Is it advisable to heat plastic in the microwave?

Domestic life is surrounded and facilitated by packaging made of synthetic material of organic origin composed of polymers. So it is very likely that we will heat plastic in the microwave. Then we ask ourselves if this practice is healthy.

Familiarity hasn't stopped alarms from going off. We know that when heating food in microwaves, molecular vibration alters its chemical composition. Similarly, the packaging can also be modified.

The debate is extensive and is full of arguments for and against the use of the microwave. There are detractors and those who argue that with the right plastic and knowing the properties of food, it is safe, as declared by the World Health Organization (WHO). Discover in this article the suitable plastics and the risks when using the microwave.

What types of plastic are there?

Plastics are classified as natural and synthetic. Synthetics include thermoplastics, thermosets, and elastomers. According to the established codification, they are identified with a Möbius triangle, the international recycling symbol, and a numbering that goes up to 7:

  1. PET (polyethylene terephthalate): it has many properties, such as transparency and admission of colorants. It's tough, lightweight, and easy to recycle. It is usually used to pack drinks.
  2. HDPE (high density polyethylene): it is flexible, although with some rigidity. Resists chemical impacts and high and low temperatures. Colorless and almost opaque, easy to print, paint or stick on. It is used in packaging for food, cleaning products or motor oil.
  3. PVC (polyvinyl chloride): It is a very flexible and transparent plastic, common in bags, laboratory containers or frozen food. Once recycled it can be used in containers, bins and pipes.
  4. LDPE (low density polyethylene): with little margin for recycling and the least used in the food chain due to its ease of releasing toxins. Resists acids. Due to its hardness, it is used for tubes, pipes, medical equipment, detergent bottles and other applications.
  5. PP (polypropylene): also resistant, with thermal stability, easy to mold and color. We see it in bottle caps, cold cuts and diapers. Resists chemical agents, boiling water and detergents. It is the only one that the World Health Organization recommends for coming into contact with food.
  6. PS (polystyrene): known as plastic glassIt is hard and is used in food, toys and laboratories.
  7. Others (plastic mix): difficult to recycle product composed of various materials. It is used in many objects such as bottles, baby cups, medical containers, car parts and compact discs.

The triangle with the connecting arrows is the recycling symbol and, in plastics, indicates that they are suitable for it.

Discover: 6 types of containers that you can recycle to make pots

Which are microwave safe?

Following the regulations and identification codes, microwave safe containers are numbered 1, 2 and 5. Either they have the inscription "Microwave safe". Only these are designed to be baked without altering their physicochemical stability and without toxic particle migration.

With bottles you have to be careful, since for decades they were made of polycarbonate. This material in the microwave releases bisphenol-A, an endocrine disruptor. Currently its manufacture is prohibited, being replaced by polypropylene or polyethersulfone, which can get hot. However, let's confirm on the product labels that they are BPA free.

As we can see, the variety of plastics is abundant and at home we usually reuse them. In fact, we convert containers that were not designed for that purpose into food or water containers; or at least not in a lasting way. Or, we believe that because they are plastic they are used to heat momentarily in the microwave.

We recommend reading: How to heat breast milk?

What are the risks?

Far from being inert, certain plastics subjected to heat or cold release dioxins, poisonous and carcinogenic substances. These pass into food in a chemical process known as migration.

Although some analyzes estimate an overestimation of the migration process, the crossing of scientific arguments calls for prudence. Let's see some examples:

  • If the container has the number 7 it means that it has bisphenol. In large quantities it can be harmful to the body. It is an exogenous substance that, according to research, is related to obesity, endocrine disorders and chronic degenerative diseases.
  • Those with the number 3 and acronyms PVC They contain phthalates, chemical compounds used as plasticizers, harmful to health.
  • Never heat food in the microwave in plastics with the numbers 4 or PVC (polyvinyl chloride) or the 6 or PS (polystyrene).

Another study revealed that people who frequently use the microwave do not know the right plastic in a high percentage. Worse still, they use any container and overheat the food. This increases the possibility of migration of foreign substances from the surface of the material to the food.

To this is added what is derived from life and work guidelines that promote reheating of high-fat foods. In fact, migration increases when products with these characteristics are heated and the contact time is extended.

Other options for not heating plastic in the microwave

If we do not have plastic suitable to enter the microwave, let's use glass or ceramics that will withstand the temperatures of heating food without problem. Even, as it could be a few seconds, resorting to paper or cardboard, preferably white, will not cover any risk.

Among the best options we have silicone and glass pyrex, which we can use in both microwave ovens and conventional ones.

The metal ones have been discarded to enter the microwave. Currently, per manufacturers' recommendations, you can afford aluminum foil. Containers made of this material designed to be used in the microwave oven are even available on the market.

Technological development allows us to currently have materials other than plastic to use in the microwave.

To heat plastic in the microwave, check the rating on the container

We recommend using the containers declared for such use by the manufacturers. The standard establishes that they come labeled with the specification of the type of plastic, so we must know and handle the information well.

On the other hand, if we have difficulty recognizing the plastic that can be safely baked into the oven, as a precaution we should opt for glass or ceramic. Necessary is also to determine if we only need to heat and not cook. For the former, the time is shorter, so that, whether it is plastic or glass, the exposure will not cover any problem.

The same does not happen when cooking. In this case, let's not undertake the task without the container identified with the characteristics required to prepare food in the microwave. Let's avoid those that have been deformed or are very wornas they are more likely to release chemicals.