Ultraviolet light and Ultrasound as non-thermal treatments for the inactivation of microorganisms in fresh ready-to-eat foods

The effects of two non thermal disinfection processes, Ultraviolet light (UV 254 nm) and Ultrasound (US) on the inactivation of bacteria and color in two freshly cut produces (lettuce and strawberry) were investigated. The main scope of this work was to study the efficacy of UV and US on the decontamination of inoculated lettuce and strawberries with a cocktail of four bacteria, Escherichia coli, Listeria innocua, Salmonella Enteritidis and Staphylococcus aureus. Treatment of lettuce with UV reduced significantly the population of E. coli, L. innocua, S. Enteritidis and S. aureus by 1.75, 1.27, 1.39 and 1.21 log CFU/g, respectively. Furthermore, more than a 2-log CFU/g reduction of E. coli and S. Enteritidis was achieved with US. In strawberries, UV treatment reduced bacteria only by 1–1.4 log CFU/g. The maximum reductions of microorganisms, observed in strawberries after treatment with US, were 3.04, 2.41, 5.52 and 6.12 log CFU/g for E. coli, S. aureus, S. Enteritidis and L. innocua, respectively. Treatment with UV and US, for time periods (up to 45 min) did not significantly (p > 0.05) change the color of lettuce or strawberry. Treatment with UV and US reduced the numbers of selected inoculated bacteria on lettuce and strawberries, which could be good alternatives to other traditional and commonly used technologies such as chlorine and hydrogen peroxide solutions for fresh produce industry. These results suggest that UV and US might be promising, non-thermal and environmental friendly disinfection technologies for freshly cut produce.     

Efficacy of neutral electrolyzed water for sanitization of cutting boards used in the preparation of foods

The effectiveness of neutral electrolyzed water (NEW) to sanitize cutting boards used for food preparation was investigated. Cutting boards made of hardwood and bamboo were inoculated with Escherichia coli K12 and Listeria innocua, dried for 1 h, washed, rinsed and sanitized with NEW, sodium hypochlorite (NaClO) solution, or tap water (control). After each washing protocol, surviving bacterial populations were determined. Results showed that both NEW and NaClO sanitizing solutions produced similar levels of bacterial reductions. In manual washing, the population reductions by NEW and NaClO were 3.4 and 3.6 log₁₀ CFU/100 cm² for E. coli, and 4.1 and 3.9 log₁₀ CFU/100 cm² for L. innocua, respectively. In the automatic washing, the reductions by NEW and NaClO were 4.0 and 4.0 log₁₀ CFU/100 cm² for E. coli, and 4.2 and 3.6 log₁₀ CFU/100 cm² for L. innocua, respectively. No significant differences (P > 0.05) were observed in surviving bacteria counts when comparing board material types.     

The potential of atmospheric air cold plasma for control of bacterial contaminants relevant to cereal grain production

The aim of this work was to investigate the efficacy of dielectric barrier discharge atmospheric cold plasma (DBD ACP) against bacteria associated with grains quality and safety. ACP inactivation efficacy was tested against biofilms formed by different strains of E. coli, Bacillus and Lactobacillus in grain model media and against B. atrophaeus endospores either in grain media or attached on abiotic surfaces. Effects were dependent on bacterial strain, media composition and mode of ACP exposure. ACP treatment for 5 min reduced E. coli spp., B. subtilis and Lactobacillus spp. biofilms by > 3 log₁₀, whereas insignificant reductions were achieved for B. atrophaeus. ACP treatment of 5–20 min reduced B. atrophaeus spores in liquids by > 5 log₁₀. Treatment for 30 min reduced spores on hydrophobic surface by > 6 log₁₀, whereas maximum of 4.4 log reductions were achieved with spores attached to hydrophilic surface. Microscopy demonstrated that ACP caused significant damage to spores. In package ACP treatment has potential to inactivate grain contaminants in the form of biofilms, as well as spores and vegetative cells.Industrial relevanceThis study demonstrates that ACP technology is a promising tool for effective bio-decontamination which offers a wide range of possible applications including inactivation of microorganisms on cereal grains. However, due to the nature of the microbial contamination of grains and complex grain structures it may be necessary to optimise the potential for surface inactivation at several stages of grain processing and storage to enhance ACP efficacy against bacterial endospores.     

