Connie,
Bill and Mitch are correct about there needing to be yeast to make
sourdough, but maybe what the salesperson was alluding to was that the
sourdough taste was not the product of fermentation.
It's possible to make really great sourdough-tasting bread (NOTE: not
the same as great-tasting sourdough bread) using a regular white-bread
recipe (which necessitates yeast, just like the supermarket stuff), with
the addition of a small quantity of fumaric and/or lactic and/or
tartaric acid. Those are all natural organic acids produced by
microbial fermentation and smell sort of "cheezy" or like sweaty gym
socks, depending on the acid and the quantity used. They are among
several organic acids yeast and bacteria produce as a normal byproduct
of their growth. In a fermenting sourdough sponge the acids accumulate
until they produce what we perceive as the characteristic taste and
aroma of sourdough bread. I suspect that much of what passes for
sourdough bread in the grocery stores is made that way.
(Ummm . . . I digressed, didn't I?) Still, if your husband cannot
tolerate yeast at all, you need to get clarification on precisely what
was meant. The salesperson's comment that when you make the bread with
sour dough there is no yeast left is correct insofar as there are no
living yeast present, but that's true for all bread. No yeast should
mean no yeast, past or present, living or dead.
Quinn
Irvine, CA