Thermal processing implications on microplastics in rainbow trout fillet

Heat treatment is an inevitable step in making meat and meat products ready for human consumption. Researches on ready-to-eat foods had shown that foods can also contain microplastics (MPs). The source of the presence of MPs in foods is: air, raw materials, food production stages, or plastics used in packaging. This study was carried out to evaluate the possible effects of the sous-vide (So-Vc) technique applied in rainbow trout (Oncorhynchus mykiss) fillets at different temperatures and time intervals on MPs degradation or migration mechanisms and the level of uptake by humans. For this purpose, 7 treatment temperature × 3 various cooking times and So-Vc technique were applied on rainbow trout fillets. Then, in these fillets, MP presence, size, and shape were researched, as well as polymer types and possible levels of MP uptake by humans were determined. In the analyses, 1.27 ± 0.54 MP/g was found in 1 g of fish tissue. Dimensionally, 67% of MPs was detected as <50 µm and 8% of 500-1000 µm. The dominant shape was determined as a fragment, and the color was black. Six polymer types were determined. The results showed that high temperature (> 65°C) applications promoted polymer degradation. MP migration from packaging material to fillets was not detected. By calculations made on these findings, the lowest intake level by a human was estimated as 6140 MPs units/year. The obtained data provided the initial data to explore and optimize the current understanding of thermally processed products in terms of MPs. This study proved that the sous vide method causes polymer degradation at high temperatures and longer time periods.