1.95, and 1.20 log CFU/g, respectively. The D₁₀‐values of E. coli O157:H7, S. typhimurium, and L. monocytogenes in shredded lettuce were 11, 26, and 42 ppm, respectively. The effect of aqueous ClO₂ treatment on the growth of pathogenic bacteria during storage was evaluated, and a decrease in the population size of these pathogenic bacteria was observed. Additionally, aqueous ClO₂ treatment did not affect the color of lettuce during storage. These results suggest that aqueous ClO₂ treatment can be used to improve the microbial safety of shredded lettuce during storage.     

Behavior of Escherichia coli O157:H7 and Listeria monocytogenes in Tryptic soy broth subjected to various low temperature treatments

The inactivation and injury of Escherichia coli O157:H7 and Listeria monocytogenes in Tryptic soy broth stored at −5, −18 and −28°C were studied. Regardless of storage temperature, viable populations of E. coli O157:H7 and L. monocytogenes determined with TSA (uninjured and injured cells) or TSAB (uninjured cells), decreased as the storage time increased. However, the least surviving population of both test organisms was noted when stored at −18°C followed by those stored at −28 and −5°C. The viable populations of E. coli O157:H7 determined either with TSA or TSAB, was reduced most drastically during the first day of storage then decreased slowly thereafter. Viable populations of L. monocytogenes declined slightly and gradually during the entire storage period. Furthermore, E. coli O157:H7 was found more susceptible to the freezing storage than L. monocytogenes. After 21-day storage at −18°C, population reduction of E. coli O157:H7 determined with TSA was ca 1.72 log CFU/ml. On the other hand, a population reduction of only 0.64 log CFU/ml was noted with L. monocytogenes. Besides, the surviving population of E. coli O157:H7 contained a larger proportion of injured cells than L. monocytogenes.     

The effect of American cranberry (Vaccinium macrocarpon) constituents on the growth inhibition,membrane integrity,and injury of Escherichia coli O157:H7 and Listeria monocytogenes in comparison to Lactobacillus rhamnosus

The antimicrobial properties of the American cranberry were studied against Escherichia coli O157:H7, Listeria monocytogenes, and Lactobacillus rhamnosus to determine the effects on growth inhibition, membrane permeability, and injury. Cranberry powder was separated using a C-18 Sep-Pak cartridge into sugars plus organic acids (F1), monomeric phenolics (F2), and anthocyanins plus proanthocyanidins (F3). Fraction 3 was further separated into anthocyanins (F4) and proanthocyanidins (F5) using an LH-20 Sephadex column. Each fraction was diluted in the brain heart infusion (BHI) broth to determine the minimum inhibitory/bactericidal concentrations (MIC/MBC). L. monocytogenes was the most susceptible to cranberry fraction treatment with the lowest MIC/MBC for each treatment, followed by E. coli O157:H7 and L. rhamnosus. Membrane permeability and potential was studied using LIVE/DEAD viability assay and using Bis (1, 3-dibutylbarbituric acid) trimethine oxonol (DiBAC₄), respectively. L. rhamnosus demonstrated the highest permeability followed by E. coli O157:H7, and L. monocytogenes. L. rhamnosus demonstrated the highest recovery followed by E. coli O157:H7, and L. monocytogenes. Each cranberry fraction demonstrated membrane hyperpolarization at their native pH, while F2, F3, and F5 demonstrated membrane depolarization at neutral pH. With this knowledge cranberry compounds may be used to prevent maladies and potentially substitute for synthetic preservatives and antibiotics.     

