Half a croissant, on a plate, with a sign in front of it saying '50c'
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Well it certainly does suck.
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If each compartment and drawer of a standard sized refrigerator could be sealed when closed and evacuated of most of its air, I think that the fridges' power consumption would be reduced, as food could be kept closer to room temperature while being preserved for even longer periods of time.

Phase diagram of water http://www.lsbu.ac.uk/water/phase.html
[Basepair, May 28 2005]


       I have a feeling this would adversely affect most food and particularly fruit and vegetables.
xaviergisz, May 26 2005

       Quite right, [j999] - freezing under vacuum is freeze-drying: the ice sublimes to water vapour without going through a liquid stage.
The thing with the freezers in the restaurant is just that they are quite big and have good door-seals; when they close, the warm room-air inside them is chilled and contracts, causing a partial vacuum. As far as I know, it's not done intentionally.
Basepair, May 27 2005

       The ice sublimes to water vapor when it's freeze dried? Huh?   

       Why would phase change take place in that direction during freezing?
bristolz, May 27 2005

       Partial pressures and equilibrium.
Laimak, May 27 2005

       I think that the basic idea--that a partial vacuum would allow food to be kept closer to room temperature--is way wrong. I cannot even figure out what led to that idea, unless it's some misunderstanding of freeze-drying, or possibly reducing oxidation.
As for preserving food, the comment by [xaviergisz] is probably understated. This would be a way of moving "freezer burn" down into the refrigerator. Dried-out bread, flabby lettuce, oozing tomatos, hard cheese--ick.
If reducing oxidation is the goal, try filling the fridge with nitrogen or something (now there's an idea).
baconbrain, May 27 2005

       //that a partial vacuum would allow food to be kept closer to room temperature... I cannot even figure out what led to that idea...Dried-out bread, flabby lettuce, oozing sp:tomatoes, hard cheese--ick.//   

       Funny you should mention cheese, it's vacuum packed when purchased, (at least at the grocers around here), this lack of air doesn't seem to make the cheese hard--ick, in fact it keeps the cheese from drying out and is where I got the idea for just evacuating the air from that one cubby in the fridge.   

       Fruits would probably split open, so only certain sections of the fridge should vacuum pack.   

       //Why would phase change take place in that direction during freezing?//
It's not the freezing, it's the vacuum. You can draw a 'phase diagram' for water (or for anything, I guess), with temperature on the horizontal axis and pressure on the vertical axis, and the diagram is divided by lines into regions where the substance is liquid, solid or gas. For water, you can go from any state to any other directly by a suitable change of pressure and/or temperature. So, at low temperature (anywhere between about 0 and -80°C) you can go directly from solid to vapour by reducing the pressure. Carbon dioxide makes this transition even at normal pressure (hence dry ice), and is only liquid at high pressures. Iodine is similar - solid iodine makes a beautiful purple vapour when heated

Water actually has many other solid states (different forms of ice) which only occur at higher pressures, so its phase diagram is messy. See link.
Basepair, May 28 2005

       Also, closed containers may explode (unless fitted with a pressure equalising valve).
xaviergisz, May 29 2005


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