Transfer of Salmonella from Skin to Flesh and Peelers during Peeling of Baby Cucumbers

Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-borne illness outbreaks, is enabled by the attachment and confinement of pathogens within microscale cavities of surface roughness (grooves, scratches). We report foodsafe oil-based slippery coatings (FOSCs) for food-processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food-grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm-2, and by 3 log CFU cm-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their antibiofilm activity after the erosion of the oil layer by surface wear with glass beads, which suggests that there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food-processing surfaces and improve food safety by reducing biofilm growth.

Food contact surfaces coated with nitrogen-doped titanium dioxide: effect on Listeria monocytogenes survival under different light sources

Biofilm control remains a challenge to food safety. A well-studied non-fouling coating involves codeposition of polytetrafluoroethylene (PTFE) during electroless plating. This coating has been reported to reduce foulant build-up during pasteurization, but opportunities remain in demonstrating its efficacy in inhibiting biofilm formation. Herein, the initial adhesion, biofilm formation, and removal kinetics of Bacillus cereus on Ni-PTFE-modified stainless steel (SS) are characterized. Coatings lowered the surface energy of SS and reduced biofilm formation by > 2 log CFU cm−2. Characterization of the kinetics of biofilm removal during cleaning demonstrated improved cleanability on the Ni-PTFE coated steel. There was no evidence of biofilm after cleaning by either solution on the Ni-PTFE coated steel, whereas more than 3 log and 1 log CFU cm−2 of bacteria remained on the native steel after cleaning with water and an alkaline cleaner, respectively. This work demonstrates the potential application of Ni-PTFE non-fouling coatings on SS to improve food safety by reducing biofilm formation and improving the cleaning efficiency of food processing equipment.

Influence of physical variables on the transfer of Salmonella Typhimurium LT2 between potato (Solanum tuberosum) and stainless steel via static and dynamic contact

Two candidate method modifications for the Atlas Listeria Environmental LE Detection Assay were compared with the U.S. Department of Agriculture (USDA)-Food Safety and Inspection Service Microbiology Laboratory Guidebook 8.09 (MLG 8.09) method for detection of Listeria spp. on stainless steel, polyvinyl chloride (PVC), and sealed concrete surfaces. For LE candidate method 1, samples were enriched in FoodChek Actero Listeria Enrichment Media [ALEM; Performance Tested MethodSM (PTM) 111201] at 35 ± 2°C for 18 to 24 h and evaluated for a range of analytical sample volumes. For LE candidate method 2, the current Roka PTM using 90 mL of Half-Fraser broth for enrichment at 35 ± 2°C was evaluated at 24 h with a reduced sample volume. These comparisons were made in multiple studies across the three environmental surfaces. Within each method and study, a total of 5 samples were uninoculated, 20 samples were inoculated with Listeria spp. at a low level to target fractional positivity, and 5 samples were inoculated with Listeria spp. at a high level to approach a probability of detection of 1. Inclusivity and exclusivity studies were also conducted for the LE method in combination with Half-Fraser and ALEM. The Atlas Listeria Environmental LE Detection Assay detected all 50 inclusive organisms, including 25 strains of L. monocytogenes and 5 strains of each of the other five common species of Listeria (L. innocua, L. welshimeri, L. ivanovii, L. seeligeri, and L. grayi) and none of the 30 exclusive organisms across all media and with both 200 and 2000 µL sample volumes. For the LE candidate method 1 studies, no significant differences were observed within the Roka ALEM method at 18, 20, or 24 h and for both the 200 and 2000 µL sample volumes as compared with the paired culture outcome. However, the ALEM method performed significantly better as compared with the unpaired reference method for sealed concrete and stainless steel. For the LE candidate method 2 studies, no significant differences were observed within the Roka HF method at 24 h for the 200 and 2000 µL samples as compared with the paired culture outcomes and unpaired reference method outcomes across the surfaces. The independent laboratory studies observed no significant differences in performance between the USDA/MLG 8.09 reference method and candidate methods 1 or 2, respectively, across the evaluated parameters. Overall, the candidate method 1 modification parameters and candidate method 2 sample parameters for the Atlas Listeria Environmental LE Detection Assay were statistically equivalent to or better than the reference method for detection of Listeria spp. on stainless steel, PVC, and sealed concrete surfaces, providing greater flexibility in method application for end users.

Food pathogens like Salmonella spp. and Listeria monocytogenes can attach to surfaces commonly found in food processing environment, increasing the risk of foodborne diseases. Therefore, the use of effective strategies to reduce bacterial adhesion on equipment surfaces is a subject of great interest for food industries. The plasma nitriding treatment has been investigated for surface modification of biomedical materials, aiming to reduce bacterial attachment. However, this technology has not yet used in food equipment surfaces. The objective of this study was to evaluate the effect of plasma nitriding surface modification of stainless steels on the adhesion of S. Enteritidis and L. monocytogenes. Coupons of stainless steel AISI 316 and AISI 304 were treated with plasma nitriding (30 Pa, 100 W), and bacterial adhesion was compared with untreated coupons. Bacterial counts and surface hydrophobicity were analyzed before and after treatment. Results showed that plasma nitriding treatment modified the hydrophobicity of the stainless steel surfaces, and the number of attached cells was reduced when compared to untreated stainless steel coupons. Based on these results, plasma nitriding treatment may be a promising technology, which can be used to hinder bacterial attachment on stainless steel surfaces.Practical ApplicationsThe modification of stainless steel surfaces with plasma nitriding can influence on the bacterial adhesion, contributing with food safety. This surface treatment can be used in industrial scale before the manufacture of stainless steel equipment used in food industries. The use of equipment treated with plasma nitriding do not compromise food with chemical or physical residues, however, it should be used as an additional control measure to microbial hazards and do not substitute Good Hygiene Practices.

