We love sourdough.
Bread has been made for thousands of years! From roughly 10,000 year ago, people were storing grains and involved in large scale wheat and barley agriculture.
The kind of bread that we make at Wild Life, with a lot of water and a soft texture with lots of large-ish bubbles, is a much more recent style, with roots in American and French baking. A lot of bread we think of as being "rustic" are actually very modern. For example, ciabatta is from the 1980s.
Bread is very simple, just flour milled from a grain and mixed with water, then baked. Most bread over the world is also fermented, but some styles aren't, such as matzo, tortillas, damper, or soda bread.
Fermentation is very complex, but at its core is very simple, in that it really just means that a process that allows micro-organisms to change the ingredients/food in a way that we like!
In baking, fermentation occurs due to yeast and a collection of various bacterias that we will simplify and just call "bacteria". Yeast lives on everything, so if you mix flour and water together, there will be some yeasts and bacteria present without adding anything. If you let this ferment for a while and then bake it, you have "sourdough" or naturally fermented bread.
Most bread in the past 150 years or so has utilized commercial yeast, which was developed in the 19th century. Commercial yeast is great, because it means you don't have to maintain a starter, and it's a lot more powerful, so it's possible to ferment loaves a lot faster. Unfortunately, a lot of the flavour in bread comes from the other bacteria in a starter, not just the yeast.
Naturally fermented bread has lots of names, but is usually called "sourdough" in Australia, due to the tendency for there to be a bit of a tang to it. It's typically called "pain au levain" in France. The longer fermentation time of a sourdough loaf does give more time for acids to build up in the dough, but it is possible to make naturally fermented loaves that don't taste sour. Confusingly, sourdough is often used to describe a particular style of loaf, which is typically a large, free-formed white loaf. In reality, all kinds of bread can be fermented naturally, although it can sometimes be more challenging than when using commercial yeast!
The terms "starter" or "sourdough starter" or "levain" or "leaven" are often used interchangeably, which can be confusing. To simplify, we'll always refer to the small amount that you refresh or feed as your sourdough starter. The larger quantity that you make to mix into the bread dough we will call the levain.
In either naturally fermented or yeasted (as in, uses added yeast), yeast feeds on the sugars in the flour and releases gas. That gas is trapped by the dough to create little air pockets throughout it, making it nice and light. Different types of flour and methods give you all sorts of options for how those air pockets are dispersed throughout the dough, whether in lots of super fine bubbles to create an even surface, or in larger, less consistent patterns that create big holes in the finished loaf.
Commercial yeast will cause a dough to ferment a lot faster than a sourdough starter, but the process is essentially the same. The big difference is in the other micro-organisms in sourdough.
A sourdough starter is made by simply mixing flour and water together, and letting the yeast that already exists on the flour to multiply naturally. While the yeast is growing, a bunch of other bacterias are growing in the starter at the same time, and it is these bacteria that cause a sourdough loaf to develop a lot more flavour than a yeasted dough. These bacteria not only create acids, they also help break down the flour to make it more digestible.
Dough needs to be able to trap all this gas to make the dough nice and light. There are a few things that will manage this, but the most common way that you'll have heard about is gluten. Gluten is a protein that is formed when wheat flours combine with water. Gluten will develop in long strands in the dough, and our goal is to get them arranged like a big web throughout the dough, so that it can trap all the gas given off by the yeast.
It is possible to make gluten free bread that traps some gas, but it's a lot harder. A common additive is xantham gum, which occurs in rye flour.
The mixing process is mainly about hydrating all the flour as much as possible, allowing it to form lots of gluten, and then starting the process of aligning it all into a web. Mixing is often described as helping to build "strength" in a dough. This is due to gluten formation.