I'm looking to develop freezer meals for my family. The meals will be frozen in plastic takeout boxes likely PET, or PET-lined paper/kraft bowls.

The frozen meals are likely to remain frozen even when opened by lunch time, and will have to be blasted in a microwave at medium for 15 minutes, or at high for 5 minutes. Either of these are practical and potentially unsafe.

It's the unsafe part I'm worried -- do these plastic boxes or paper bowls that say "microwave safe" really suitable for high power microwave?

  • I have already done this for a bit already. No issues with either material, visually. Except that one time I covered them in the microwave, the steam built up so much that the plastic had started to deform.
    – wearashirt
    Aug 3, 2019 at 0:52
  • You can reduce the peak local temperature by stirring a couple of times. Even with lasagne you can cut it in half and rotate each half. You can also start with the box upside down, especially if frozen. All to make the heating more even, which also means you get your food sooner.
    – Chris H
    Aug 3, 2019 at 13:43

2 Answers 2


Not all PET plastic are microwave safe; make certain the containers you buy are labelled as such.

see this link.

"Unlabeled plastic containers aren't necessarily unsafe for the microwave. But the lack of label just means that these plastics haven't gone through the battery of tests required to ensure microwave safety. Because there's no way to tell if these containers can hold up to microwave heat, it's best not to use them in the microwave."

and this;

"Many of our manufactures do not recommend HDPE for the microwave and we suggest that you avoid it unless the manufacture has specifically approved it. PET and polycarbonate should not be used for microwaving as they tend to absorb heat."


In the USA, the FDA requires testing of microwavable containers. According to this site:

Microwave-safe containers go through stringent FDA testing to ensure that, at temperatures reached in the microwave oven, the amount of chemicals that leach out of the plastic is no more than 100 to 1,000 times less than the amount shown to harm lab animals.

If they say "microwave safe" they are supposed to have met the above standard.

They go on to further state that the descrtiptor PET (polyethylene terephthalate), is not enough information to determine safety in the microwave, as some PET containers/material are/is microwave safe, while others are not.

You can also look at the container itself, as you can see here, there are several symbols that indicate whether a container is safe in the microwave.

But...there is some debate about the actual meaning of "microwave safe"...does it mean non-toxic? ....does simply mean the container will not melt and potentially burn the user?

Personally, I would avoid melting or shape changing containers, as that might mean a higher risk. In the end, you will have to be the judge for you and your family. I know it's less convenient, but, if you are really concerned, you could certainly remove the food from the storage container and into something like ceramic or glass to reheat.

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