Taking a “moment” to mean, let’s say, a one second interval starting at the exact point the timer reaches zero. Is your food getting hotter or colder during this second?
Depends on how much moisture is present in the air and on the surface of the food, I think.
The moisture would continue to heat up? Why?
Depends on if the temperature of the food. If it’s still semi-frozen it’s going to be getting warmer. If it’s hotter than the air it will cool.
The moisture wouldn’t continue to heat, but the food would absorb some of it in time for its heat to be transferred.
I don’t know if that would be enough to offset the instantaneous cooling.
I believe that is it. The nanosecond the microwave shuts off, there won’t be any more microwave energy going to the food so we can’t magically have any more heat affecting it. The only issue is whether the food is hotter or colder than the air inside the microwave. Most of the time, the air will be much cooler so the food will be cooling off at that split second.
As a whole, unless the inside of the microwave is hotter than the average temperature of the food, it is getting colder. Individual parts of the food, such as the center, may warm up as heat flows from the hottest parts to cooler parts. That’s one reason some instructions suggest waiting a bit before eating, or stirring before eating, the heat is not evenly distributed right away.
Once the microwave is off, though, there is no more energy being delivered to the food, all the heat energy it has at that moment, is all the heat energy it’s going to have.
Agree. Some instructions which say to allow food to “finish cooking” after microwave is turned off may lead to the misconception that the food continues to get hotter after it’s turned off. What in fact happens is the hottest part of the food is the outside, and it will conduct heat to the inside, which will continue to cook.
The same thing happens when cooking in a conventional oven; it’s an art to know when to take food out of the oven and how long to let it “rest.”
Nitpick actually.
Considering that the energy going into the food is not heat but microwaves, and the microwaves are converted to heat via the vibration of the fats and water in the food, isn’t it possible that for a brief time (probably microseconds) some heat is created after the wave action stops because of the inertia movement of the vibrating molecules?
OK - I’ll leave quietly
That’s exactly what I was wondering about when I brought this up, actually. But after most of the responses seemed to be about transfer of heat / moisture, I thought I’d better refresh my knowledge on how microwaves work before restating my question. But you beat me to it!
So, how about it? Any opinioins on BubbaDog’s theory?
Most books on microwave cooking say that the food molecules continue to vibrate (and cook) after the microwave energy has stopped.
Even in conventional cooking, food will continue to get hotter after you remove the food from heat. You can jab a digital thermometer into it and see for yourself. If I take a steak off the grill and put it on a cool plate, it will gain another 5-10 degrees before it gets to the table.
I think it’s the surface temperature of the food that counts, not the average temperature. If the center still frozen but the surface is 100F, then heat is flowing from the surface of the food to the surrounding air.
It’s a myth that water molecules are resonating with the microwave. It’s more accurate to think of the microwave forcibly pushing the water molecules back and forth. As soon as that force stops, the water molecules stop gaining energy. There’s no way heating can continue as long as a microsecond. (A microsecond is a very long time - light travels 1000 ft in that time.)
Molecular vibration and heat are the same thing.
Cheesesteak has it right.
Yep, :smack: shoulda thought of that before I posted. It makes sense then that no additional energy is created, only transferred from hotter sections of the food to cooler sections.
“Most books” are wrong about that.
This is what the “most books” are referring to and the food as a whole is definitely not getting hotter. What you are seeing is the continued transfer of heat from the outside to the inside of the meat. Instead of sticking the meat thermometer into the center of the meat, insert it barely below the surface and see if it goes up over time.
You have to recognize a difference between “cooking” and “getting hotter”. Getting hotter is a thermodynamic statement that follows strict physical laws, cooking is a culinary statement about how foods change when heated.
Put some tough stew meat in a crock pot and it will be at full temperature after 1 hour but will continue to cook (and needs to cook) for hours longer. Even if it doesn’t get a single degree hotter, the food changes.
In the microwave example, the system won’t get any hotter, but the food can undergo important changes in that resting time, that we can properly describe as cooking.
More likely picoseconds.
No power input of microwaves, no heat input, any perception of the heat increasing is a problem with perception. Not heating/cooling the instant the power stops.