Expert: Keith Patton - 1/23/2008

Question
hi
can i use glass casserol to rost beef in microwave

Answer
Sheny:

The only way you can roast in a microwave is if you have a convection microwave.  This combines heat with the use of the microwave's radiation.  You are probably too young to remember when one brand of microwave was the Amana Radar Range.  Microwave essentially use radar waves or micro waves on the electromagnetic spectrum to cook food.  There are apocraphal stories of air force technians getting ill or injured when high intensity radar units in the noses of aircraft were turned on during servicing.  The high intensity microwaves cause the molecules in a substance to vibrate as they pass through them.  This causes heat.  The heat causes the cooking.  That is why solids heat up faster than liquids in a microwave, the molecules are closer to together so they heat faster.  That is also why the heating can be uneven and all microwaves now come with rotating plates inside them to turn the food.

The fact that they use radar waves explains the pretty spectacular results when you put something metal in the range.  It sparks and heats up and will self destruct.  This is because the high intensity energy is reflected by the metal back into the machine.  Just like how the military can use radar to detect metallic targets and why they cover the stealth aircraft with radar energy absorbing non metallic tiles.

Roasting is a combination of irradiated heat meaning the heat given off by a fire or heat source, like the heat you feel when you hold your hand in front of a fire.  This causes a browning reaction on the surface and a slow heating of the meat from the inside out.  Microwave generated heat cannot do this. A convection microwave also uses heated air like your oven and circulates, hence convection the movement of heat, to brown the outside.

What you would end up with trying to cook the meat in the microwave is a very tough dried out hunk of inedible meat.
As muscle fibers are heated, they contract.  Continuous heat causes the protein to break down eventually but before that happens the myoglobin, the pink liquid people mistake for blood, which is actually intercellular fluid, is squeezed out as the fibers contract.  The protein coagulates, this is the stage when the meat turns gray.  As it contracts and coagulates it gets firmer and harder and tougher.  In a microwave you have little control over it because it happens so quickly in a microwave.

Having said all that, you might try experimenting a bit and see if you can find a happy medium (or rare ha ha!) between pre-cooking the meat in the microwave and finishing the browning in a pre heated oven.

Keith