Erythrosine B (Red Dye No. 3): A potential photosensitizer for the photodynamic inactivation of foodborne pathogens in tomato juice

The objectives of this study were to evaluate the efficacy of erythrosine B (ERY, Red No. 3)-mediated photodynamic therapy (PDT) for inactivating Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in tomato juice. The inoculated tomato juice was subjected to xenon light (E − L+), ERY (E + L−), or xenon light and ERY combination (E + L+) treatments. Treatment with E + L+ for 15 min decreased the cell counts of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 6.77, 2.74, and 6.43 log CFU/mL, respectively, without generating sublethally injured cells. The cell count reductions of E. coli O157:H7 and L. monocytogenes in the E + L+ treatment group were higher than the sum of cell count reductions in the E − L+ and E + L− treatment groups, which indicated the synergistic activity of the treatment combination. The T_3d and T_5d values calculated by the Weibull model indicated that S. Typhimurium exhibited higher resistance to the E + L+ treatment than the other two pathogens. Compared with control group, the E + L+ treatment group exhibited higher lycopene content and a* (red) value, whereas the pH value and sensory attributes were not significantly (p > .05) altered. These results suggest that ERY-mediated PDT can be potentially applied to control foodborne pathogens in tomato juice products without negatively affecting the product quality.     

Inactivation of foodborne pathogens in ready-to-eat salad using UV-C irradiation

To examine the applicability of ultraviolet (UV)-C irradiation on the inactivation of foodborne pathogen in ready-to-eat salad, it was inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and then irradiated with UV-C light. Radiation dose required for 90% reduction (d _R) values of E. coli O157:H7 and L. monocytogenes were determined to be 0.21 and 2.48 J/m², respectively. Foodborne pathogen populations significantly (p<0.05) decreased with increasing UV-C irradiation. UV-C irradiation at 8,000 J/m² reduced the populations of E. coli O157:H7 and L. monocytogenes on ready-to-eat salad by 2.16 and 2.57 log CFU/g, respectively.     

Preparation of red algae film containing grapefruit seed extract and application for the packaging of cheese and bacon

Red algae (RA) film containing grapefruit seed extract (GSE) was used as a wrapping film for cheese and bacon. RA film containing 1% GSE was prepared to inhibit the growth of pathogenic bacteria such as Escherichia coli O157:H7 and Listeria monocytogenes. Wrapping of cheese and bacon with the film decreased the populations of E. coli O157:H7 and L. monocytogenes. After 15 days of storage, wrapping of cheese with the RA film reduced the populations of E. coli O157:H7 and L. monocytogenes by 1.21 and 0.85 log CFU/g, respectively, compared to control. Bacon wrapped with the RA film also decreased the populations of E. coli O157:H7 and L. monocytogenes by 0.45 and 0.76 log CFU/g, respectively. Wrapping of bacon with the RA film decreased peroxide and thiobarbituric acid values. These results suggest that RA film containing GSE is a useful wrapping material for extending the shelf lives of cheese and bacon.     

Assessment of the ability of five culture media for the detection of Escherichia coli O157

Cattle are a common reservoir for Escherichia coli O157:H7. Prior to confirming its presence in a sample, proper isolation of E. coli O157 is necessary. Consequently, this study evaluated the ability of five commercial plating media to isolate E. coli O157 from 138 samples of fresh cattle faeces, water from water trough and pond, and surfaces of water trough and hay bunk. For the isolation of E. coli O157, samples were enriched in tryptic soya broth, followed by immunoseparation and then plating on SMAC, CT‐SMAC, CHROMagar^? O157, Tellurite CHROMagar^? O157 and Vancomycin Cefixime Cefsoludin CHROMagar^? O157. Real‐time PCR targeting genes stx₁, stx₂ and wzy_O157 was used to confirm selected isolates. When analysed together, CT‐SMAC and CHROMagar^? O157 were the best combination for isolating E. coli O157, giving 79% true‐positive results and only 0.05% false‐negative results.     

