What's the best cure for long shelf life

I'm guessing they were stored in a sealed container of sorts...  Jar, plastic bag etc...   Stored in the open, in the refer, they may have made it..   The refer is a dehydrator and they would have continued to dry...   The freezer would be a good choice for container storage..   Vac-packed bags would work in the freezer..

As far as a chemical treatment, like you find in the store, below are some suggestions....  

http://www.meatsandsausages.com/sausage-making/additives

http://www.malabarsuperspice.com/ref_meatproadd.htm