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

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/cm² 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/cm² in 2 h.