Microplastic contamination in seafood: Comparison between fresh and canned samples

• First study comparing MPs in fresh and canned seafood of the same species. • Canned seafood had higher MPs contamination frequency and concentration than fresh. • All four species had more MPs per meal of canned samples compared to fresh ones. • Canned samples showed more variability in polymer types, colours and MPs sizes. • Canning processes may increase/alter MPs contamination, affecting food safety. Awareness of microplastics (MPs) pollution has grown in recent years, with studies reporting MPs contamination in marine ecosystems and seafood and raising concerns for human health. This study addresses a key knowledge gap by comparing MPs contamination in fresh and canned samples of four seafood species: European pilchard, Atlantic chub-mackerel, common octopus, and Mediterranean mussel. MPs were extracted (digestion in 30% hydrogen peroxide), quantified and characterized (polymer composition determined with Fourier Transform Infrared Spectroscopy), revealing a higher frequency of contamination (FC) and concentration in canned samples (FC= 60%, 0.107 ± 0.123 MPs g⁻¹) compared to fresh samples (FC= 37%, 0.038 ± 0.025 MPs g⁻¹). All species presenting a higher concentration of MPs per meal in the canned samples, mainly the Atlantic chub mackerel (0.037 ± 0.076 MPs g -1 of fresh tissue and 0.13 ± 0.15 MPs g -1 of canned tissue) and common octopus (0.005 ± 0.006 MPs g -1 of fresh tissue and 0.12 ± 0.13 MPs g -1 of canned tissue) that presented significantly higher MPs content in the canned meal ( p < 0.05). Principal Component Analysis indicated that canned samples had greater variability in polymer types, colours, and larger particle sizes, indicating possible contamination sources introduced during canning processing. The present findings suggest that canning processes can be an additional source of MPs, highlighting potential implications for consumer exposure and food safety. This emphasizes the need for further research to help understand the mechanisms of MPs transfer within seafood processing facilities.