A Time-Course Study on a Food Contact Material (FCM)-Certified Coating Based on Titanium Oxide Deposited onto Aluminum.

Aluminum is the second most widely used metal worldwide. It is present as an additive in cosmetics, pharmaceuticals, food, and food contact materials (FCM). In this study, we confirm the bactericidal effect of a special anodizing method, based on TiO2 nanoparticles (DURALTI®) deposited on aluminum disks with different roughness and subjected to two sanitizing treatments: UV and alcohol 70%. Consequently, we perform a time-course evaluation against both Gram-negative and Gram-positive bacteria to better frame the time required to achieve the best result. Approximately 106 CFU/mL of Escherichia coli ATCC 25922; Salmonella Typhimurium ATCC 1402; Yersinia enterocolitica ATCC 9610; Pseudomonas aeruginosa ATCC 27588; Staphylococcus aureus ATCC 6538; Enterococcus faecalis ATCC 29212; Bacillus cereus ATCC 14579 and Listeria monocytogenes NCTT 10888 were inoculated onto each aluminum surface and challenged with UV and alcohol 70% at 0, 15", 30", 1', 5', 15', 30', 1, 2, 4 and 6 h. DURALTI® coating already confirmed its ability to induce a 4-logarithmic decrease (from 106 to 102 CFU/mL) after 6 h. Once each sanitizing treatment was applied, an overall bacterial inhibition occurred in a time ranging from 15'' to 1'. The results are innovative in terms of preventing microbial adhesion and growth in the food industry.

Time-Course Study of the Antibacterial Activity of an Amorphous SiOxCyHz Coating Certified for Food Contact.

One of the most-used food contact materials is stainless steel (AISI 304L or AISI 316L), owing to its high mechanical strength, cleanability, and corrosion resistance. However, due to the presence of minimal crevices, stainless-steel is subject to microbial contamination with consequent significant reverb on health and industry costs due to the lack of effective reliability of sanitizing agents and procedures. In this study, we evaluated the noncytotoxic effect of an amorphous SiOxCyHz coating deposited on stainless-steel disks and performed a time-course evaluation for four Gram-negative bacteria and four Gram-positive bacteria. A low cytotoxicity of the SiOxCyHz coating was observed; moreover, except for some samples, a five-logarithm decrease was visible after 1 h on coated surfaces without any sanitizing treatment and inoculated with Gram-negative and Gram-positive bacteria. Conversely, a complete bacterial removal was observed after 30 s-1 min application of alcohol and already after 15 s under UVC irradiation against both bacterial groups. Moreover, coating deposition changed the wetting behaviors of treated samples, with contact angles increasing from 90.25° to 113.73°, realizing a transformation from hydrophilicity to hydrophobicity, with tremendous repercussions in various technological applications, including the food industry.

Antibacterial Effect of Aluminum Surfaces Untreated and Treated with a Special Anodizing Based on Titanium Oxide Approved for Food Contact.

One of the main concerns of the food industry is microbial adhesion to food contact surfaces and consequent contamination. We evaluated the potential bacteriostatic/bactericidal efficacy of aluminum surfaces with different large-scale roughness (0.25, 0.5 and 1 µm) before and after the surface treatment with a special anodizing based on titanium oxide nanotechnology (DURALTI®) and after 3 different sanitizing treatments, e.g., UV, alcohol and a natural product named Gold lotion. Four Gram-negative (Escherichia coli ATCC 25922, Salmonella typhimurium ATCC 1402, Yersinia enterocolitica ATCC 9610 and Pseudomonas aeruginosa ATCC 27588) and four Gram-positive (Staphylococcus aureus ATCC 6538, Enterococcus faecalis ATCC 29212, Bacillus cereus ATCC 14579 and Listeria monocytogenes NCTT 10888) bacteria were screened. As far as concerns aluminum surfaces without nanotechnology surface treatment, an overall bacteriostatic effect was observed for all strains with respect to the initial inoculum that was 106 CFU/mL. Conversely, an overall bactericidal effect was observed both for Gram-negative and -positive bacteria on DURALTI®-treated aluminum disks, regardless of roughness and sanitizing treatment. These results are innovative in terms of the great potential of the antibacterial activity of nanotechnologically treated food contact surfaces and their combination with some sanitizing agents that might be exploited in the food industry.