AOAC Method 955.16 Available Chlorine in Disinfectants

Purpose of Test

The AOAC Available Chlorine in Disinfectants test method is a suspension-based test method used to evaluate halide-based water soluble powders and non-volatile liquid products intended for use as sanitizing rinses on previously cleaned, food-contact surfaces for registration with the U.S. EPA. (Examples of halide-based products include iodophors and chlorine-bearing chemistries.) In addition, this test method may be used to evaluate hand sanitizers used in food processing plants for registration with the U.S. FDA.

Summary of Test

In this method, a sample of the disinfectant is inoculated with a suspension of representative test organism. After 1 minute, a sample is removed and transferred to a tube containing a liquid subculture medium specifically selected to neutralize the test substance active and to recover any surviving test organism. Thirty seconds later, the same sample is re-inoculated. After an additional 1 minute of exposure, a second sample is removed and recovered. This is repeated until 10 samples have been removed. Side-by-side controls are identically evaluated using 50 ppm , 100 ppm and 200 ppm sodium hypochlorite. The subculture tubes are incubated, examined for growth, and the test subcultures are compared to the control sodium hypochlorite tubes. For food-contact sanitizing rinses, test results should demonstrate product concentrations equivalent in activity to 50, 100, or 200 ppm of sodium hypochlorite. For hand sanitizers, test results should demonstrate product concentrations equivalent in activity to 50 ppm of sodium hypochlorite. Typical test organisms include Staphylococcus aureus and Salmonella enterica serovar Typhi. Other foodborne pathogens are often tested as well.