Lipid Indexes and Quality Evaluation of Omega-3 Rich Oil from the Waste of Japanese Spanish Mackerel Extracted by Supercritical CO2

Trash to Treasure: An Up-to-Date Understanding of the Valorization of Seafood By-Products, Targeting the Major Bioactive Compounds

Fishery production is exponentially growing, and its by-products negatively impact industries' economic and environmental status. The large amount of bioactive micro- and macromolecules in fishery by-products, including lipids, proteins, peptides, amino acids, vitamins, carotenoids, enzymes, collagen, gelatin, chitin, chitosan, and fucoidan, need to be utilized through effective strategies and proper management. Due to the bioactive and healthy compounds in fishery discards, these components can be used as functional food ingredients. Fishery discards have inorganic or organic value to add to or implement in various sectors (such as the agriculture, medical, and pharmaceutical industries). However, the best use of these postharvest raw materials for human welfare remains unelucidated in the scientific community. This review article describes the most useful techniques and methods, such as obtaining proteins and peptides, fatty acids, enzymes, minerals, and carotenoids, as well as collagen, gelatin, and polysaccharides such as chitin-chitosan and fucoidan, to ensure the best use of fishery discards. Marine-derived bioactive compounds have biological activities, such as antioxidant, anticancer, antidiabetic, anti-inflammatory, and antimicrobial activities. These high-value compounds are used in various industrial sectors, such as the food and cosmetic industries, owing to their unique functional and characteristic structures. This study aimed to determine the gap between misused fishery discards and their effects on the environment and create awareness for the complete valorization of fishery discards, targeting a sustainable world.

Formation of Lipid-Derived Flavors in Dry-Cured Mackerel (Scomberomorus niphonius) via Simulation of Autoxidation and Lipoxygenase-Induced Fatty Acid Oxidation

In this study, lipoxygenase (LOX) extracted from dry-cured mackerel was purified, resulting in a 4.1-fold purification factor with a specific activity of 493.60 U/min·g. LOX enzymatic properties were assessed, referring to its optimal storage time (1-2 days), temperature (30 °C), and pH value (7.0). The autoxidation and LOX-induced oxidation of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:2n9c), linoleic acid (C18:2n6c), arachidonic acid (C20:4), EPA (C20:5), and DHA (C22:6n3) were simulated to explore the main metabolic pathways of key flavors in dry-cured mackerel. The results showed that the highest LOX activity was observed when arachidonic acid was used as a substrate. Aldehydes obtained from LOX-treated C18:1n9c and C18:2n6c oxidation, which are important precursors of flavors, were the most abundant. The key flavors in dry-cured mackerel were found in the oxidative products of C16:0, C18:0, C18:1n9c, C18:2n6c, and C20:4. Heptanaldehyde could be produced from autoxidation or LOX-induced oxidation of C18:0 and C18:1n9c, while nonal could be produced from C18:1n9c and C18:2n6c oxidation. Metabolic pathway analysis revealed that C18:1n9c, C18:2n6c, EPA, and DHA made great contributions to the overall flavor of dry-cured mackerel. This study may provide a relevant theoretical basis for the scientific control of the overall taste and flavor of dry-cured mackerel and further standardize its production.

Screening of Lesser-Known Salted-Dried Fish Species for Fatty Acids, Tocols, and Squalene

The fillets and roes of 29 species of dry-salted fishes consumed in Eurasian countries were analyzed for fatty acids (FAs), tocols, and squalene, looking for derived health benefits. FAs were analyzed by GC-FID, and tocols and squalene were analyzed by HPLC-DAD. With some exceptions, docosahexaenoic (DHA, 22:6n-3), eicosapentaenoic (EPA, 20:5n-3), and arachidonic (ARA, 20:4n-6) acids were the prominent polyunsaturated fatty acids (PUFAs). The fillets of Scardinius erythrophthalmus reached the highest amounts of total FAs, ARA, and DHA (23.1, 1.82, and 2.49 mg/100 g). The fillets of Seriola quinqueradiata showed the highest percentages of DHA (34.4% of total FAs). Nutritional quality indices for fish lipids were favorable in all samples, especially the n-6/n-3 PUFA ratio, which was below 1 in most cases. α-Tocopherol was found in all fillets and roes, especially in Cyprinidae and Pleuronectidae species, and the highest value was found in the roes of Abramis brama (5.43 mg/100 g). Most samples contained tocotrienols at trace levels. The fillets of Clupeonella cultriventris contained the highest amounts of squalene (1.83 mg/100 g). Overall, dry-salted fish stand out due to their high concentrations of ARA, EPA, and DHA, as well as for α-tocopherol concentrations in roes.