Behavior and control of Listeria innocua during manufacture and storage of Turkish White Cheese

The physico-chemical changes occurring in Turkish White Cheese and the survival of Listeria innocua, total aerobic count (TAC) and lactic acid bacteria (LAB) in artificially inoculated Turkish White Cheese during manufacture and storage periods (45 days), with respect to different contamination levels of L. innocua were investigated. Turkish White Cheese was manufactured by the short-set procedure in pilot-plant-sized vats in a commercial dairy plant. Pasteurized cow's milk was inoculated with L. innocua to a final level of 3.84 (low dose) and 7.12 (high dose) log₁₀ CFU/ml. Bacterial loads of inoculated milk, whey, post-ripened curd and post-salted cheese was determined during processing at 23 °C. Cheeses were stored in 16% saline solution at 4 °C up to 45 days. Samples were taken from each treatment and analyzed at 5-day intervals. Total reduction in viable cell numbers of L. innocua in Turkish White Cheese with each inoculum dose was approximately 2 log₁₀ cycles during the storage period with a first-order-rate of inactivation at 4 °C. Variations in initial number of LAB in L. innocua seeded cheeses after overnight pressing were observed as 3.84, 4.24, 5.85 log CFU/ml at conditions of high-dose, low-dose inoculation of L. innocua and without inoculation as control sample, respectively. The salt concentration, pH, starter activity and storage time were determined to be the main causes of this reduction in LAB. The results had shown that L. innocua was able to survive during the manufacture and storage due to inadequate pasteurization or post-process contamination. The storage period has been defined as a critical control point (CCP) for consumption of Turkish White Cheese and calculated to be at least 90 and 178 days at refrigeration temperature, in low and high inoculum doses of L. innocua, respectively, for a safe consumption. This study, which gives the result of behavior of low and high dose of Listeria monocytogenes during storage as CCP, can even guide the future risk assessment studies on Listeria in Turkish White Cheese.     

Efficacy of Neutral Electrolyzed Water,Quaternary Ammonium and Lactic Acid‐Based Solutions in Controlling Microbial Contamination of Food Cutting Boards Using a Manual Spraying Technique

Bactericidal activity of neutral electrolyzed water (NEW), quaternary ammonium (QUAT), and lactic acid‐based solutions was investigated using a manual spraying technique against Salmonella Typhimurium, Escherichia coli O157:H7, Campylobacter jejuni, Listeria monocytogenes and Staphylococcus aureus that were inoculated onto the surface of scarred polypropylene and wooden food cutting boards. Antimicrobial activity was also examined when using cutting boards in preparation of raw chopped beef, chicken tenders or salmon fillets. Viable counts of survivors were determined as log₁₀ CFU/100 cm² within 0 (untreated control), 1, 3, and 5 min of treatment at ambient temperature. Within the first minute of treatment, NEW and QUAT solutions caused more than 3 log₁₀ bacterial reductions on polypropylene surfaces whereas less than 3 log₁₀ reductions were achieved on wooden surfaces. After 5 min of treatment, more than 5 log₁₀ reductions were achieved for all bacterial strains inoculated onto polypropylene surfaces. Using NEW and QUAT solutions within 5 min reduced Gram‐negative bacteria by 4.58 to 4.85 log₁₀ compared to more than 5 log₁₀ reductions in Gram‐positive bacteria inoculated onto wooden surfaces. Lactic acid treatment was significantly less effective (P < 0.05) compared to NEW and QUAT treatments. A decline in antimicrobial effectiveness was observed (0.5 to <2 log₁₀ reductions were achieved within the first minute) when both cutting board types were used to prepare raw chopped beef, chicken tenders or salmon fillets.     

