Since aluminum foil has shiny and matte sides, most of the resources found on search engines say this: When cooking food wrapped or covered with aluminum foil, the shiny side should face down, facing the food, and the dumb side Glossy side up. This is because the glossy surface is more reflective, so it reflects more radiant heat than matte, making the food easier to cook.
Is it really? Let's analyze the heat conduction method:
There are three basic ways to transfer heat: conduction, convection and radiation. Conduction is when heat is transferred through contact between one object and another hot object. This is what happens when we cook on the stove.
Convection is the transfer of heat through the physical movement of the surrounding fluid (liquid or gas). Radiation is light waves, radio waves, microwaves, X-rays, etc. that transfer heat energy from one surface to another.
Any object with a temperature higher than absolute zero will emit infrared radiation. This means that the heating coils, sides and shelves in the oven emit infrared energy. Even heated containers and heated food themselves release this energy.
However, when you cook food in the oven, the main source of cooking heat is convection. The hot air of the oven transfers heat to the food being cooked. Don't be confused by the "convection oven". All ovens use convection, and convection ovens only use fans to improve convection efficiency. Very little heat transfer in the oven is through infrared radiation, which is invisible light.
A shiny surface will not affect convection, but it will affect radiation. A shiny surface reflects more waves than a matte surface. The reason that one side of the aluminum foil is more shiny than the other is that it is smoother and has fewer blemishes. Therefore, the bright side of the foil should reflect more radiation than the matte side, which will better capture the incident wave, but it should not affect convection (convection is the main source of heat transfer).
Consider grilling food. When wrapping food in aluminum foil for baking, you may tend to put the dull side on the outside. In fact, in the process of baking food for a long time, the working principle of either party is basically the same. The aluminum foil will be heated by convection, and the energy will be transferred to the food. As the moisture in the food is heated, the food will be cooked by steam.
Rather than which side comes out, the tightness of the food package may make a bigger difference. Any air trapped in the aluminum foil bag and surrounding the food may act as a thermal barrier, thereby slowing the transfer of heat. Therefore, wrap the food tightly before baking.
Therefore, when grilling food with aluminum foil, should the shiny side face up or the matte side up? You should have an answer to this question, at least for the heating effect, there should not be much difference, so you can decide by yourself.