Assessment of lipid oxidation in fish and fish products processed by cold plasma technologies

• Cold plasma technologies expect to accelerate lipid oxidation in fish products • Most studies are limited to global indices of primary and secondary oxidation products • There are contradictory results on the effects of cold plasma on lipid oxidation • Only few data on toxic oxidation products have been published so far • Biopreservatives effectively counteract the oxidative pressure of plasma reactive species Plasmas generated at or near ambient temperature are emerging as mild, selective and environmentally friendly technologies for extending the shelf-life of perishable fish and fish products. However, the high degree of unsaturation makes fish lipids highly susceptible to the reactive oxygen and nitrogen species (RONS) of plasmas, which can trigger the onset and/or progression of lipid oxidation, leading to the formation of off-flavours, the loss of nutritionally valuable components (polyunsaturated fatty acids, proteins, vitamins) and the formation of risky or toxic substances. Despite numerous experiments on the decontamination effects of cold plasma on fish and fish products, the evaluation of lipid oxidation has been limited to a few parameters. Most studies have focused on measuring global indices of primary and secondary oxidation products (peroxide value and thiobarbituric acid reactive substances, respectively) and some researchers have analysed total fatty acid composition as an indirect measure of the degree of oxidation. However, more advanced analytical methods for the direct quantification of volatile and non-volatile chemical species derived from the oxidation of fatty acids and sterols have been performed only to a very limited extent. The results on the effects of cold plasma on lipid oxidation in fish and fish products are contradictory. Although several studies show a pro-oxidant effect of RONS, others report no significant effects on lipid oxidation and even a lower rate of lipid oxidation during storage of fish products.