| A new method for rapid identification of bacterial biofilms on food processing materials was developed and then used to evaluate biofilm growth on materials commonly used in the food processing industry and to evaluate the efficiency of several sanitizers of different concentrations when applied to biofilms. The identification method consisted of nucleic acid staining and epifluorescence microscopy, followed by image analysis. Biofilm growth was evaluated on several surfaces; glass, polyethylene, and stainless steel with different surface morphologies: polished, brushed, treated with a fly cutter, and scribed with a diamond. In addition, several methods of sanitation were evaluated: sodium hypochlorite (50 and 200 ppm of free chlorine), ozone (3.5 to 5 ppm) and phenol (0.5% and 1%), and the surface treatments of rinsing, and ultrasound. The effect of sodium hypochlorite on the shape and coverage of biofilm on steel surfaces of different morphologies was evaluated, as were all sanitizers on biofilms grown on glass, polished steel and polyethylene. Finally, the effects of all sanitizers on the complete array of steel surfaces with different morphologies were evaluated. From the results, it could be concluded that 200 ppm free chlorine detached biofilms to a significant extent, while 50 ppm free chlorine merely killed the biofilm without detachment. In addition, 0.5% phenol did not kill any biofilm to a significant extent while 1% phenol caused detachment and killing. Ultrasound caused significant detachment without any killing of young and small biofilms. Further, it was shown that the biofilms on polished and scribed stainless steel surfaces reached their maximum coverage at 12 hours, and thereafter started to detach. Brushed stainless steel surfaces reached their maximum growth at 24 hours. Biofilms did not grow well on glass, and grew fairly slowly on polyethylene surfaces, reaching a maximum growth at 24 hours.; The conclusions from the studies give valuable information regarding precautions when cleaning materials. They can therefore be used as a base for the development of a general cleaning protocol for industrial food processing materials. Although a wild type E. coli was used in this study, it was anticipated that development and investigation of biofilms from other strains of E. coli, such as E. coli O157:H7 would be possible, using similar procedures. |
