To make "sourdough" bread, you need sourdough starter. It's a mixture of yeast and good bacteria that you add to your dough in order to flavor and leaven the bread. You can buy it, or you can make it. To make it, you need to carefully tend a batch of flour and water in order to cultivate a stable colony of wild yeast and lacto-bacteria. The yeast provide the lift and some flavor, the bacteria provide the sour. The basic process is pretty simple to describe: mix a specific ratio of flour and water, cover and let it sit. There are wild yeast all over flour, especially whole grain flour, so most starter recipes say to start with whole rye or whole wheat flour. And to get your starter started, you just need to encourage this wild yeast to grow. The next day, it will hopefully smell like beer. Then you discard some of the original mixture and feed the remains with generic all-purpose flour and water. Repeat, discarding and feeding for a week or so, until the mixture is just right. And that 'just right' is the trick. Done right, the yeast and the good bacteria will create a mutually beneficial environment: just acidic enough to keep out unwanted critters, but not acidic enough to kill the good critters. Done wrong, the unwanted critters set up shop and out-compete the good ones.
The ratio of water to flour in the feedings is important. The frequency of feedings is important. The temperature of the water is important. The ambient temperature is important. And it all just depends.
A month or so ago I managed to make a viable sourdough starter. I made one decent loaf of bread with it, then my starter got contaminated by something and I had to throw it out. So, I've been trying for weeks now to get another starter up to speed.
They all looked promising on their first and second days. They rose up vigorously and smelled like beer (yeast in action) and pleasantly sour yogurt (bacteria). But by day four or five, the yeast gave up - no more rise, just a few bubbles (bacteria emit CO2 and H2, just not in the quantity that yeast does). And then they all started to smell nasty - not rotting nasty, but chemically nasty - nail polish remover. I think that was due to a bacterium called Clostridium acetobutylicum, which out-competed the other bacteria and was happily turning the sugars and starches in the flour into acetone. And acetone kills yeast. The reason, as best I can tell, is that our kitchen is slightly too warm which that gives the acetone makers a slight edge over the lactic acid makers. And in the 2-cup Pyrex Thunderdome where this is all taking place, every advantage is taken.
So, the AC temp is down to 72 (not 74) today. And try #5 is bubbling away on the counter. It's day three. When I get home today, it should be funky and bubbly. But it better not smell like muthafunkin acetone! If it does, I'm going to give up and stick with insipid commercial yeast.
