Elucidating Critical Factors for Practical Dry Cleaning Applications on Low-Moisture Food Contact Surfaces

Recent outbreaks linked to flour-based products have highlighted the need for improved cleaning and sanitation methods in low-moisture environments. The factors affecting adhesion forces of flour particles, and the effective vacuum cleaning methodologies to overcome these forces, need to be better understood. The objectives of this study were to: (1) Measure electrostatic charge build-up in flour under different environmental conditions (20, 40, 60% relative humidity at room temperature), (2) quantify how powder size (US standard No. 60 – 80 or 80 – 100 mesh), electrostatic charge (charged and uncharged), and relative humidity impact the force required to remove the powder from an electropolished 304 stainless steel coupon (8 × 8 × 0.2 cm), and (3) determine the most effective vacuum nozzle angle (0, 45, 90° relative to the surface) for cleaning. Chargeability (nC) of flour samples was assessed using a Faraday cup electrometry, while the surface adhesion force of the flour particles was measured using a custom-built impact tester. Additionally, the surface cleanliness after vacuum treatments was assessed using ATP (adenosine triphosphate) swabs and a luminometer. Charged flour samples at 20% RH exhibited a significantly higher charge compared to those at 40 and 60% RH. Within the 60 – 80 mesh range, charged flour showed higher adhesion rates than uncharged samples at both 20% and 40% RH. However, in the 80 – 100 mesh range, charged flour did not show a significant difference in adhesion when compared to uncharged samples at any relative humidity level. Additionally, at 60% RH, surface residues measured by ATP were significantly lower for vacuum angle 90° than for 0° across both 60 – 80 mesh and 80 – 100 mesh size ranges of wheat flours.