Biofilm-forming ability and resistance to industrial disinfectants of Staphylococcus aureus isolated from fishery products

Adhesion and biofilm-forming ability of twenty six S. aureus strains previously isolated from fishery products on stainless steel was assessed. All strains reached counts higher than 10⁴ CFU/cm² after 5 h at 25 °C. Most strains also showed a biofilm-forming ability higher than S. aureus ATCC 6538 – reference strain in bactericidal standard tests – by crystal violet staining. In addition, it seems that food-processing could have produced a selective pressure and strains with a high biofilm-forming ability were more likely found in highly handled and processed products.The efficacy of the industrial disinfectants benzalkonium chloride (BAC), sodium hypochlorite (NaClO) and peracetic acid (PAA) against biofilms and planktonic counterparts was also examined in terms of minimum biofilm eradication concentration (MBEC) and minimum bactericidal concentration (MBC), respectively. Biofilms showed an antimicrobial resistance higher than planktonic cells in all cases. However, no correlation was found between MBEC and MBC, likely due to differences in biofilm extracellular matrix (composition, content and architecture) between strains. BAC resistance increased as biofilms aged. Generally, biofilm formation seemed to attenuate the effect of low temperatures on BAC resistance. PAA was found to be most effective against both biofilms and planktonic cells, followed by NaClO and BAC. Resistance did not follow the same order for each biocide, which remarks the need of using a wide collection of strains in standard tests of bactericidal activity to ensure a proper application of disinfectants. Doses recommended by manufacturers for BAC, PAA and NaClO to disinfect food-contact surfaces were lower than doses for complete biofilm removal (i.e. MBEC) under some environmental conditions common in the food industry, which questions bactericidal standard tests and promotes the search for new strategies for biofilm removal.     

Use of lactic acid bacteria (LAB) biofilms for the control of Listeria monocytogenes in a small-scale model

The antilisterial activity in biofilms developed in a small-scale model by two LAB (lactic acid bacteria) bacteriocin producers (Lactobacillus plantarum 35d, Enterococcus casseliflavus IM 416K1) and by two non-producers (L. plantarum 396/1, Enterococcus faecalis JH2-2) was evaluated against Listeria monocytogenes NCTC 10888. The LAB biofilms showed the capability to influence the survival and the multiplication of the pathogen with differences among the strains. L. plantarum 35d displayed the highest efficacy reducing L. monocytogenes by 5.4 log in the planktonic population and by 3.9 log in the adherent population at the end of the experiment (10 days). L. plantarum 396/1 reduced L. monocytogenes by 3.8 log in the adherent cells and by 4.9 log in the planktonic cells and this outcome could be attributed to the pH reduction.The E. casseliflavus IM 416K1 biofilm caused a L. monocytogenes reduction of 3.7 log in the adherent cells and of 4.8 log in the planktonic cells and the role of the bacteriocin production seemed to be predominant as the pH values did not significantly decrease. This hypothesis is confirmed by a slight capability to influence the L. monocytogenes survival by the non-bacteriocinogenic E. faecalis JH2-2. Studies performed with L. monocytogenes in co-culture with a Pseudomonas putida strain, revealed a reduction of the antilisterial activity only for the biofilms produced by lactobacilli.     

Inhibition of Staphylococcus aureus on beef by nisin-containing modified alginate films and beads

Nisin, a bacteriocin, was immobilized into palmitoylated alginate-based films or in activated alginate beads. Sterile beef muscle slices or ground beef were inoculated with Staphylococcus aureus at a level of 10⁴ CFU/g. Sliced beef was then coated with palmitoylated alginate-based films containing 0, 500 or 1000 IU/mL of nisin. Also, ground beef was mixed with 0, 500 or 1000 IU/mL of nisin covalently linked to activated alginate beads in order to evaluate the effect of nisin concentration on S. aureus level. The content of S. aureus in beef was determined during storage at 4 °C. Results demonstrated that after 7 days of storage, a reduction of 0.91 and 1.86 log CFU/cm² was observed on sliced beef covered with film containing 500 or 1000 IU/mL of nisin, respectively. After 14 days of storage, when nisin solution (500 or 1000 IU/g) was mixed with ground beef, 2.2 and 2.81 log CFU/g reductions of S. aureus counts were respectively observed. However, when nisin (500 or 1000 IU/g) was linked into activated alginate beads, 1.77 and 1.93 log CFU/g reductions of S. aureus counts were respectively observed (P ⩽ 0.05). These results suggest that sterile, hydrophobic and biodegradable films or beads incorporating various amounts of nisin could be used efficiently to control the growth of pathogens or microorganisms responsible of spoilage at the surface of round beef or other meat products.     

