Making impure or corrupt by adding extraneous materials "the adulterating effect of extraneous materials" - adulterant
Verb: adulterateu'dúltu`reyt
Corrupt, debase, or make impure by adding a foreign or inferior substance; often by replacing valuable ingredients with inferior ones "adulterate liquor" - load, stretch, dilute, debase
See also: adulterant, adulterator, extraneous, foreign