Influence of aqueous ozone, blanching and combined treatments on microbial load of red bell peppers, strawberries and watercress

The effectiveness of ozone in aqueous solution treatment on microbial inactivation was studied for three combinations microorganism/food: Listeria innocua/red bell peppers (artificially inoculated), total mesophiles/strawberries, and total coliforms/watercress, with two concentrations (0.3 and 2.0 ppm). Blanching treatments (50-60 °C) were also individually applied and in combination with ozone, for studying possible synergistic effects. In relation to ozone treatments, the highest microbial reductions were obtained for the highest concentration with the highest treatment time (3 min). Under those conditions, L. innocua/peppers, total mesophiles/strawberries and total coliforms/watercress were reduced respectively 2.8 ± 0.5, 2.3 ± 0.4 and 1.7 ± 0.4 log-cycles. However, a substantial portion of the microbial populations were reduced by water washing alone, and the presence of ozone generally added an additional reduction of 0.5-1.0 log-cycles.If ozone at the highest concentration is used, the treatment impacts on L. innocua/peppers and total mesophiles/strawberries load reductions were equivalent to a blanching at 50 °C (for the same treatment times).Combining blanching and ozone did not generate synergistic effects, and in some situations microbial reductions were lower than the ones observed when treatments were applied independently.     

A Combination of Chemical and Ultrasonication Treatments to Reduce Campylobacter jejuni on Raw Poultry

Cost-effective and acceptable decontamination technologies that can be readily applied to the broiler-processing industry have been proposed as a strategy to reduce pathogenic organisms on carcasses and improve food safety. The objective of this study was to determine the potential of combining chemical and ultrasonication processes to reduce Campylobacter, total viable counts (TVCs) and total Enterobacteriaceae counts (TECs) on broiler carcasses. Drumsticks were inoculated with Campylobacter jejuni and immersed in 12 % (w/v) trisodium phosphate (TSP), 2 % (w/v) citric acid (CA) or 5 % (w/v) capric acid sodium salt (CP) solutions for 1 min, while ultrasonication was performed at 40, 60 or 80 kHz. In addition, chemicals were administered in sequential combination (TSP?+?CA, TSP?+?CP or CA?+?CP) while ultrasonication was performed at the frequencies mentioned. The sequential treatment of TSP and CP with ultrasonication at 80 kHz achieved the greatest reductions for C. jejuni (4.5–4.6 log₁₀ colony forming units (CFU)/cm²) and TVC (1.9 log₁₀ CFU/cm²). Enterobacteriaceae were susceptible to the sequential application of CA and CP and ultrasonication at 80 kHz (2 log₁₀ CFU/cm²). This study demonstrated that combining chemical decontaminants with ultrasonication can significantly (p?相似文献   

Cold atmospheric gas plasma disinfection of chicken meat and chicken skin contaminated with Listeria innocua

Gas plasmas generated at atmospheric pressure and ambient temperatures offer a possible decontamination method for poultry products. The efficacy of cold atmospheric gas plasmas for decontaminating chicken skin and muscle inoculated with Listeria innocua was examined. Optimization of operating conditions for maximal bacterial inactivation was first achieved using membrane filters on which L. innocua had been deposited. Higher values of AC voltage, excitation frequency and the presence of oxygen in the carrier gas resulted in the greatest inactivation efficiency, and this was confirmed with further studies on chicken muscle and skin. Under optimal conditions, a 10 s treatment gave > 3 log reductions of L. innocua on membrane filters, an 8 min treatment gave 1 log reduction on skin, and a 4 min treatment gave > 3 log reductions on muscle. These results show that the efficacy of gas plasma treatment is greatly affected by surface topography. Scanning electron microscopy (SEM) images of chicken muscle and skin revealed surface features wherein bacteria could effectively be protected from the chemical species generated within the gas plasma. The developments in gas plasma technology necessary for its commercial application to foods are discussed.     

