Does a microwave cook from the inside out?

In this brief article we will answer the question does a microwave cook from the inside out and three factors affecting cooking in microwave

Does a microwave cook from the inside out?

Technically, no. Microwaves cook food from outside in. The principle is to excite the water and fat molecules in the food using radio waves. These waves first excite the surface molecules and then penetrate deep. You might have noticed that sometimes food is hot on the outside but completely cold from the inside. This is because the waves couldn’t penetrate that deep within the time period.

What is microwave:

A microwave oven is an electronic device which uses electromagnetic radiations to heat up the food or cook it. The electromagnetic radiation used in microwave oven are radio waves which are compressed and have short wavelengths

Microwaves channel the heat energy into the food with the help of radiations. The waves resonate with the proteins and water of food and it gets heated due to the motion created by them. As it reaches directly to the particles inside the food it cooks evenly and properly.

How microwave works:

Microwaves are simple devices and they have different instruments inside them that helps it work. In microwaves there is a high voltage device called magnetron which directs short radio waves to food items.

These short radio waves bounce around in the metal box of the microwave oven. When these waves come in contact with food surfaces they encounter specific substances like proteins, water, fats, sugars, polymers, ceramics, etc.

The microwaves make the particles of these substances excited and give them energy. This makes the temperature of the food overall hot.

Inside-out cooking:

Many people believe that microwaves cook inside out and they start cooking the food from the core. This is a myth and it does not happen in microwaves. Microwaves start heating the food from the surface and then reach inside.

Microwave oven works on the principle of convection and heat the free molecules in food. If a food is dielectric the waves rotate and try to align the fields. This alignment of food particles takes time. In case of thawing microwaves need to align food before heating it that’s why it takes time to thaw food.

As microwaves directly reaches the inside surface and excites the particles there, some people might think it cooks inside out. But actually what happens is microwaves excite any particle it encounters. When a food item is placed the food is cooked evenly by exciting particles here and there. Instead of cooking inside out microwaves cook evenly.

Factors affecting microwave heating:

Microwaves work on food items when they come in contact with them, some microwaves bounce back, some excite the particles, and some get diffracted. But microwave cooking makes sure the food is evenly cooked. There are still some factors that affect microwave cooking. Some of them are:

Ingredients of food:

How microwave will heat the food depends on the ingredients a food is made from. Sometimes a food looks solid but has many free water particles in it. This type of food will be cooked quickly as compared to food made of all solids

Physical nature of food:

Food is in the form of liquids: drinks and beverages, Solids: Meat, eggs or semi solids: Jellies. The physical nature of food actually affects the heating capacity of food. When a food gets heated the radiations interact with its particles.

In case of liquid foods there are many free particles and water molecules to interact with, so liquid foods get cooked quickly. In solid foods the particles are often tightly bound and there are rarely free particles. This affects the heating time of food too, as it will get cooked slowly.

Size of food:

Microwave heating of food also depends on the size of food you are heating in the oven. A small food will get heated quickly as the surface area is small. In case of large sized foods, the oven takes time.

The radio waves when come in contact with the surface of food it penetrates. Sometimes if a food is large in size the penetration will take time as first the surface particles will get heated. And cooking all of the large size food is also a long process as microwave cooks evenly, the radio waves will take their time to cook every part of food.

Efficiency of microwave ovens:

Cooking in a microwave oven is more efficient and time saving than conventional cooking on stoves. Microwave cooking is a good choice when you are cooking something big in less time. But cooking everything in the microwave is not the best option out there.

In microwaves the electromagnetic radiations cook food, and these radiations if don’t come in contact with food bounce around in the metal box. If you are cooking something small the radiations will bounce around a lot. These radiations will make the metal surface hot resulting in a hot oven which might be dangerous. It is better to avoid cooking all the time in microwave ovens


In this brief article, we have answered the question does a microwave cook from the inside out and three factors affecting cooking in microwave