Ahtiril, I am not sure of what you refer to, but if it is to the bacterial content of gelatin, there is no sure way to destroy bacterial or fungal spores by methods such that the gelation properties of gelatin for photographic purposes are not destroyed. So, all gelatin is tested for biological contents.

Phenol is an antiseptic and other materials kill (antiseptic) or retard growth (bacteriostat). Residual ammonia is not good for gelatin or emulsion.

PE