Applicability of Controllable Normal Force Platform for Study of Bacteria Removal During Dry Cleaning in Dry Food...

Microbial safety in low-moisture foods (LMFs) has attracted widespread public attention due to the multiple outbreaks and recalls in recent years. Dry cleaning methods are typically used in LMFs production environments. However, there is no standardized and consistent method for controlling normal force and measuring the shear force of cleaning tool applied on food contact surfaces during dry cleaning. A dry-cleaning platform with the normal force controllable feature was custom-designed, and its performance was evaluated as the primary objective of the study. Effects of various factors (bacterial type, surface material, surface roughness, and normal force) on the shear force and removal of Salmonella enterica Enteritidis PT 30 (S. PT 30) and Enterococcus faecium NRRL B2354 (E. faecium) during dry wiping were investigated using the developed platform. The performance evaluation indicated that the platform was adequately stable during standardized and consistent dry cleaning. Surface roughness, normal force, and surface material significantly affected shear force (p < 0.05) applied on food contact surfaces. The bacterial type significantly affected the shear force on stainless steel (p < 0.05). No significant difference (p > 0.05) was observed in removing S. PT 30 from inoculated surfaces after dry wiping under all investigated conditions. Surface material significantly affected the removal of E. faecium (p < 0.05). The removal of E. faecium was numerically higher than that of Salmonella under the same conditions. Thus, E. faecium may not be a suitable surrogate for S. PT 30 removal at the end of dry cleaning under the wiping conditions tested. The potential applications of the platform were also discussed for future studies on how to enhance dry cleaning efficiency. Shear force can guide the disruption of cohesion and adhesion in surface microorganisms/residues, thereby enhancing cleaning efficiency. The custom-designed dry-cleaning platform with the controllable normal force feature has potential applications in further laboratory dry cleaning studies.