Can You Reheat Food In Styrofoam ? No, And Here’s Why

So you’ve just come home with the world’s best takeout, ever. You can’t wait to eat, sit down with your favorite show, and call it a day. So you walk confidently to your microwave and then pause. You remember something vague about plastic and microwaves. Whatever it was, it wasn’t good.

So can you reheat your food in styrofoam or not ? If not, why not ? What is styrofoam anyway ? And why do restaurants and takeout places even use styrofoam if it’s not safe ? There’s  a lot we need to clear up, so read on.

styrofoam reheat

Can you reheat food in styrofoam ?

You should not reheat food in styrofoam, because it starts to soften at 100 C/212 F, and even burn and melt at 240 C/464 F. Both microwaves and ovens can exceed those temperatures, especially for longer cooking times.

Styrofoam is not meant to heat or reheat food, it’s simply meant to keep food insulated and warm until you get home. It may be very convenient to simply stick the container in the microwave and heat it for a couple of minutes. But the chemicals it releases as it heats up are toxic and can eventually lead to health issues.

What is styrofoam ?

Styrofoam is actually misnamed here, since real material used for those containers is polystyrene. It’s a type of styrene, which is a derivate of benzene. It’s manufactured by injection into molds, and the result is a lightweight, fairly sturdy container.

It’s normally used to transport food, beverages, and it’s what packing peanuts are made of. It’s also the exact same product that comes when you buy large electronics, the big white boards.

Transfer the food to a heat-proof container

So what should you do if you don’t reheat your food in the styrofoam container it came in ? Transfer it to an adequate food container, and reheat with that instead. It kind of defeats the whole comfort of not having to do the dishes, but it’s in your best interest, in the end.

Safe materials to reheat your leftovers

What kind of material you use to reheat your food is up to you, as long as it is suitable for the method you’re using. So for example:

  • Metal containers and plates go well in the oven and toaster oven, and even air fryer and stove. Do not use in a microwave, even if it’s just a thin metallic strip.
  • Glass and ceramic are both good for ovens and microwaves, but be careful when setting them down on cold surfaces. They are most likely not tempered, so place a kitchen towel on the table before you set the plates down. Do not use these on a stove top.
  • Microwave-safe plastic is a good option for microwaves, but do not use it anywhere else because it may melt. There should be a wavy symbol on the safe containers.

How can you tell if styrofoam is microwave safe ?

Microwave-safe styrofoam and polystyrene have a label or small sign on them. It’s usually a square with wavy lines, but it does not refer to regular ovens. Just microwaves. This is because microwaves work very differently than ovens and toaster ovens or air fryers.

Read also: Can You Reheat Curry ?

Microwaves heat the food by making the molecules inside the chamber vibrate at a microscopic level, while ovens heat through the air. A container that is structurally sound and made to withstand microwaves may not withstand the pure heat of an oven. This applies to anything that is deemed microwave safe, not just plastic or styrofoam.

What temperature can styrofoam withstand ?

Styrofoam will start to soften at 100 C/212 F, and melt at 240 C/464 F. An oven, toaster oven, and air fryer can easily get to those temperatures, so your styrofoam or polystyrene container is likely to melt. Worse, if you keep at it the container can eventually catch fire.

In a microwave it may behave differently, but it won’t come out in one piece if you heat it for long periods of time. Whatever you heat will eventually start to boil. And where it touches the styrofoam, the heat is much higher, and it begins to burn and melt.

This is why, even with microwave-safe contaieners made of anything, you should stir the food every now and then.

Is melted styrofoam toxic ?

Yes, melted styrofoam is toxic in that the fumes it releases are toxic on their own. A one-off episode of accidentally melting styrofoam won’t affect your overall health that much. But regularly eating reheated food in styrofoam containers will eventually lead to serious health issues.

The styrofoam itself, if ingested, is unlikely to actually melt in your stomach. So it may pass through intact. Even so, it’s generally a bad idea to eat from melted styrofoam containers. Even if you didn’t inhale the fumes or ingest the plastic, the fumes do settle onto the food itself.

Why do restaurants use styrofoam if it’s not heat-proof ?

The main reason restaurants and takeout places still use styrofoam containers is because they’re not meant to be reheated, they’re only meant to transport food. The food is safe if it’s hot and cooling down, but it’s not safe if it’s reheated in them.

As transport containers, styrofoam boxes and cups do the following:

  • are great insulators, keeping food and drinks hot or cold, as needed
  • are cheap, and lightweight, meaning the establishment doesn’t shell out a fortune for something they use heavily everyday
  • are only meant for transport, not reheating and eating out of them

What we, as customers, do at home with the styrofoam containers is really not the restaurant or takeout place’s responsibility. We tend to reheat the food right in the delivery container, since it’s easy, simple, and means we don’t have to wash any dishes afterwards.

But nowhere on the container does it explicitly state ‘please reheat this as is’. You may sometimes find containers that say they are microwave-safe, but that’s not very often and not the norm.

So in short, restaurants and takeout places only provide you with styrofoam containers to safely get your food home. It’s then your decision as a customer what you do with the food. The best thing to do is to transfer the food in a glass, metal, or ceramic container or plate and use that in an appropriate way to reheat the food. Even if it means washing a few dishes afterwards.

We know, because we’ve been there are we had a place that we routinely bought stews and soups from. And for quite some time, we reheated the soup in those containers, and we saw the edges start to soften a little. We stopped after doing some research, and after we noticed the containers never had that microwave-safe symbol on them.

So it may be wise for you to do the same. Transfer your food into something safe, and do what you want to the food. If you’ve got any other food curiosities be sure to check the related articles below, we’re always adding more food facts to make your life that much easier.