Environment, food residue, and dry cleaning tool all influence the removal of food powders and allergenic residues from stainless steel surfaces

Abstract The aim of this study was to investigate how the properties of powered food (particle size and chemical composition), food contact surface (surface roughness), and the environment (ambient relative humidity) impact the efficacy of brushing and scraping in removing wheat flour and non-fat dry milk (NFDM) from stainless steel coupon surfaces. Scraping was significantly less effective than brushing in the removal of powder under all conditions. The number of brush passes (7 ± 2) required to remove NFDM at 0.81 aw was significantly greater than for samples at lower aw levels. Moreover, surface protein residues were still detected following brush removal of NFDM at 0.69 and 0.81 aw. Adhesion and cohesion in samples equilibrated at different relative humidity levels (i.e. different resulting aw) were measured using custom test cells to quantify shear force. Greater adhesion and cohesion were detected for NFDM at higher aw levels. Adhesion and cohesion of NFDM at 0.81 aw were determined to be 129 ± 60 N/m2 and 5418 ± 633 N/m2, respectively. In addition, the particle size of NFDM (75, 180 and 355 μm) and the interaction between particle size and surface roughness (Ra = 0.17 ± 0.09, 0.77 ± 0.12, 1.08 ± 0.37 and 2.05 ± 0.40 μm) had significant effects on residual ATP following brushing. However, surface roughness did not significantly affect cleaning outcomes under the tested conditions. Overall, these findings highlight the potential for allergenic residue retention after conventional dry cleaning using hand tools. By better understanding the baseline efficacy of conventional hand tools used in dry cleaning under different scenarios, more effective cleaning technologies can be developed.