Fermentation & leavening
The starter (and your dough) are alive with naturally occurring, or "wild" microbes. These yeasts and lactobacilli exist naturally on the wheat. Depending on geography and other factors, different regions produce slightly different strains of microbes. These 'germs' therefore are in your flour and are the living agents responsible for fermentation and leavening.
In the preparation of the starter, we aim to promote the growth of these organisms, and avoid the growth of unwanted microbes (germs that would be harmful to our starter and dough) hence the emphasis on cleanliness.
A great number of factors influence the leavening, it's vigour, the speed at which it occurs and the taste of the bread produced. These include:-
where the wheat comes from (different parts of the world have different microbes)
the type of wheat from which the flour is made
the protein content of the flour
how it's milled and refined
the ambient temperature at which we prepare our starter or knead our dough
the amount of salt used
The process of leavening of starter or dough is a complex microbiological and biochemical process which involves the microbes feeding on the carbohydrates of the flour, releasing various 'waste products' such as lactic or acetic acid, carbon dioxide gas, and ethanol.
"a little leaven, leavens the lump"
Merely by combining the flour and the water we activate a process which starts a reaction, changing the mixture into a "dough". Autolysis means 'unbinding itself' so we let it rest - around 30mins. Water hydrates the flour particles. Enzymes such as proteases and amylases are activated. The proteases act on the flour's proteins (gluten and gliadin), causing changes to their structure and promoting a re-alignment of these molecules into interconnecting web-like chains. This creates a protein matrix. The amylases break down the complex carbohydrates into simple sugars, more readily fermented by the yeasts.
These processes are happening before any kneading is done. Too much kneading can result in an over-oxidised dough which detracts from the finished prosphoro's shaping, stamping, colour, flavour and the texture of the bread. Allowing an autolysis at the start of the process reduces the kneading time required and this reduces the oxidation of the dough. (Warm temperatures exacerbate dough oxidation)
Theoretically it is best to autolyse without salt and add it later. I have tried both ways and found no difference, other than greater difficulty incorporating the salt evenly into the low hydration dough when added later.
After autolysis, we start the kneading process which develops our dough. You will not fail to notice changes in the appearance and feel of the dough. The techniques for kneading prosphoro strengthen and reinforce the matrix in order to improve the ability of the dough to keep its shape and to better retain the impression of the stamp throughout the period of maturation and rising. As you knead, you will notice the dough changes. After a rest period it feels more most, sticky and very soft. A few minutes into a kneading session and it firms a little and becomes more rubbery. Towards the end of the kneading period, it should be very smooth, with a completely uniform texture.