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Old 06-28-2012, 11:24 AM   #11
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understanding

so what does the previous person mean lasg. doesnt steam food?
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Old 06-28-2012, 12:03 PM   #12
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GLC defined steaming as heat from steam that's separate from the food. e.g. a steamer basket in a pan of boiling water. The heat source heats the water to make steam and the steam then cooks the lasagna. Lasagna cooks mostly from the heat of the oven. Any moisture in the lasagna that heats up and turns to steam is part of the cooking process but not the primary heat source. You cover the lasagna because it will trap the heat and cook faster and keep moisture from escaping and drying out the food.
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Old 06-28-2012, 12:17 PM   #13
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Lasagna is not cooked on account of any steam generated. Little steam can form, anyway. The internal temperature of fully cooked lasagna is typically 170F and never more than 190F, too cool for steam to form, except perhaps right at the surface, and that would only be during the uncovered period. Lasagna is normally started covered and finished uncovered.

Let's make clear a distinction here. There is water vapor, the gas phase of water. Obviously, water vapor can be created by a number of different means and certainly doesn't require high temperature. You see water vapor condensing from your breath on a cold morning, and you're not boiling inside. Nor are clouds boiling.

Steam is also water vapor, but steam refers only to water vapor created by boiling water. So steaming requires boiling water and a temperature of at least 212F at sea level pressure.

Water vapor can be formed by evaporation, and it evaporates faster with heat. Because of the physics involved and the fact that when a water molecule changes phase to become vapor, it takes away a parcel of heat, evaporation results in cooling of the liquid. If you contain the vapor in a vessel with the water, it will reach equilibrium, and no more evaporation can take place. And so, since no molecules are changing state and taking heat with them, the temperature can rise. If the vapor is not contained, evaporation and heat loss can continue. You can only do this to a limited extent with common covered pots. They still leak vapor. So a covered vessel will cook more efficiently, but it's nothing to do with steam. And we wait until the end to uncover and brown our lasagna, because we don't want to dry it out earlier from water vapor leaving the food.

So there's a not very clear distinction between steaming and other methods. We could, for instance, put our vegetables in the steamer and heat the water only to 190F. The water would not boil, but hot water vapor would be released and more or less contained, and the vegetables would eventually become cooked by exposure to this hot vapor. But not steamed, because there was never any steam. And there wouldn't be any advantage to this sort of wet heat cooking.

It seems like a silly point, but think of it this way. Why do we steam? Well, aside from things like preserving nutrients lost in boiling, we steam because we can't, without special equipment make water vapor any hotter than steam at 212F. If we want to cook faster than that with the same effect, we could put our steamer inside our pressure cooker, and the steam would become much hotter.

You can cook beans that way. It's tricky with vegetables. With the high temperature steam, they cook very quickly, and it's hard to get the pressure down quickly enough to get them out to stop the cooking. Not worth it, when regular steaming takes so little time.
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Old 06-28-2012, 01:00 PM   #14
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i think i understand now....with the baked potato it is baked ...(.the heat source )and the steam is from being covered by the foil. Wrapped in foil just makes softer skin.
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Old 06-28-2012, 01:23 PM   #15
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I have to change a few of GLC's points. Mostly, I agree. The part that I'm adding is that in a sealed environment, such as a lasagna pan covered tightly with foil, steam is generated when the water is heated. This steam is trapped, creating a moist environment. Teh steam isn't cmopletely vaporized and exists as tiny droplets of water, moving in the air currents within and above the food. Straight, low humidity air is a poor conductor, and so is also not good at transferring energy into food. The moist air is much more efficient at transferring trapped heat energy back into the food, which also speeds the cooking process.

Cooking, is by definition, the process of transferring heat into a food, be it by radiation, or conduction. We also talk about convection. As air touches food, just like everything else that touches the food, if the heat energy of the air is greater than that of the food, their will be a transfer of energy into the food. If the air is dry, and static (non-moving), as the air touching the food is giving up it's energy, it must absorb more energy from it's surrounding air before ti can transfer more. And remember, air is more insulate than conductive. By moving the air in an oven with a small fan, the food is constantly touched with hot, fresh air, transfering heat more evenly and more quickly into the food.

