The Power of Salt
In addition to improving bread flavor, salt is useful in controlling the activity of preferments. When a preferment, such as poolish or sponge, is maturing too quickly due to warmer temperatures, adding .2 to .3% salt is just enough to slow down activity without interfering with aroma. Just remember that when the quantity of salt in the final dough is calculated, the amount of salt used in the preferment must be considered.
When a stiff levain is becoming liquid or mushy in the center, this is a sign of undesirably intense enzyme activity (protease) between feedings. As little as .1% of salt incorporated during the feeding of the culture will be enough to noticeably slow down the protease of the flour and bring your sourdough culture to a normal consistency-without interfering with the microorganism activity of the sourdough.