Functional and Bioactive Components from Mackerel (Scomber scombrus) and Blue Whiting (Micromesistius poutassou) Processing Waste

The use of fish processing waste from an oily fish model (mackerel, Scomberscombrus) and a white fish model (blue whiting, Micromesistius poutassou) as a source of functional and bioactive compounds was investigated.Gelatines were extracted from fish heads and skins using pre-treatment withdifferent organic acids (acetic, citric, lactic, tartaric and malic acids). Gelatines from fish bones were extracted after pre-treating the bones either chemically or enzymatically. The type of pre-treatment affected the yield, colour, turbidity, amino acid profiles as well as functional properties of fish gelatines. Mackerel gelatines formed stronger and more stable gels than blue whiting. Acetic acid pre-treatment of mackerel and blue whiting heads and skins produced stronger gelatine gels. The enzymatic pre-treatment of fish bones resulted in gelatines with poor rheological properties.Hydrolysates obtained from the hydrolysis of mackerel head and skingelatines with pepsin exhibited the highest antioxidant activity (DPPH ~ 80 %). These hydrolysates had high anti-inflammatory activity (inhibition of SSAO activity by 50 %) and antihypertensive activity (inhibition of ACE activity by 75 %). Skin gelatine hydrolysates, were also able to inhibit platelet aggregation.The hydrolysis of mackerel viscera with Flavourzyme produced hydrolysateswith high antioxidant activity (73 %) and inhibited the SSAO activity by 45.8 % and ACE by 60 %.Different procedures (chemical, physical or enzymatic) were developed to extract oil rich in ω-3 fatty acids from mackerel heads and skins. The yield varied significantly (p < 0.05) depending on the extraction method. The physicochemical properties of the majority of oils extracted were acceptable according to the Codex Alimentarius criteria. Polar oil fractions extracted from mackerel heads after enzymatic hydrolysis with Alcalase had high DPPH radical scavenging activity which was due to the presence of carotenoids.