When the same air and processes are involved, but with moist air, the water droplets that touch the food give up their energy much more quickly than does the same temperature dry air. And as the water molecules move around, they also absorb heat energy more quickly from the heat source, to again pass into the food.

And just so everyone knows, steam can reach temperatures much hotter than 212'F. The Catapults on an aircraft carrier used steam in excess of 1200' F. to operate. Steam at that temperature is a true vapor, and can be used under high pressure to cut steel.

For the example of the potato in foil, as the potato is heated, within its foil shell, the water begins to turn to steam before the potato meat has broken down into that cooked stage that we enjoy. That steam creates internal pressure, at least a little bit, and migrates to the outside, wetting the skin of the potato, keeping it soft. So yes, the foil wrapped potato does cook through steam, but also through conduction and convection. The hot air of the oven heats the foil (convection), which then transfers that heat directly to the potato, and all of the water within the potato (conduction), which creates steam. As the steam is not the original source of heat, the potato is considered baked. But steaming, is part of the cooking process, where convective and radiation are the heat sources in a potato that is baked with no foil, or other covering.

And that's why a foil-wrapped potato, whether cooked in an oven, or thrown into the hot embers of a campfire, is considered a steamed potato.

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Old 06-28-2012, 02:20 PM   #16
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Quote:
Originally Posted by Chief Longwind Of The North View Post
I have to change a few of GLC's points. Mostly, I agree. The part that I'm adding is that in a sealed environment, such as a lasagna pan covered tightly with foil, steam is generated when the water is heated.
I don't disagree with that. Lasagna is a somewhat wet concoction, so there is always some water in contact with the pan. And the pan certainly exceeds 212F, so some steam is formed. But the cover cannot hold any significant pressure, so the steam cannot exceed 212F. The air, of course, can get hotter. But I would not call the method "steaming," because the heat is not being applied primarily by steam from water that is not in contact with the food, although during the covered part of the cooking time, there is probably little air in contact with the food because of the dense water vapor atmosphere under the cover.


Quote:
And that's why a foil-wrapped potato, whether cooked in an oven, or thrown into the hot embers of a campfire, is considered a steamed potato.
Since I've never tried to steam a whole potato in the usual way of steaming vegetables, I'll have to try it. The exercise would compare the cooking times. One potato in a steamer insert, set above boiling water. The other wrapped in foil in a hot oven. And a control, a bare potato.

I'm guessing that the steamed potato (the one over boiling water) will take longer. I reason that the foiled potato is in a very hot oven, far hotter than the steamer steam can be. I suppose, to really test, I should wrap one potato as tightly as possible, pressing the foil closely to the skin. And wrap the other loosely. I had better weigh the potatoes, too, to see how much water is lost.

My store sells packages of four almost perfectly matched russet potatoes that will be perfect for this, and I was going to bake some anyway in the next few days.
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Old 06-28-2012, 03:24 PM   #17
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ok guys ....u all been very helpful. just to make sure i got it for braising,would the heat source be the steaming from the water or is this consider the process of braising?
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Old 06-28-2012, 03:26 PM   #18
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Braising, the food is in the liquid and covered.

Steaming, the food is out of the liquid and covered.
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Old 06-28-2012, 03:38 PM   #19
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so the heat source of braising say in the oven is baking and the process of braising is the steaming ... guess i am hitting a rock bec. not understanding heat source and process. I am thinking bec. most of the cooking the meat in braising is done by steaming?
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Old 06-28-2012, 04:35 PM   #20
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i didnt write that the right way.(dont see a delete,sorry).i do understand heat source and process its just like with braising i think steaming is the biggest part in cooking the meat here in the braising,so i thought the heat source should be steaming .
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