AOAC 955.16

Chlorine Equivalency Method for Sanitizers Officially named, Chlorine (available) in Disinfectants Germicidal Equivalent Concentration

Summary

AOAC Method 955.16 is the recommended test method required by the U.S. Environmental Protection Agency for evaluating the efficacy of products with a label recommendation for the treatment of previously cleaned, non-porous, food contact surfaces (eating/drinking utensils, food processing equipment) as a sanitizing rinse. The test is designed for halide chemical products (water-soluble powders and liquids): sanitizing rinses formulated with iodophors, mixed halides, and chlorine-bearing chemicals.

The test compares preparation(s) of the product to a control standard prepared at three known germicidal concentrations of available chlorine. For initial efficacy claims, testing against Staphylococcus aureus and Salmonella enterica serovar Typhi is required; additional foodborne organisms may be tested as well.

Test Overview

• A sample of the prepared product is inoculated with an aliquot of the test organism. 
• A calibrated timer is started and runs continuously for the duration of testing.
• One minute after inoculation, a sample is removed and transferred to recovery broth with neutralizers. 
• At 1.5 minutes, the product is inoculated with an additional aliquot of the test organism.
• At 2.5 minutes, a sample is removed and transferred to recovery broth with neutralizers.
• This pattern of inoculation and sampling is repeated a total of 10 times resulting in sampling intervals of 1, 2.5, 4, 5.5, 7, 8.5, 10, 11.5, 13, and 14.5 minutes.
• The same procedures are performed using a standard control solution containing 50 ppm, 100 ppm, and 200 ppm sodium hypochlorite.
• All test and control samples are incubated and observed for growth. 

For food-contact sanitizing rinses, results from the test samples should demonstrate product concentrations equivalent in activity to each concentration of the control solution.