Effective control of Listeria innocua by combination of nisin,pH and low temperature in liquid cheese whey

The effect and interactions of pH (5.5, 6.0 and 6.5), temperature (7 °C and 20 °C) and nisin (100  IU/ml; 300 IU/ml), on the growth and survival of Listeria innocua in liquid cheese whey (LCW) were studied.Growth data were analyzed by non-linear regression analysis to generate “best fit” Gompertz and logistic models. The growth kinetics of L. innocua was dependent on the interaction of the three variables, particularly on the lag phase duration.The effectiveness of nisin in controlling the growth of L. innocua in LCW was more pronounced at 7 °C than at 20 °C and as the pH decreased from 6.5 to 5.5. As a consequence, this combined treatment may provide LCW with a degree of protection against this microorganism, particularly if employed in conjunction with low temperature.     

Antibacterial activity of lactic acid bacteria against spoilage and pathogenic bacteria isolated from the same meat small-scale facility: 2—Behaviour of pathogenic and spoilage bacteria in dual species biofilms including a bacteriocin-like-producing lactic acid bacteria

The survival of Listeria innocua ATCC 33090, Staphylococcus aureus E1S-5 and/or Hafnia alvei E1E-25 in dual species biofilms with bacteriocin-like producing lactic acid bacteria (5 Vagococcus carniphilus, 3 Enterococcus faecium, 1 Lactobacillus sakei and 1 Enterococcus sp.) was investigated. The aim was to select strains able to repress the growth of undesirable bacteria in biofilms, i.e., the real mode of bacterial attachment.Two E. faecium and 3 V. carniphilus species were highly antagonistic to L. innocua, S. aureus and H. alvei repressing their growth by reduction levels able to reach 2, 2.7 and 2.4 log₁₀ cfu/ml compared to the positive control made of sole the target microorganism. Furthermore, planktonic cells were more sensitive to the bacteriocin-like substances than sessile ones.First results suggest the possibility of selecting bio-preservatives among the endogenous house flora of the studied small-scale facility, that could be implemented on the processing surfaces to repress the growth of undesirable microorganisms.     

Sanitization potency of slightly acidic electrolyzed water against pure cultures of Escherichia coli and Staphylococcus aureus,in comparison with that of other food sanitizers

The sanitization potency of slightly acidic electrolyzed water (SAEW) on pure cultures of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated. The potency was compared with that of strong acidic electrolyzed water (StAEW) and sodium hypochlorite (NaOCl) solution. SAEW (ca. pH 5.8 and 21 mg/l available chlorine concentration; ACC) resulted into >5 log₁₀CFU/ml reduction of E. coli and S. aureus after 90 s of exposure. The relative bacterial reduction potency at each exposure time was in the order StAEW > NaOCl > SAEW and increased with exposure time, with relative effect being 90 s > 60 s > 30 s. The results indicate that SAEW with low ACC and near neutral pH can potentially sanitize E. coli and S. aureus within a short period of exposure presenting a potential replacement to NaOCl solution commonly used in the food industry.     

Non starter lactic acid bacteria biofilms: A means to control the growth of Listeria monocytogenes in soft cheese

The possibility to consider non starter lactic acid bacteria (NSLAB) biofilms as a means to control the growth of Listeria monocytogenes in soft cheeses was evaluated. In particular, the aptitude to form biofilm of four NSLAB strains (Lactobacillus plantarum DSM1055, Lactobacillus casei DSM20011, Lactobacillus curvatus DSM20019 and Lactobacillus paracasei DSM20207) was investigated. All tested strains were able to form biofilm on stainless steel and the highest quantities were produced when NSLAB were present simultaneously (about 6 Log CFU cm^?2). Then, experimental cheeses were made in presence of chips containing 7-days NSLAB biofilms and inoculated with L. monocytogenes (about 2 Log CFU g^?1). Results demonstrated that NSLAB biofilms can be considered a useful means to delay the growth of L. monocytogenes in soft cheeses: the maximum cell load attained at the stationary phase was about 6 Log CFU g^?1 in experimental cheeses against about 7 Log CFU g^?1 observed in control samples.     

