Collagen characteristics of farmed Atlantic salmon with firm and soft fillet texture

Comparative Analysis of Nutritional Quality, Serum Biochemical Indices, and Visceral Peritoneum of Grass Carp (Ctenopharyngodon idellus) Fed with Two Distinct Aquaculture Systems

This study scrutinized the nutritional quality and serum biochemical indices of grass carp (Ctenopharyngodon idellus) cultivated in traditional pond intercropping (TPI) and in-pond raceway system (IPRS) aquaculture setups. The findings showed that the TPI group exhibited a superior water-holding capacity, while the IPRS showcased heightened crude lipid content and levels of textural properties such as springiness. Moreover, significant differences emerged in the fatty acid profiles, with the TPI group manifesting higher total polyunsaturated fatty acids (ΣPUFAs), EPA, DHA, and Σn-3, while the IPRS group exhibited elevated total saturated fatty acids (ΣSFAs). In terms of amino acids, valine and histidine levels were notably higher in the IPRS group, whereas lysine levels were reduced. Volatile compound analysis revealed significant variations, with the IPRS group containing more volatile substances with a better aroma, resulting in a better odor. The IPRS group performed better in serum biochemistry analysis. Additionally, grass carp in the IPRS group displayed an improved structure and greater coverage area of the visceral peritoneum, appearing lighter in color compared to the TPI group. TPI mainly influences nutritional elements; IPRSs primarily affect muscle texture, serum biochemistry, and overall health. This study aims to fill the gap in quality comparison research and provide an important scientific basis.

Increasing Functionality of Fish Leather by Chemical Surface Modifications

Fish skin is a by-product of the fishing industry, which has become a significant environmental pollutant in recent years. Therefore, there is an emerging interest in developing novel technologies to utilize fish skin as a versatile raw material for the clothing and biomedical industries. Most research on finishing procedures is conducted on cattle leather, and practically very limited information on fish leather finishing is found in the literature. We have developed three functional surface finishing treatments on chromium (CL)- and vegetable (VL)- tanned salmon leather. These treatments include hydrophobic, oil repellent, and electro-conductive ones. The hydroxyl functional groups present on the surface of the leather were covalently grafted with bi-functional aliphatic small molecule, 10-undecenoylchloride (UC), by esterification reaction forming hydrophobic coating. The surface hydrophobicity was further increased via covalent binding of perfluorodecanethiol (PFDT) to the double bond end-groups of the UC-modified leather via thiol-ene click chemistry conditions. The oleophobic coating was successfully developed using synthesized fluorinated silica nanoparticles (FSN) and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), showing oil repellency with a contact angle of about 100° for soybean oil and n-hexadecane. The electrically conductive coating was realized by the incorporation of conjugated polymer, polyaniline (PANI), via in situ polymerization method. The treated leather exhibited surface resistivity of about 5.2 (Log (Ω/square)), much lower than untreated leather with a resistivity of 11.4 (Log (Ω/square)).

Comparative study on nutritional quality and serum biochemical indices of common carp (Cyprinus carpio) aged 11 to 13 months aged cultured in traditional ponds and land-based container aquaculture systems

In the study, the physical characteristics, nutritional composition, mineral elements, volatile substances, and serum biochemistry of common carp (Cyprinus carpio) after rearing for two months were compared and analyzed to reveal the differences in muscle nutritional quality and serum biochemical indices between fish raised in traditional ponds (TP) and land-based container recirculating aquaculture systems (C-RAS). One hundred fish were selected from each aquaculture mode for the following experiments. Results show that: in terms of physical properties, C-RAS frozen seepage rate was significantly lower than that in TP (P < 0.05), the chewiness, gumminess, springiness, resilience, adhesiveness, cohesiveness, and shearing of C-RAS group were significantly higher than in TP (P < 0.01). Regarding muscle nutrients, the moisture, the crude lipid contents of C-RAS group were significantly lower than that of the TP group (P < 0.05), and the crude protein content of C-RAS group was extremely significantly higher than that in TP (P < 0.01). The saturated fatty acids (ΣSFA) and polyunsaturated fatty acids (ΣPUFA) in the muscle of C-RAS were significantly higher than that in TP (P < 0.01), and monounsaturated fatty acids (ΣMUFA) of C-RAS were significantly lower than that in TP (P < 0.01). Methionine content in C-RAS was significantly higher than that in TP (P < 0.05). In terms of mineral elements, the contents of K and Se in C-RAS were significantly higher than those in TP, and the content of Zn in C-RAS was significantly lower than that in TP (P < 0.05). In terms of volatile substances, nonanal, octanal, and benzaldehyde in C-RAS were significantly lower than those in TP(P < 0.01), 2,3-diethyl-5-methylpyrazine, ethyl 3-methylpentanoate, butyl formate were significantly higher than those in TP (P < 0.01). In terms of serum biochemistry, the glucose index in C-RAS was extremely significantly lower than that in TP group, total protein, albumin, alkaline phosphatase, and triglyceride were extremely significantly higher than those in TP (P < 0.01). Experiments show that the aquaculture mode has a large impact on the physical properties of the common carp, nutrients, mineral elements, volatile matter, and serum biochemical. In conclusion, the common carp cultured in C-RAS systems had better muscle nutritional quality, which provides a reference for future regulation of fish nutritional quality by C-RAS.

