Development of Titanium Dioxide (TiO₂) Nanocoatings on Food Contact Surfaces and Method to Evaluate Their Durability and Photocatalytic Bactericidal Property

Abstract

Titanium dioxide (TiO2 ) is a well-known photocatalyst for its excellent bactericidal property under UVA light. The purpose of this study was to develop physically stable TiO2 coatings on food contact surfaces using different binding agents and develop methods to evaluate their durability and microbicidal property. Several types of organic and inorganic binders such as polyvinyl alcohol, polyethylene glycol, polyurethane, polycrylic, sodium and potassium silicates, shellac resin, and other commercial binders were used at 1:1 to 1:16 nanoparticle to binder weight ratios to develop a formulation for TiO2 coating on stainless steel surfaces. Among the tested binders, polyurethane, polycrylic, and shellac resin were found to be physically more stable when used in TiO2 coating at 1:4 to 1:16 weight ratio. The physical stability of TiO2 coatings was determined using adhesion strength and scratch hardness tests by following standard ASTM procedures. Further, wear resistance of the coatings was evaluated based on a simulated cleaning procedure used in food processing environments. TiO2 coating with polyurethane at a 1:8 nanoparticle to binder weight ratio showed the highest scratch hardness (1.08 GPa) followed by coating with polycrylic (0.68 GPa) and shellac (0.14 GPa) binders. Three different techniques, namely direct spreading, glass cover-slip, and indented coupon were compared to determine the photocatalytic bactericidal property of TiO2 coatings against Escherichia coli 0157:H7 at 2 mW/cm(2) UVA light intensity. Under the tested conditions, the indented coupon technique was found to be the most appropriate method to determine the bactericidal property of TiO2 coatings and showed a reduction of 3.5 log CFU/cm(2) in 2 h.

Broad-Spectrum Antimicrobial Effects of Photocatalysis Using Titanium Dioxide Nanoparticles Are Strongly Potentiated by Addition of Potassium Iodide

“…Researchers are attempting to dope the TiO 2 nanoparticles with platinum (31), nitrogen (32), graphite (33), or other materials in order to shift the activation wavelength away from the UV into the visible range (34). Other groups have fabricated different types of titania nanostructures such as TiO 2 nanotubes (35) and nano-coated thin films for food preservation (36). Silver nanoparticles were combined with TiO 2 to produced a triply enhanced bactericidal effect by nano-Ag alone, increasing the light absorption in the visible region, and by acting as electron traps to promote charge separation of photoinduced electrons (e Ϫ ) and holes (h ϩ ) (37).…”

Nanomaterials for products and application in agriculture, feed and food

“…The most common NM added to food packaging to confer antimicrobial properties are silver, chitosan, zinc oxide (Li, Li, Zhang, & Xing, 2011), TiO 2 (Yemmireddy, Farrell, & Hung, 2015) and nisin (de Azeredo, 2013;Ravishankar Rai & Jamuna Bai, 2011;Trbojevich & Fern andez, 2015). Chitosan is a very promising option for antimicrobial food packaging, and has great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties (Aresta et al, 2013;Dutta, Tripathi, Mehrotra, & Dutta, 2009).…”

“…Chitosan is a very promising option for antimicrobial food packaging, and has great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties (Aresta et al, 2013;Dutta, Tripathi, Mehrotra, & Dutta, 2009). Due to its strong photocatalytic activity under UV irradiation nanostructured titanium dioxide has been suggested to be effective in eliminating pathogenic microorganisms in food contact surfaces and thereby enhancing food safety (Ravishankar Rai & Jamuna Bai, 2011; Yemmireddy et al, 2015).…”

Using Photocatalyst Metal Oxides as Antimicrobial Surface Coatings to Ensure Food Safety—Opportunities and Challenges

“…For example, George and others () used pyrex wells mounted on thermally sprayed TiO2 coatings on stainless steel using a silicone rubber to contain bacterial solutions onto the coated substrate. Similarly, Cushnie and others () and Bonetta and others () used an aseptically sealed glass cell ring on the surface of the photocatalyst‐coated glass slides and ceramic tiles to contain the bacterial culture, while Yemmireddy and others () used an indented stainless steel coupon to create a TiO2 coating using different binders to test antimicrobial efficacy. However, the relative complexity of mounting a well with good seal stability or making correct indentation is a major drawback of this type of system.…”

“…The hardness of a coated surface is then expressed by a scratch hardness number in GPa. Commercial devices fitted with nano‐indenter (Sobczyk‐Guzenda and others ) as well as in‐house developed (Yemmireddy and others ) systems to measure the scratch hardness of metal oxide coatings have been reported. The adhesive strength of the coating are determined by using a Scotch tape test (Yemmireddy and others ).…”