Microplastics have become ubiquitous in the environment and are increasingly found in a variety of matrices, including in animal feed. At the same time, the presence of plastics from packaging materials in animal feed is still prohibited in the European Union. This is a major barrier preventing certain organic waste streams from being repurposed as feed. However, issues associated with the presence of plastic particles in feed for ‘conventional’ livestock such as poultry and pigs (e.g. accumulation in stomach/other tissues) may not pose a problem to reared insects such as black soldier fly larvae (BSFL). In the hypothetical absence of such transfer, insects reared on feed contaminated with plastics could potentially be repurposed as feed. Such reuse would be a major opportunity for a more circular food chain. The aim of this exploratory study was to develop a method to determine the potential transfer of microplastics from the substrate to biomass of reared BSFL. Tested plastics consisted of low-density polyethylene (LDPE) of three different sizes, and polyethylene terephthalate (PET); to mimic the types of synthetic polymers commonly used for food packaging. The results showed no significant effects of dietary exposure of tested (micro-)plastics on larval yield and survival. We benchmarked fluorescence microscopy through Nile Red staining against a newly developed technique utilizing polarised light optical microscopy to identify plastic particles in BSFL. Tested LDPE particles were virtually absent from the post-exposure larvae. PET was recovered from the larvae, although it is unclear what the exact mechanism for this transfer was. More research is needed to validate these experimental findings with plastics of different types and particle sizes.

Food-grade titanium dioxide (E171) is widely used in food, feed, and pharmaceuticals for its opacifying and coloring properties. This study investigates the formation of reactive oxygen species (ROS) and the aggregation behavior of E171 using the TNO Gastrointestinal (GI) model, which simulates the stomach and small intestine. E171 was characterized using multiple techniques, including electron spin resonance spectroscopy, single-particle inductively coupled plasma–mass spectrometry, transmission electron microscopy, and dynamic light scattering. In an aqueous dispersion (E171-aq), E171 displayed a median particle size of 79 nm, with 73–75% of particles in the nano-size range (<100 nm), and significantly increased ROS production at concentrations of 0.22 and 20 mg/mL. In contrast, when E171 was mixed with yogurt (E171-yog), the particle size increased to 330 nm, with only 20% of nanoparticles, and ROS production was inhibited entirely. After GI digestion, the size of dE171-aq increased to 330 nm, while dE171-yog decreased to 290 nm, with both conditions showing a strongly reduced nanoparticle fraction. ROS formation was inhibited post-digestion in this cell-free environment, likely due to increased particle aggregation and protein corona formation. These findings highlight the innate potential of E171 to induce ROS and the need to consider GI digestion and food matrices in the hazard identification/characterization and risk assessment of E171.