Surface finishes on stainless steel reduce bacterial attachment and early biofilm formation: Scanning electron and atomic force microscopy study

Three common finishing treatments of stainless steel that are used for equi pment during poultry processing were tested for resistance to bacterial con tamination. Methods were developed to measure attached bacteria and to iden tify factors that make surface finishes susceptible or resistant to bacteri al attachment and biofilm formation. Samples of the treated surfaces (sand- blasted, sanded, and electropolished) were exposed to natural bacterial pop ulations from chicken carcass rinses to allow growth of bacteria and develo pment of biofilms on the surfaces. The kinetics of bacterial growth during surface exposure was followed by UV-visible spectrophotometry, and counts o f bacteria and early biofilm formation were measured following scanning ele ctron microscopy (SEM). The surface morphology of the samples was analyzed by atomic force microscopy (AFM) with samples from each of the batches of t reatments used in the SEM studies. Relative differences in the surface morp hology, including fractal dimensions, Z ranges, roughness, and other measur ements corresponded by treatment with the differences in reduction of bacte rial counts shown by SEM. The surface types varied in affinity for bacteria , and both physical and electrochemical treatments improved resistance of s tainless steel to bacterial attachment. Electropolished stainless steel was the least rough surface and showed significantly fewer bacterial cells and beginning biofilm formations than the other treated surfaces. Food safety could be improved if bacterial populations could be reduced during processi ng by increasing the use of materials that are resistant to bacterial conta mination. These findings will aid equipment manufacturers and processors in selecting materials and finishes that are most resistant to bacteria and b iofilm formation.