Inactivation of Escherichia coli O157:H7 on Inoculated Alfalfa Seeds with Pulsed Ultraviolet Light and Response Surface Modeling

: Escherichia coli O157:H7‐inoculated alfalfa seeds with seed layer thicknesses of 1.02 to 6.25 mm were subjected to pulsed UV light for up to 90 s at a 8‐cm distance from the UV strobe. Population reductions higher than 4 log₁₀ colony‐forming units (CFU)/g were achieved. For effect of distance from the UV strobe, seeds with 6.25‐mm layer thickness were treated 3 to 13 cm from the strobe. Reductions at shorter distances, such as 60 s at 5 cm (1.93 log₁₀ CFU/g) and 60 to 90 s at 8 cm (4.89 log₁₀ CFU/g), were significantly higher (P≤ 0.05). Data from the treatments were used to develop empirical models as a function of distance or layer thickness and treatment time for predicting the population of E. coli O157:H7 during pulsed UV‐light treatment. This study demonstrates that pulsed UV light holds promise for eliminating pathogens from alfalfa seeds, and the models developed can be useful predictive tools.     

Inactivation of Escherichia coli O157:H7, Salmonella and human norovirus surrogate on artificially contaminated strawberries and raspberries by water-assisted pulsed light treatment

This study investigated the inactivation of Escherichia coli O157:H7, Salmonella and murine norovirus (MNV-1), a human norovirus surrogate, on strawberries and raspberries using a water-assisted pulsed light (WPL) treatment. The effects of combinations of WPL treatment with 1% hydrogen peroxide (H₂O₂) or 100 ppm sodium dodecyl sulfate (SDS) were also evaluated. Strawberries and raspberries were inoculated with E. coli O157:H7 and treated by WPL for 5–60 s. E. coli O157:H7 on both strawberries and raspberries was significantly reduced in a time-dependent manner with 60-s WPL treatments reducing E. coli O157:H7 by 2.4 and 4.5 log CFU/g, respectively. Significantly higher reductions of E. coli O157:H7 were obtained using 60-s WPL treatment than washing with 10 ppm chlorine. Compared with washing with chlorine, SDS and H₂O₂, the combination of WPL treatment with 1% H₂O₂ for 60 s showed significantly higher efficacy by reducing E. coli O157:H7 on strawberries and raspberries by 3.3- and 5.3-log units, respectively. Similarly, Salmonella on strawberries and raspberries was inactivated by 2.8- and 4.9-log units after 60-s WPL–H₂O₂ treatments. For decontamination of MNV-1, a 60-s WPL treatment reduced the viral titers on strawberries and raspberries by 1.8- and 3.6-log units, respectively and the combination of WPL and H₂O₂ did not enhance the treatment efficiency. These results demonstrated that the WPL treatment can be a promising chemical-free alternative to chlorine washing for decontamination of berries destined for fresh-cut and frozen berry products. WPL–H₂O₂ treatment was the most effective treatment in our study for decontamination of bacterial pathogens on berries, providing an enhanced degree of microbiological safety for berries.     

Synergistic Processing of Skim Milk with High Pressure Nitrous Oxide,Heat, Nisin,and Lysozyme to Inactivate Vegetative and Spore-Forming Bacteria

