Green extraction of type A protein concentrate from Long-jawed Mackerel (Rastrelliger kanagurta) leftovers using choline chloride-based deep eutectic solvents

Protein concentrate (PC) represents a viable approach to mitigating the global undersupply of accessible animal-derived protein, and Indonesian Long-jawed Mackerel (Rastrelliger kanagurta) is a good raw material. This study examines the influence of extraction parameters on the nutritional quality of ChCl:urea-based mackerel protein concentrate (FPC), which has lower toxicity than conventional solvents. The best-performing conditions within the tested range for FPC production were identified as a ChCl:urea (1:2) mixture at 60 °C, with a fish mass-to-solvent volume ratio (FMSVR) of 1:2 for 60 min. The resulting FPC was classified as Type A, the highest grade, with protein, lipid, and moisture contents of 84.49%, 0.28%, and 9.22%, respectively. SDS-PAGE analysis confirmed that the mackerel FPC contains 15 protein bands with molecular weights (MW) varying from 5 to 250 kDa. The primary MW range of 33 – 120 kDa identified in FPC indicates a complex protein profile, which suggests potential oil-binding and thickening properties. Given these characteristics, the FPC serves as a promising candidate for further investigation in functional food products.