If you’re wondering what I meant when I said that I generally let my starter ferment for five days to make sure I “clear all the suckers out” it’s because starter bowls can occasionally grow some funky stuff. Actually, maybe I should take part of that back. They always grow some funky stuff, but occasionally some funky something-or-other comes to dominate the microbial culture. Here in the Ohio Valley, that something-or-other is frequently a bug by the name of clostridium perfringens.
This bacterium is a food pathogen, one that can, has, and does make people sick, sometimes seriously so. This however doesn’t stop some people (mostly hill folk) from raising their bread with it. Why? Because unlike just about every other microbe that can grow in a starter bowl other than yeast, C. perfringens creates quite a lot of CO2 as a by-product of its metabolism. In fact the rise you get from it is every bit as good, maybe even better, than actual yeast. People have thus made bread with it for hundreds of years, relying on the heat of the oven to kill the bacteria, making the bread safe to eat. This type of bread is called salt rising bread, and it still has its fair share of adherents, even here in Louisville.
It don’t care for the cheesy flavor of salt rising bread, but I’m even less enthused about having a culture of a microbe like that in my kitchen. Therefore, when it happens, I simply wait it out. The telltale sign of C. perfringens contamination is the smell. The critter produces an awful lot of butyric acid as it feeds, and that particular compound, as longtime readers of joepastry.com know, smells like vomit. Yet the thing about C. perfringens is that it can’t survive for very long in a high-acid environment. After 36 hours or so it peters out, paving the way for other bugs that can survive in a high acid environment, to take over.
Yeasts are among these, not surprisingly. And in fact a tolerance for both acid and alcohol (which they themselves create) is very likely a competitive adaptation. Both are poisons to microbes that would compete with them for food in a wet, sugar-rich environment. Knocking them out of the picture means more food for them and their progeny. The King Kong of these is a type of yeast called Saccharomyces cerevisiae, which, again unsurprisingly, is the yeast most bread and beer is made from. It will ultimately dominate a well-maintained in a starter. Sure there are a few types of lactic acid bacteria that can stand the environment Saccharomyces cerevisiae helps to create, but those aren’t harmful to humans and in fact help flavor the bread. Very cool.
That said, it always pays to be careful. If you have a starter that smells rank, even after a week of fermentation, throw it out and start over, this time using bottled water. No sense taking a chance on a several day vacation to your own bathroom if you can help it. A good starter should be pale and uniform in color (not blotchy or dark), responsive to feedings and smell tangy/sour, not horrible. Anything that deviates from these general criteria isn’t a starter, just a culture, and should be pitched.
That goes for starters that might be well established, but have for some reason fallen off their game. Though Saccharomyces cerevisiae is one bad M.F. microbe, it does happen on occasion that another bug stages a coup. Sometimes when that happens no amount of feedings can tip the balance of the starter back in your favor. Again, throw it out and start over.