Effect of combined ozone and organic acid treatment for control of Escherichia coli O157:H7 and Listeria monocytogenes on enoki mushroom

This study evaluated the effects of ozonated water (1, 3, and 5 ppm) alone with different exposure times (0.5, 1, 3, or 5 min), and combinations of 3 ppm ozone with 1% organic acids (acetic, citric, or lactic acids) during 5-min exposure for control of Escherichia coli O157:H7 and Listeria monocytogenes on enoki mushroom and to observe the regrowth of these pathogenic bacteria on treated enoki mushroom during storage for 10 days at 15 °C. Results showed that ozone treatment gave less than 1.0- and 0.5-log count reductions on E. coli O157:H7 and L. monocytogenes, respectively. Efficacy was improved with combined 3 ppm ozone and 1% citric acid treatment, resulting in 2.26- and 1.32-log count reductions, respectively. During storage at 15 °C (10 days) after combined treatment and packaging, populations of E. coli O157:H7 and L. monocytogenes increased to more than 8.0 log cfu/g, indicating that the combined treatment did not have a residual antimicrobial effect during storage. Although the storage study did not show control of these pathogens, the combined ozone–organic acid treatment was more effective than individual treatments in reducing initial population levels of these pathogens on enoki mushroom.     

Anti-listerial properties of garlic shoot juice at growth and morphology of Listeria monocytogenes

The anti-listerial effect of garlic shoot juice (GSJ) was investigated against the four strains of Listeria monocytogenes ATCC 19116, 19118, 19166 and 15313. Various concentrations of (1%, 2.5% and 5%) were used and applied for 0, 4, 7, 10 and 14 days at 4 °C and 0, 6, 12, 18 and 24 h at 37 °C. 5% GSJ showed the strongest anti-listerial effect of 3–4 log cfu/ml against all the bacterial strains tested as compared to control at 37 °C. At 4 °C, 2.5% GSJ showed a strong growth inhibitory effect of about 2–3 log cfu/ml against all the bacterial strains when compared to control after 14 days, and 5% GSJ rather decreased the number of bacterial cell when compared to initial polulation and showed general lysis of cytoplasm, lysis of cell wall and cellular swelling, and on scanning electron microscopy (SEM) observation, strain L. monocytogenes ATCC 19118 showed swelling, partially distorted shape, pore formation and empty cell formation inside the cell.     

Lactic acid bacteria in an alginate film inhibit Listeria monocytogenes growth on smoked salmon

Antimicrobial packaging with lactic acid bacteria incorporated into the film matrix is a novel approach for controlling the growth of food-borne pathogens in ready-to-eat food. The overall objective of this study was to assess the effect of two strains of lactic acid bacteria (LAB) and nisin trapped in an alginate matrix, on Listeria monocytogenes growth on vacuum packed cold-smoked salmon. A film was formulated containing two LAB strains and nisin (100 IU/mL). LAB viability and bacteriocin like substance production (BLS) were assessed using the plate antagonism technique. To check the film antagonistic activity, pieces of salmon (4.0 × 4.0 cm²), inoculated with L. monocytogenes at a final concentration of 10⁴ CFU/cm², were covered with film containing both LAB strains plus nisin and stored at 4 °C. L. monocytogenes colonies on OXA agar were counted after 0, 7, 14, 21 and 28 days to evaluate pathogen inhibition. All treatments led to effective diffusion of the BLS that inhibited L. monocytogenes for 20 days after film preparation, with inhibition zones of 5.7 cm² for film coupons of 8 mm in diameter. After 28 days, salmon pieces covered with the film without inhibitors showed an increase of 2.4 log cycles in L. monocytogenes growth. In contrast, films with either LAB strain or a combination of both strains and nisin had a bacteriostatic effect on the pathogen over a period of 28 days, which exceeds the industrial standard shelf life for smoked salmon. The results demonstrate that these films inhibit L. monocytogenes growth on salmon during refrigerated storage.     