Individual and combined effects of high pressure nitrous oxide (HPN₂O), heat, and antimicrobials on the inactivation of Escherichia coli, Listeria innocua, and Bacillus atrophaeus endospores in milk were all evaluated after 20-min treatments. Stand-alone milk treatments with HPN₂O (15.2 MPa), heat (45 and 65 °C), or nisin (50 and 150 IU mL^?1) resulted in log₁₀ reductions ranging only from 0.1 to 2.1 for E. coli and L. innocua. Combining HPN₂O (15.2 MPa) with heat (65 °C) inactivated 6.0 and 5.1 log₁₀ in the vegetative bacteria, respectively. Similarly, reductions of 5.9 and ≥ 6.0 log₁₀ of respective E. coli and L. innocua cells in milk were achieved through a combination of HPN₂O (15.2 MPa), heat (65 °C), and nisin (150 IU mL^?1). A 2.5 log₁₀ cycle inactivation of spores was obtained by HPN₂O, nisin (at both 50 and 150 IU mL^?1), and lysozyme (50 μg mL^?1) at 85 °C. Combining these processing techniques resulted in significantly greater microbial inactivation (p < 0.05) than the sum of individual reductions from each treatment alone, indicating synergistic effects. HPN₂O irrespective of processing temperatures did not cause any occurrence of sub-lethally injured cells or disruption in colloidal stability of milk at 65 and 85 °C (p ≥ 0.05). Color and pH changes in milk following the most demanding treatment conditions were minimal.     

Nanoencapsulation and immobilization of cinnamaldehyde for developing antimicrobial food packaging material

Use of antimicrobial coatings on food packaging is one of the important technologies of active packaging for improving food safety. There is growing demand for natural antimicrobials because of fear of adverse health effects of synthetic preservatives. The objectives of this study were to compare antibacterial properties of free and nanoencapsulated cinnamaldehyde in solution; polylactic acid (PLA) surfaces cast with cinnamaldehyde; and glass and PLA surfaces coated with cinnamaldehyde nano-liposomes. Cinnamaldehyde was nano-encapsulated by lipid bilayers of polydiacetylene – N-hydroxysuccinimide (PDA–NHS) nano liposomes and immobilized on glass slides and PLA films. Glass surfaces immobilized with nano-encapsulated cinnamaldehyde showed significant antibacterial activity against Escherichia coli W1485 and Bacillus cereus ATCC 14579, with reductions of 2.56 log₁₀ CFU/ml and 1.59 log₁₀ CFU/ml respectively in 48 h. PLA films cast with cinnamaldehyde also showed significant antibacterial activities against E. coli W1485 (2.01 log₁₀ CFU/ml reduction) and B. cereus (4.81 log₁₀ CFU/ml reduction). However, when the liposomal encapsulated cinnamaldehyde was immobilized on PLA films, it did not show any antibacterial activity. Glass surfaces coated with nano-encapsulated cinnamaldehyde may be used as an active packaging material in preserving liquid foods; however, further study is required to improve antimicrobial activities of PLA surfaces.     

Effect of single and combined UV-C and ultra-high pressure homogenisation treatments on inactivation of Alicyclobacillus acidoterrestris spores in apple juice

Alicyclobacillus acidoterrestris is a spore-forming bacterium that can survive thermal pasteurization and acidic conditions. It produces changes in the odour and flavour of fruit juices leading to economical loses. A. acidoterrestris CECT 7094 spores were inoculated in clarified and cloudy apple juices (Golden delicious var.) in the range of 5–6 log₁₀ spores/mL and submitted to different short-wave ultraviolet light (UV-C) doses (7.2–28.7 J/mL) and ultra-high pressure homogenisation (UHPH) treatments (100–300 MPa), including their combination. A. acidoterrestris could be inactivated in clarified apple juice at a level of 4.8 log₁₀ CFU/mL by a 300 MPa-UHPH treatment when the inlet temperature was 80 °C. UV-C treatments showed to be more efficient achieving a lethality of 5.5 log₁₀ CFU/mL with a dose of 21.5 J/mL at 20 °C. In cloudy apple juice (2357 NTU) UV-C treatments were less efficient with a maximum lethality of 4.07 CFU/mL after a dose of 28.7 J/mL. A previous application of UHPH contributed with UV-C to obtain higher reductions of A. acidoterrestris spores at the doses of 14.3 and 21.5 J/mL compared with UV-C single treatments. On the other hand, this previous treatment also changed the properties of particles in the matrix which apparently reduced the effectiveness of UV-C at 28.7 J/mL.     

