Salt: The Osmotic Brake
Role: The Solvent
Function: Enzyme Activation & Gluten Mobility
Spec: H₂O (Ideally Mineralised)In the culinary world, salt is a seasoning. It makes food taste "more like itself." In the biological world of sourdough, salt is a weapon. It is the primary control mechanism you have to regulate the speed, strength, and safety of your fermentation.
Without salt, your dough is not just bland; it is biologically out of control.
The Chemistry: Understanding Osmotic Pressure
Salt (NaCl) works through a process called osmotic stress.
When salt dissolves in your dough, it creates a hypertonic environment. Water molecules are drawn towards the salt ions. This effectively "steals" water from the yeast and bacteria cells, dehydrating them slightly.
This does not kill them, but it slows them down. It acts as a biological brake.
Without Salt: Fermentation is rapid and chaotic. The yeast consumes sugar too fast, leading to over-proofing and a breakdown of the gluten network.
With Salt (1.8%–2.2%): Fermentation is measured. The microbial activity is throttled to a pace that allows for flavour development and gluten organisation.
The Interaction: How Salt Tightens Gluten
Beyond the microbes, salt has a profound electrochemical effect on the gluten network itself.
Gluten proteins (gliadin and glutenin) are charged molecules. Salt ions neutralize these charges, allowing the proteins to pack closer together. This "tightens" the gluten structure.
Visual Cue: If you mix a dough without salt, it will feel sticky and slack. Add the salt, and you will feel the dough immediately tighten and become more elastic. It transforms from a paste into a muscle.
The Protocol: Best Ratio, Timing & Type
The Golden Ratio: 2% of the total flour weight. (e.g., 1000g Flour = 20g Salt).
The Timing: Add salt after the Autolyse. Adding it too early tightens the gluten before it has fully hydrated, making mixing more difficult.
The Type: Use non-iodized sea salt. Iodine is an antimicrobial agent that can inhibit your starter's activity. Fine grain dissolves best; coarse grain can leave "hot spots" of salinity.
