Salt isn’t just added to bread to improve its flavour, although that is really important. It has a few important roles in the development of the dough and the quality of the final loaf.
Salt is added to bread at a rate of between 1-2% of the flour weight. For a dough that is made with 500g flour that means between 5-10g. I normally aim for about 7g as that suits my personal taste.
Very few breads are made without salt, the exception being Tuscan bread, which they serve with salty topping or use as an ingredient in their salads. When you do make a bread without salt you know about it from the pale crust, the stickier than usual dough and the profound lack of taste.
The role that is most noticed by us when we eat our bread is salt’s ability to improve the flavour of the bread. It doesn’t just provide a salty taste. In fact it shouldn’t taste salty at all and if it does try reducing the amount you use next time. Instead salt brings out the aromas and flavours that are in the dough. Without the addition of salt, the final loaf tastes of very little; it is bland and nondescript. By adding a small amount of salt you bring out the flavours of the wheat and the sour, sweet and tangy aromas that have developed during fermentation.
As Harold McGee writes in McGee on Food & Cooking:
“It’s the only natural source of one of our handful of basic tastes, and we therefore add it to most of our foods to fill our their flavour. Salt is also a taste enhancer and taste modifier: it strengthens the impression of aromas that accompany it, and it suppresses the sensation of bitterness.” p. 640
And Samin Nosrat notes in Salt, Fat, Acid, Heat:
“The primary role that salt plays in cooking is to amplify flavour. Though salt also affects texture and helps modify other flavours, nearly every decision you’ll make about salt will involve enhancing and deepening flavour”
Tightening effect on gluten
Salt tightens the gluten in the dough, improving the volume of the finished loaf.
If you are making a sourdough (where salt is usually added after the dough has had an initial rest) or using a preferment you will notice how slack and sticky the dough is before you add salt and how quickly it tightens after the salt is added. It is almost like you have performed a magic trick.
This is because salt is made up of positive and negative ions, which when the salt is in crystal form are tightly bound together with the opposite ions attracting strongly. Once you dissolve salt in water the ions are released from their opposite attraction and start to react with other molecules in the dough including the proteins. The salt ions furl and unfurl the protein chains and tighten them, strengthening the gluten network
Salt slows fermentation
Salt draws water out of the yeast and bacteria cells within the dough dehydrating them. The dehydration causes the cells to slow down their consumption. In the case of the yeast, it slows its rate of sugar consumption. In the case of bacteria (particularly in sourdough) it slows the rate at which they digest the proteins.
This slowing down has a beneficial effect on the dough.
Too much yeast activity can mean that the natural sugars in the flour are exhausted too quickly and the dough can over prove. Oven spring might not occur and the dough will flatten out in the oven. The finished loaf will also be pale as there will be few remaining sugars to caramelise on the crust during baking.
If the bacteria had free reign to digest the proteins the gluten network would be damaged, the dough would become sticky and slack and the dough would be difficult to shape and would flatten out in the oven.
More information about the science of fermentation can be found here.
Emily Buehler, Bread Science: The Chemistry and Craft of Making Bread, (available as a Kindle book in the UK)
Harold McGee, 2004, On Food and Cooking, An Encyclopaedia of Kitchen Science, History and Culture, Hodder & Stoughton
Samin Nosrat, 2017, Salt, Fat, Acid, Heat: Mastering the Elements of Good Cooking, Canongate Books
NB: The links to the books listed above will take you to Amazon. If you buy the book using this link I will earn a small commission at no extra cost to you.