Why do microwaves not cook evenly
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Why do Microwaves Cook Unevenly? (Reason explained and solved)

Microwave ovens are a convenient and quick way to cook. They can be used for many different types of dishes, but there is one problem: they don’t always cook evenly!

Do you want to know why microwave ovens don’t cook evenly?

The answer has to do with the behavior of the radiation emitted in a microwave. Microwaves beam rays of radiation in a fixated path into the chamber bouncing from wall to wall. Unfortunately, these rays don’t move around. Ultimately, if the area of the food is not in the path of the rays, it will create a cold zone in which results in that specific area not being heated. Microwaves have built-in spinning trays that help move the food which helps distribute the rays. However, it isn’t perfect and there are things you can do to make sure your food is cooked more evenly.

When microwave turntable is not rotating
When microwave turntable is not rotating

In this blog post, we will discuss the reasons for uneven cooking in microwaves and how you can avoid it. We will also provide some tips on cooking with your microwave so that you get perfectly cooked food every time!

You can test this yourself

If you are interested in seeing this with your own eyes, try this. Get a few chocolate candy bars and lay them flat on a tray. Try to cover the tray up as much as possible but also make sure the candy bars are all laying flat side-by-side.

Remove the spinning tray from the microwave and place the tray full of chocolate bars into the microwave. We don’t want the rotating tray to move the tray. We want the tray to stay in one place.

Turn on the microwave and let it cook for about 30 to 40 seconds. When done, remove the tray of chocolate and examine how and where on the tray the chocolate bars have melted.

You’ll notice that only certain spots of the chocolate are melted, not the entire chocolate.

The heated area is cooked but the uncooked area is what we call the cold spots.

You should now start to develop a theory about how microwaves cook and recognize that microwaves do, in fact, cook unevenly.

Why do microwaves cook unevenly?

So you must be wondering why microwaves cook so unevenly. It can be frustrating when your plate of food is microwaved and half the veggies are still cold.

There have been many studies done on this topic, but I’ve found some really compelling studies. There are a few reasons why.

Standing wave of microwave rays heating and nodes
In standing waves with peaks moving up and down and nodes staying still Wikimedia Commons

Microwave rays contain areas that don’t produce heat

The real answer lies in the physical of the radiation rays and how they behave. When you continuously emit rays of waves into a chamber like a microwave that doesn’t spin your food, you’ll find cold spots.

This is because the waves in a microwave don’t spread evenly throughout the food. The rays will bounce a few times around the walls and some of them will make contact with your food and some won’t.

Take a look at the picture above. The wave parts that are moving up and down are where the heat is produced. However, its the red dots or what most people call the nodes that stay still and don’t produce head causing the cold spots

These waves can also be described as standing waves that go up and down with certain points that just stay still called nodes. These nodes are where no energy is emitted while the waves moving up and down is where heat is produced.

If you find a cold spot on your meal, that’s probably the area where the node resided.

Almost all microwaves try to solve this issue by making the bottom plate spin so that the food will have a better chance of making contact with the ray. This works. Unfortunately, it’s not perfect. You’ll still find cold spots.

Some microwaves have settled on moving the waves inside the compartments of the microwave instead. And this has helped as well. These are microwaves use a fan above the chamber that helps reflect the microwave beams to different locations as it turns.

Waves have trouble penetrating food that is too thick

When you are trying to cook a very bulky, very thick type of food such as a thick steak, you’ll notice more cold spots.

The reason being is again due to how the microwave rays heat. When two opposing microwaves collide, it is at that point where heat is produced. Now, the waves can only travel so far into that piece of meat. And the cold spots are created because there is less heat being produced at those points in time

The thicker it gets, if you do not adjust cooking times accordingly also with microwaves that don’t have a rotating tray inside then more of these hot and cool zones will start to emerge as well.

Microwaves don’t cook frozen foods well

Frozen food is an interesting case study. Ice is extremely dense and microwaves can’t often cook icy foods well. The problem with placing a frozen meal into a microwave is that for one thing, it can’t penetrate ice as well as water.

When that ice transforms into water.

