Development of Lipid Changes Related to Quality Loss During the Frozen Storage of Farmed Coho Salmon (<Emphasis Type="Italic">Oncorhynchus kisutch</Emphasis>)

Lipid changes related to quality loss were evaluated during frozen storage of coho salmon for up to 15 months. Biochemical indices concerning lipid hydrolysis (free fatty acids, FFA) and oxidation (peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescent compounds, FR; polyene index, PI) were determined and compared to sensory (odor and taste) and endogenous antioxidant (tocopherol isomers and astaxanthin) assessments. As a result of the frozen storage, lipid hydrolysis was shown to develop according to the increase in FFA content (p < 0.05). However, most biochemical lipid oxidation indices (PV, TBA-i and FR) led to a low degree of rancidity development (p < 0.05) when compared to other fatty fish species under similar frozen storage conditions. The PI value decreased (p < 0.05) at month 10 but then remained unchanged until the end of the experiment. Rancid odor and taste development were shown to be low throughout the experiment, according to the biochemical indices mentioned above. However, a progressive decrease (p < 0.05) in the original fresh odor and taste of salmon fish flesh occurred with increasing frozen storage time, such that fish samples had the poorest scores by month 15. Endogenous antioxidants were remarkably stable throughout the experiment and which might contribute to the oxidative stability of frozen farmed coho salmon lipids.     

Rancidity development during frozen storage of mackerel (Scomber scombrus): effect of catching season and commercial presentation

Hydrolytic and oxidative rancidity development and its effect on quality loss were studied in frozen mackerel (Scomber scombrus) by biochemical and sensory indices. The effect of the lipid content on fish damage at a commercial freezer temperature (?20 °C) was studied for up to 12 months; thus, mackerel caught at two different times of the year (May and November) was checked, May being the period of minimum lipid content, while November is known to be the time of maximum lipid content. The study was also focused on two different kinds of fish products (whole fish and fillets). Increasing lipid hydrolysis was observed for all kinds of samples during the frozen storage; no differences (p >0.05) between whole fish and fillets were found for free fatty acid formation; however, mackerel from May showed a higher (p <0.05) hydrolysis development than its counterpart from November. Increasing lipid oxidation (peroxide value and thiobarbituric acid index) was observed for all kinds of samples during the frozen storage. Fillet lipid oxidation was found to be higher (p <0.05) than in whole fish. Fattier mackerel (November fish) showed a higher (p <0.05) oxidation development than its counterpart from May in the case of fillet products. Results of fluorescence assessment, related to interaction compound formation, proved to be higher (p <0.05) in fillets than in whole fish, although they were higher (p <0.05) in May samples. Sensory analysis corroborated the biochemical analyses, so that fillets showed a shorter shelf life (1 and 3 months for November and May fish, respectively) than their whole fish counterparts (5 months for November and May mackerel).     

Lipid damage in farmed rainbow trout (Oncorhynchus mykiss) after slaughtering and chilled storage

The flow ice system including ozone (OFI condition) was tested for slaughtering and storage (up to 16 days) of farmed rainbow trout (Oncorhynchus mykiss). Lipid damage analyses were carried out and compared to sensory acceptance and instrumental colour changes. Comparison to individuals processed with the flow ice system in the absence of ozone (FI condition) was undertaken. Rainbow trout slaughtered and chilled under FI and OFI conditions showed a low lipid damage development, according to lipid oxidation and hydrolysis events and lipid composition (polyunsaturated fatty acids, phospholipids and endogenous antioxidants) changes. Additionally, both icing conditions led to largely good quality and shelf life times and to the absence of changes in colour properties. It is concluded that flow ice as such, or including the presence of ozone, can be considered as ideal strategy to be employed as slaughtering and storage system during the commercialisation of the actual farmed species. The ozone presence has shown some profitable effects as leading to an extended shelf life time by quality retention of several sensory parameters; in contrast, some negligible negative effects could be observed on the secondary and tertiary lipid oxidation development. However, the oxidation values reached by individuals kept under OFI conditions cannot be considered as particularly high.     

