AOAC 955.16

AOAC 955.16 Test Method

• Standard chlorine solutions with concentrations of 200 ppm, 100 ppm, and 50 ppm are prepared as a reference for comparison with the test substance.
• A timer is started, as the test microorganism is introduced into the 200 ppm standard chlorine solution.
  1. 1. After 1 minute, a 4 mm sterile loop is used to move a small portion of the solution into a subculture tube.
     2. After 1.5 minutes, more of the test microorganism is added to the standard chlorine solution.
     3. At 2.5 minutes, another transfer of the solution is made to a subculture tube
• This process of adding the test microbe culture and transferring the solution to a subculture is repeated 10 times.
• The remaining standard chlorine solutions and the test solutions are subjected to the same procedure.
• All subculture tubes are incubated at 36°C for 48 hours.
• The subculture tubes from the standard chlorine solutions are checked for growth and compared to the subculture growth of the test substance solutions in order to determine the chlorine activity equivalent of the test substance.
• The test microorganisms should display similar growth in consecutive tubes as observed in standard solutions.