Valorization of Salmo salar Skin Waste for the Synthesis of Angiotensin Converting Enzyme-1 (ACE1) Inhibitory Peptides

One of potential inhibitors which is widely used for the clinical treatment of COVID-19 in comorbid patients is Angiostensin Converting Enzyme-1 (ACE1) inhibitor. A safer peptide-based ACE1 inhibitor derived from salmon skin collagen, that is considered as the by-product of the fish processing industry have been investigated in this study. The inhibitory activity against ACE1 was examined using in vitro and in silico methods. In vitro analysis includes the extraction of acid-soluble collagen, characterization using FTIR, Raman, UV-Vis, XRD, cytotoxicity assay, and determination of inhibition against ACE1. In silico method visualizes binding affinity, molecular interaction, and inhibition type of intact collagen and active peptides derived from collagen against ACE1 using molecular docking. The results of FTIR spectra detected amide functional groups (A, B, I, II, III) and imine proline/hydroxyproline, while the results of Raman displayed peak absorption of amide I, amide III, proline/hydroxyproline ring, phenylalanine, and protein backbone. Furthermore, UV-Vis spectra showed typical collagen absorption at 230 nm and based on XRD data, the chain types in the samples were α-helix. ACE1 inhibition activity was obtained in a concentration-dependent manner where the highest was 82.83% and 85.84% at concentrations of 1000, and 2000 µg/mL, respectively, and showed very low cytotoxicity at the concentration less than 1000 µg/mL. In silico study showed an interaction between ACE1 and collagen outside the active site with the affinity of - 213.89 kcal/mol. Furthermore, the active peptides of collagen displayed greater affinity compared to lisinopril, namely HF (His-Phe), WYT (Trp-Tyr-Thr), and WF (Trp-Phe) of - 11.52; - 10.22; - 9.58 kcal/mol, respectively. The salmon skin-derived collagen demonstrated ACE1 inhibition activity with a non-competitive inhibition mechanism. In contrast, the active peptides were predicted as potent competitive inhibitors against ACE1. This study indicated that valorization of fish by-product can lead to the production of a promising bioactive compound to treat COVID-19 patient with diabetic comorbid.

Graphical Abstract

Histological and transcriptomic analysis of muscular atrophy associated with depleted flesh pigmentation in Atlantic salmon (Salmo salar) exposed to elevated seawater temperatures

Tasmania is experiencing increasing seawater temperatures during the summer period which often leads to thermal stress-induced starvation events in farmed Atlantic salmon, with consequent flesh pigment depletion. Our previous transcriptomic studies found a link between flesh pigmentation and the expression of genes regulating lipid metabolism accompanied by feeding behavior in the hindgut. However, the impact of prolonged exposure to elevated water temperature on muscle structural integrity and molecular mechanisms in muscle underlying pigment variation has not been elucidated to date. In this study, we investigated the effect of prolonged exposure to elevated water temperature on the farmed salmon flesh pigmentation and structural integrity, using muscle histological and transcriptomic analysis. On April 2019, after the end of the summer, two muscle regions of the fish fillet, front dorsal and back central (usually the most and least affected by depletion, respectively), were sampled from fifteen fish (weighing approximately 2 kg and belonging to the same commercial population split in two cages). The fish represented three flesh color intensity groups (n = 5 fish per group) categorized according to general level of pigmentation and presence of banding (i.e. difference in color between the two regions of interest) as follows: high red color-no banding (HN), high red color-banded (HB) and Pale fish. Histological analysis showed a distinction between the flesh color intensity phenotypes in both muscle regions. Muscle fibers in the HB fish were partly degraded, while they were atrophied and smaller in size in Pale fish compared to HN fish. In the Pale fish, interstitial spaces between muscle fibers were also enlarged. Transcriptomic analysis showed that in the front dorsal region of the HN fish, genes encoding collagens, calcium ion binding and metabolic processes were upregulated while genes related to lipid and fatty acid metabolism were downregulated when compared to HB fish. When comparing the back central region of the three phenotypes, actin alpha skeletal muscle and myosin genes were upregulated in the HN and HB fish, while tropomyosin genes were upregulated in the Pale fish. Also, genes encoding heat shock proteins were upregulated in the HN fish, while genes involving lipid metabolism and proteolysis were upregulated in the Pale fish. Starvation, likely caused by thermal stress during prolonged periods of elevated summer water temperatures, negatively affects energy metabolism to different extents, leading to localized or almost complete flesh color depletion in farmed Atlantic salmon. Based on our results, we conclude that thermal stress is responsible not only for flesh discoloration but also for loss of muscle integrity, which likely plays a key role in pigment depletion.

