Supermarkets increasingly offer vegetables that, with just a few minutes of microwaving in the same plastic bag in which they were purchased, are ready to eat.
Potatoes, cabbages or mixtures of various vegetables come already pre-cooked and, according to the producers' instructions, it is not necessary to change them to another container to cook them, although it is certainly necessary to bring them to the table.
Research shows that perhaps it would be better to change the support before cooking them.
Researchers from the University of Almería, led by Francisco José Díaz Galiano, have discovered that this microwave cooking process causes a “very pronounced” transfer, they explain, of plastic components from the bag to the vegetable.
The research, published in the journal
Food Chemistry
, has also identified that the action of the microwave in these cases creates a new compound in the potato, which they called HMPP-maltose.
According to Díaz Galiano, it is a “potentially toxic” compound, although new studies are still required to ensure or not that toxicity.
It does mean, in any case, a new way of ingesting a toxic component of plastic that adheres to the food itself.
The researchers from Almería had the feeling that “in a very energetic situation like that of the microwave, it was more than possible for certain components of the plastic to migrate into the food.”
And they began to do all kinds of tests with potatoes from different brands dispensed in bags and ready to be cooked in them.
They were made with all possible variants: “In the microwave in a plastic bag and in a microwave in a glass container, in both cases using the recommended time for the bag, or cooked in water over a fire.
In this case we gave them more time, between 10 and 15 minutes,” says Díaz Galiano, who remembers that the potatoes were also analyzed before cooking them.
They did 27 replicates of the experiment and “the same differences always appeared.”
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The experimentation gave rise to two results, “one intuited and another totally unexpected,” comments the researcher.
The one that did not cause them special surprise is the transfer of polymer from plastic to food.
“It has been demonstrated that there is a very pronounced migration of polypropylene glycol (PPG) polymers from plastic bags to potatoes only when they are cooked in the microwave in contact with the plastic.
That is, these PPGs, if present in the bags, are not transferred to the food, unless they are cooked together as is done in the microwave,” says Díaz Galiano.
This specific transfer, he adds, does not rule out that of “other compounds present in plastic.
"It is possible that others migrate to the food only by contact, but, in this case, we have focused on the differences during the cooking process in contact with the food."
For the researchers, the conclusions are undoubtable because "there are chemical compounds that are the exclusive result of the cooking process of the potato in contact with the plastic that are not observed either in the raw potato, or in the one cooked in water, or in the boiled one. in glass in the microwave.”
And along with this more or less expected result, the experience offered an unforeseen one that still has a way to go until its importance is determined.
It is the appearance of a new compound.
Plastics, Díaz Galiano details in a simple way, have among their components “synthetic photoinitiators, reactive compounds eager to interact and find something to join to create new plastic molecules, new polymers that will arise from the creation of structures that multiply and multiply.
And the microwave energy on the bag," he adds, "seems to trigger a process whose final result is a combination between one of those synthetic photoinitiators used in the synthesis of plastics, HMPP, and maltose, a natural product component of starch. the potato.
Since this structure, which they have provisionally named HMPP-maltose, “had not been described before, its properties cannot yet be determined, including its toxicity or safety,” says the researcher.
The signs, however, are not positive for health because, in any case, explains the also professor of analytical chemistry, “we can affirm on the one hand that HMPP –2-hydroxy-2methylpropiophenone– in itself is toxic and, on the other hand, that studies using
software
models indicate that the HMPP-maltose combination is potentially toxic to living beings.”
For now, they are investigating possible synthetic routes to create said compound.
“Then, its properties can be evaluated,” he concludes.
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The toxicity or not of a plastic for food use has been regulated by the European Union since 2011 in its Regulation on plastic materials and objects intended to come into contact with food.
In summary, the suitability of the material is determined from tests that analyze the interaction of foods with the so-called “food simulants”, products that in the tests simulate being plastic wrappers.
There are six simulants, five of them liquid – acetic acid, vegetable oil and three dilutions in different proportions of ethanol and water – and a final solid, called Tenax TA, which is used, for example, to analyze powdered soup sachets.
The interaction between food and these simulants determines their safety based on whether or not they are transferred to the food.
Díaz Galiano believes that the method is not totally reliable today because they reduce all food possibilities to only six groups and because after experimenting with potatoes also with simulants, no transfer of these to the tubers was determined, so they did not finish to exercise its theoretical plastic role judging by the results with the real material.
“The tests determined that there was no transfer of the food simulant either by mere contact with the plastic, neither before nor after cooking,” he says, which contradicts what happens when cooking the potato in its bag.
“The transfer of plastic polymer components and their additives to food is a well-known and studied issue,” comments Nicolás Olea, doctor, professor at the Faculty of Medicine of the University of Almería, when analyzing this study from the University of Almería. Granada and expert in health and environment.
This transfer "places plastic materials for food and kitchen use, in continuous doubt about their safety and in the imperative need to subject any new material to analysis, given the plethora of chemical compounds that plastic transfers to food, continues .
“Unfortunately, as the researchers of this pioneering work demonstrate, the protocols to investigate this transfer fail in two aspects.
On the one hand, because they do not cover all possible combinations of cooking methods and type of food.
On the other hand, what is most striking in this work is that it has never before been evaluated which new chemical compounds appear in food when plastics are used in its preparation.”
The conclusion for Olea is resounding: “Not only is stricter control of any proposed innovation necessary—a task that far exceeds the possibilities of the current food safety and control system—but it is the obligation of the producer and the seller to warn the public. about the risks in changes to the usual way of cooking.
It is not ethical to wait for the European Food Safety Authority (EFSA) to give its opinion on the issue; you should simply let the public know that cooking potatoes in the microwave using ready-to-cook plastic containers poses a risk of exposure to toxic contaminants that you would never encounter. boiling them in your usual pot.
There is nothing simpler,” concludes the Granada researcher, author of the book
Liberate yourself from toxics
.
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