Can aluminum foil keep food warm? (yes, but not quite)

Are you trying to keep the food warm but not sure if aluminum foil will be ideal for that? This post is for you. In this post, I will discuss whether aluminum foil can keep the food warm or not.

Summary:

Aluminum foil will somewhat keep the food warm for some time when the food doesn't touch it because it blocks radiation from passing through it. However, even if the food doesn't touch the foil, it'll inevitably cool because the steam from it will touch the foil, resulting in the loss of heat.

Related: Can aluminum foil keep things cold?

does foil keep food warm?

To answer this question, we'll have to have an understanding of how heat is transferred. How heat is transferred depends on the material that it has to pass through, for example, air, liquid, and a solid object. Here is how heat is transferred:

• Conduction:

  The transfer of heat energy through a solid object. The rate at which the heat is transferred depends on the conductivity of the object.

  For example, metals have high conductivity and allow heat to be transferred faster compared to plastics.

• Radiation:

  That's the transfer of heat energy through space, and this transfer is at the speed of light.

  One example of radiation is heat from the Sun.

• Convection:

  Movement of hotter particles through liquid to lower temperature areas. For example, when the water is boiling, hotter particles will be moved to the top.

The only two heat transfer processes that can occur when hot or warm food is wrapped in aluminum foil are conduction and radiation.

When the food inside an aluminum foil is in contact with the aluminum foil, conduction will occur because heat will be transferred from the food directly to the aluminum foil.

When the food is not in contact with the foil, heat can only be transferred by radiation because conduction can't occur.

However, due to the reflective properties of aluminum foil, radiation will be blocked, and heat can't be transferred through the process of radiation.

When wrapping food with aluminum foil to keep it warm, ensure that the shiny side of the aluminum foil faces inward. This will ensure that the heat doesn't pass through it through radiation.

While aluminum foil can keep the food warm by blocking radiation, it's not that effective, and here is why:

Even if you make sure that the food doesn't touch aluminum foil, the food will inevitably cool when wrapped in foil. This is because when warm or hot food is wrapped in aluminum foil, it releases steam or water vapor. This steam is hot and it'll touch the aluminum foil and thus transfer the heat to the aluminum foil.

How long can aluminum foil keep food warm?

We've discussed how aluminum foil can keep food warm, and we also discussed its disadvantages in keeping the food warm.

What we haven't discussed is how long can aluminum foil keep the food warm, and this will depend on several factors.

Two main factors that will determine how long food will stay warm in foil are:

• The amount of food:

  More food will typically take more time to cool. If you wrap a lot of rice with aluminum foil, it will stay cool longer. However, when you wrap less food, expect to get disappointed because it'll cool so fast.

• The weather or season:

  In summer, when the weather is generally hot, food will stay warm longer as compared to winter.

  Winter is cold, and the food cools pretty quickly during this season. So when you are wrapping food with aluminum foil in winter, keep in mind that it may cool quickly.

In general, aluminum foil will only keep the food warm for a few hours(about 3 to 5 hours). Whether it's winter or summer, aluminum foil is not ideal for keeping the food warm overnight; the food will cool.

Should I use foil or plastic containers to keep food warm?

When choosing between aluminum foil and plastic containers to keep food warm, two things have to be taken into consideration: which one will keep the food longer, and which one will not alter the taste of the food by leaching chemicals into the food.

What keeps the food warm longer — foil or plastic container?

When hot food is wrapped in a foil or plastic container, it will release water vapor. This water vapor is hot and it will touch aluminum foil or plastic container, even if the food itself is not in contact with the container.

When a plastic container is used for wrapping, it will insulate the heat energy from the steam of the food, and thus keep the food warm longer.

Aluminum foil, however, will conduct heat energy from the water vapor of the food, resulting in a shorter cooling time of the food.

So because plastic containers are good insulators, they are a better option for keeping the food warm longer when compared to aluminum foils. Aluminum foils are not as effective because they will conduct the heat from the steam of the food.

What will not alter the taste of the food — foil or plastic container?

When aluminum foil is used for wrapping food, hot food in particular, it leaches aluminum into the food. This will cause the food to be somewhat metallic in taste.

Moreover, there are certain types of foods that can't be wrapped in aluminum foils. For example, spicy foods, acidic foods, etc. When these foods are wrapped in aluminum foils, more aluminum will leach into them.

When aluminum foil is used for wrapping foods, it's best to ensure that the food doesn't touch it if you want to reduce the aluminum leakage.

So because aluminum foil alters the taste of the food by leaching aluminum, a plastic container is a better option for keeping food warm.

Summary

Wrapping the food with aluminum foil will keep it warm because the aluminum foil will reflect radiation from passing through it. This will result in heat energy not escaping and therefore makes the food warm.

However, because the food will release water vapor, it will get cold. This water vapor will touch the food and transmit heat energy to the foil and the heat energy will eventually escape, causing the food to cool.

The best material for keeping food warm longer is plastic. Wrapping food in plastic containers will keep it longer because a container is an insulator and will not conduct heat energy to its outside.