[PLB]

My chef is claiming that all blanching should be done in water that was as cold as possible before bringing it up to a boil because it holds more oxygen having not benn held hot, thus protecting color better. My guess is that by the time cold or hot water reach around a simmer they will be exactly equal in oxygen content either way. Can someone inform me of the scientific truth? Some sort of reference article would be wonderful. McGee doesn't seem to cover it. Thanks

[kuan]

He's right, but only if he's blanching in cold water.

Things that make you go hmm...

[Suzanne]

Yeah, he's probably right about the cold water starting out with (ever-so-slightly) more O2. However, you're right too: by the time the water reaches a boil, the amount of O2 is probably not that different, whatever the starting temperature. And for blanching, you need to keep the water at a full boil, which will release even more O2 as you proceed.

AFAIK, the best way to protect color when blanching is to NOT OVERCOOK, and to stop the cooking immediately by chilling the blanched food as fast as possible. That's why we use ice baths. (I'm still not sure about which side of the salt-in-the-blanching-water versus no-salt-in-the-blanching-water debate I'm on.)

[Pete]

I am not sure about the scientific thought behind salting your blanching water, though I have been told it helps set the color, but I do for taste purposes. As for as I am concerned, using unsalted water is like seasoning your meat after grilling it. The flavor just doesn't penetrate as much.

[kuan]

Always salt, since blanching is actually cooking. That's my technique reason.

[MarkV]

Salt, as far as I know does not play a role in the color preservation aspect of blanching. It's the heat and the water medium.

Green vegetables are green because of chlorophyll, their primary pigment. Chlorophyll’s archenemy is heat which causes it to break down and form other compounds that are less green. Despite the heat involved, blanching still preserves the vegetable’s color. Green vegetables are actually greener than they appear. Trapped within their cellular network are gases that partially obscure their hue by refracting light. Sort of like looking at a colored object through a veil of smoke. The first thing the boiling water does is to allow the dissemination of these gases into the air and surrounding water. Thus, the veggies “become” greener. But, as stated, heat can destroy their pigments. This is because the same heat that freed the gases is also releasing acids from the plant’s cells which will reap havoc with the chlorophyll. But, because of the water, these acids become dispersed and diluted in the fluid medium.

Chlorophyll’s salvation however, is short lived. Beyond 6-7 minutes in the boiling water and acids or not, the sustained heat will eventuate in the complete breakdown of the plant’s structures and substances. Fortunately, most vegetables can be blanched in a fraction of that time

[phatch]

Oxygen is, well, an oxidizer. Not too good for keeping things color natural once you start applying heat.

Phil

[Jock]

maybe I'm missing something here but I'm

A water molecule contains 2 hydrogen atoms and one oxygen atom. If that proportion changes at all it is no longer water. Therefore water at any temperature contains the same amount of oxygen otherwise it wouldn't be water, right???

Jock

[KeeperOfTheGood]

Originally Posted by Jock

maybe I'm missing something here but I'm

A water molecule contains 2 hydrogen atoms and one oxygen atom. If that proportion changes at all it is no longer water. Therefore water at any temperature contains the same amount of oxygen otherwise it wouldn't be water, right???

Jock

Only from the point of view of water that has been filtered and then disstilled, and then filtered and disstilled a second time, and sent directly to a vaccume chamber for sealed bottleing. Don't laugh, it is made this way. 99.99999 something really stupid pure. Only in labs do you need water to ever be that vacent of any other product.

Otherwise, water is THE best solvent out there. Into water will dissolve enything. My chem teacher used to get the kids on that one too. Even if measured in the 10^-100, all things dissolve into water. Air will do so readaly, and that includes all the components of air. Different components to different degrees, but all of them. So, a bottle of disstilled water from a pharmacy is water and whatever air it has come into contact with.

All that being said, as to the chemical activity level of those dissolved gasses.... well, its not all that strong. Barely noticable in fact. And in labs, it is usually measured over the course of days, and not in a 5 minute blanch.

[Suzanne]

The short version of KOTG's answer is: all regular water has gasses dissolved in it.

[scott123]

Dissolved gases in water play a role in the brewing of tea, but I've never hear them mentioned in relation to blanching.

[britt]

Of course a liquid medium supports a gaseous component. Fish and plants aren't fusion reactors, yet they breathe oxygen and co2 respectively.
britt

[Flash]

I don't want to bother with the oxygen question, seems to me that is irrelevant with the process of blanching. It is however, in my humble opinion, best to begin your blanching process with the coldest possible water (and of course salt too, another "question" I don't care to bother with right now). WHY the coldest water?

Pipes, you know, those things that carry the water to your vessel.

some are copper, some PVC, some etc. etc.

Do pipes ever get clogged? (rhetorical question)

pipes are like arteries, they accumulate "stuff", and depending on whether they are metal or poly-, will do so to various degrees.

bottom line, heat (i.e. hot water) will tend to loosen debris and or metal pipe "residues" --thank god we don't live with lead that much these days.

anyway...COLD water tends to lessen this effect, AND helps prevent any unwanted "adulterants" that might disflavor your blanching product, and/or react with the salt.

So, Like stock, use cold water for blanching, bring it to a boil with some salt, and use iced water for shocking.




flash

[KeeperOfTheGood]

Hey oh

Actually, I have heard a version of that too. I know that the local city water people say its a not true (been debated here a lot as 50,000 houses are fed with lead pipes!). I have heard that the hot water tank is the bigger culprit. Its enviroment concentrates minerals and as a result the water from the hot water system is harder than the cold water.

[miahoyhoy]

Originally Posted by PLB

My chef is claiming that all blanching should be done in water that was as cold as possible before bringing it up to a boil because it holds more oxygen having not benn held hot, thus protecting color better. My guess is that by the time cold or hot water reach around a simmer they will be exactly equal in oxygen content either way. Can someone inform me of the scientific truth? Some sort of reference article would be wonderful. McGee doesn't seem to cover it. Thanks

Nope. Nope. Nope.

What will affect the color is the PH level. Acids and Minerals. Like blanching red cabbage with a little vinegar in the water will brighten the red.
Get yourself a copy of "On Food and Cooking"
Check it out.
Too much techie stuff for me to type out here.

Water out of the hot water shouldn't be used because it can taste off because of going through the water heater. Perhaps that stuff about the particles is true too. Dunno.