Can you elaborate? In Norma's aromatic yeast thread, you made the statement that it was likely not a real sourdough due to the ph being too high.
I don't remember the specific comment. I will be happy to address it further if you point it out. In the beginning, my opinion was that it was not a sourdough because the aromatic yeast as delivered from Lallemand was effectively devoid of LAB per the included spec sheets. In a typical SD, we would expect LAB to outnumber yeast by 10X to 100X. In the aromatic yeast, it was several orders of magnitude in the opposite direction. A relatively high pH (compared to a typical Type I SD) would be an expected observation. I later speculated based on the dropping pH that perhaps a LAB strain had established itself in the culture. If that was the case, it might be a sourdough culture. I don't know if we could say that it was stable however given the limited data.
As far as I know, Type I sourdough encompasses all symbiotic yeast-LAB cultures suitable for baking. Depending on the specific species and strains, the sourness can vary greatly.
Sourdough doesn't have to have yeast or leavening ability. Type II and III sourdoughs add flavor and acidity only and require the addition of baker's yeast for leavening.