Salmon (Salmo salar) Side Streams as a Bioresource to Obtain Potential Antioxidant Peptides after Applying Pressurized Liquid Extraction (PLE).

The pressurized liquid extraction (PLE) technique was used to obtain protein extracts with antioxidant capacity from salmon muscle remains, heads, viscera, skin, and tailfins. A protein recovery percentage ≈28% was obtained for all samples except for viscera, which was ≈92%. These values represented an increase of 1.5-4.8-fold compared to stirring extraction (control). Different SDS-PAGE profiles in control and PLE extracts revealed that extraction conditions affected the protein molecular weight distribution of the obtained extracts. Both TEAC (Trolox equivalent antioxidant capacity) and ORAC (oxygen radical antioxidant capacity) assays showed an outstanding antioxidant activity for viscera PLE extract. Through liquid chromatography coupled with electrospray ionization triple time-of-flight (nanoESI qQTOF) mass spectrometry, 137 and 67 peptides were identified in control and PLE extracts from salmon viscera, respectively None of these peptides was found among the antioxidant peptides inputted in the BIOPEP-UMP database. However, bioinformatics analysis showed several antioxidant small peptides encrypted in amino acid sequences of viscera extracts, especially GPP (glycine-proline-proline) and GAA (glycine-alanine-alanine) for PLE extracts. Further research on the relationship between antioxidant activity and specific peptides from salmon viscera PLE extracts is required. In addition, the salmon side streams studied presented non-toxic levels of As, Hg, Cd, and Pb, as well as the absence of mycotoxins or related metabolites. Overall, these results confirm the feasible use of farmed salmon processing side streams as alternative sources of protein and bioactive compounds for human consumption.

A Narrative Review of the Anti-Hyperglycemic and Satiating Effects of Fish Protein Hydrolysates and Their Bioactive Peptides.

Prevalence of type 2 diabetes and overweight/obesity are increasing globally. Food supplementation as a preventative option has become an attractive option in comparison to increased pharmacotherapy dependency. Hydrolysates of fish processing waste and by-products have become particularly interesting in a climate of increased food wastage awareness and are rapidly gaining traction in food research. This review summarizes the available research so far on the potential effect of these hydrolysates on diabetes and appetite suppression. Scopus and Web of Science are searched using eight keywords (fish, hydrolysate, peptides, satiating, insulinotropic, incretin, anti-obesity, DPP-4 [dipeptidylpeptidase-4/IV]) returning a total of 2549 results. Following exclusion criteria (repeated appearances, non-fish marine sources [e.g., macroalgae], and irrelevant bioactivities [e.g., immunomodulatory, anti-thrombotic]), 44 relevant publications are included in this review. Stimulation of hormone secretion, regulation of glucose uptake, anorexigenic potential, identified mechanisms of action, and research conducted on the most potent bioactive peptides identified within these hydrolysates are all specifically addressed. Results of this review conclude that despite wide methodological variation between studies, there is significant potential for the application of fish protein hydrolysates in the management of bodyweight and hyperglycemia.

Optimization of the Maillard reaction of xylose with cysteine for modulating aroma compound formation in fermented tilapia fish head hydrolysate using response surface methodology.

Aroma defects limit the application of fish protein hydrolysates as flavourings. This study aimed to develop a flavour concentrate from fermented tilapia fish head hydrolysate bymaximising the Maillard reaction production of meaty and roasted aroma associated compounds. We studied the optimal conditions of the Maillard reaction of xylose with cysteine to form meat-like odorants using response surface methodology. A 3-factored and 3-leveled Box Behnken design was employed, where the independent variables were cysteine concentration (A, w/v, %), heating temperature (B, °C) and heating time (C, min). 2-Methyl-3-furanthiol and 2-furfurylthiol were used as response factors. The optimal conditions were obtained as follows: A, 0.80%; B, 183.80 °C; C, 89.34 min. Compared with the controls, Maillard reaction products enriched the meaty and roasted aroma associated compounds in the treated hydrolysate. In conclusion, the treated tilapia fish head hydrolysate may be used as a base in development of new fish-based flavourings.

Effect of two-step microwave heating on the gelation properties of golden threadfin bream (Nemipterus virgatus) myosin.