A Mixture of Full-Fat and Defatted Hermetia illucens Larvae and Poultry By-Products as Sustainable Protein Sources Improved Fillet Quality Traits in Farmed Barramundi, Lates calcarifer

The physicochemical quality and shelf-life of fillets from barramundi, which were fed for 56 days on a mixture of poultry by-product meal (PBM), full-fat Hermetia illucens (FHI), and defatted HI (DHI), were investigated and compared to a fishmeal (FM) control diet. The proximate and total amino acids compositions of the fillets were unaffected by the test diets, while the mixture of PBM and HI larvae improved the sensory quality. An eight-day shelf-life study showed that PBM-HI-based diets improved the texture profile based upon the chewiness, cohesiveness, gumminess, and hardness, regardless of the storage time. The improved texture was aligned with comparatively less degradation of the microstructure of the muscle tissue in the same diets. An improvement in the quality index (QI) value, an increase in pH, and a decrease in lipid oxidation were also found in the fillets of barramundi fed test diets compared with the control diet during the storage time. The test diets positively influenced flesh lightness and redness, while the color profiles were negatively influenced by the storage time. Overall, the maintenance of compositional attributes; the enhancement of fillet sensory attributes, texture, and brightness; and the improved raw fillet shelf-life support the inclusion of PBM-HI-based diets in aquafeed.

Dietary protein improves flesh quality by enhancing antioxidant ability via the NF-E2-related factor 2/Kelch-like ECH-associated protein 1 signaling pathway in softshell turtle (Pelodiscus sinensis)

An 8-week feeding trial was performed to assess the influence of a gradient of protein levels (14.38-45.23%) on flesh quality, skin color, amino acid profile, collagen, antioxidant capability, and antioxidant-related signaling molecule expression of the softshell turtle (Pelodiscus sinensis). Hardness, gumminess, chewiness, and yellowness values in the plastron and carapace, along with collagen, superoxide dismutase, catalase, total antioxidant capacity, and glutathione peroxidase, all improved with elevating dietary protein up to 26.19%, after which they leveled off. Additionally, total amino acids, flavor amino acids, essential amino acids, and non-essential amino acids in the muscle, as well as the expression of copper/zinc superoxide dismutase, glutathione peroxidase, catalase, manganese superoxide dismutase, NF-E2-related factor 2 were all enhanced by increasing the dietary protein level but not changed by higher protein levels. When dietary protein levels were less than 26.19%, the mRNA expression of Kelch-like ECH-associated protein 1, malondialdehyde, and redness values in the carapace and plastron were reduced, as was the lightness values of the carapace, all of which plateaued at higher protein levels. Using catalase activity and malondialdehyde as the indicators and applying a broken-line analysis, the optimal dietary protein level for P. sinensis was inferred to be 26.07 and 26.06% protein, respectively. In summary, an optimal protein input improved turtle flesh quality by strengthening antioxidant capacity in muscle tissue and by regulating the expression of antioxidant-related enzymes via the Nrf2/keap1 signaling pathway.

An Evaluation of Replacing Fishmeal with Chlorella Sorokiniana in the Diet of Pacific White Shrimp (Litopenaeus Vannamei): Growth, Body Color, and Flesh Quality

This study was conducted to investigate the effects of replacing fishmeal (FM) with Chlorella sorokiniana on growth and flesh quality of Pacific white shrimp, Litopenaeus vannamei. A control diet was formulated to contain 560 g/kg FM, and then chlorella meal was used to replace 0% (C-0), 20% (C-20), 40% (C-40), 60% (C-60), 80% (C-80), and 100% (C-100) of dietary FM, respectively. The six isoproteic and isolipidic diets were fed to shrimp (1.37 ± 0.02 g) for 8 weeks. The results showed that weight gain (WG) and protein retention (PR) of C-20 group were significantly higher than those of C-0 group (P < 0.05), while no significant differences were observed in WG and PR between C-0 and C-40 groups (P > 0.05). When the replaced level of FM by chlorella meal reached 60%, the WG of shrimp decreased and feed conversion ratio (FCR) increased significantly (P < 0.05). The quadratic regression analysis indicated that substituted fishmeal levels with chlorella meal were 20.50% and 28.25%, respectively, to obtain the highest WG and lowest FCR. In C-40 and C-60 groups, the body surface presented higher redness than the control (P < 0.05). No significant differences in the whole body and muscle composition, SOD, T-AOC, GSH-PX activities, MDA contents, total collagen content, steaming loss, texture property, free delicious amino acids contents, PUFAs, and n-3/n-6 PUFAs in flesh were observed among the three groups of C-0, C-20, and C-40 (P > 0.05). Compared to the control group, C-60, C-80, and C-100 groups showed lower flesh hardness, chewiness, shear force, and higher steaming loss and resilience (P < 0.05). There were no significant differences in serum TP, TG, GLU, and ALB contents, boiling loss, freezing loss, total free amino acids, SAFs and MUFAs among all the groups (P >0.05). Conclusively, in a diet containing 560 g/kg FM, chlorella meal could replace 40% dietary FM without negative effects on the growth and flesh quality, while increase the body redness of white shrimp.

