The properties of brewery CIP disinfectants are discussed with particular reference to their chemical stability when in contact with other substances likely to be present in brewing equipment during CIP (especially those with a pH very different from that of the particular disinfectant involved) and the effects of the physical forces acting on them during pumping, spraying, etc., on their disinfecting capabilities. Peroxyacetic acid is neutralized by alkaline solutions, breaks down (releasing oxygen) in contact with trivalent iron ions (e.g. from corroded iron or steel) and becomes so unstable when diluted as to lose its disinfecting power within a few days (or as little as 12 hours if blended with certain detergents). Biguanides react with alkaline solutions to form a sticky insoluble polymeric substance which can cause serious fouling. Chlorine based disinfectants (chlorine dioxide, dissolved chlorine gas and sodium hypochlorite) react with acids, causing the release of chlorine gas from solution, which can also occur under certain physical stresses (e.g. when emerging from a spray nozzle) and not only leads to a loss of disinfecting capability but also creates both environmental and human safety problems. It was concluded, on the basis of comparative trials, that chlorine dioxide is probably the safest and most stable of the chlorine based products, provided that it is applied through low pressure sprayballs to avoid excessive physical stress.
Keywords : CIP comparative test disinfectant stability