Biofilm formation comparison of Vibrio parahaemolyticus on stainless steel and polypropylene while minimizing environmental impacts and transfer to grouper fish fillets

New strategy to delay food spoilage: Application of new food contact material with antibacterial function

Efficacy of gaseous chlorine dioxide in inactivating Bacillus cereus spores attached to and in a biofilm on stainless steel

Worldwide, around 600 million people are affected by foodborne illnesses each year which highlights the importance of food safety. It is important to ensure the cleanliness of the working surfaces in food processing facilities. Stainless steel is widely used in the food industry as a food contact surface. Endowing stainless steel with a potent rechargeable antibacterial function offers the prospect of a reusable and clean surface. In this study, a "clickable" coating for stainless steel was developed. Quaternized azido-hydantoin (C1), quaternary ammonium compound (C2), and azido-hydantoin (C3) were bonded to stainless steel primed with the clickable coating to yield three samples: SSMC1, SSMC2, and SSMC3, respectively. The coating was stable during the chlorination process which was used to convert the immobilized C1 and C3 to their N-chloramine counterparts (SSMC1-Cl and SSMC3-Cl, respectively). It was shown that SSMC1-Cl had the best antibacterial activity with 100% reduction of E. coli and S. aureus after 1 and 2 h of contact, respectively. SSMC1-Cl also showed the best performance in high protein medium (HPM) against bacteria, demonstrating 100% and 99.9% bacterial reduction against E. coli and S. aureus, respectively, after 3 h of contact. After five cycles of chlorination-dechlorination, SSMC1-Cl sustained a kill efficiency of 100% for both E. coli and S. aureus within 2 h of contact. This result reveals that SSMC1-Cl has the ability to maintain its antibacterial activity after repetitive cycles, which emphasizes its rechargeable nature. Altogether, this study presents an effective quaternized N-chloramine-based biocidal coating on stainless steel (SSMC1-Cl) that is rechargeable, durable, and effective against Gram-positive and Gram-negative bacteria.

Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel by synergistic effects of tap water-based neutral electrolyzed water and lactic acid.

Human norovirus transfer to stainless steel and small fruits during handling.

Synergistic effect of a combination of ultraviolet–C irradiation and sodium hypochlorite to reduce Listeria monocytogenes biofilms on stainless steel and eggshell surfaces

This research investigates the migration of metals from stainless steel containers used for patient food in hospitals. The study evaluates the risk associated with metal migration from stainless steel containers sourced from four hospitals in Bangkok: A, B, C and D hospitals, including both new and previously unused containers. Experiments were conducted at 25°C and 70°C, revealing average migration levels of 0.0532 ± 0.0196 mg/cm 2 and 0.0949 ± 0.0131 mg/cm 2 , respectively. Specific migration of iron (Fe), nickel (Ni), and chromium (Cr) was measured using Graphite Furnace Atomic Absorption Spectrophotometry (GF – AAS). At 25°C, the average migration levels were 4.2704 ± 0.3662 μg/cm 2 for Fe, 2.0649 ± 3.0914 μg/cm 2 for Ni, and 0.0065 ± 0.0153 μg/cm 2 for Cr. At 70°C, these levels were 3.9714 ± 0.6777 μg/cm 2 for Fe, 1.8815 ± 1.9336 μg/cm 2 for Ni, and 0.0038 ± 0.0018 μg/cm 2 for Cr. For the unused stainless steel containers, the migration levels were significantly lower (p<0.05). Based on the standards set by the European Food Safety Authority (EFSA) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the metal migration levels observed in this study are within safe limits, ensuring the safety of stainless steel containers for food use.

Nanopatterning and anti-biofilm characterization of self-cleanable surfaces on stainless steel substrates were demonstrated in the current study. Electrochemical etching in diluted aqua regia solution consisting of 3.6% hydrogen chloride and 1.2% nitric acid was conducted at 10 V for 5, 10, and 15 min to fabricate nanoporous structures on the stainless steel. Variations in the etching rates and surface morphologic characteristics were caused by differences in treatment durations; the specimens treated at 10 V for 10 min showed that the nanoscale pores are needed to enhance the self-cleanability. Under static and realistic flow environments, the populations of Escherichia coli O157:H7 and Salmonella Typhimurium on the developed features were significantly reduced by 2.1–3.0 log colony-forming unit (CFU)/cm2 as compared to bare stainless steel (p < 0.05). The successful fabrication of electrochemically etched stainless steel surfaces with Teflon coating could be useful in the food industry and biomedical fields to hinder biofilm formation in order to improve food safety.