I like the fact that we can have this reparte about yeasts. Its important because it helps clarify some points and dispell the myths.
Varasano. Actually you CAN coax a San Francisco sour dough taste out of a common starter. i did it for 4 years at a very prominent artisan bakery in Phila. The key is the relationship between the candida species of yeast and the lactobacillus bacteria. Candida does not consume maltose like other yeasts do and this is what the bacteria need so it works out real well. We were forced to retard the SF dough overnight to slow down the yeast in our starter and give the bacteria a chance to get established. I would put it up against any authentic SF sourdough. I think it would do very well, but it WAS a pain to get right and keep right.
In another post (lehmans, i think) you said "you can age forever with bakers yeast and it won't make a difference. Its a particular breed of plant. it has no flavor" Now i KNOW you don't think bakers yeast is a breed of plant....right?
Cheesy. your right , we do use different yeast to assist us in making different products because of their different sensitivities (time, temp., pH, etc.) However, whether your talking about beer,wine, or champagne, these yeasts all do the same thing: consume a sugar to produce CO2 (respiration) and alcohol (fermentation).
Heres my point. You can start a starter from grapes, rye flour, potatos, $16.00 internet yeast, or a $1.59 pack of redstar. The yeast that will predominate will be the yeast that are able to thrive under the conditions that you provide. This will happen after 3 or 4 refreshments of your starter. Thats just the way yeasts work. If they didn't, there would be no such thing as "San Francisco Sourdough" for example. Alot of times you'll hear people say that their starter was great but NOW its "acting funny" or "not like it was" or "must have gotten contaminated". This is whats happening, and its all very natural. If some schlockmeister is trying to talk you into that "special strain" of yeast....well, he's probably tryin ta sell ya sumthin' ^-^
Pizzanapoletana. I'm glad you said "mix of wild yeast and bacteria" because thats what a natural starter is...a mix. Thats what your starter is, thats what my starter is. It is not only "one strain" of yeast that will be present unless you have laboratory like conditions and a sterile environment in which to reinnoculate on a regular basis...and who does. Every time you add flour, tap water, open the container, touch the starter with hands or utensils, you invite "visitors". One can't prevent this by simply being careful when managing their starter.
Here's a funny thing that happened at a sourdough course offered at the San Francisco Baking Institute which i attended years ago. In discussing the starter or liquid levain we would be using:
class: How old is the starter that we will be using?
teacher: THIS starter came over on the Mayflower.
teacher: Would it make any difference to you if i told you i made it 2 days ago?
class: silence. dumb looks.
teacher: well, it shouldn't. now lets get to work.
The teacher was kind of a ball buster but that still makes me laugh.