Boiling vegetables: salt the water? water temperature?

[AlainV]

I have a simple question.

Many recipes state : cook vegetables (carrots, green beans, cauliflower, broccoli ...) in salted boiling water. But how much salt ?

I have read concentration as little as 5 per thousand (1 teaspoon salt per liter water). However Harold Mc Gee recommends "salt in the cooking water at about the concentration of seawater, 3 %". This is a big difference.

What is the correct concentration ?

Edited August 29, 2024 by Smithy
Adjusted title (log)

[rooftop1000]

I have always been told seawater concentration ...or so can actually tast salt in the water.

tracey

[Mallet]

Add as much as you think is necessary, then add a bit more

[LD-NL]

Someone said to never EVER place vegetables, and potatoes, in cold water to boil them, because if you do they oxidise.

❓

 

I wonder how this happens. And of course: if this is true.

If the vegetables are under water they can't really react to oxygen, unless they somehow* bond with the O atoms in the H2O molecule. But that would be weird.

Can someone explain how this would work, and how cold water would allow them to oxidise much more than in boiling water?

 

* I edited due to a typo; someone instead of somehow.

Edited September 4, 2024 by LD-NL
* I edited due to a typo; someone instead of somehow. (log)

[gfweb]

Theres enough O2 in water to oxidize, but thats not what id see as the issue. The color change in fruit and veg is usually enzymatic. Heat inactivates the enzymes which is one of the reasons to blanch veg. 

 

To me the bigger reason to start with hot water is determining cooking time. Water volume determines time to boiling. If you start with boiling, the cooking time will be the same, big pot or small. 

[pastrygirl]

They were incorrect.

[LD-NL]

Thank you both.

If I understand correctly (from what I learned), changing colour is not the same as oxidising, and I understand there are different types of colouring molecules that can be affected in different ways such as heat, simply cutting, and the acidity of their environment.

So all in all it should not matter if veggies are placed in cold or hot water, right?

 

 

[pastrygirl]

13 minutes ago, LD-NL said:

So all in all it should not matter if veggies are placed in cold or hot water, right?

 

Honestly not sure about color, but your texture results will be different.  I cook potatoes starting with cold water because I want them cooked all the way through and it's ok if they heat up as the water heats.  For broccoli, green beans, or anything I want a little crunchy, I drop them in boiling water so they only cook briefly on the outside.

[weinoo]

Generally, start root vegetables in cold water. 

[Alex]

1 hour ago, pastrygirl said:

 

Honestly not sure about color, but your texture results will be different.  I cook potatoes starting with cold water because I want them cooked all the way through and it's ok if they heat up as the water heats.  For broccoli, green beans, or anything I want a little crunchy, I drop them in boiling water so they only cook briefly on the outside.

 

Yes, this

[haresfur]

Hmm, I always thought you were supposed to start potatoes in cold water, particularly prior to making chips because they pass more slowly through the lower temperature where enzymes make them fluffier. That's what I do and they don't seem to suffer.

[LD-NL]

Thanks all.

I found more information and it seems oxidisation doesn't happen such a lot; it's more the damaging that changes the colour molecules. It seems root vegetables that contain anthocyans for instance, and carotenoids, are very stable, and that green is quite fragile because the chlorophyl damages so easily; even in the fridge. And that even acidity affects the colour more than oxidising does.

Next step will tell them they were wrong. This requires some serious bracing 😬 I might actually simply create a new entry explaining what I found and make it unrelated because I don't want them to feel bad.

[gfweb]

3 hours ago, LD-NL said:

Thanks all.

I found more information and it seems oxidisation doesn't happen such a lot; it's more the damaging that changes the colour molecules. It seems root vegetables that contain anthocyans for instance, and carotenoids, are very stable, and that green is quite fragile because the chlorophyl damages so easily; even in the fridge. And that even acidity affects the colour more than oxidising does.

Next step will tell them they were wrong. This requires some serious bracing 😬 I might actually simply create a new entry explaining what I found and make it unrelated because I don't want them to feel bad.

 

I don't think there were wrong comments, just ones that address different aspects of the question.

[Alex]

By a pleasant coincidence, Ottolenghi chimes in: 

 

Quote

What salt does do, however, is raise the boiling temperature of the water, which is especially helpful if you’re cooking green beans, say, because if the temperature comes down too far, this activates an enzyme that destroys chlorophyll and, hence, the colour. Salting also helps enhance the vegetable’s flavour.

 

The most practical way to ensure that the water temperature doesn’t fall too much when the vegetables are added is not to overcrowd the pan, so, whenever possible, cook your vegetables in batches (or in a very large pot), which will mean the water comes back to a boil as quickly as possible. Another common theory to maintain a vegetable’s green vibrancy is not to cover the pot, but in fact the lid helps the water return to a boil more quickly, which helps retain that “green-ness”.

 

[gfweb]

3 hours ago, Alex said:

By a pleasant coincidence, Ottolenghi chimes in: 

 

 

 

The addition of salt doesn't change the boiling point much. Sea water, about 3%, boils around 102C. And I doubt blanching water is often as much as 3% salt

[Alex]

Just now, gfweb said:

 

The addition of salt doesn't change the boiling point much. Sea water, about 3%, boils around 102C. And I doubt blanching water is often as much as 3% salt

 

Right. The implication, though, was to start green vegetables (except green potatoes, which you should toss ^_^) in boiling water.

[AAQuesada]

18 hours ago, gfweb said:

And I doubt blanching water is often as much as 3% salt

Thomas Keller's latest recommendation for hard green vegetables is blanching in 6% salt! Ice water now gets salted at 3% and stay in the ice bath for the same time they were cooked for 

[weinoo]

52 minutes ago, AAQuesada said:

Thomas Keller's latest recommendation for hard green vegetables is blanching in 6% salt! Ice water now gets salted at 3% and stay in the ice bath for the same time they were cooked for 

Keller’s a pain in the ass.

[Dave the Cook]

On 8/24/2024 at 1:49 PM, Alex said:

. . . cook your vegetables in batches (or in a very large pot), which will mean the water comes back to a boil as quickly as possible . . . 

 

(To be clear, Alex is quoting Yotam Ottolenghi here.)

 

In any case, it's not true, generally speaking, that a large pot of water will return to the boil more quickly than a small pot. See the proof here (go to 5:23).