Biofilms (layers of microorganisms adhering to surfaces) can constitute a serious problem in food and beverage production facilities. In breweries, they are most commonly found on conveyors and in pasteurizing equipment, but only rarely in pipes, tanks, etc. Nevertheless, some beer spoilage microorganisms (e.g. Lactobacillus brevis, Enterobacter agglomerans and certain species of the genus Acetobacter) can form biofilms on materials used for the inner surfaces of brewery pipes and vessels. Tests are described in which the "Tubular Flow System", which simulates brewery CIP operations, was used to compare the performance of different detergents and combinations of detergents and disinfectants in the removal of biofilm forming bacteria from stainless steel surfaces. Used alone, both chlorinated and nonchlorinated alkaline detergents removed over 94% of bacteria from a surface within 15 to 20 minutes at 63 degrees C, killing almost all those not physically removed, while acid detergents removed between 74 and 85% (as did water at the same temperature). At 27 degrees C, chlorinated alkaline detergents removed at least 81% after 10 minutes and 91% after 20 minutes, while the others fell in the same range as water (63 to 84%). At 7 degrees C none of the detergents performed significantly better than water. Washing with any of the detergents tested at 63 degrees C followed by exposure to any of the disinfectants used for 2 minutes removed over 99% of bacteria and killed virtually all the remainder. At 26 degrees C, this result was achieved by chlorinated alkaline detergent followed by chlorine/iodine disinfection for 10 minutes, alkaline detergent followed by disinfection with organic chlorine or peracetic acid for 2 minutes, and washing with a dual purpose acidic detergent/disinfectant for 30 minutes (or 15 minutes in the absence of carbon dioxide). Since disinfectants alone are much less effective against biofilms, it is surmised that as well as removing much of the bacterial population, detergents may make the surviving bacteria more vulnerable to the disinfectant.
Keywords : bacteria brewery CIP comparative test detergent disinfectant disinfection equipment