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I have consistently observed that a given vegetable simmering in a soup (that is, with multiple other vegetables and herbs, and usually salted) takes five to ten times longer to get soft than when the same vegetable is simmered alone in plain water. This especially pertains to root vegetables. Why is this?

John H
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  • I never simmer vegetable in plain (salted) water; I'm curious why I would do it – Max Sep 15 '19 at 12:22
  • By "plain water" do you mean salted, or unsalted? Also, are the vegetables cut exactly the same in both situations? – moscafj Sep 16 '19 at 11:04
  • @Max To avoid the agitation of a full boil and/or to allow denser vegetables like potatoes or dried and soaked beans to cook without their outer parts dissolving to a mush before the centre is done. – Spagirl Sep 16 '19 at 11:05
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    I haven't observed this to be true, and suspect that you may be reporting perceptual time rather than clock time. Have you done an actual test, with times etc.? – FuzzyChef Sep 16 '19 at 22:08
  • @moscafj Unsalted plain water. Yes the vegetables are cut the same in both. – John H Sep 17 '19 at 17:30
  • @FuzzyChef I have not done any side by side comparisons, but have observed the actual clock time difference over many years. This has proven a significant factor in my meal preparation when time is a concern. – John H Sep 17 '19 at 17:39
  • So, in simmering salt water it takes small potatoes (or 3-5cm potato chunks) approximately 20 to 25 minutes to get soft. Are you saying that when you cook a stew it takes 1.75 to 3 hours? – FuzzyChef Sep 17 '19 at 18:20
  • I think that 5-10 times is based on perception, it is too big of a difference, even considering a crowded pan x almost empty pan. Ebullioscopic effect has been long debunked as being relevant for cooking times. – Juliana Karasawa Souza Sep 18 '19 at 08:04
  • @FuzzyChef I can cook 1/2 inch carrot pieces, for example, in unsalted water in about 5 minutes or less (after water starts boiling). In a soup, they can easily take 45 minutes or more. With potato chunks, the effect may not be quite as dramatic. The effect is seen with sweet potatoes as well. – John H Sep 26 '19 at 22:57
  • @JulianaKarasawaSouza The Ebullioscopic effect has to do with boiling point elevation (yes?) and if anything would speed cooking in a salted soup if temperature is the primary cooking time consideration. I suspect this effect has more to do with osmosis of unsalted water into plant cells being greater than water with solutes in, such as salt. Maybe cell rupture is what constitutes the softness of cooked vegetables? – John H Sep 26 '19 at 23:06
  • @JohnH the softness of cooked vegetables is brought in a large part by changes in the structure of the cellulose matrix of the vegetables. If anything, osmotic effect of the vegetables getting water from the environment makes them "harder" as you can observe when you put sliced potatoes in unsalted water before frying to make them crisper. I still think that you're not comparing apples to apples - cooking has to do with energy distribution, so unless you're not noting a large difference in pan size and crowding, 5-10 times is exaggeration. – Juliana Karasawa Souza Sep 27 '19 at 07:53
  • @JulianaKarasawaSouza Yes, I now remember water crisps up veggies, such as wilted carrots or celery, or is why markets mist the produce. Crowding here is not an issue in my case; the veggies are fully surrounded in boiling water. Have you experienced this effect to any degree? Even if only a 50% increase in cook time, might you hypothesize why? I submit that small veggie chunks heat up to 212 inside in only a matter of a couple of minutes. It seems plausible that at elevated temperatures, infused water would accelerate matrix denaturing, yes? – John H Sep 28 '19 at 19:03
  • @JohnH Not really. What I'm thinking is that you have more water competing for the energy of the denaturation and the quantities involved are not really relevant to make this big of a difference (x5 / x10 is too much, I tested it when I was using up my stock of old potatoes. Part of them I simmered in water for puree and part of them I simmered in stock for soup, there was a 2 minutes difference - with the water cooking faster because the soup pan was far crowdier) – Juliana Karasawa Souza Oct 01 '19 at 09:01
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    @JulianaKarasawaSouza I love that word; crowdier. Thank you for testing this! – John H Oct 07 '19 at 22:04

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