Effect of high‐pressure treatment on microbial activity and lipid oxidation in chilled coho salmon

This work studies the effect of a previous hydrostatic high‐pressure (HHP) treatment on chilled farmed coho salmon (Oncorhynchus kisutch). Three different HHP conditions were applied (135 MPa‐30 s, 170 MPa‐30 s, and 200 MPa‐30 s for treatments T‐1, T‐2, and T‐3, respectively) and compared to untreated (control) fish throughout a 20‐day chilled storage. Microbial activity and lipid oxidation development were analyzed. Assessment of aerobe, psychrotroph, Shewanella spp. and Pseudomonas spp. counts and trimethylamine formation showed a marked inhibitory effect (p <0.05) of HHP treatment on microbial activity, with this effect increasing with the pressure value employed. Related to lipid oxidation development, higher peroxide mean values (day 10–20 period) were found in control samples and fish treated under T‐1 condition when compared to their counterparts corresponding to T‐2 and T‐3 treatments. On the contrary, quantification of thiobarbituric acid‐reactive substances and fluorescent interaction compounds showed higher levels (p <0.05) in fish samples corresponding to T‐2 and T‐3 treatments. In spite of the lipid oxidation development found, polyene index and tocopherol isomer (α and γ) content did not provide differences (p >0.05) as a result of previous HHP treatment.     

Lipid deterioration during chilled storage of Atlantic pomfret (Brama brama)

Lipid damage produced during Atlantic pomfret (Brama brama) chilled storage (up to 19 d) was studied. The formation of various lipid parameters, such as free fatty acid and conjugated dienes (CD), peroxide value, thiobarbituric acid reactive substances and fluorescent compounds was measured in 2 different white muscle zones (dorsal and ventral). The results were compared with the formation of volatile amines (total volatile base‐nitrogen, TVB‐N, trimethylamine‐nitrogen, TMA‐N). A gradual lipid hydrolysis was observed in both zones during the entire experiment. CD and peroxides formation was prominent during the experiment, whereas peroxides showed the highest value at day 15 in both zones followed by a peroxide breakdown at day 19. Interaction of oxidized lipids with nucleophilic compounds present in the fish muscle led to a gradual development of fluorescent material during storage in both zones. The mean value of the lipid content tended to be higher in the ventral zone than in the dorsal one, although significant differences could not be detected (p >0.05). Concerning the lipid damage, very small differences (p <0.05) could be assessed between both zones. TVB‐N content showed no variation till day 15. At day 19, a sharp increase was observed for both muscle zones. In the case of TMA, a gradual increase was observed in both muscles during the 19‐day storage. Higher mean values of TVB‐N and TMA‐N indices were obtained for the ventral than for the dorsal zone. This might be due to the fact that the ventral zone is close to the viscera, where microorganisms are known to concentrate. Of all the different indices tested for quality assessment, TMA‐N and the formation of fluorescent compounds were strongest related to the duration of storage (r²≥0.87). These might therefore be the most accurate parameters to follow quality loss of chilled Atlantic pomfret.     

Distribution and identification of the fatty acids from the coho salmon,Oncorhynchus kisutch (Walbaum)

