Monitoring of the lipid oxidation of dehydrated by-products coming from tuna processing

The increase in waste generated by the fish supply chain has a significant impact on environment and moreover it represents a big economic problem; in addition, it is necessary to consider the loss, within fish leftovers and their processing by-products [1], of precious compounds with high nutraceutical interest, with a view of a “zero waste economy”. University of Genoa is one of the 34 partners in EcoeFISHent, a European Union’s Horizon project (H2020-LC-GD-2020-3, https://cordis.europa.eu/project/id/101036428/it) implementing systemic solutions through multilevel circular value chains for an eco-sustainable valorization of fishing and fish industries side-streams. By-products coming from canned tuna processing, made up of fillets scraps, fishbones, heads, once separated from viscera, have been dehydrated by a patented process in order to stabilize this highly perishable biomass and obtaining a powdered material with a residual humidity of about 5%. The bromatological analysis of the biomass before and after the dehydration step have been performed (humidity, protein, lipid, ash, and carbohydrates contents). Since lipid oxidation [2] may be considered one of the most dangerous modification in such an unsaturated food matrix, its monitoring seems mandatory in order to evaluate the possibility of further valorize these by-products. As far as fish oils are concerned, the analytical determinations suggested by Codex Alimentarius [3] are the Peroxide value (PV) and the Anisidine value (AV) to evaluate primary and secondary oxidation products respectively and combining them in the Total oxidation value (ToTox). Looking for greener and more rapid approaches exploitable for the lipid oxidation monitoring of tuna byproducts, the following determinations have been proposed: - the Hara-Radin method to extract the lipid fraction has been proposed to replace the Folch method in order to avoid the use of halogenated solvents ; - the spectrophotometric analyisis of the conjugated dienes was performed alternatively to PV test for the primary oxidation products evaluation ; - the TBARS (Thiobarbituric Acid Reactive Substances) test [4] directly applied on the food samples, avoiding the lipid extraction step, has been proposed to evaluate the secondary oxidation products.