A long time ago, I read somewhere, that there is a very specific reason, why we put salt in the water for cooking pasta: The point is to hinder the water from absorbing flavor and nutrients from the pasta. With soup its the other way around: We want to absorb the flavors into the water, which is why we salt it only at the end.

The explanation was, that salt "ionizes" water, which somehow makes it less likely to absorb things.

Is there any truth to this theory?




Because pure water draws salts and other soluble nutrients from the interior of vegetables, salting vegetable cooking water also minimizes nutrient loss.

  • LOL - So if salt draws out all the flavor why do you salt a country ham? You're just mixing up multiple ways of using salt trying to find one answer.
    – MaxW
    Feb 4 '19 at 22:39

As a chemist, I'd say that you have it all wrong.

You add salt to pasta water to have the salt infuse into the pasta. So as the dry pasta absorbs water, salt comes into the pasta too. Salted pasta tastes better than unsalted pasta.

Salted soup tastes better than unsalted soup. Salt enhances our perception of the flavors in the soup, but it does not extract the flavors.

  • But wouldn't salt in theory saturize the water and prevent it from taking in more stuff? Feb 4 '19 at 21:57
  • hmmm, thought that's what I wrote....
    – moscafj
    Feb 4 '19 at 22:59
  • 4
    Water can dissolve a lot of salt before it becomes saturated. A boiling, saturated saltwater solution is 28% salt by weight. A gallon of water weighs about 8.3 pounds, so you would need to dissolve about 2.3 pounds of salt to saturate it. Basically, pasta water is never saturated with salt. Feb 5 '19 at 6:42
  • 1
    Osmosis has space in this discussion , though it just influences water and sodium in/out movement. Boiling in very salty water could prevent zucchini to absorb even more water than what they have (I am inventing here :) . Still interstitial water might be then to salty. I am just pointing to a phenomenon at work, I.e. osmosis.
    – Alchimista
    Feb 5 '19 at 10:09
  • I think I did my math wrong. The weight of the salt is 28% of the total, not 28% of the water's weight - so if the weight of the water is 72% of the total, then it's about 3.2 pounds of salt in a gallon of water. Feb 5 '19 at 20:03

This theory is news to me. I would be curious of its origins. From what I know, salt is added to pasta water to make pasta taste good... works for soup too! The reason to add salt at the end when making soups and sauces, is that evaporation occurs when using longer cooking times. If you add salt at the beginning, the end product could end up being over-salted due to evaporation and concentration of flavors.

By the way, dissolving salt in water does not make its atoms ionize (your salt is probably already ionized), and tap water also likely already contains ionized atoms from naturally occurring mineral salts.

While I linked the explanation for "ionized water" above, I will point out that there is some controversy, and not much science, supporting the health benefits of ionized alkaline water...or whether "ionized water" really has any meaning at all. Perhaps this is related to the origin of your theory.

  • Your concepts of ionization are just wrong. // Water that contains ions, eg sodium cations and chloride anions, isn't ionized. The ions are what is ionized, not the water. // water does ionize into H+ and OH- ions, but that is an entirely different matter.
    – MaxW
    Feb 4 '19 at 21:50
  • I think I found the link: finecooking.com/article/the-science-of-salt Quote: "Because pure water draws salts and other soluble nutrients from the interior of vegetables, salting vegetable cooking water also minimizes nutrient loss." Feb 4 '19 at 21:58
  • @MaxW edited to reflect your clarification.
    – moscafj
    Feb 4 '19 at 22:54
  • @user1721135 thanks...would sure like to see the science. Which nutrients? How much minimization? Is it meaningful?
    – moscafj
    Feb 4 '19 at 22:56

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