Inhibition of biofilm formation,adhesion and invasion in Caco-2 cells by foodborne pathogens using phyto-mediated synthesised silver nanoparticles from industrial wastes

Certain foodborne diseases are associated with antibiotic resistance, a significant problem throughout the world. Silver nanoparticles (AgNPs) using industrial waste from Eucalyptus camaldulensis and sericin, a protein derived from Bombyx mori, were synthesised by a one-step approach. Spherical-shaped nanoparticles with the average size of 17.19 nm exhibited strong antioxidant activity. The minimum bactericidal concentrations against foodborne pathogens including Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, Klebsiella pneumoniae, Salmonella Typhimurium, Shigella sonnei, Vibrio cholerae and Vibrio parahaemolyticus were between 2.96 and 11.83 µg/mL. Killing against L. monocytogenes and E. coli O157:H7 was observed within 4 h. Treatment with AgNPs at 0.25 – 0.5 × MIC significantly reduced biofilm production in all isolates (P < 0.05). AgNPs significantly impeded adhesion to and invasion of human epithelial Caco-2 cells by L. monocytogenes and E. coli O157:H7 (P < 0.05). Biocompatibility assessment of AgNPs with Caco-2 and human red blood cells demonstrated no toxic effects.     

Antimicrobial activity of recombinant human lactoferrin from <Emphasis Type="Italic">Aspergillus awamori</Emphasis>, human milk lactoferrin and their hydrolysates

The antibacterial activity of human lactoferrin from milk (hLF), recombinant human lactoferrin from Aspergillus awamori (rhLF) and their hydrolysates obtained with pepsin was investigated against Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogenes. The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) were determined for all the bacteria and the proteins assayed. Taking into account the MICs found for both lactoferrins studied, we can say that they behave very similarly, except for L. monocytogenes for which rhLF was more active. We studied the effect that heat treatments exerted on the antibacterial activity of the two types of lactoferrin and the only heat treatment that had a negative effect on that activity was 85 °C for 10 min. The activity of hLF and rhLF in UHT milk and whey against E. coli O157:H7 and L. monocytogenes, was also assayed. Our results showed a reduction in the number of viable cells for both microorganisms when were incubated with rhLF or hLF, but this decrease was lower than in broth media.     

Detection of Escherichia coli O157:H7 in Food Using Real-Time Multiplex PCR Assays Targeting the stx 1, stx 2, wzy O157, and the fliC h7 or eae Genes

Escherichia coli O157:H7 is an important foodborne pathogen, and foods of bovine origin and fresh produce have been linked to outbreaks. Real-time multiplex PCR assays were developed to detect E. coli O157:H7 in different foods. Apple cider and raw milk (25 ml) and ground beef and lettuce (25 g) were inoculated with 2 or 20 colony-forming units (CFU) of E. coli O157:H7 380-94 and subjected to enrichment in RapidChek E. coli O157:H7 broth at 42°C. One milliliter of the enrichments was removed at 8 and 20 h, and following DNA extraction, real-time multiplex PCR assays targeting the stx ₁, stx ₂, and wzy _O157 genes in combination with probes and primers targeting either the fliC _h7 or the eae genes were performed using OmniMix HS beads and the SmartCycler. The sensitivity of the real-time multiplex PCR assay was about 225 CFU/PCR. E. coli O157:H7 was detected (fluorescent signal generated for all gene targets) in apple cider, raw milk, lettuce and ground beef samples inoculated with 2 or 20 CFU/g or 25 ml after both 8 and 20 h of enrichment. Enrichments of uninoculated food samples were negative using the multiplex PCR targeting the stx ₁, stx ₂, wzy _O157, and eae genes; however, using the assay targeting the stx ₁, stx ₂, wzy _O157, and fliC _h7 gene combination, a positive result was always obtained for the fliC _h7 gene using uninoculated ground beef enrichments. Use of other primer sets targeting the fliC _h7 gene gave similar results. The real-time multiplex PCR assays targeting the stx ₁, stx ₂, eae, and wzy _O157 or the fliC _h7 genes are sensitive and specific and can be used for the detection of E. coli O157:H7 in food, except that the fliC _h7 gene may not be a suitable target for the detection of E. coli O157:H7 in ground beef.     

