Packaged potatoes can be contaminated with plastic in microwave: study

Scientists from the University of Almería have discovered that microwaving potatoes in the plastic bags they are sold in can cause some plastic materials to contaminate the potatoes. They have demonstrated for the first time that this process creates new substances that could potentially impact our health.

The Discover Foundation explained that the researchers looked at food sold in supermarkets. This food goes through many steps to make sure it’s safe to eat. One of these steps involves plastic. If they don't make the plastic to handle high heat, it can melt or allow harmful substances to enter the food.

To prevent this, there are special containers that can handle the heat of cooking. These are used for meals that are already cooked. But, as researcher Francisco José Díaz Galiano said, “We don’t know all the possible chemical transfers that happen when we heat packaged food.”

Frequently consumes it

"We chose this food because it is basic and is usually consumed frequently. In addition, it has a chemical composition that could interact differently with plastic materials," Díaz Galiano detailed.

Scientists carried out this first case study in what they call 'undirected analysis', meaning they performed chemical analytical tests without knowing exactly what they were looking for. This process required them to exhaustively examine the samples, and it enabled them to identify all the substances that emerged during the cooking process of the potatoes in the plastic containers.

Thus, the experts first purchased bags of potatoes from a local supermarket in Almería, which had packaging specifying their suitability for combined cooking. Then they cooked them in various ways: crushed, whole, bagged, or unbagged. They boiled the potatoes in distilled water and microwaved them using the original packaging and a microwave-safe glass container.

The experts explained that they followed the cooking times specified on the product labelling, and for comparison, they also studied the uncooked potatoes.

Next, they used a substance known as a simulant in laboratory tests to simulate the interaction between materials like food packaging and real food. The experts replicated the chemical interactions between packaging and potatoes using the simulants to understand how the plastic in the bags affects the molecular composition of cooked potatoes. The industry widely uses this method in the agri-food sector to determine the safety of packaging.

Finally, using an analytical technique called high-resolution mass spectrometry, the experts identified the chemical substances and compounds in a sample, in this case, potatoes cooked differently.

Compound formation

In this way, experts identified a series of polymers (plastics) that only transfer when cooking the potatoes inside the bag in the microwave. Thus, they found an unknown compound made up of two molecules, like two pieces in a puzzle.

A natural product, maltose, is the source of one of them. Cooking certain foods produces this sugar. It poses potential harm due to its high glycemic index. Consumption in large quantities can impact blood sugar levels because of its rapid conversion into glucose.

"On the other hand, they have not yet been able to identify the synthetic product from which the other molecule originates," continues Díaz Galiano. Experts deduce that the heating of plastic and food in microwaves instigates chemical reactions, thereby forming the compound 'in situ'.

"We understand the formation process, but we haven't precisely determined what the compound is or its exact origin". However, Díaz Galiano explains that we know it is produced in this manner and since maltose partially composes it, the health implications remain unclear.

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