Reduction of Salmonella Typhimurium and Listeria monocytogenes on produce by trisodium phosphate

The application of trisodium phosphate (TSP) on produce against food-borne bacteria has not been extensively evaluated. This research studied the effect of 20 and 50 mg/ml TSP in reducing Salmonella Typhimurium (ST) and Listeria monocytogenes (Lm) on model produce (lettuce and peppers). Washed and air-dried Iceberg lettuce (3 × 3 cm²) and Jalapeno peppers (25–30 g) were spiked with S. Typhimurium or L. monocytogenes (～7 log₁₀ CFU/ml). Samples were treated with 20 or 50 mg/ml TSP, 200 mg/L sodium hypochlorite (for comparison with traditional washes) or water (control rinse) for 15 or 30 s. Treatments were immediately neutralized with trypticase soy broth (TSB) containing 30 mg/ml beef extract, serially diluted, plated on Xylose Lysine Tergitol 4 (XLT4) agar for ST and Tryptic Soy Agar (TSA) for Lm and incubated at 37 °C for 24–48 h. Results showed that 20 mg/ml TSP and 200 mg/L sodium hypochlorite caused 5–6 log₁₀ CFU/ml reduction in ST on both lettuce and peppers after 15 s and 30 s, while 50 mg/ml TSP reduced ST to undetectable levels on both produce at both contact times. For overnight Lm cultures, a mere reduction of 0.21 and 0.28 log₁₀ CFU/ml was obtained using 20 and 50 mg/ml TSP after even 5 min, while 200 mg/L sodium hypochlorite decreased Lm by ～1 log₁₀ CFU/ml after 30 s and 1 min on lettuce, and decreased pure culture Lm to undetectable levels after 3 min. Thus, 50 mg/ml TSP appears effective against ST with negligible effects against Lm, whose mode of action needs to be understood.     

Vapor-phase Decontamination of Apples Inoculated with Escherichia coli

Improved methods of decontaminating apples containing human pathogens are required. In this study, application of gaseous antimicrobial agents was investigated. An apparatus, which transfers vapor from hot antimicrobial solutions to a treatment vessel, was evaluated with Golden Delicious apples inoculated with E. coli. Vapor from glacial acetic acid at 60°C provided population reductions exceeding 3.5 log₁₀ CFU/g but induced discoloration. Vapor from heated hydrogen peroxide and chlorine dioxide solutions gave reductions ≤ 2 logs. However, chlorine dioxide gas, applied at 20°C in an airtight container, achieved a 4.5 log reduction, with minimal quality loss. Reductions achieved with this treatment greatly exceed those obtained by other decontamination methods for raw commodities.     

Plasma-activated water as an alternative nitrite source for the curing of beef jerky: Influence on quality and inactivation of Listeria innocua

The aim of this study was to evaluate the potential of plasma-activated brine (PAB) as a nitrite source for the curing of beef jerky. The effects of PAB on quality parameters and on the microbial reduction of inoculated L. innocua were monitored. Beef slices were cured for ~18 h at 4 °C in brine solutions containing 0, 100 or 150 ppm of sodium nitrite, 150 ppm of sodium chloride (NaCl) and 100 ppm of sugar and subjected to plasma treatment. PAB were generated by a plasma beam system operating at 20 kHz and supplied with air or nitrogen (N₂) gas. Results showed significant higher levels (p < .05) of nitrites in brines activated by air-plasma (90–184 ppm) compared to N₂ gas (3–17 ppm). No significant differences were found in the texture and lipid oxidation levels of samples cured in PAB compared to standard curing. However, a significant higher a* value (6.45 ± 0.50, p < .001) was observed in samples cured in PAB. Significant reductions (p < .01) of 0.5 log CFU/mL in the population of L. innocua were observed in the brines and of 0.85 log CFU/g reduction in the jerky when cured in PAB. These results showed that plasma-curing could supply a suitable source of nitrite for meat products and, further optimisation of the technology could have applications for meat decontamination.     