Role of arginine supplementation on muscular metabolism and flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in freshwater

It is no doubt that the improvement of flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in freshwater contributes to its development potential in aquaculture. In this study, we aimed to explore the effect of arginine supplementation on the flesh quality of L. vannamei reared in freshwater and its mechanism. L. vannamei were randomly fed with three diets for 56 days, of which arginine level was 10.15 g kg^–1 (arginine-deficient diet), 21.82 g kg^–1 (arginine-optimal diet), and 32.46 g kg^–1 (arginine-excessive diet), respectively. Each diet was randomly assigned to triplicate tanks, and each tank was stocked with 35 shrimps (initial weight: 1.70 ± 0.02 g). Results showed the arginine-optimal diet increased the weight gain, flesh percentage, crude protein and flavor amino acid contents in muscle, and improved the flesh hardness by conversing fast myofibers to slow myofibers, increasing myofiber density and myofibrillar length, and promoting ornithine and collagen synthesis. The arginine-optimal diet influenced the purine metabolic pathway by reducing hypoxanthine, xanthine, and inosine contents. Ornithine, citrulline, and glutamate were identified as the key metabolites affecting flesh quality traits after arginine treatments. Only increasing the levels of dietary arginine did not result in an increase in endogenous creatine synthesis in muscle and hepatopancreas. Overall, the arginine-optimal diet improved the flesh quality traits of L. vannamei reared in freshwater due to the enhanced muscular hardness, protein deposition, and flavor, which may be contributing to the transformation of muscle fiber type and increase in protein synthesis by the metabolites of arginine (ornithine, citrulline, and glutamate).

Mechanically Enhanced Salmo salar Gelatin by Enzymatic Cross-linking: Premise of a Bioinspired Material for Food Packaging, Cosmetics, and Biomedical Applications

Marine animal by-products of the food industry are a great source of valuable biomolecules. Skins and bones are rich in collagen, a protein with various applications in food, cosmetic, healthcare, and medical industries in its native form or partially hydrolyzed (gelatin). Salmon gelatin is a candidate of interest due to its high biomass production available through salmon consumption, its biodegradability, and its high biocompatibility. However, its low mechanical and thermal properties can be an obstacle for various applications requiring cohesive material. Thus, gelatin modification by cross-linking is necessary. Enzymatic cross-linking by microbial transglutaminase (MTG) is preferred to chemical cross-linking to avoid the formation of potentially cytotoxic residues. In this work, the potential of salmon skin gelatin was investigated, in a comparative study with porcine gelatin, and an enzymatic versus chemical cross-linking analysis. For this purpose, the two cross-linking methods were applied to produce three-dimensional, porous, and mechanically reinforced hydrogels and sponges with different MTG ratios (2%, 5%, and 10% w/w gelatin). Their biochemical, rheological, and structural properties were characterized, as well as the stability of the material, including the degree of syneresis and the water-binding capacity. The results showed that gelatin enzymatically cross-linked produced material with high cross-linking densities over 70% of free amines. The MTG addition seemed to play a crucial role, as shown by the increase in mechanical and thermal resistances with the production of a cohesive material stable above 40 °C for at least 7 days and comparable to porcine and chemically cross-linked gelatins. Two prototypes were obtained with similar thermal resistances but different microstructures and viscoelastic properties, due to different formation dynamics of the covalent network. Considering these results, the enzymatically cross-linked salmon gelatin is a relevant candidate as a biopolymer for the production of matrix for a wide range of biotechnological applications such as food packaging, cosmetic patch, wound healing dressing, or tissue substitute.

Dietary Supplementation With Hydroxyproline Enhances Growth Performance, Collagen Synthesis and Muscle Quality of Carassius auratus Triploid

