To make sourdough you will need a sourdough starter, which is essentially flour and water mixed and left to gather bacteria. Yes, sourdough is sour because of bacteria, which in turn eat away at the starter and produce waste (lactic acid). Yeast itself will produce alcohol when left to its own devices, which is why it is used to ferment things such as...well, alcohol. The bacteria eat that too, leaving behind what essentially amounts to vinegar. Neat.
Note: Thank you for the clarification, atomictesting. Fixed for correctness.
A fair warning before we get started: Completing this instructable can take anywhere from one week to several months, depending on the amount of time you are willing to spend and how many times you accidentally screw up.
I will not be using active-dry or rapid rise yeast at any point during this instructable at all.
Why wild yeast?
Why not? It's neat and, given the right about of time, your sourdough will take on its own distinct flour not quite like any other starter.
Why is it sour?
Bacteria and wild yeast. When you let the starter and the bread sit as long as you will be (days and weeks) it takes on that distinctive sour flavor.
How long does this take?
Forever. It's an ongoing process.
How much experience do you have?
Not a lot. I'm a hobbyist. I'm very open to suggestions or corrections if someone out there knows something that I don't know.
Step 1: Starting the Starter
Other than that, a lot of this is just trial and error. If you don't like your result, scrap it and start over.
For this step you will need the following ingredients:
- A glass or tupperware container that can be sealed.
- White (standard, all purpose or bread) flour. Do not use self-rising flour. Buy the 5lbs all-purpose.
- Whole-grain wheat flour. Same rules apply as with the white flour.
- Warm, clean water (90-115 degrees Fahrenheit)
- A clean measuring cup.
- Something you can stir with. Non-metal spatulas work just dandy, and are preferred.
- Time. You will need to deal with this sucker once every 12 hours or so.
- Heat. Room temperature is great. The starter must be stored at room temperature (or close).
First things first. Pick a time when you will be available every day to start, and be sure that you will be available every day 12 hours later as well. I started mine at 7p.m. because I knew I would be awake at 7a.m. and home by 7p.m. Once you pick your time, gather your supplies.
This first step will be quick and painless.
Put 1/4c (cup) each of the white and wheat flours into your container. That is 1/2c total flour.*
*You do not have to use wheat flour. In fact, you can use only white flour or only wheat flour. It's a matter of taste. I like to add a little wheat flour to all of my bread, but that's just me. Maybe you don't.
Now, add 1/4c clean, warm water.
Stir 'em up. The water and flour should form a thick, sticky ball. Try to get all of the flour in there. Don't worry about it sticking to the walls. It's going to stick to everything.
Once you're happy, close it up and set it somewhere warm.
Walk away. For 12 hours. You can look, but don't touch.
Leave it alone.