Why would heating left-overs in a ring heat them more evenly
microwave
I just saw this tip on Reddit to heat leftovers in a ring.
Why would this only work with left overs?
How does this ring cause the heating to be more even?
Best Answer
I believe the unspecified context of this question is cooking in an oven or microwave. No matter what your cooking method, the heat is introduced at the outside of the food:
Microwaves only penetrate a short distance; the rest of the cooking through to the center is by conduction (or convection, if the food is liquid)
Conduction/convection in an oven only interact with the surface of the food
Radiant heat (infrared essentially), one of the main cooking modes in an oven, again only affects the surface
By creating a ring shape, if it is practical, you create more surface for the heating modality to interact with the food.
This is the reason for an angel food cake pan or bundt pan having a tube at the center--it allows more surface area to be involved in the cooking process.
Also, with the metal pan, the metal has a higher conductivity of heat than does air. This is why parts of the cake in contact with the pan (or a non-insulated metal cookie sheet, or whatever) generally brown more than the parts exposed to the air.
However, in practice except for things cooked in tube pans, I wouldn't really worry about this affect. If you can stir occasionally, it becomes close to moot.
Note that in pan frying or sauteing or or griddling or stir frying (depending on the term used in context), the main surface area that is relevant is the bottom of the food, that which is contact with the pan. A ring doesn't help much here, compared to spreading the food out.
I looked at the first part of that thread. It does not seem to be a hot bed of science and knowledge of cookery.
Microwaves specifically heat water molecules in the food. This turns them to steam, and because the air in the microwave is actually cool, the steam then condenses. There is often not proper air circulation to move the steam away from the food. Often times the outside edges of the food will not be soggy, but rather burnt, because they receive more energy and the water can totally vaporize.
For better results when reheating food, do not reheat your food on "high" or the default power. Reheat it at a lower setting for longer time. For pizza specifically, I heat it in the microwave only to room temperature and then finish it in the toaster oven or in a pan.
See this wikipedia page, it states that if not crumpled aluminum foils is generally safe, so make sure you do not crumple it.
Then it says
The USDA recommends that aluminum foil used as a partial food shield in microwave cooking cover no more than one quarter of a food object, and be carefully smoothed to eliminate sparking hazards.
However, small pieces of aluminum foil can be used to “shield” areas of foods,
such as poultry drumsticks and wings, to prevent overcooking.
It also states
General Rules for Safe Use of Aluminum Foil:
Use new, smooth foil only. Wrinkled foil can cause arcing (sparks).
Cover no more than 1/4 of the food with foil.
Shape the foil smoothly to the food so no edges stick out
It makes no difference which side of foil (shiny or dull) is facing out.
Do not place the foil closer than one inch from the oven walls.
If the microwave oven has metal shelves OR a metal turntable, don’t
microwave food in foil containers or metal pans, and don’t let foil used for
shielding touch or be close to the shelves or turntable.
If you see arcing (sparks), immediately remove the foil shielding; transfer
frozen food from foil container to a microwave-safe utensil.
My bolding.
So make sure you only cover the top of the cup and make the foil smooth, do not crumple it and it should be safe.
The reason to use this as stated in the blog is speed, a few minutes compared to much longer.
Best Answer
I believe the unspecified context of this question is cooking in an oven or microwave. No matter what your cooking method, the heat is introduced at the outside of the food:
By creating a ring shape, if it is practical, you create more surface for the heating modality to interact with the food.
This is the reason for an angel food cake pan or bundt pan having a tube at the center--it allows more surface area to be involved in the cooking process.
Also, with the metal pan, the metal has a higher conductivity of heat than does air. This is why parts of the cake in contact with the pan (or a non-insulated metal cookie sheet, or whatever) generally brown more than the parts exposed to the air.
However, in practice except for things cooked in tube pans, I wouldn't really worry about this affect. If you can stir occasionally, it becomes close to moot.
Note that in pan frying or sauteing or or griddling or stir frying (depending on the term used in context), the main surface area that is relevant is the bottom of the food, that which is contact with the pan. A ring doesn't help much here, compared to spreading the food out.
I looked at the first part of that thread. It does not seem to be a hot bed of science and knowledge of cookery.