An eight-week experiment was undertaken to examine the effect of dietary hydroxyproline (Hyp) supplementation on growth performance, collagen synthesis, muscle quality of an improved triploid crucian carp (Carassius auratus Triploid) (ITCC). Six isonitrogenous (340 g/kg diet), isolipidic (60 g/kg diet) and isocaloric (17.80 MJ/kg diet) diets were formulated containing a certain amount of Hyp: 0.09% (the control group), 0.39, 0.76, 1.14, 1.53 and 1.90%. Each diet was randomly assigned to three tanks and each group was fed two times daily until apparent satiation. The results showed that growth performance and feed utilization of ITCC were significantly improved with the dietary Hyp level was increased from 0.09 to 0.76%. Crude protein, threonine and arginine content in the dorsal muscle in 0.76% hydroxyproline group were significantly higher than those in basic diet group (p < 0.05). The muscle textural characteristics increased remarkably with the amount of Hyp in the diet rising from 0.09 to 1.53% (p < 0.05). Meanwhile, the contents of type I collagen (Col I) and Pyridinium crosslink (PYD) in the muscle of fish were significantly increased by dietary Hyp (p < 0.05). The muscle fiber diameter and density of the fish were significantly increased when fed with 0.76% Hyp (p < 0.05). Furthermore, dietary supplementation with an appropriate concentration of Hyp substantially increased the expression of genes involved in collagen synthesis (col1a1, col1a2, p4hα1, p4hβ, smad4, smad5, smad9, and tgf-β) and muscle growth (igf-1, tor, myod, myf5, and myhc) (p < 0.05). In conclusion, dietary supplementation of Hyp can enhance fish growth performance, collagen production, muscle textural characteristics and muscle growth of ITCC. According to the SGR broken-line analysis, the recommended supplementation level of Hyp was 0.74% in the diet for ITCC, corresponding to 2.2% of dietary protein.

The Interaction of Dried Distillers Grains With Solubles (DDGS) Type and Level on Growth Performance, Health, Texture, and Muscle-Related Gene Expression in Grass Carp (Ctenopharyngodon idellus)

The aim of this study was to estimate the possible synergetic effects of the two levels of dietary dried distillers grains with solubles (DDGS) from different sources (US-imported and native) on the growth, health status, muscle texture, and muscle growth-related gene expression of juvenile grass carp. Four treatments of fish were fed with 4 isonitrogenous diets, namely, native DDGS20, native DDGS30, US-imported DDGS20, and US-imported DDGS30 for 60 days. The US-imported DDGS30 group showed the better growth and feed efficiency. Additionally, we observed a significant increase in hepatopancreatic total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) in native DDGS groups. Moreover, raw muscle collagen increases considerably in the US-imported DDGS30 compared with the native DDGS30 group. In comparison with the native DDGS groups, the US-imported DDGS groups showed significantly decrease in all textural properties and fiber density, while increased fiber diameter. Dietary native DDGS inclusion significantly showed the upregulation of myog, myhc, and fgf6a expression in muscle, while the downregulation of the expression of myod and myf5. Overall, US-imported DDGS30 had a beneficial influence on growth via regulating genes involved in myogenesis and hypertrophy, the formation of collagen, but had negative impacts on antioxidant capacity and cooked muscle texture.

Gene expression profiling of trout muscle during flesh quality recovery following spawning

Background

Sexual maturation causes loss of fish muscle mass and deterioration of fillet quality attributes that prevent market success. We recently showed that fillet yield and flesh quality recover in female trout after spawning. To gain insight into the molecular mechanisms regulating flesh quality recovery, we used an Agilent-based microarray platform to conduct a large-scale time course analysis of gene expression in female trout white muscle from spawning to 33 weeks post-spawning.

Results

In sharp contrast to the situation at spawning, muscle transcriptome of female trout at 33 weeks after spawning was highly similar to that of female trout of the same cohort that did not spawn, which is consistent with the post-spawning flesh quality recovery. Large-scale time course analysis of gene expression in trout muscle during flesh quality recovery following spawning led to the identification of approximately 3340 unique differentially expressed genes that segregated into four major clusters with distinct temporal expression profiles and functional categories. The first cluster contained approximately 1350 genes with high expression at spawning and downregulation after spawning and was enriched with genes linked to mitochondrial ATP synthesis, fatty acid catabolism and proteolysis. A second cluster of approximately 540 genes with transient upregulation 2 to 8 weeks after spawning was enriched with genes involved in transcription, RNA processing, translation, ribosome biogenesis and protein folding. A third cluster containing approximately 300 genes upregulated 4 to 13 weeks after spawning was enriched with genes encoding ribosomal subunits or regulating protein folding. Finally, a fourth cluster that contained approximately 940 genes with upregulation 8 to 24 weeks after spawning, was dominated by genes encoding myofibrillar proteins and extracellular matrix components and genes involved in glycolysis.

Conclusion

Overall, our study indicates that white muscle tissue restoration and flesh quality recovery after spawning are associated with transcriptional changes promoting anaerobic ATP production, muscle fibre hypertrophic growth and extracellular matrix remodelling. The generation of the first database of genes associated with post-spawning muscle recovery may provide insights into the molecular and cellular mechanisms controlling muscle yield and fillet quality in fish and provide a useful list of potential genetic markers for these traits.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08228-3.

