Studies of the Technic to Evaluate the Efficiency of Several Chlorine Sterilizers for Dairy Use

Summary Sterile sample bottles containing sodium thiosulphate were found more suitable than the usual sample bottle for obtaining samples of chlorinated dairy solutions intended for bacteriological examination. The iodometric and ortho-tolidine tests do not necessarily measure the germicidal powers of used chlorine sterilizers as measured by the actual conditions evidenced by bacteriological tests. In actual practice using the sodium thiosulphate treated sample bottle the hypochlorite sterilizers were found to be effective against the organisms in the dairy equipment. The used solutions in all concentrations were found to display a marked germicidal action against Esch. coli when tested in the laboratory. The chloramine T compound as used in these experiments displayed a delayed germicidal action which might make it objectionable as a dairy sterilizer under certain conditions. Hypochlorite rinse solutions with residual chlorine contents as low as 6 p.p.m. were found effective in the disinfection of dairy equipment. In reference to hypochlorites, any chlorine in excess of 6 p.p.m. constituted a safety margin. The use of large volumes of rinse is more important than high chlorine residuals. This is particularly important in the use of chloramine T compounds which require a longer period of exposure to effect sterilization.