Sorry if this has been covered before but I couldn’t think of a better place to ask.
Why is it, that after you’ve heated something in the microwave it loses it’s heat much faster than it would if you’d heated it by more conventional means - eg, in the oven, on the stovetop?
I started noticing this a long time ago… but recently my brother commented on the same thing. I’d figured it was just my imagination. Right now my microwave is dead so I’m doing things the old fashioned way and it really does make a difference in the legth of time things stay hot.
It’s the way the microwaves heat the food. Contrary to popular beliefe, microwaves do not cook food from the inside out. Much of the energy is absorbed in the outer layers of the food, especially foods containing a high percentage of water. Thus, although the outside may be very hot indeed, the inside may not be so.
Also an oven will tend to dry the surface of food, leaving an oily coating. Wet surfaces cool quickly because of evaporation, so if your microwave-heated food is wet, it might cool significantly faster. (Try spraying it with veg. oil first and see if that makes a difference?)
Also: if you put out two identical bowls of water, but place a drop of oil on one water surface, then after a few hours the oil-free water will be much cooler than the water with the thin oil coating.
That would apply equally to water heated in a conventional oven or on the stovetop. In fact, any heating method at all. The oil keeps the water from cooling due to evaporation.
Not at all. A conventional oven pumps heat into a thin surface layer of food. Depending on the food type, it would tend to rapidly remove surface moisture and to cook any surface oils down into a fairly solid coating. The surface temperature of food in microwave ovens wouldn’t be so different than the temperature inside the food, so it might lack this thin baked layer.
So find some food that lacks surface oil. Vegetables? Does broccoli and mashed potatoes cool slower after heating in a conventional oven? Or is it just the greasy foods which display the effect?
it seems to be any food at all… from my experience, not just the oily stuff - canned spaghetti for example is less than 1% fat… it cools much quicker after being heated in the micro. I would say the same for vegetables…frozen peas/corn, or fresh broccoli…all cool quicker if cooked in the micro.
I think that if we think about this logically, the idea that something cools quicker or longer having been cooked in a microwave vs. conventional heating can’t be possible. We could run some tests, but we’d have to compare different types of conventional heating, too, I think. I imagine we could break down all modes something along these lines:
[list=1]
[li] microwave[/li][li] boiled[/li][li] deepfried[/li][li] contact heat (such as sauce in a pan)[/li][li] direct heat (such as a grill or broiler)[/li][li] indirect heat (such as an oven)[/li][/list=1]
I do perceived that sometimes microwaved food seems to cool down quicker, but I think it’s really just not evenly heated to begin with. Sometimes, it’s just the opposite: hot water in the microwave seems to get hotter than boiled water on the stove, well, because I know when it’s boiling on the stove. In the microwave it seems like it gets superheated (if there is such a thing, no vaporization?) and I have no idea it’s at the boiling point until I throw in the sugar and cocoa or salt or whathaveyou.
Say you put some maize kernals (I’ll call it corn you foreigners!) in the microwave. At first they seem super hot. The surface is really hot, and you could burn yourself. You can’t really notice that the inside of the corn is really only lukewarm. But as the food rests for a couple of minutes, the inside of the corn that didn’t get fully heated is absorbing some of that heat. Thus it appears it’s cooling faster. The “average” overall temperature of the entire grain of corn was never as hot as it would have been had you boiled it.
Physically speaking, given two identical pieces of corn that have the same consistent temperature all the way through at the same given point of time should cool off at the same rate. It doesn’t matter how the molecules got excited, only that they have the same excitation. They should thus cool at the same rate. If you make the argument that you only heated the water in the microwave and not the corn solids, and that the transference of heat from the water to the solids results in rapidly decreasing temperature, the answer’s the same. The average overall heat was never reached, thus the perceptual difference.