The effects of different microwave heating (MH) methods on gelation properties of golden threadfin bream myosin and related mechanism were investigated in this study. Compared with conventional heating and one-step MH methods, myosin gel developed by 100 W coupled with 300 W MH method (MH100 + MH300) had stronger gel strength (p < 0.05) with more immobilized water (p < 0.05). Raman analysis suggested that this two-step method promoted the suitable unfolding of myosin before aggregation formation, and contributed to stabilizing the ordered secondary structure. Confocal laser scanning microscopy images revealed that 100 W microwave followed by 300 W MH produced a compact networked structure with small cavities and a thick cross-linked gel wall. Furthermore, from a perspective of molecular forces, the improvement of gelation properties by the MH100 + MH300 method were mainly involved in the enhancement of regular hydrophobic interaction and stabilization of weak protein-water hydrogenbonds.

Debittering of salmon (Salmo salar) frame protein hydrolysate using 2-butanol in combination with ß-cyclodextrin: Impact on some physicochemical characteristics and antioxidant activities.

Impacts of 2-butanol and ß-cyclodextrin (ß-CD) at various ratios and treatment times on bitterness, physicochemical and functional properties of Alcalase salmon frame protein hydrolysate (ASF) were investigated. ASF treated with 2-butanol at a ratio of 1:4 (w/v) for 20 min (ASFB) or with ß-CD at a ratio of 1:1 (w/w) for 30 min (ASF-C-1) had lower bitterness score than ASF (p < 0.05). Bitterness score of ASF (8.45) was reduced to the lowest score (1.32) when ASFB was subsequently treated with ß-CD at a 1:1 ratio (w/w) for 30 min (ASFB-C-1). Surface hydrophobicity of all debittered samples was lower than that of ASF sample (p < 0.05). The level of aromatic amino acids-containing peptides was reduced in ASFB-C-1 as shown by gel permeation chromatography. ASFB-C-1 sample had higher overall-likeness score but lower antioxidant properties than ASF (p < 0.05). The desired antioxidant activity could be achieved via increasing the amount of protein hydrolysate without imparting undesirable taste.

Enhancing tilapia fish myosin solubility using proline in low ionic strength solution.

The effects of using proline to solubilise fish myosin under low ionic strength conditions were studied. After solubilising myosin in 0.1 M NaCl containing 5, 10, 15, and 20 mM proline, respectively, it was observed that more than 80% of the myosin was effectively solubilised using 10 mM proline. The addition of 10 mM proline lowered the surface hydrophobicity of myosin from 18.25 to 8.22 mg/g, increased the amount of ß-sheet structure from 33.87% to 46.88%, both of which facilitated solubilisation. As revealed by transfer free energy measurements, the interactions between proline and tyrosine and tryptophan residues were more favourable. Furthermore, the ability of proline to shield hydrophobic sites of myosin and to partially break disulphide bonds helped to form myosin oligomer aggregates. Transmission electron microscopy images verified the effects of proline on myosin proteins. A solubilisation mechanism based mainly on chemical interactions between myosin and proline was proposed.

Prevention of protein oxidation and enhancement of gel properties of silver carp (Hypophthalmichthys molitrix) surimi by addition of protein hydrolysates derived from surimi processing by-products.

Surimi processing industry generates huge quantities of underutilized surimi processing by-products (SPB). This study aimed to investigate the potential antioxidant-cryoprotective and gelation-enhancing effects of SPB hydrolysates on silver carp (Hypophthalmichthys molitrix) surimi based on protein oxidation, protein degradation, and gel-forming ability analysis. Results showed that untreated surimi was particularly susceptible to frozen-induced protein degradation and oxidation as well as rapid deterioration in gelation properties. Compared with 4% sucrose-added surimi, partial replacement of sucrose with 2% trypsin- and alcalase-treated SPB hydrolysates effectively delayed the oxidation of cysteine, carbonylation of amino acids, loss of Ca2+-ATPase activity, and the destroy of structural integrity of myofibrillar protein in surimi. Moreover, addition of SPB hydrolysates significantly (P < 0.05) increased the initial gelation properties and reduced the loss in gelation and water-holding capacity in surimi with prolonged frozen storage. Therefore, SPB hydrolysates could be used as natural antioxidant-cryoprotectant and gel texture enhancer in freshwater fish surimi.

Effect of tyrosinase and caffeic acid crosslinking of turbot parvalbumin on the digestibility, and release of mediators and cytokines from activated RBL-2H3 cells.

