Salting Water for Vegetable Cookery

[docsconz]

I am personally excited that you are here for this discussion. I had hoped to read your latest edition prior to this discussion, but alas, I have yet to receive my ordered copy.

An area of controversy here on eGullet in the past is whether the old dictum of cooking green vegetables in salted water to preserve the green color is necessary. What are your latest thoughts on the matter and what is the science behind it?

[Harold McGee]

My first copies just arrived, so I hope yours has too. On salted water: it’s sometimes said that salted water boils at a higher temperature and therefore cooks vegetables faster and preserves color. Not true: it takes way too much salt to make a significant difference in the boiling point. However, try the experiment of cooking two batches of vegetables in two pots side by side, one with salted water, one unsalted. The salted water ends up less discolored. That’s because plain water is an osmotically unbalanced cooking medium. Since there’s nothing dissolved in it, it draws substances dissolved in the plant cell fluids—salts, sugars, amino acids—out of the cells, and the water itself flows into the cells, diluting what’s left. With salt pre-dissolved in the cooking water, the fluids inside and outside are more balanced, and less of the vegetable’s substance is drawn out into the water.

So cooking vegetables in salted water helps retain more of the vegetables’ nutrients and flavor. Are the differences significant or easily noticed? It probably depends on the vegetable and how it’s subsequently prepared. I’m not aware of any careful studies of this question.

[Bux]

It pays to have a close contact at the publisher. I've had my copy for over a week now and it's much handier than the proof that lacked an index. I've always believed salt water boiled at a significantly highter temperature than fresh water and was about to post that opinion here in another thread a few days ago, but I thought I'd check On Food and Cooking to see if I could offer some information on how much hotter the boiling salt water might be. I was surprised to learn how much salt it took to make very little difference.

Is there any reason to add salt to the water in which pasta is cooked, other than to salt the pasta? Do vegetables generally absorb some salt and might there be a better solution (no pun intended) than salt water in which to cook some vegetables?

[docsconz]

My first copies just arrived, so I hope yours has too. On salted water: it’s sometimes said that salted water boils at a higher temperature and therefore cooks vegetables faster and preserves color. Not true: it takes way too much salt to make a significant difference in the boiling point. However, try the experiment of cooking two batches of vegetables in two pots side by side, one with salted water, one unsalted. The salted water ends up less discolored. That’s because plain water is an osmotically unbalanced cooking medium. Since there’s nothing dissolved in it, it draws substances dissolved in the plant cell fluids—salts, sugars, amino acids—out of the cells, and the water itself flows into the cells, diluting what’s left. With salt pre-dissolved in the cooking water, the fluids inside and outside are more balanced, and less of the vegetable’s substance is drawn out into the water.

So cooking vegetables in salted water helps retain more of the vegetables’ nutrients and flavor. Are the differences significant or easily noticed? It probably depends on the vegetable and how it’s subsequently prepared. I’m not aware of any careful studies of this question.

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Thank you for the response. I really can't wait to get my hands and eyes on a copy.

I'm also looking forward to your response to Bux' addendum.

[Guest Mandy Davis]

I had a follow up question about the salted water -- when I was cooking on a yacht this summer we had limited fresh water so I would use sea water when blanching vegetables, cooking potatoes and root vegetables (to mash), or boiling shrimp & crab. It worked great for me & added great flavor to the mashes (I'm sure the bits of seaweed helped too).

I know that sea water has other minerals in it than just NaCl -- is it okay (healthwise) to use sea water in this way?

Thanks for answering all these questions -- I feel 2x as lucky after getting a chance to ask you questions two weeks ago as well -- now I have a chance to ask you some of the ones that didn't quite fit in the interview. Thanks!

[Harold McGee]

Salt absorption came up in the "sodium levels" post--pasta absorbs a fair amount because it almost doubles its weight with absorbed cooking water; potatoes less, and mainly at the surface because it's already wet. The only other common osmotic agents in the kitchen are sugars; and alternative salts (potassium chloride, calcium chloride) tend to be bitter.

Thanks, Mandy! Sea water does contain other trace minerals, as well as bacteria and one-celled algae and all kinds of other microbes. The minerals are fine and mostly good for us; but given the microbes, it's especially important to make sure the water boils. Especially when you're sailing close to civilization.