A pilot-scale evaluation of using gaseous chlorine dioxide for decontamination of foodborne pathogens on produce and low-moisture foods

Small-scale studies have shown that chlorine dioxide gas, ClO_2(g), was effective for decontamination of produce, nuts, and spices. This study conducted a pilot-scale evaluation to identify effective ClO_2(g) treatment parameters for commercial-scale applications. The gas was produced by a generator utilizing sodium chlorite and chlorine gas for decontamination of Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella inoculated on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns. Inoculated samples and 45 kg tomatoes in a 1,246-L treatment chamber were exposed to various ClO_2(g) concentrations (mg/L) and times 9 (hr) at 70–95% RH to determine the treatment effects on the pathogen reductions. Results showed that the treatment caused higher reductions on produce. A ClO_2(g) treatment of 1 mg/L-3 hr at 70% RH reduced 4.9–6.8, 5.1–5.6, and 4.2–6.3 log CFU/g of STEC, L. monocytogenes, and Salmonella, respectively, on produce, with the highest reductions on baby-cut carrots. For almonds and peppercorns, ClO_2(g) treatments under higher RH caused higher reductions. The treatment of 2 mg/L-9 hr or 3 mg/L-4 hr at 95% RH reduced >4.0 log of STEC and Salmonella on almonds, and 1 mg/L-5 hr at 85% RH achieved >5.0 log reductions on peppercorns. Applying moisture to the surfaces of almonds caused >4.0 log reductions using 1 mg/L-5 hr at 95% RH. This study identified effective ClO_2(g) treatment parameters for achieving >4.0 log reductions of common pathogens on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns and showed that ClO_2(g) generator is suitable for large-scale decontamination. These findings can be used for pilot-scale ClO_2(g) decontamination of these products and for testing using ClO_2(g) for commercial-scale decontamination trials.     

Evaluation of overhead spray-applied sanitizers for the reduction of Salmonella on tomato surfaces

Abstract: Efficacy of sanitizers in an overhead spray and brush roller system was examined for reducing Salmonella on unwaxed, mature green tomatoes. Surface inoculated tomatoes were treated in the overhead spray system for 5, 15, 30, and 60 s. A sodium hypochlorite (NaOCl) study tested NaOCl (25, 50, and 100 mg/L) against a water control. A sanitizer study examined NaOCl (100 mg/L), chlorine dioxide (ClO₂; 5 mg/L), peroxyacetic acid (PAA; 80 mg/L), and water. The overhead spray system was also compared to a scale‐model flume. All NaOCl concentrations were significantly more effective at removing Salmonella than water and achieved at least a 3‐log₁₀ CFU/mL reduction at different treatment times (P < 0.05). NaOCl (100 mg/L) achieved a 4 ± 1.8 log₁₀ CFU/mL reduction at 15 s. In the sanitizer study, NaOCl, ClO₂, and PAA achieved at least a 3‐log₁₀ CFU/mL reduction at 15 s and between 3.9 and 5.5 log₁₀ CFU/mL reductions at 30 to 60 s. NaOCl (100 mg/L) in the overhead spray system significantly reduced more Salmonella than in the flume at 15 to 60 s. NaOCl flume treatment only reached a 1.3 ± 1.1 log₁₀ CFU/mL reduction at 15 s. Results of this study demonstrate the ability of sanitizers in the laboratory model overhead spray system to reduce Salmonella on tomato surfaces. An overhead spray system could be implemented instead of flumes to achieve higher pathogen reduction with less water and sanitizer use, thereby lowering packing costs. Practical Application: The use of a non‐recirculating, overhead spray brush roller system could offer a cost effective and efficacious way of washing tomatoes. The use large communal dump tanks in tomato processing has been suspected as a source of contamination in the tomato processing process. If effective, the brush roller system could augment or possible replace currently used dump tanks.     

