In all kinds of breads and pastries, from chewy focaccia to melt-in-your-mouth shortbread, salt is a key flavor component. But salt does more than enhance flavor: it interacts with other ingredients, sometimes creating beneficial effects, sometimes being a downright nuisance. Knowing what salt does can help you decide when to add it to your recipe (and sometimes how much to add). You can then take advantage of salt’s good effects, like making bread dough nice and elastic, and avoid potential problems, like making pastry doughs tough.
The most significant thing to know is that salt strengthens gluten. Gluten is made of water and two proteins. Salt tightens the molecular bonds between these components, possibly by removing some of the water. This tightening is a mixed blessing: adding salt to a yeast dough increases dough strength and prevents weakness and stickiness, but it also increases the mixing time needed to reach maximum dough development. If you start kneading a dough without salt, when you do add the salt you can literally see the dough tighten. If you stretch the dough before and after the addition of salt, you will feel an amazing difference in the strength of the gluten. You can see this in photos on the opposite page.
Some bakers like to knead the dough first and then work in the salt because dough is easier to knead and requires a shorter kneading time without the salt. Then the salt can be mixed in to strengthen the dough just before the rising and shaping. Other bakers worry that the salt may not be evenly distributed throughout the dough when added at the end. You may want to try both methods to see which you prefer. The type of salt can make a major difference in how well it blends. Flaky sea salt and Diamond Crystal kosher salt dissolve and blend faster and better than granular table salt because they are fragile flakes that have much greater surface than granule.
Salt’s effect on gluten is also an issue in pastry-making, where tight, strong dough is not desirable. The stage at which you add the salt can determine whether you develop too much gluten, but as with bread dough, you need to balance the desire to control gluten with the need for the salt to be well distributed. Some cooks like the ease of adding it to the flour at the start; they feel that the salt gets distributed well enough. Others like to add it to the liquid for more even distribution.
If you mix the salt with the flour, some of the salt will be greased by the fat and therefore it probably won’t affect gluten formation, yet it will still be there for taste. Adding the salt to the liquid risks greater gluten formation and toughness, since gluten can only form in flour when it comes in contact with water. Also, in many pastry recipes, the water is added little by little until you have the right consistency—you may not add all of it and therefore not all the salt. To be sure that you get all the salt in, put all the salt in part of the liquid, add that, and then add as much of the remaining liquid as you need.
Salt and yeast is another tricky combination, as salt can be harmful to yeast activity. Even a small amount, such as 1/3 teaspoon of salt per cup of flour, slows yeast growth noticeably by killing some of the yeast cells and so reducing the number of cells that are reproducing. In fact, some bakers will deliberately slow the rise of a batch of dough (for example, until the next shift at the bakery arrives) by adding a little more salt to the dough.
Salt’s capacity to slow yeast activity poses a real dilemma for the baker since salt is such an important flavor component of bread. If you’ve ever tasted bread without salt, you know how strange it tastes. The very small amount of salt in bread does not provide a strong saltiness but does bring out the delicious flavor components of freshly baked bread. So what can you do? If more than 1/3 teaspoon per cup of flour risks interfering with yeast, then one solution is to glaze the bread with a fairly salty glaze.