I made the mistake of taking the rubber seal off my sourdough jar and it changed my culture. I had read on the Breadtopia site that he recommended taking the seal off the jar - I should have stuck with what worked for me for 2 years. Luckily, I had a small amount of my original culture in a small jar and was able to revive it.
My culture is from Mustang Grapes. I've made 1000's of pizzas from it and it has always preformed under all conditions - great oven spring and flavor.
Grimaldi, your post is a bit confusing. Did you mean to say that you had read on breadtopia and the site recommended to NOT take the seal off of the jar? It sounds like you did and your culture changed?
Can you describe in what way? Was it a flavor change, leavening strength, or both? And again, just to be clear, everyone using starters is familiar with the differences in flavor and acidity levels depending on when you use the starter, early versus late, young versus mature. It is still the same startrer but can vary quite a bit in flavor depending on when you use the starter. To get a good idea of where the starter is at, especially if you can not tell by looking at it or smelling it, is to actually taste the raw starter. If you do this often enough, you can actually pinpoint how active your starter is and when you want to use it.
I myself, have never gotten sick from tasting raw starter, but I only taste with the tip of my tongue. I am not actually recommending that anyone eat spoonfuls of the stuff.
I'm just tossing that out there, so folks can understand why their starters may taste different at different times. BTW, none of my 5-6 starters are in jars that seal. I use regular glass jars without sealing lids and have yet to have a contamination or take over problem.
Also I have kept both a cake yeast and IDY starter for the purpose of testing for "take overs" and have not seen it. I create these commercial yeast starters by mixing flour + water + CY or IDY. Let it get active and feed and maintain as any other starter. I used both side by side and maintained them for several months without any contamination issue. That is both stayed true to their lack of sour dough flavors while providing good leavening strength.
If yeast from the flour can "easily" take over starters, then I would have seen some flavor change in these 2 (CY and IDY) starters over the 2 months. Now I will say that if I left either one of these out at room temps long enough without feeding, both will develop acids and taste acidic. BUT if I discard 99% of it, refeed, and allow them to come back, they are as flavorless (CY slightly sweet) as day one at their active state. After several months, I was satisfied with my results and have since gotten rid of these starters to make room for others. I am not discounting other people's experiences, just sharing my own.