Raúl Pérez-Gálvez

Lipid characterization and properties of protein hydrolysates obtained from discarded Mediterranean fish species

BACKGROUND Discards are an important fraction of the by-products produced by the fishing industry. As a consequence of their low commercial acceptance, it is necessary to provide added value to these underutilized materials. In this study the lipid fraction of three discarded fish species in the western Mediterranean Sea, namely sardine (Sardina pilchardus), mackerel (Scomber colias) and horse mackerel (Trachurus trachurus), was characterized and the angiotensin I-converting enzyme (ACE)-inhibitory and antioxidative activities of their protein hydrolysates were evaluated. RESULTS Processing of these biomaterials led to oils with a high content of omega-3 polyunsaturated fatty acids (PUFAs), ranging from 220.5 g kg(-1) for horse mackerel to 306.0 g kg(-1) for sardine. Regarding the protein fraction, most of the hydrolysates presented ACE inhibition values higher than 60%, corresponding to IC50 values varying from 345 µg protein mL(-1) for mackerel to 400 µg protein mL(-1) for sardine. Moreover, most of the hydrolysates exhibited acceptable antioxidative activity, namely 35-45% inhibition of 1,1-diphenyl-2-picrylhydrazyl (DPPH). CONCLUSION This study suggests that the three discarded species evaluated are valuable raw materials for the production of bioactive ingredients such as omega-3 PUFAs and protein hydrolysates exhibiting antihypertensive and antioxidative activities.

Functional, bioactive and antigenicity properties of blue whiting protein hydrolysates: effect of enzymatic treatment and degree of hydrolysis

BACKGROUND Fish discards represent an important under-utilisation of marine resources. This study evaluated the up-grading of the protein fraction of blue whiting (Micromesistius poutassou) discards by the production of fish protein hydrolysates (FPHs) exhibiting functional, antioxidant, angiotensin-I converting enzyme (ACE)-inhibitory and antigenicity properties. RESULTS FPHs with low DH (4%) showed better emulsifying, foaming and oil binding capacities, particularly those obtained using only trypsin. FPHs with DH 4% exhibited also the stronger antioxidant activity, especially the one obtained using only subtilisin (IC50 = 1.36 mg protein mL-1 ). The presence of hydrophobic residues at the C-terminal of the FPH produced using subtilisin also led to the stronger ACE-inhibitory activity. However, FPHs with high DH (12%), which implies a higher proportion of short peptides, was required to enhance ACE-inhibition (IC50 = 172 µg protein mL-1 ). The antigenic levels of the FPH were also reduced with DH independently of the enzymatic treatment. Nevertheless, the highest degradation of fish allergens (e.g. parvalbumin) was also obtained when using only subtilisin. CONCLUSION These results suggest that added-value products for food applications can be produced from the protein fraction of discards.

Optimisation of the hydrolysis of goat milk protein for the production of ACE-inhibitory peptides

Goat milk protein was hydrolysed with subtilisin and trypsin. As input variables, temperature was assayed in the interval 45-70 °C for subtilisin and 30-55 °C for trypsin, while the enzyme-substrate ratio varied from 1 to 5%. The effect of the input variables on the degree of hydrolysis and ACE-inhibitory activity (output variables) was modelled by second order polynomials, which were able to fit the experimental data with deviations below 10%. The individual maximum values of the degree of hydrolysis and the ACE-inhibitory activity were found at conflicting conditions of temperature and enzyme-substrate ratio. Since such maximum values could not be reached simultaneously, a bi-objective optimisation procedure was undertaken, producing a set of non-inferior solutions that weighted both objectives.

Fish Discards as Source of Health-Promoting Biopeptides

Abstract The vast diversity of marine organisms is a source of enormous potential for obtaining bioactive compounds for use in the food industry. In this context, discards, which are defined as the fraction of the fish catch that is not retained onboard but rejected to the sea due to commercial standards, fishing regulations, or them being nontarget species, are regarded as a waste of resources and an environmental problem. The new EU Common Fisheries Policy introduced a discard ban for pelagic species on January 1, 2015. The composition of discarded materials (1%–18% lipids and 15%–20% proteins) means that they are receiving increased attention for their use in biotechnological applications. The six species studied in this chapter, namely, the axillary seabream ( Pagellus acarne ), small-spotted catshark ( Scyliorhinus canicula ), sardine ( Sardina pilchardus ), horse mackerel ( Trachurus mediterraneus ), bogue ( Boops boops ), and blue whiting ( Micromesistius poutassou ), represent more than 85% of the total discards in the Alboran Sea. This chapter mainly focuses on upgrading the protein fraction of the aforementioned species into biopeptides. To this end, compacting and separation stages were designed to obtain the lipid and protein fractions. The influence of enzymatic hydrolysis on the antihypertensive, antioxidant, anticholesterolemic, and antimicrobial activities of the proteins was also analyzed. In addition, the bioavailability of the biopeptides was analyzed using simulated gastrointestinal digestion. Finally, the methods employed for the characterizing and identification of the active peptides are also described. These biopeptides can be employed in the formulation of functional food.