Efficacy of chemical sanitizers against Bacillus cereus on food contact surfaces with scratch and biofilm

Abstract

This study was performed to investigate the efficacy of chemical sanitizers (viz., chlorine, chlorine dioxide, alcohol, and quaternary ammonium compound) against Bacillus cereus on five food contact materials under different conditions (smooth vs. scratched and with vs. without biofilms). After incubating materials in B. cereus suspension, cell adhesion on a smooth surface (10 cm²) was in the following ascending order: stainless steel (7.36 ± 0.08 log CFU), glass (7.51 ± 0.26 log CFU), polyethylene (7.66 ± 0.30 log CFU), polypropylene (7.76 ± 0.30 log CFU), and wood (8.02 ± 0.33 log CFU). The efficacy of sanitizers was dramatically reduced in the presence of a biofilm on all materials. Among four different chemical sanitizers, chlorine showed the best bactericidal activity against B. cereus on the surface with scratch and biofilm. Selection of adequate materials, maintenance of a smooth surface, and inhibition of biofilm formation are good practices for food safety.

Keywords: Bacillus cereus; Biofilm; Food contact surface; Sanitizing efficacy; Scratched surface.

Fig. 1

The population count and morphology of Bacillus cereus on various food contact surface materials, with and without scratches and biofilms. (A) The food contact surfaces (10 cm²) were made of stainless steel (SUS), glass (GL), polyethylene (PE), polypropylene (PP), or wood. Values are expressed as the mean ± standard deviation (n = 3). Mean values with different letters are significantly different at p < 0.05 by Duncan’s multiple-range test. Statistical differences among the mean values within the same surface condition are indicated by the letters A–D, whereas those among the mean values within the same material are indicated by the letters a–d. (B) Morphology of Bacillus cereus on smooth (uppercase letters) or scratched (lowercase letters) surface materials with biofilm formation was visualized by field emission-scanning electron microscopy. Relatively hydrophilic surfaces are stainless steel with smooth (I) and scratched (i) surfaces, glass with smooth (II) and scratched (ii) surfaces. Relatively hydrophobic surfaces are polyethylene with smooth (III) and scratched (iii) surfaces, polypropylene with smooth (IV) and scratched (iv) surfaces; and wood with smooth (V), and scratched (v) surfaces