Quote Originally Posted by dwross View Post
Photographic gelatin is one the world's most purified products. Eastman Gelatine has been able to transition to supplying the pharmaceutical industry because the purity requirements for photography meet or exceed medical and food standards. A bioassay is provided to prove that a batch of gelatin meets stringent industry standards -- i.e. no contaminants found.

Give it a moment's thought. If gelatin grew a bunch of evil organisms when it got wet, how could gelatin be used as a culture medium in a biology lab? If there were biological contaminants, they would rapidly overgrow the desired culture. But no, if you practice sterile inoculation technique, you are almost guaranteed a pure culture. No tuberculosis, staph, strep, or E.coli. I've grown things in a petri dish of gelatin that you don't want to know about, but it wasn't by accident. We don't have to fear gelatin.
Unfortunately, all of my samples come with analysis that show some "bugs" present, but at what are considered safe levels. In the bio labs, these gelatins are mixed with boiled water and are heat treated to destroy any residual microorganisms, but during emulsion making we do not start with boiled water nor do we heat treat the gelatin. In fact, we do not use masks and gloves. As a result, our emulsions are far from "sterile" and therefore use of biocides is very useful. So useful in fact, that just about everyone uses them including (as seen above) carbon printers. Others who use raw gelatin also find it useful to preserve their gelatin.

No, we do not need to fear gelatin. We need to be able to keep it for a reasonable time though. That is the purpose of a biocide.