Turbot can induce allergy in susceptible individuals due to the presence of parvalbumin (PV), a major fish allergen. This study aimed at evaluating the digestibility and the ability of PV to elicit the release of cellular degranulation, following treatment with tyrosinase (PV-Tyr), caffeic acid (PV-CA) and in combination (PV-Tyr/CA), using in vitro digestion and RBL-2H3 (passive rat basophil leukemia) cell line. The digestion assay products revealed that the stability of PV in simulated gastric fluid (SGF) was stronger, while in simulated intestinal fluid (SIF) was rather weak. Western blot analysis revealed that the IgG-binding abilities of the cross-linked PV were markedly reduced. Moreover, crosslinking hampered the release of cellular degranulation process in RBL-2H3 cell lines. PV-Tyr/CA showed highly significant reduction in the release rate of ß-hexosaminidase (66.02%), histamine (35.01%), tryptase (29.25%), cysteinyl leukotrienes (29.72%), prostaglandin D2 (34.96%), IL-4 (43.99%) and IL-13 (38.93%) and shown potential in developing hypoallergenic fish products.

Effects of l-arginine and l-histidine on heat-induced aggregation of fish myosin: Bighead carp (Aristichthys nobilis).

This research focused on the effects of l-arginine (l-Arg) and l-histidine (l-His) on the heat-induced aggregation of fish myosin. l-Arg/l-His increased the pH of the myosin solution from 6.82 to 8.74 and 7.24, respectively, and decreased the turbidity, aggregate size, shear modulus, and breaking force. The incorporation of l-Arg/l-His decreased the surface hydrophobicity during setting, but increased it during the two-step heating. The heat-induced aggregation of myosin was suppressed by both amino acids, with the inhibitory effect being greater for l-Arg than l-His. On one hand, the change in the pH played a critical role in suppressing the heat-induced aggregation of myosin. On the other hand, the characteristics of l-Arg/l-His themselves, such as net charges and particular R-groups, were another main contributor to aggregation suppression. Particularly, l-Arg/l-His could interact with exposed aromatic residues of myosin, and the interactions may dominate and overwhelm the burial of aromatic residues during two-step heating.

Ultrasound treatment improved the physicochemical characteristics of cod protein and enhanced the stability of oil-in-water emulsion.

Effects of ultrasonic pretreatment on the physicochemical changes of cod protein and the characteristics of subsequent oil-in-water emulsions were investigated. Ultrasonic treatment led to a reduction of particle size of cod protein. With increasing ultrasonic power, a significant increase in surface hydrophobicity of cod protein was found, due to the decrease of aggregates size as well as protein conformational changes of protein, but a decrease in total sulfhydryl group content was observed, probably because of the formation of disulfide bonds. Ultrasonic pretreatment promoted the adsorption of cod protein on oil droplets, resulting in higher ratios of adsorbed proteins. Diagonal electrophoresis illustrated that larger aggregates in adsorbed proteins were composed of cod actin. Reducing SDS-PAGE showed that adsorbed proteins contained a large amount of cod actin and two faint bands of light chains of myosin, and non-adsorbed proteins were composed of actin, tropomyosin, and the three light chains of myosin. More homogenous microstructures with smaller size of oil droplets were observed for the emulsions stabilized by higher intensity ultrasound treated cod protein, and the coalescence effect was improved obviously. The enhancement of the stability of cod protein coated-oil emulsions might be due to the smaller size of oil droplets and reduced oil droplets attraction by higher ratios of adsorbed proteins.

Using WPC-inulin-fucoidan complexes for encapsulation of fish protein hydrolysate and fish oil in W1/O/W2 emulsion: Characterization and nutritional quality.

The double emulsions and freeze-dried microcapsules containing fish protein hydrolysate (FPH) and fish oil (FO) were stabilized by complexs of whey protein concentrate (WPC) with inulin (Inu) and fucoidan (Fuc) in terms of physical characteristics (particle size distribution, morphology, encapsulation efficiency, solubility, …), oxidative stability, nutritional quality and in vitro release. Higher encapsulation efficiency and solubility were observed in Fuc-WPC microcapsules (86.31% and 30.26 mg/100 g, respectively). The combination of Fuc-WPC in the wall material showed higher oxidative stability than other wall material. The higher values of PUFA and SFA were observed in Inu-WPC Fuc-WPC microcapsules, respectively. The Fuc-WPC and Inu + Fuc-WPC micrographs showed a more porous structure compared to Inu-WPC. The mean particle size ranged from 536.8 ±â€¯52.70 to 842.36 ±â€¯21.41 nm. No significant differences were observed in the released oil and the fatty acid composition during gastrointestinal digestion. Sensory evaluation of fortified natural yogurt with microcapsules showed lower fishy flavor in Inu-WPC samples than those fortified with Fuc-WPC and Inu + Fuc-WPC. In general, the use of inulin with WPC as a wall materal resulted in good characteristics and sensory attributed, although the use of fucoidan with WPC conferred higher oxidative stability during storage.