This Kitchen Mystery is one of my own, as I wondered "aloud" on twitter about why we salt pasta water instead of, say, salting the pasta dough directly. This sparked a lively discussion and gave rise to some theories, but no conclusive evidence. Yet.
First, let's talk about why we salt pasta water at all. There are people who have been told that adding salt to pasta water will increase the temperature that the pasta cooks, and while this is technically true, there are two major problems with it. The primary issue is that the increase in temperature is negligible for the amount of salt that you should be adding. The secondary issue is that there's no advantage that I can think of to having your pasta cook at a higher temperature.
The reason we salt pasta water is because pasta dough doesn't have any salt in it, so the salt transfers from the water to the pasta during cooking, thus allowing you to taste your pasta. This is all well and good, but with nearly all of our other flour-based goods, we add salt to the dough before it's cooked. The exception to that is Tuscan bread, which, frankly tastes weird because of its lack of salt, but I'm sure the Tuscans are cool with it.
There are some theories about why we might not salt the pasta. They fall broadly into these categories:
- Tradition. For whatever reason, when Italians first started making pasta, they didn't season the dough, and that stuck. Maybe people used sea-water to cook pasta in (which would explain the advice to salt the water until it tastes like sea water). Maybe it's because of the Tuscans and their salt-hating ways.
- Protein formation. Pasta has a specific feel to it, and fresh pasta has a different feel from dried pasta. Perhaps the salt causes problems with the protein formation in some way, which affects its texture.
- Consistency. Adding salt to the water makes it easy to send a consistent amount of salt throughout all the pasta. Distributing the salt through all of the dough evenly is trickier. Though not significantly trickier than any other dough.
- Transfer to water. Salt in the water transfers to the pasta. It seems likely that some of the salt would transfer out of the pasta into the water, and maybe too much would, thus making the pasta relatively flavorless.
For restaurants, I am reasonably convinced that #4 is the most important reason, because they will cook pasta in the same water throughout the night. This is handy for them, as the water becomes starchy, which gives them something they can splash into their sauces for extra flavor and texture. If there were salt in the pasta, and it leeched out into the water, then as the night went on, the pasta water might become over-saturated with salt, and the flavor would drastically change as the night went on. Maybe it would reach an equilibrium, but more likely the later pasta would be drastically over-seasoned.
For home cooks, this is not a problem, but you don't want to make different pasta for restaurants as you would for home cooking, so it could be as simple as that. But, just in case, I'm lining up a blind tasting with one of the local chefs so we can see if there are any texture or flavor differences that we can detect from salting the dough directly vs. unsalted dough in salty water. I'll let you know if we discover anything.
Update: When the conversation was passed along to Mario Batali, he suggested that the "tradition" route was the correct answer.
Though there was controversy even from his followers.
grandma put no salt in doughRT.- Mario Batali (@Mariobatali) August 22, 2012
@eastbco: False - salt strengthens gluten structure in dough - there is more than tradition.its science."