Seafood Intake as a Method of Non-Communicable Diseases (NCD) Prevention in Adults

Seafood (fish in particular) is one of the main food groups in nutrition models with proven health benefits. Seafood has long been considered a very valuable dietary component, mainly due to presence of n-3 polyunsaturated fatty acids (n-3 PUFA) but it is also an important source of protein (including collagen), anserine, taurine, iodine, selenium, vitamin A, vitamin K, vitamin D, tocopherols, B vitamins and astaxanthin. Considering the beneficial effects of these ingredients on blood pressure, lipid profile and the inflammatory process, seafood should be an essential component of the diet. Non-communicable diseases (NCD) such as cardiovascular diseases, cancer, diabetes and mental disorder, chronic respiratory diseases are common diseases associated with advanced age. Promotion of a healthy lifestyle (including proper nutritional behavior) and prevention of diseases are the most effective and efficient ways to decrease premature mortality from NCD and to maintain mental health and well-being. This review article shows the potential preventive and therapeutic effects of seafood with an emphasis on fish. Our narrative review presents the results of systematic reviews and meta-analysis.

Dietary isoleucine improved flesh quality, muscle antioxidant capacity, and muscle growth associated with AKT/TOR/S6K1 and AKT/FOXO3a signaling in hybrid bagrid catfish (Pelteobagrus vachelli♀ × Leiocassis longirostris♂)

Background

Muscle is the complex and heterogeneous tissue, which comprises the primary edible part of the trunk of fish and mammals. Previous studies have shown that dietary isoleucine (Ile) exerts beneficial effects on growth in aquatic animals. However, there were limited studies regarding the benefits of Ile on fish muscle and their effects on flesh quality and muscle growth. Thus, this study was conducted to explore whether dietary Ile had affected flesh quality and muscle growth in hybrid bagrid catfish (Pelteobagrus vachelli♀ × Leiocassis longirostris♂).

Methods

A total of 630 hybrid fish, with an initial average body weight of 33.11 ± 0.09 g, were randomly allotted into seven experimental groups with three replicates each, and respectively fed seven diets with 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile/kg diets for 8 weeks.

Results

In the present study, we demonstrated that Ile significantly: (1) increased muscle protein and lipid contents and the frequency distribution of myofibers with ≤ 20 μm and ≥ 50 μm of diameter; (2) improved pH value, shear force, cathepsin B and L activities, hydroxyproline content, resilience, cohesiveness, and decreased cooking loss, lactate content, hardness, springiness, gumminess, and chewiness; (3) decreased reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl (PC) contents, GCLC and Keap1 mRNA levels, and up-regulated CuZnSOD, CAT, GPX1a, GST, and Nrf2 mRNA levels; (4) up-regulated the insulin-like growth factor 1, 2 (IGF-1, IGF-2), insulin-like growth factor 1 receptor (IGF-1R), proliferating cell nuclear antigen (PCNA), Myf5, Myod, Myog, Mrf4, and MyHC mRNA levels, and decreased MSTN mRNA level; (5) increased muscle protein deposition by activating AKT-TOR-S6K1 and AKT-FOXO3a signaling pathways.

Conclusion

These results revealed that dietary Ile improved flesh quality, which might be due to increasing nutritional content, physicochemical, texture parameters, and antioxidant ability; promoting muscle growth by affecting myocytes hyperplasia and hypertrophy, and muscle protein deposition associated with protein synthesis and degradation signaling pathways. Finally, the quadratic regression analysis of chewiness, ROS, and protein contents against dietary Ile levels suggested that the optimal dietary Ile levels for hybrid bagrid catfish was estimated to be 14.19, 12.36, and 12.78 g/kg diet, corresponding to 36.59, 31.87, and 32.96 g/kg dietary protein, respectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00572-4.

Dietary inclusion of Antarctic krill meal during the finishing feed period improves health and fillet quality of Atlantic salmon (Salmo salar L.)

There is an urgent need to find alternative feed resources that can further substitute fishmeal in Atlantic salmon diets without compromising health and food quality, in particular during the finishing feeding period when the feed demand is highest and flesh quality effects are most significant. This study investigates efficacy of substituting a isoprotein (35 %) and isolipid (35 %) low fishmeal diet (FM, 15 %) with Antarctic krill meal (KM, 12 %) during 3 months with growing finishing 2·3 kg salmon (quadruplicate sea cages/diet). Final body weight (3·9 (se 0·04) kg) was similar in the dietary groups, but the KM group had more voluminous body shape, leaner hearts and improved fillet integrity, firmness and colour. Ectopic epithelial cells and focal Ca deposits in intestine were only detected in the FM group. Transcriptome profiling by microarray of livers showed dietary effects on several immune genes, and a panel of structural genes were up-regulated in the KM group, including cadherin and connexin. Up-regulation of genes encoding myosin heavy chain proteins was the main finding in skeletal muscle. Morphology examination by scanning electron microscopy and secondary structure by Fourier transform IR spectroscopy revealed more ordered and stable collagen architecture of the KM group. NEFA composition of skeletal muscle indicated altered metabolism of n-3, n-6 and SFA of the KM group. The results demonstrated that improved health and meat quality in Atlantic salmon fed krill meal were associated with up-regulation of immune genes, proteins defining muscle properties and genes involved in cell contacts and adhesion, altered fatty acid metabolism and fat deposition, and improved gut health and collagen structure.