Importance and efficiency of in-depth antimicrobial activity for the control of listeria development with nisin-incorporated sodium caseinate films

The effect of antimicrobial sodium caseinate-based films was investigated on inhibition of Listeria innocua in cheese. Nisin was incorporated into sorbitol-plasticized sodium caseinate films at 1000 IU/cm² and the films were prepared by casting methods. Mini red Babybel® cheese was chosen as a semi-soft cheese model. The antimicrobial activity was studied based on the contact between antimicrobial films and surface-contaminated as well as in-depth contaminated cheese samples during a 7-day storage at 4 °C. The active films produced resulted in a reduction of 1.1 log CFU/g reduction in L. innocua counts in surface-inoculated cheese samples after 1 week of storage as compared to control samples. Regarding in-depth inoculated cheese samples, antimicrobial effectiveness was found to be dependent on the distance from the contact surface with the films containing nisin to the cheese matrix. The inactivation rates obtained were 1.1, 0.9 and 0.25 log CFU/g with slice 1 (distance from contact surface d = 1 mm), slice 2 (d = 2 mm) and slice 3 (d = 3 mm), respectively. Our study demonstrates the potential application of antimicrobial films as a promising method to overcome problems associated with post-process contamination, thus enhancing the safety and extending the shelf life of food products.     

Synthesis and evaluation of some new demulsifiers based on bisphenols for treating water-in-crude oil emulsions

The present paper endeavors to synthesize nine types of demulsifiers based on bisphenols (bisphenol A (BA), bisphenol AC (BAC) and bisphenol CH (BCH)) having different ethylene oxide units (n = 27, 34, 45) namely; E (x + y) (where E represents BA, BCH or BAC and (x + y) which represents the ethylene oxide units (27, 34, 45)). The chemical structures of the prepared demulsifier were elucidated using FT-IR and ¹H NMR spectra. Effect of the chemical structure (hydrophobic and ethoxylated degree of hydrophilic parts) and the mechanism of demulsification process was investigated. The data were discussed on the light of the chemical structure of the demulsifiers and the factors, effecting the demulsification process. The efficiency of these demulsifiers was tested on water-in-oil emulsions (w/o) at different concentrations (100, 200 and 300 ppm), 7.4% asphaltene content and 30%, 50% and 70% water content. From the obtained data the best demulsifier was E(34)BA which shows 100% demulsification after 58 min at 30% water content and 300 ppm of the demulsifier.     

Inactivation effect of newly developed low concentration electrolyzed water and other sanitizers against microorganisms on spinach

The efficacy of newly developed low concentration electrolyzed water (LcEW) was investigated to inactivate the pathogens on spinach leaves as a convenient and safe alternative sanitizer and it was compared to other sanitizers. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and dip treated with deionized water (DIW), LcEW, strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl) for 3 min at room temperature (23 ± 2 °C). For all pathogens, the similar pattern of microbial reduction on spinach was apparent with LcEW and SAEW washing. In the present study, it was found that LcEW inactivated, at maximum, 1.64–2.80 log cfu/g and DIW resulted in lowest reduction, 0.31–0.95 log cfu/g of background or pathogenic microflora present on spinach leaves compared to the unwashed control. The findings of this study indicate that LcEW and SAEW did not differ significantly (P > 0.05) in reducing background or pathogenic microflora on spinach and LcEW may be a promising sanitizer for washing vegetables without environmental pollution instead of using electrolyzed oxidizing (EO) water or SAEW.     

Inactivation by ozone of Listeria innocua on salmon-trout during cold-smoke processing

