Making a sourdough starter might be frustrating but it’s pretty simple. I’ll give you some easy steps to follow and then the rest is really up to the yeast!
First sterilize the jar you’ll be using for your starter. You don’t want any bad bacteria to get in there and kill your yeast. I have beer brewing equipment so I used the sanitizer for beer bottles, but you can use a little bleach in a sink full of water. Let it sit for 5ish minutes, rinse and let dry.
Then there’s different kinds of starters, soupy or more like dough. I usually do soupy, so I use 50/50 flour and warm water (usually 1/2 cup). You can use any flour: white, whole wheat or rye (whole wheat and rye are pretty good for the growth of yeast because it contains more minerals). It’s recommended to use an acidic liquid like pineapple juice (most recommended), lemon juice or even ascorbic acid (vitamin C) instead of water. There’s some bacteria called Leuconostoc that can interfere with your yeast but the acid takes care of them. After a day or two, you can switch over to warm water (un-chlorinated preferably!)
If you don’t have anything acidic, don’t worry! Usually the environment of the starter gets to the point where it becomes to acidic for this bacteria to live anyways (however it’s a risk!)
In your sterile jar, pour in your flour and water. In this instance I’ve use my fresh ground whole wheat and warm water with some lemon juice. Stir the mix together in the jar until the flour is hydrated and let it sit in room or warm temperature for 48 hours, cover on (not sealed) or some plastic over top. I usually forget, but you can stir it a couple of times a day to give the yeast more oxygen which helps in its growth.
There’s a couple of myths about sourdough like needing to use grapes or getting wild yeast from the air to get the sourdough flavour.
Really you’re just getting the yeast off of the wheat. Fruit can be used for food for the yeast and bacteria, but you really don’t need it and who knows if it’s pesticide free. And there isn’t enough wild yeast in the air to do anything to your sourdough starter.
Basically the wild yeast from the wheat start to grow with a bacteria called lactobacillus. This bacteria is the reason for the sourdough flavour. It comes from everywhere, yourself and whatever your touching. It raises the acidity level to make it perfect for this wild yeast to survive and not have to fight against other bacteria. Supposedly commercial yeast can’t survive the acidity level to make sourdough. (Remember there’s nothing wrong with commercial yeast – it’s yeast! But commercial yeast is produced with molasses and in a non-bacteria environment).
This picture is commercial yeast mixed with flour and water about 2 hours later. Eventually your sourdough starter should look like this!
This is 10 hours later for my sourdough starter. Just a little liquid in there.
So after 48 hours you should have some bubbles. Now add another 1/2 cup flour and warm water (with a little lemon juice), stir it up and let it ferment. This is about 72 hours for my starter. I refreshed it every day and now it has a good about of alcohol.
It might take a day or up to 4 days to bubble. Once it bubbles, add another 1/2 cup flour and warm water. Stir and let it sit until it bubbles and increases in size. Could be 2 days to 4 days.
Throw out all but 1/2 cup of the starter and add as much starter as you want, let’s say 1 to 2 cups flour and warm water. Stir it up and this should bubble faster, just wait until it bubbles a lot. This is about 4 1/2 days later. Got really bubbly.
It will smell vinegar-y or alcohol-y and might have some liquid on the top (alcohol waste from the yeast). Now you can put it in the fridge.
I’d refresh it every 5 days (I’ve left it up to a week). To refresh: Let it come to room temperature. Discard about two-thirds of it, and feed it 1 to 2 cups flour and warm water. Let it bubble again and put it back in the fridge. If you need to leave it for a couple of weeks, make a stiffer starter by adding more flour than water and don’t let it bubble.
If using for bread, take whatever you want from it and then refresh the rest of the starter.
When using for bread, take the starter you’ll be putting in the dough and put it in a separate bowl. Feed it some flour and water and let it bubble. If you don’t know if it’s ready, try the float test. If a little dough floats in water, it’s ready to be used! Then add the rest of the ingredients for your bread.
Some good references are Peter Reinhart’s books and very technical info from The Bread Builders.
I went away for 2 weeks to Canada, and when I came back I found my starter jar moldy on the sides. Got to start over again. Sometimes it happens.. ah well.