Interesting to hear from one of our shops that they have been approached by another baker who makes sourdough.
Yeast was listed as an ingredient on the label of their sourdough.
When asked by the shop why it contained yeast they claimed "we don't have the conditions for cultivating the sourdough, or a prover so we add yeast instead".
The conditions for cultivating sourdough are patience & a tub with a lid.
The conditions for proving it are patience & a plastic bag to cover the bread.
It's not sourdough if it contains yeast.
You can't rush real sourdough.