Incorporation of Essential Oils and Nanoparticles in Pullulan Films to Control Foodborne Pathogens on Meat and Poultry Products

The incorporation of essential oils and nanotechnology into edible films has the potential to improve the microbiological safety of foods. The aim of this study was to evaluate the effectiveness of pullulan films containing essential oils and nanoparticles against 4 foodborne pathogens. Initial experiments using plate overlay assays demonstrated that 2% oregano essential oil was active against Staphylococcus aureus and Salmonella Typhimurium, whereas Listeria monocytogenes and Escherichia coli O157:H7 were not inhibited. Two percent rosemary essential oil was active against S. aureus, L. monocytogenes, E. coli O157:H7, and S. Typhimurium, when compared with 1%. Zinc oxide nanoparticles at 110 nm were active against S. aureus, L. monocytogenes, E. coli O157:H7, and S. Typhimurium, when compared with 100 or 130 nm. Conversely, 100 nm silver (Ag) nanoparticles were more active against S. aureus than L. monocytogenes. Using the results from these experiments, the compounds exhibiting the greatest activity were incorporated into pullulan films and found to inhibit all or some of the 4 pathogens in plate overlay assays. In challenge studies, pullulan films containing the compounds effectively inhibited the pathogens associated with vacuum packaged meat and poultry products stored at 4 °C for up to 3 wk, as compared to control films. Additionally, the structure and cross‐section of the films were evaluated using electron microscopy. The results from this study demonstrate that edible films made from pullulan and incorporated with essential oils or nanoparticles may improve the safety of refrigerated, fresh or further processed meat and poultry products.     

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

Abstract: 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. D¹⁰‐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.     

Behavior of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium in teewurst, a raw spreadable sausage

The fate of Listeria monocytogenes, Salmonella Typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on teewurst, a traditional raw and spreadable sausage of Germanic origin. Multi-strain cocktails of each pathogen (ca. 5.0 log CFU/g) were used to separately inoculate teewurst that was subsequently stored at 1.5, 4, 10, and 21 °C. When inoculated into commercially-prepared batter just prior to stuffing, in general, the higher the storage temperature, the greater the lethality. Depending on the storage temperature, pathogen levels in the batter decreased by 2.3 to 3.4, ca. 3.8, and 2.2 to 3.6 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, during storage for 30 days. When inoculated onto both the top and bottom faces of sliced commercially-prepared finished product, the results for all four temperatures showed a decrease of 0.9 to 1.4, 1.4 to 1.8, and 2.2 to 3.0 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, over the course of 21 days. With the possible exceptions for salt and carbohydrate levels, chemical analyses of teewurst purchased from five commercial manufacturers revealed only subtle differences in proximate composition for this product type. Our data establish that teewurst does not provide a favourable environment for the survival of E. coli O157:H7, S. Typhimurium, or L. monocytogenes inoculated either into or onto the product.     

Production and characterisation of skate skin gelatin films incorporated with thyme essential oil and their application in chicken tenderloin packaging

In this study, skate skin gelatin (SSG) was used as a new biodegradable film source and a SSG film was prepared. In addition, thyme essential oil (TEO) was incorporated in the SSG film as an antimicrobial agent for the preparation of an antimicrobial film. The tensile strength (TS) of the film decreased, whereas elongation at break (E) increased by the addition of TEO. The SSG film containing TEO showed increased antimicrobial activity against Listeria monocytogenes and Escherichia coli O157:H7 as TEO concentration increased. To apply the SSG film to food packaging, chicken tenderloin samples were wrapped with the film containing 1% TEO. The packaging of chicken tenderloin with the TEO‐containing SSG film inhibited the growth of L. monocytogenes and E. coli O157:H7 compared to the control during storage. Therefore, the SSG film with added TEO has potential as active food packaging to extend the shelf life of chicken tenderloin.