Sustainable Recovery of Valuable Constituents from Octopus (Octopus vulgaris) Cooking Liquor

Cooking liquor (CL) from marine species processing has been reported to include a wide range of valuable constituents. In this study, the chemical composition of CL from octopus (Octopus vulgaris) processing, with and without a filtration process, was analysed. Regarding non-filtered CL, values of 15.30, 0.29, 8.85 and 174.53 g·L−1 CL for protein, lipids, ash, and total volatile base-nitrogen (TVB-N), respectively, were detected. The most abundant fatty acids (FAs) (g·100 g−1 total FAs) were C16:0 (37.8), C18:0 (20.8), and C22:6ω3 (13.4). Values of 0.40 and 2.10 were obtained for polyunsaturated FA/saturated FA and ω3 FA/ω6 FA ratios. Macroelement content varied from 0.036 (Ca) to 1.81 (Na) g·L−1 CL. For microelements, values ranged between 0.0015 (Co) and 1.95 (As) mg·L−1 CL. Industrial filtration of CL led to decreased values of protein, lipid, ash, TVB-N, and C22:5ω3; in contrast, an increased presence of C14:0, C18:1ω9, C20:1ω9, and C22:1ω9 was detected. Filtration led to a ca. 50% decrease in macroelement presence. For microelements, this process led to losses of 20–40% (Ba, Pb), 40–60% (As, Fe, Mn), 60–70% (Co, Zn), and 84% (Cd). This study provides a first comprehensive characterisation of octopus cooking liquor as a potential source of bioactive compounds.