What types of containers are safe to use in the microwave and oven?

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Microwaves have been a great invention for our busy, modern lives, enabling us to enjoy meals within minutes. A bonus is that microwaves can cook food while retaining nutrients just as well as conventional methods such as steaming, according to the CSIRO.

Regular ovens are also an excellent cooking method for such meals as roasts. It is also a healthier cooking method than pan-frying and other methods, with less oil required and more nutrients preserved your food. Roasting also gives your food a deeper and more tasty caramelised flavour. Of course, the oven is where you can make all those tasty baked treats like cakes, cupcakes, and brownies, too.

Whether you are using the microwave or the oven, you need to consider the suitability of containers and cookware that you will cook with for your health and safety. You should think twice about reusing your plastic takeaway container in the microwave. 

The concerns mainly relate to the chemicals in these containers that can melt and leach into your food. For example, Bisphenol A (BPA) and phthalates in plastic have been linked with numerous health issues. The chemicals can interfere with hormones like oestrogen and testosterone, negatively affecting some organ systems. Science Line reports consuming phthalates is associated with health disorders, including high blood pressure and cardiovascular disease, while consuming BPA is associated with kidney disorders.

The other safety issue is that some containers may catch fire in the microwave.

Here is what you need to know about which containers and cookware to enjoy cooking various meals, knowing you won't burn the house down and with peace of mind for your health. 

Containers that are safe to use in the microwave

Glass, ceramic, and plastic containers labelled for microwave oven use, are recommended as safe by The US Food and Drug Administration (FDA). 

The key factor in determining which containers are designed as suitable for microwave cooking is by checking for the microwave-safe label on the containers. If it does not have the label, it would be best not to use the container to microwave your food.

However, according to the CSIRO, "There are no standards currently available for claims such as 'microwave-safe.' Any concerns about the safety of such products should be referred to the manufacturer."

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Some additives used in the manufacture of plastics may migrate into food, especially at high temperatures, the CSIRO reports. Even if a container has been labelled microwave safe, it is still unclear whether any plastics and how much can leach into your food. 

First, the microwave-safe label only means it won't warp or melt the plastic. As an article by Science Line explains, the container can still contain harmful chemicals such as BPA and phthalates. Look for the label to see if they have such chemicals. 

"Looking at the recycling number on your plastic can give a helpful hint (but not necessarily a definitive one)" Science Line states. Steer clear of those labelled with #3, #6, and #7.

Second, it's still unclear what level of exposure to plastics' endocrine-disrupting chemicals can lead to adverse health outcomes. Even so, scientists recommend limiting unnecessary exposure to the heating of plastics. Heat is a crucial factor that increases the risk of exposure to harmful chemicals in plastic.

In summary, it's best to use glass or ceramicware labelled as "microwave safe" when cooking or reheating food. Where possible, take the food out of plastic and reheat it in the microwave in a glass or ceramic container.

Containers that are NOT safe to use in the microwave

The following types of containers are considered unsafe for microwave use, so be sure to transfer their contents into a microwave-safe container before reheating.

  • Styrofoam containers. As Choice explains, you should be wary of heating Styrofoam takeaway containers as heating them may cause harmful chemicals to leach into your food.
  • Plastic wrap. Some types of plastic wrap are microwave safe and some aren't. To be extra cautious, remove it completely or at the very least ensure any plastic wrap does not come into contact with your food when microwaving.
  • Metal, metal-edged or glazed bowls, aluminium foil and even twist ties. These materials should never be used, as Fire and Rescue NSW warns, as the metal can cause arcing, which can lead to a fire. 
  • Recycled paper in microwave ovens. This is also advised against unless they are specifically approved for microwave use. Fire and Rescue NSW states, "recycled products, including paper towels, have minute metal flecks which can cause sparks and even flames."

Containers that are safe to use in the oven

As with microwave ovens, the easiest and best way to determine whether you should use a piece of cookware in your oven is the oven-safe symbol. 

Generally, oven-safe pans are usually made of copper, ceramic, cast iron, stainless steel, and food-grade silicone. However, be aware of pans with plastic or wood handles, as these cannot be used in the oven.

Some pans have a non-stick coating which may make the pans less heat resistant. They may also have a lid that is not oven safe. Check the instructions with the pan or contact the manufacturer about both of these factors.

Ceramics are generally suitable; however, check for the oven-safe label on those decorated with adhesive designs or if the ceramics are glazed. 

While oven-safe glass is fine to use in the oven, try not to subject it to temperature shocks. For example, avoid placing it straight in a scorching oven or moving it from a hot oven to cold water.

Containers that are NOT safe to use in the oven

The following types of containers are not safe for use in the oven.

  • Plastic. Some plastics can withstand heat, but they can be challenging to identify. So unless you can check with the manufacturer, it would be best to avoid using plastic cookware in the oven.

  • Wood. There's a high chance wood will warp. You will likely get splits along the glue lines if it's glued.

  • Cardboard. Even if your oven is set to its lowest temperature, putting cardboard into an oven increases the fire risk.

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Tracey Cheung
Written by
Tracey Cheung

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