What is the best way to catch wild yeast for sourdough?

There are two schools of thought as to where wild yeast comes from for a sourdough starter. One is that is in the air, the other that it is present in flour.

Having made a few starters myself and trying different methods, I am of the opinion that the latter is more likely. I have had just as much success with starters I have simply mixed and put in a sealed jar as with the ones I have walked around the kitchen, vigorously stirring with my hands and so on.

You can maximise your chances of having plenty of yeast in your flour by buying organic, as there will have been no chemical treatments which might destroy the yeasts, but any decent flour should have more than enough yeast naturally present to make a starter with.

Yeast, however, is just one aspect of sourdough - you are also looking to cultivate various Lactobacillus species which produce lactic and acetic acid, which is what makes sourdough sour. These are everywhere and so there is no problem with finding them.

However, there are also 'bad' bacteria species that can make your starter go bad. To minimise the chances of this bad bacteria multiplying, it's a good idea to lower the pH of your starter, and for this reason I have had much more success with starters that use pineapple juice. Follow the recipe in this blog, replacing the water on days 1 and 2 with normal, unsweetened pineapple juice, and you'll be on your way.

There are several great articles from catching yeast. Apparently is very possible.The wild yeast you catch in the air does rise considerably slower than it's commercial counterparts.

Nonetheless, if you have time to invest you can catch your own wild yeast to make sourdough bread.

How stuff works has a good simplified write up about how to catch yeast. The article says that you just need the following:

• A pottery crock, plastic container or glass jar, preferably with a loose-fitting lid
• A wooden spoon
• A piece of cloth
• Some flour (preferably without any preservatives in it) and water

With some time, yeast should build because yeast is everywhere and especially in kitchens where baking. Make sure that all the materials are clean and sanitized.

How stuff works provides some instructions on what to do with your sanitized materials:

To start a culture, mix two cups of flour and two cups of water in a glass or pottery bowl (in the old days, a baker probably had a special clay crock for starter). Lay a cloth over the top and let it sit on the kitchen counter. It turns out that there is yeast floating in the air all around us all the time, and some of this yeast will make its way to your flour/water mixture. It will then start growing and dividing.

After 24 hours, you pour off about a cup of the mixture and feed it with another cup of flour and another cup of water. In a few days, the mixture will become frothy as the yeast population grows. The froth is caused by the carbon dioxide that the yeast is generating. The starter will also have a bacteria, lactobacilli, in it. This lends to the slightly acidic flavor of the bread by creating lactic acid! The alcohol that the yeast creates and the lactic acid together are the source of sourdough bread's unique flavor!

There seems plenty of advice about how to grow yeast cultures, but not about how to catch it in the wild. While it is true that yeast is floating about in the air and you can catch it that way, it is far more efficient to collect it from a place that has been catching and growing it for you for some time before you go looking for it. I'm talking about the surface of some leaves and berries, they tend to have a little sap and be slightly acidic so the yeast that lands has good conditions to start growing and outstriping the other organisms that you don't want such as bacteria or mould. You can usually even see the colony because the fruit has a white dusting that is not natural. Sloes, Plums and Damsons are good examples. Autumn is a good time because the air is cool and damp, which helps the yeast grow. But you should be aware, some plants produce a white dusting called farina that is part of the plants growth, this not yeast (primulas and poplars)

I'm trying right now to catch some yeast from some organic blueberries. I mixed equal parts flour and water with a little bit of sugar to help boost it and have left it uncovered over night next to an assortment of fruits and vegetables all well ripened. I heard that in medieval England bread was made to rise by placing flour and water in the middle of a field over night and that by morning yeast would be present. I also have done some research into the discovery of leavened bread, and it came down to bakers reusing left over dough from the day before with the discovery that it would lead to a fluffy loaf. the longer you keep the left over mix the stronger the flavour will become turning a regular loaf into sourdough.