Obtaining glycoconjugates of marine origin via Maillard reaction and their cytotoxic effect: an alternative for the use of animal byproducts

BACKGROUND

Protein glycation by Maillard reaction is commonly used to improve the functional and bioactive properties of food proteins. It is also known that this glycation method can be accelerated by heat without the need for chemical reagents that could be harmful to health. In this study, glycoconjugates were obtained from a mixture of connective tissue proteins (CTP) from jumbo squid (Dosidicus gigas) and two different sugars, dextran (DEX; 10 kDa) and glucose (GLU), using protein-to-carbohydrate ratios of 1:2 and 1:3, in solution at 50 °C for 6 h. The glycation products were characterized by means of their physicochemical properties and cytotoxic effect.

RESULTS

The intensity of the browning measured at A_420nm and A_294nm in glycoconjugates showed no significant difference (P < 0.05). CTP-DEX (1:2) and CTP-DEX (1:3) were those products with the greatest fluorescence related to the intermediate stage in the Maillard reaction, and also with the highest degree of glycation, which was confirmed using o-phthaldialdehyde assay and Fourier transform infrared analysis. The values of cellular viability for CTP-GLU (1:3), CTP-DEX (1:2, 1:3) as well as CTP (0, 6 h) were around 92-103%.

CONCLUSIONS

The operational parameters used in the glycation process achieved the formation of glycoconjugates from proteins of D. gigas, showing no cytotoxic effect on the HaCaT cell line. This research proposes an alternative for the modification of proteins and opens the way to future investigations regarding the bioactivity of these macromolecules to have applications for the use of byproducts in food science and technology. © 2020 Society of Chemical Industry.

Physicochemical and Functional Properties of Type I Collagens in Red Stingray (Dasyatis akajei) Skin

Collagen is widely used in the pharmaceutical, tissue engineering, nutraceutical, and cosmetic industries. In this study, acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted from the skin of red stingray, and its physicochemical and functional properties were investigated. The yields of ASC and PSC were 33.95 ± 0.7% and 37.18 ± 0.71% (on a dry weight basis), respectively. ASC and PSC were identified as type I collagen by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis, possessing a complete triple helix structure as determined by UV absorption, Fourier transform infrared, circular dichroism, and X-ray diffraction spectroscopy. Contact angle experiments indicated that PSC was more hydrophobic than ASC. Thermal stability tests revealed that the melting temperature of PSC from red stingray skin was higher than that of PSC from duck skin, and the difference in the melting temperature between these two PSCs was 9.24 °C. Additionally, both ASC and PSC were functionally superior to some other proteins from terrestrial sources, such as scallop gonad protein, whey protein, and goose liver protein. These results suggest that PSC from red stingray skin could be used instead of terrestrial animal collagen in drugs, foods, cosmetics, and biological functional materials, and as scaffolds for bone regeneration.

Air Exposure in Catshark (Scyliorhinus canicula) Modify Muscle Texture Properties: A Pilot Study

Sharks are captured by tons for human consumption. Improving the quality of their meat will produce fillets that may have a higher economic value in the market, and thus be beneficial for the management of this fishery. In other animal species destined for human consumption, a negative relationship between pre-slaughtering stress and meat quality has been demonstrated. By studying the commercial small-spotted catshark (Scyliorhinus canicula), this work aimed at linking pre-slaughter handling of captured sharks and muscle fillets quality. An experimental group of adult and subadult living catsharks captured by hand and exposed to air (for 18 min, which is the minimum time this species is exposed to air in the fishing deck during fisheries procedures), and an undisturbed group, were evaluated. After air exposure, catsharks returned to water for recovery. Muscle lactate and water content were quantified after acute exposure (for 18 min), 5 h and 24 h. This challenge elicited stress responses in the muscle such as increased lactate levels and immediate dehydration, followed by recovery of lactate levels and overhydration. Muscle consistency, a relevant variable describing quality of seafood according to its ability to be swallowed by the consumer, paralleled muscle water content changes. The results indicated for the first time that handling alive sharks exposed to air results in muscle fillets with different texture properties. Whether these changes in muscle texture induce higher quality fillets has yet to be proven. Our recommendation is to minimize time of air exposure experienced by sharks when captured, including fast slaughtering instead of leaving them to die by asphyxia, as current on-board procedures.

