The oven a microwave It is now present in almost all kitchens, it works by emitting electromagnetic waves that make the water molecules contained in food vibrate: it is precisely the transformation of this kinetic energy (movement energy) in thermal energy to heat the food very quickly.
Not all containers, however,, they get along with the microwave. For example, metals, such as aluminum or iron, reflect the electromagnetic waves generated by the microwave, preventing uniform cooking, and in rare cases they can also generate sparks. Plastic and polystyrene, during microwave heating, can instead deform or release dangerous substances in food, such as phthalates. According to the FDA (Food and Drug Administration) The glassceramic, cardboard and some types of plastics, but only those that report the wording “SAFE microwave“, That is “safe to use in the microwave”, or the special symbol.
What to avoid putting in the microwave: the materials not to heat
To understand why metals should not be inserted in the microwave, we have to do a couple of premises. The atoms consist of three elementary particles: protons (positively loaded), electrons (negatively loaded) and neutrons (which as the name says, have a neutral electric charge). Protons and neutrons focus in the center of the atom by constituting the nucleus, while the electrons orbit you, that is, they turn around (this is a great simplification, but we will have to satisfy us).
Metals such as aluminum, iron and copper
When metal atoms (such as aluminumcopper or iron) bind together they do not keep their electrons tight more external, but in part they give them back: the electrons become delocalizedMeaning what free to move in all the material. Using a metaphor, we can imagine a sea made of electrons and, here and there, of the islands of lonely nuclei. It is precisely this cloud of mobile electrons that makes metals Excellent conductors both electric and heat current.
Microwaves are a type of electromagnetic wave: Like all waves of this type, they are formed by the union of two invisible fields, one electric and one magnetic one, which travel in the space oscillating. When these waves affect our food wrapped in foil (made of aluminum), the free electrons of aluminum atoms move following the oscillation of the electric field, in turn producing a New electromagnetic field which opposes that of the electromagnetic wave generated by the microwave. The result is that the wave does not penetrate, but comes rejectionthat is, reflected as on a mirror: The cooking of the food will therefore not be efficient.
But it did not end here: the concentration of electric charges in some particular points – such as edges, tips, folds, typical of the crumpled foil – can be very high, precisely because the electrons are shared and free to move. In these areas, such an intense electric field can be generated ionize the surrounding air molecules, i.e. from tear them some electrons. This process generates sparks (in technical jargon, “arcing“), who can damage the oven or, in the worst cases, trigger a fire.
Some types of plastic are not sure
Another material to be used with caution is the plastic. Not all plastics are the same: some are designed to resist heat and report the wording “SAFE microwave“or a pictogram depicting a small oven or waves, while others, if heated in the microwave, can deform or even release dangerous substances in food.
A study shown on Europe PMCfor example, explains that some domestic containers contain called molecules phthalatesused as plastici, which during heating in the microwave can migrate to foodrepresenting a problem as they are classified as Endocrine interfering (EDC), i.e. chemical compounds capable of altering the organism’s hormonal balance.
In another study published by some researchers of Rochester Institute of Technology Three materials were heated in the microwave widely used in food packaging: the polyethylene Tereftolato (Pet), Polistirene (which many know how polystyrene), and polypropylene (Pp). The results showed that these polymers can release small quantities of organic compounds and other migrant substances that end up in food: we therefore use them in the microwave only if they report the wording that are suitable for doing it.
What can be put in the microwave oven: what are the safe materials
In addition to plastics with the appropriate symbol, we can also use other containers to cook or heat lunch in the microwave. According to Food and Drug Administration (FDA), materials such as glassceramic and paper or cardboard They are safe, because electromagnetic waves cross them without encountering resistance and without doing any damage. The only problem: the heat of the food can also warm the dish, then be careful not to burn yourself!