This study was conducted to evaluate the efficacy of gaseous ozone exposure on Listeria innocua 2030c growth during cold-smoke processing of Oncorhynchus mykiss (salmon-trout). Three sets of experiments were performed: inoculation with L. innocua 2030c followed by a 20 min ozone exposure were applied to (a) fresh salmon-trout after filleting, (b) to fresh whole fish, and (c) to fresh whole fish after removal of the fish slime. In sets (a) and (b) fillets were subsequently cold-smoked but not in set (c). The ozone concentration inside the exposure chamber after 20 min reached 0.1 × 10⁻³ g/l.Counts of L. innocua 2030c were performed after treatment for sets (a), (b) and (c), after smoking and weekly during 21 days in vacuum packs at 5 °C, for sets (a) and (b). Sampling for total Aerobic Plate Counts (APC) of non-inoculated samples was also performed in set (a). The percentage of salt in the water phase, peroxide values and the effect of treatment on sensory properties of cold-smoked salmon-trout fillets were also determined in the first and second set. In the first set, a decrease of less than 1 log₁₀ in L. innocua numbers occurred on ozone treated samples in all sampling occasions. APC was slightly lower on fresh fillets after treatment and on smoked fillets at 3 weeks of storage at 5 °C (less than 1 log₁₀ CFU/g). In the second set, a reduction greater than 1 log₁₀ L. innocua/g occurred on smoked fillets at the end of the storage period. In the third set, the slime removal resulted in a 1 log₁₀ L. innocua/g reduction on fresh treated samples.Ozone treatment had no significant (p > 0.05) effect on L. innocua counts on samples compared to those on untreated fish. In both sets, no significant differences among ozone treated/untreated samples were noticeable by sensory evaluation (p > 0.05).     

Removal of residual pesticides on vegetable using ozonated water

Degradation of the four pesticides by dissolved ozone was investigated in order to establish the effect of operational parameters: methyl-parathion, parathion, diazinon and cypermethrin. They were commonly used as broad-spectrum insecticides in pest control, and high residual levels had been detected in vegetables. In the present study, the effectiveness in pesticide oxidation in aqueous solution using low level of dissolved ozone was determined using solid-phase micro-extraction (SPME) and GC–MS. Dissolved ozone (1.4 mg/l) was effective to oxidize 60–99% of methyl-parathion, cypermethrin, parathion and diazinon in aqueous solution in 30 min and the degradation was mostly completed in the first 5 min. Trace amounts and unstable paraoxon and diazoxon were tentatively identified as primary ozonation byproducts of parathion and diazinon. The feasibilities of using low level of dissolved ozone (1.4–2.0 mg/l) for removal of the four pesticides residue on vegetable surface (Brassica rapa) were also tested. Ozone was mostly effective in cypermethrin removal (>60%). The removal efficiency of pesticides highly depended on the dissolved ozone levels and temperature. The present study validated that ozonation is a safe and promising process for the removal of the tested pesticides from aqueous solution and vegetable surface under domestic conditions.     

Antimicrobial properties of selected essential oils in vapour phase against foodborne bacteria

The aim of this study was to identify antimicrobial properties of essential oils in vapour phase. In vitro antibacterial activity against five foodborne bacteria (Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enteritidis, Staphylococcus aureus) was evaluated by disc volatilization method. The results were expressed as minimum inhibitory concentrations (MIC) in μl/cm³ of air. Thirteen of the 27 essential oils were active at least against one bacterial strain in the range of tested concentrations (0.0083–0.53 μl/cm³). The best results were shown by Armoracia rusticana (MIC 0.0083 μl/cm³) against all of the strains, followed by Allium sativum > Origanum vulgare > Thymus vulgaris > Satureja montana, Thymus pulegioides > Thymus serpyllum > Origanum majorana > Caryopteris x clandonensis, Hyssopus officinalis, Mentha villosa, Nepeta x faassenii, Ocimum basilicum var. grant verte. In conclusion, certain essential oils are highly effective in vapour phase and could be used in control of foodborne bacterial pathogens.     

Essential oils to control Alternaria alternata in vitro and in vivo

The inhibitory effects of five essential oils (thyme, sage, nutmeg, eucaptus and cassia) against Alternaria alternata were tested at different concentrations (100–500 ppm) in vitro. The cassia oil and thyme oil both exhibited antifungal activity against A. alternata. The cassia oil inhibited completely the growth of A. alternata at 300–500 ppm. The thyme oil exhibited a lower degree of inhibition 62.0% at 500 ppm. Spore germination and germ tube elongation of the pathogens in potato dextrose broth was strongly inhibited in the presence of 500 ppm cassia oil. Irreversible inhibition of fungal growth could be caused by exposure to 300 ppm and 400 ppm cassia oil for 6 days and 500 ppm cassia oil for 3 days. Cassia oil at 500 ppm reduced the percentage of decayed tomatoes. The experiments on reducing natural decay development of tomatoes gave similar results. Therefore, essential oils could be an alternative to chemicals for control of postharvest phytopathogenic fungi on fruits or vegetables.     

