Hey oh
Bearing in mind that the same factory that makes such chemicals as sodium benzoate, also makes citric acid.
Here is a list of links that is very extencive and informative. Lots of reading to do, thats for sure.
http://science.uniserve.edu.au/schoo.../presadds.html
Also, I have to ask, how do you plane on testing the shelf life of your product? There are laboratories that will, for a fee, run all such tests for you. You can submit your recipe even, for an evaluation of its projected shelf stability. Remmember, some 90 year old widow gives one of your treats to her littly fluffy and he dies, and you have not established suitably the stability and safety of your product... well, some of those dogs can run into the very many thousands of dollars.
The same applies to foods for human consumption that are not made for immediate consumption. There are a few members here that are well versed in that type of food safety.