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Microscopy method can detect microplastics in farmed insects

Researchers from Wageningen Food Safety Research (WFSR), part of Wageningen University & Research, have developed a method for detecting microplastics in farmed insects. This is important because insects can be reared on residual flows or food waste, which may contain plastic packaging materials. This is seen as a promising source of sustainable and circular proteins.

The researchers have tested the method by growing black soldier fly larvae on a nutrient substrate to which commonly used plastics had been added, polyethylene and PET. After the larvae were fully grown, they were analyzed and found to contain little to no plastic particles.

These results could be a first step towards making the food and animal feed chain more circular and sustainable with the help of insects. In addition, animal feed can also become cheaper with insects as a source of protein.

The work is in the Journal of Insects as Food and Feed.

The method

The detection of microplastics in, for example, water, beer or other liquids has been possible for some time and is based on filtering. However, finding microplastics in an insect sample requires a completely different approach. In the study, the researchers deliberately mixed the insect food of the larvae with plastics. After the larvae were fully grown, they were removed from the nutrient medium, cleaned and processed for sampling.

This processing consisted of first grinding the insects, then dissolving as much of the organic material as possible in hydrochloric acid and hydrogen peroxide, and then filtering. It was checked in advance that these solvents would not affect the tested microplastics. The undissolved exoskeletons (insect shell) and any microplastics could be distinguished from each other using an optical microscope with polarized light.

Broader application

The new method and results are promising for broader application, but more research is needed to check whether other types of plastics show the same results. In March 2024, a public-private project (PPP) was started under the name "Safety of packaging material in insect feed."

This project will also include the transfer of chemical contaminants that may be present in packaging materials. If this research shows that there is hardly any transfer of plastics and chemicals to insects, the tolerance limit for packaging materials in insect food may possibly be increased in the future.