Aqueous extracts of Hibiscus sabdariffa calyces as an antimicrobial rinse on hot dogs against Listeria monocytogenes and methicillin-resistant Staphylococcus aureus

Contamination of ready-to-eat meat products by foodborne pathogens is a major concern in the food industry. Novel methods to control foodborne pathogens are made necessary by continuing outbreaks as well as the development of antibiotic-resistant pathogens. Hibiscus sabdariffa extracts could be useful as a natural source of antimicrobial rinse on ready-to-eat products to control pathogens. In this study, lyophilized Hibiscus flower extracts were examined for their antimicrobial activity as a rinse on all-beef hot dogs against Listeria monocytogenes and methicillin-resistant Staphylococcus aureus (MRSA). Beef hot dogs were dip inoculated in overnight cultures of 1:1 mixtures of L. monocytogenes strains Scott A and 101 or MRSA strains ATCC 33591 and ATCC 33593 and were placed at 4 °C overnight to allow for bacterial attachment. Hot dogs were rinsed with extracts (120, 240 mg/mL) or water (control) for 5, 15, 30, or 60 min and then plated immediately (0 h; no storage) or stored at 4 °C overnight and plated at 24 h. Serial dilutions were plated in duplicate on both TSA and selection media, Modified Oxford (Listeria) or Baird Parker (MRSA), and the entire experiment was replicated 3 times. Higher extract concentrations, longer rinse times, and longer storage times were the most effective at inhibiting and/or killing L. monocytogenes and MRSA on hot dogs. L. monocytogenes was reduced to ca. 1.5 log CFU/g while MRSA was reduced to undetectable levels following rinsing of hot dogs with extracts at 240 mg/mL for 60 min and stored for 24 h. Both L. monocytogenes and MRSA were reduced ca. 2 log CFU/g following rinsing of hot dogs with extracts at 120 mg/mL for 60 min and stored for 24 h. This research demonstrates the effectiveness of Hibiscus extracts against L. monocytogenes and MRSA as an antimicrobial rinse on ready-to-eat meat products.     

Effect of combined physico-chemical treatments based on enterocin AS-48 on the control of Listeria monocytogenes and Staphylococcus aureus in a model cooked ham

Enterocin AS-48 was tested alone or in combination with chemical preservatives and/or heat against Listeria monocytogenes and Staphylococcus aureus in a cooked ham model system. AS-48 (20, 40 and 60 μg g⁻¹) alone was active against L. monocytogenes at 5 and 15 °C, but it was not sufficient to avoid regrowth of Listeria during the 60 days storage. Combination of AS-48 (40 μg g⁻¹) with nitrite/nitrate, pentasodium tripolyphosphate, sodium benzoate or potassium sorbate improved the anti-listeria effect during storage at 5 °C. The most effective combination was AS-48-nitrite/nitrate (0.007%) that reduced listeria below detection level from the beginning to end of storage. Although much more resistant, S. aureus was also inhibited by AS-48 alone at 5 °C, and especially in combinations with nitrite/nitrate, pentasodium tripolyphosphate, sodium lactate and sodium acetate. Best results against both pathogens were obtained when sodium pyrophosphate was applied in combination with 60 μg g⁻¹ AS-48. Sub-lethal heat (60 °C, 2 min) clearly increased AS-48 activity against both Listeria and Staphylococcus.     

Effect of gamma irradiation on Listeria ivanovii inoculated to iceberg lettuce stored at cold temperature

A low-dose gamma irradiation considerably reduced the total plate counts, psychrotrophic bacteria, lactic acid bacteria, and inoculated Listeria ivanovii on shredded iceberg lettuce. The total plate count of the lettuce irradiated at 1.0 kGy was reduced by 3.38 log₁₀ cfu/g on 0 storage day and to below the limit of detection (<2 log₁₀ cfu/g) as the cold storage was extended. Irradiation at 0.5 kGy effectively reduced the psychrotrophic bacterial counts and lactic acid bacterial counts in the lettuce to below the limit of detection (2 log₁₀ cfu/g). Irradiation at 1.0 kGy reduced L. ivanovii inoculated onto the shredded iceberg lettuce to below the limit of detection. The results showed that an irradiation at 1 kGy eliminates the bacterial contamination from the lettuce sample without any sensorial quality defect.