The Code environment has selective properties to the accumulation of CGB (escherichia coli group bacteria). Selectivity due to the presence of sulfanol (alkylaryl sulfonate). This component has an inhibitory effect on many microorganisms but does not affect the development of the CGB. In addition, the growth of bacteria capable of fermentation of lactose is accompanied by a change in color of the medium from green to yellow.

In the preparation of the environment should take into account that sulfanol provokes foaming, in particular when boiling.