Weakening Pin Bone Attachment in Fish Fillets Using High-Intensity Focused Ultrasound

High Intensity Focused Ultrasound (HIFU) can be used for the localized heating of biological tissue through the conversion of sound waves into heat. Although originally developed for human medicine, HIFU may also be used to weaken the attachment of pin bones in fish fillets to enable easier removal of such bones. This was shown in the present study, where a series of experiments were performed on HIFU phantoms and fillets of cod and salmon. In thin objects such as fish fillets, the heat is mainly dissipated at the surfaces. However, bones inside the fillet absorb ultrasound energy more efficiently than the surrounding tissue, resulting in a “self-focusing” heating of the bones. Salmon skin was found to effectively block the ultrasound, resulting in a significantly lower heating effect in fillets with skin. Cod skin partly blocked the ultrasound, but only to a small degree, enabling HIFU treatment through the skin. The treatment of fillets to reduce the pin bone attachment yielded an average reduction in the required pulling force by 50% in cod fillets with skin, with little muscle denaturation, and 72% in skinned fillets, with significant muscle denaturation. Salmon fillets were treated from the muscle side of the fillet to circumvent the need for penetration through skin. The treatment resulted in a 30% reduction in the peak pulling force and 10% reduction in the total pulling work, with a slight denaturation of the fillet surface.

Muscle Protein Profiles Used for Prediction of Texture of Farmed Salmon (Salmo salar L.)

A soft texture is undesired in Atlantic salmon as it leads to downgrading and reduced yield, yet it is a factor for which the cause is not fully understood. This lack of understanding highlights the need for identifying the cause of the soft texture and developing solutions by which the processing industry can improve the yield. Changes in muscle protein profiles can occur both pre- and postharvest and constitute an overall characterization of the muscle properties including texture. The aim of this study was to investigate this relationship between specific muscle proteins and the texture of the salmon fillet. Samples for 2D-gel-based proteomics were taken from the fillet above the lateral line at the same position as where the texture had been measured. The resulting protein profiles were analyzed using multivariate data analysis. Sixteen proteins were found to correlate to the measured texture, showing that it is possible to predict peak force based on a small subset of proteins. Additionally, eight of the 16 proteins were identified by tandem mass spectrometry including serum albumin, dipeptidyl peptidase 3, heat shock protein 70, annexins, and a protein presumed to be a titin fragment. It is contemplated that the identification of these proteins and their significance for the measured texture will contribute to further understanding of the Atlantic salmon muscle texture.

Effect of selective breeding on collagen properties of Atlantic salmon (Salmo salar L.)

Collagen content and properties of skeletal muscle were studied among selected (FP) and unselected (WP) Atlantic salmon lines that were reared together to avoid any environmental effects. The FP group had significantly higher body weight at harvesting, softer texture and lower connective tissue yield compared with the WP group. The relative collagen fractions (acid, pepsin, insoluble) were similar, but the FP group had a greater abundance of amino acids involved in collagen triple helix conformation and stabilisation (Gly, Pro, Hyp and Hyl), whilst the Lys content was greater for the WP group, indicating a more aggregated collagen. The connective tissue denaturation temperature was lower for the FP group, coinciding with a lower degree of collagen self-assembly and intermolecular-crosslinks. It is concluded that selective breeding has resulted in lower connective tissue stability of Atlantic salmon fillets.

Matrix metalloproteinases in fish biology and matrix turnover

Matrix metalloproteinases have important functions for tissue turnover in fish, with relevance both for the fish industry and molecular and cellular research on embryology, inflammation and tissue repair. These metalloproteinases have been studied in different fish types, subjected to both aquaculture and experimental conditions. This review highlights studies on these metalloproteinases in relation to both fish quality and health and further, the future importance of fish for basic research studies.

Soft texture of atlantic salmon fillets is associated with glycogen accumulation

Atlantic salmon (Salmo salar L.) with soft fillets are not suited for manufacturing high quality products. Therefore fillets with insufficient firmness are downgraded, leading to severe economic losses to the farming and processing industries. In the current study, morphological characteristics of salmon fillets ranging from soft to hard were analysed. Different microscopic techniques were applied, including novel methods in this field of research: morphometric image analysis, periodic acid Schiff staining, immunofluorescence microscopy, transmission electron microscopy and fourier transform infrared microscopy. The results showed that the myocytes of soft muscle had detached cells with mitochondrial dysfunctions, large glycogen aggregates and enlarged inter cellular areas, void of extracellular matrix proteins, including lower amounts of sulfated glycoproteins. Myofibre-myofibre detachment and disappearance of the endomysium in soft muscles coincided with deterioration of important connective tissue constituents such as Collagen type I (Col I), Perlecan and Aggrecan. In summary our investigations show for the first time an association between soft flesh of Atlantic salmon and massive intracellular glycogen accumulation coinciding with degenerated mitochondria, myocyte detachment and altered extracellular matrix protein distribution. The results are important for further understanding the etiology of soft salmon.