Effectiveness of cleaning techniques used in the food industry in terms of the removal of bacterial biofilms.

The effectiveness of cleaning was investigated through food factory trials and laboratory experiments using a naturally occurring biofilm from a food factory environment and generated biofilms. The efficacy of factory cleaning and disinfection programmes was assessed by swabbing and total viable count (TVC) analysis of surfaces before cleaning, after cleaning and after disinfection. Cleaning produced a 0.91 log reduction in the attached population. Investigation of the effectiveness of a variety of cleaning methods in the removal of a naturally occurring food factory biofilm showed that the high pressure spray and the mechanical floor scrubber, which use a high degree of mechanical action, were most effective. Cleaning trials with biofilms of Pseudomonas aeruginosa or Staphylococcus aureus showed that spraying with water at pressures of 34.5, 51.7 and 68.9 bar did not significantly increase the removal, as assessed by direct epifluorescent microscopy (DEM) and swabbing and TVC analysis, beyond the three log reduction observed at 17.2 bar. The effect of spray time at 17.2 bar showed that increasing spray time from 1 to 10 s did not significantly increase removal of Ps. aeruginosa biofilm. Investigation of the optimum distance of the spray lance from the surface at 17.2 bar was found to be between 125 and 250 mm. The use of an alkaline, acidic or neutral detergent prior to spraying with water at 17.2 bar did not significantly increase the removal of Ps. aeruginosa or Staph. aureus. However, the acidic and alkaline products significantly (P = 0.05) affected the viability of Staph. aureus and Ps. aeruginosa, respectively, thereby minimizing the potential for the spread of contamination.