Agreed. Both products will give the sausage the signature tanginess. Of course the real way is with starter cultures which you can buy at www.butcher-packer.com
. I have not yet used the culture myself and have great results with Fermento.
Semi-dry sausages like summer sausages do have low pH to get the tanginess. Many people do use the starters but as I just mentioned, it can be cheated with the addition of the above.
My first summer sausage was made with the pioneer method of "mix it with not-so-clean-hands and hope the right kind of bacteria take over". We ate it but it was a real bomb
. I always use the right stuff now.