Removal of Microorganisms from Polymer Bottles by Caustic Washing

Abstract

Six different materials (glass, high density polyethylene (HDPE), polyethylene terephtalate (PET), polypropylene (PP), polycarbonate (PC) and polyvinylchloride (PVC)) used for bottle production were tested for their microbial rinsability. A comparative study was made between the roll-culture method and the rinsing method to determine the remaining microorganisms on caustic cleaned PET bottle inner surfaces. Only one-third of the microorganisms detected with the roll-culture method were detected with the generally applied rinsing method. Staphylococcus aureusand Bacillus cereuswere compared in their potential to attach to the different bottle materials and Bacillus cereusshowed less persistency against caustic cleaning compared to Staphylococcus aureus. The influence of the caustic cleaning parameters on the remaining microorganisms was examined. Temperature had a limited influence on the removal of microorganisms from surfaces. The effect of the commercial additive and the caustic concentration used was clearly more pronounced but depended strongly on the type of material. Optimization of the caustic cleaning process led to much better cleaning effectiveness. When optimal conditions were applied, the following classification in decreasing order of microbial rinsability of the examined materials could be made: glass > PET > PC > PP = PVC > HDPE.