Bacterial biofilm in silver-impregnated contact lens cases

PurposeThis study investigated the efficacy of pre-conditioning lens cases on bacterial biofilm formation and removal.MethodsSilver impregnated (MicroBlock / ProGuard™ & i-Clean) and control storage cases were pre-conditioned for 24 h with their respective multipurpose solutions (MPDSs). Cases were then inoculated with 2 ml of 10⁶ CFU/mL of ocular isolates of either P. aeruginosa or S. aureus and incubated for 48 h. Cases were subsequently disinfected (4−6 hours) as per the manufacturer’s recommended disinfecting time (MRDT) followed by the recommended case hygiene procedures - recapping wet (MicroBlock / ProGuard™ cases only) or rinse and air-dry or rinse, tissue-wipe and air dry (mechanical disruption). Surviving bacteria were enumerated using standard techniques.ResultsPre-conditioning the MicroBlock / ProGuard™ cases with MPDS significantly reduced biofilm formation (-1.1 log₁₀ CFU, p < 0.01 for P. aeruginosa & -1.3 log₁₀, p < 0.001, CFU for S. aureus) compared to the i-Clean lens cases. Maintaining the MicroBlock / ProGuard™ lens cases wet after the MRDT resulted in partial removal of bacterial biofilms (-2.9 log₁₀ CFU, p < 0.001 for P. aeruginosa and -2.6 log₁₀ CFU, p < 0.001 for S. aureus). Air-drying of all three types of lens storage cases after MRDT significantly reduced the bacterial biofilm (-5.4 log₁₀ CFU, p < 0.001 for P. aeruginosa and -3.5 log₁₀ CFU, p < 0.001 for S. aureus). Mechanical disruption produced the greatest reduction in the levels of bacterial biofilm in all 3 types of lens cases tested (-6.8 log₁₀ CFU, p < 0.001 for P. aeruginosa and -4.5 log₁₀ CFU, p < 0.001 for S. aureus). Synergi MPDS was significantly better than AQuify MPDS in removing bacterial biofilm from all 3 lens case types for case hygiene treatments with an air-drying step.ConclusionPre-conditioning of silver-impregnated ProGuard™ lens cases inhibited initial bacterial biofilm formation. Synergi MPDS was more effective than AQuify MPDS in removing bacterial biofilm in silver impregnated cases and tissue-wiping significantly improved biofilm removal.     

Fate of Listeria on various food contact and noncontact surfaces when treated with bacteriophage

Study objective was to determine efficacy of a bacteriophage suspension against Listeria spp. when applied to three common types of materials used in food manufacturing facilities. Materials included two food contact materials (stainless steel and polyurethane thermoplastic belting) and one noncontact material (epoxy flooring). Coupons of each material were inoculated with a cocktail containing L. monocytogenes and L. innocua (4 to 5-log₁₀ CFU/cm²). Two phage concentrations and a control, 0, 2 × 10⁷ and 1 × 10⁸ PFU/cm² were evaluated. Treated samples were held at 4 or 20°C for 1 and 3 hr to determine the effect of temperature and treatment time. Reductions in Listeria populations ranged from 1.27 to 3.33 log₁₀ CFU/cm² on stainless steel, from 1.17 to 2.76 log₁₀ CFU/cm² on polyurethane thermoplastic belting, and from 1.19 to 1.76 log₁₀ CFU/cm² on epoxy resin flooring. Higher phage concentration (1 × 10⁸ PFU/cm²), longer treatment time (3 hr), and processing area temperature of 20°C showed a greater (p ≤ .05) reduction of Listeria on the stainless-steel and polyurethane thermoplastic belting coupons. Overall, Listeria reduction by phage treatment occurred on all three materials tested, under all conditions.