Now in the water state, microwaves have no problem cooking water up really fast. This results in what you can imagine as a slow, then fast cooking process. Obviously at this point, if other areas of the food are still frozen, there’s a good chance the water areas are already cooked.

This creates an imbalance of effective heating, thus, adding to the hot and cold spots dilemma.

Don’t eat food that’s not fully cooked

Uncooked food is a breeding ground for bacteria. The main reason that we cook most, if not, all of our food is that we want to kill off any bacteria that might be living or growing on food. Heating our food up will most likely kill the majority of harmful bacteria that might be living on our food.

The main reason for this is that bacteria will not survive at temperatures above 140 degrees Fahrenheit, and microwaves can cook up to a temperature of about 170-180° F (77 – 82 °C).

According to the World Health Organization (WHO), most bacteria are killed when temperatures on food reach or exceed 149°F (65°C).

However, as stated in this article, cold spots do happen, and if those bacteria are found in these cold spots, there’s a good chance they are alive and well.

Tips on how to evenly cook food with a microwave

Here are a few tips I think will help you prevent and avoid your food from having too many cold spots. Microwaves, no matter how advanced they are, will have cold spots. It’s just the nature of the design and the physics that bind it from being a full-body cooking machine.

Make sure you stir your food

In between microwave cooking, simply stop the microwave and stir the food completely. This will help distribute and spread out any hot spots from each other to make sure that your meal is fully cooked, not just part of it.

This works well for mixtures of food like soups, creamy and chunky meals.

Spread your food out

This probably goes without saying, but as I explained above, microwaves can only travel so far into the food.

The thicker the item being microwaved, like a steak for example…the larger its interior will be and this can lead to cooking inconsistencies or cold spots.

The best way in my opinion is just simply to make sure you spread out your meal as evenly as possible on whatever plate that’s going into it.

This means meat should be separated from the sides on a plate that’s large enough, or if you’re microwaving a single item like bread, it should be laid out on the plate in an even layer.

Move your plate to the outer edge of the spinning plate

You can even punch a hole into the middle section of the plate devoid of food. This is similar to what a donut would look like. What this does is it gives the food a better chance at being cooked more evenly.

If you think about this, it makes sense.

Picture how much movement you get if you were to place yourself at the end of a spinning circle. Then picture how much movement you’d get if you were placed in the middle of this spinning circle. You’re not going anywhere in the middle.

Leaving food mostly on the furthest end of a spinning place can help make it more probable that it will make contact with heated spots.

Place a lid over the container

In this method, I’m not saying you should place a lid over the bowl and shut it tight. That might either damage the lid or cause a pressure build-up.

What I mean is just to place the lid over the top of the bowl. Allow small areas where air can escape to avoid the buildup of pressure and any problems with contacting food or condensation.

This method attempts to prevent heat and hot moisture from leaving the vicinity of the bowl too quickly. With heat and moisture trapped between the food and the lid, it has a better chance of conducting itself back into the food keeping it one step warmer.

Let it sit after cooking

Heat dissipates. This means that if you leave heat alone, it will try to spread out naturally. My advice would be to allow the heat time to spread as far as it can throughout the microwaved meal.

I’m sure you’ve noticed how a lot of frozen dinners will have instructions on the back of the box with the last direction to let it sit for x amount of minutes.

This serves two purposes. One is to not burn the meal prepper, and the second is to allow the heat to evenly spread throughout the food.

Buy using a food thermometer

You can dig it into the center of your steak or mixed set of food to check the temperature. Refrigerators normally keep foods cold at 40° F (4° C). So anything close to this number is potentially not cooked.

Cook at lower power

One thing I’ve recently discovered is that cooking at lower power on a microwave really doesn’t mean that it has the ability to actually lower its temperature or heating power.

It isn’t a dial like what you would find in a stovetop oven. Lowing the power settings simply forces the microwave cycle between turning on and off throughout the cooking time.

If you listen very closely, you might even hear the magnetron turn itself on and off through a humming noise.

During the offs, the heat can potentially dissipate throughout the food and cook more evenly.

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