To study the fatty acids of the coho salmon, entire fish were homogenized and the total lipids extracted with methanol-chloroform. The fish ranged in size from 75 to 85 mm total length and contained from 2.1%–6.9% lipid in the tissues. Methyl esters of the fatty acids were produced with anhydrous methanol and HCl. Qualitative identification of the fatty acid methyl esters was accomplished by gas-liquid chromatography. Thin layer silver nitrate-silicic acid plates were used to separate the component methyl esters according to the number of double bonds. Location of the ethylenic groups of the unsaturated fatty acid methyl esters was established by reductive ozonolysis and identification of the aldehydes and aldehyde-esters produced. The number of carbons in the unsaturated fatty acid methyl esters was determined by hydrogenation of each of the fractions. Fatty acids found in the highest concentrations were: 16∶0, 16∶1, 18∶0, 18∶1, 18∶4, and 22∶6. Fatty acids 16∶0, 18∶1, 18∶2, 20∶5, and 22∶6, differed markedly from concentrations found in tubificid worms, the exclusive diet of the fish during the experiment. Technical Paper No. 2059, Oregon Agricultural Experiment Station Work supported in part by research Grant No. EF105, U.S.P.H.S.     

FA composition of the oil extracted from farmed atlantic salmon (Salmo salar L.) viscera

The FA composition of visceral oil extracted from farmed Atlantic salmon (Salmo salar L.) viscera was studied. Seventeen FA were identified in the extracted visceral oil, and the major FA were 18∶1n9, 16∶0, 16∶1n7, 20∶5n3 (EPA), 14∶0, and 22∶6n3 (DHA). The percentages of saturated, monounsaturated, and polyunsaturated FA in the total FA were 31.7, 36.0, and 32.2%, respectively. Compared with other fish oils, oil from farmed Atlantic salmon had much higher EPA (1.64 g/100 g) and DHA (1.47 g/100 g) contents. The FA profile of the salmon visceral oil was similar to that of the salmon fillet. Thus, the salmon visceral oil could be a replacement for the oil obtained from edible salmon fillet and used in functional foods or feeds requiring a high level of omega-3 FA. Furthermore, producing visceral oil is also beneficial to salmon fish industry by adding value back to the processing waste.     

Field test of the pheromone hypothesis for homing by pacific salmon

Experimental groups of juvenile coho salmon (Oncorhynchus kisutch) were released to elucidate the relative importance of site-specific (imprinted) odors and intraspecific odors (pheromones) in homing. Adult salmon returned to their release site rather than a hatchery containing both adult and juvenile salmon of their population. Furthermore, salmon sharing the same parents returned to different sites, suggesting that local movements are not strongly influenced by siblings or other conspecifics.     

Characterization of farmed and wild salmon (Salmo salar) by a combined use of compositional and isotopic analyses

Gas chromatography, isotope ratio mass spectrometry, and high-resolution ²H site-specific natural isotope fractionation/nuclear magnetic resonance spectroscopy have been used to study the different kinds of fish oils and lipids extracted from muscle of wild and farmed salmon (Norway, Scotland). A statistical analysis of the fatty acid compositions, overall ²H and ¹³C isotope ratios, and molar fractions of the isotopomeric deuterium clusters was carried out to select the most efficient variables for distinguishing the different groups of salmons and fishes studied. A classification analysis based on four fatty acid compositions, three deuterium molar fractions, and the overall (D/H)_tot isotope ratio of fish oils completely assings the oils to the right group.     

Quality loss related to rancidity development during frozen storage of horse mackerel (<Emphasis Type="Italic">Trachurus trachurus</Emphasis>)

The development of rancidity and its effect on quality loss were studied in frozen horse mackerel (Trachurus trachurus). Two different kinds of fish products (whole fish and fillets) were stored at a commercial freezer temperature (−20°C) for up to 12 mon and were compared to samples stored at a much lower temperature (−80°C). Analyses included: lipid hydrolysis (FFA formation) and oxidation (PV, thiobarbituric acid index, fluorescent compound formation), loss of endogenous antioxidant (α-tocopherol), protein changes (electrophoretic analysis of sarcoplasmic and SDS-soluble fractions), and sensory analysis (skin, eyes, gills, flesh odor, consistency, flesh appearance). According to biochemical indices, fillets stored at −20°C showed susceptibility to rancidity development, leading to a shelf life of 1 mon, whereas whole fish at the same temperature were still edible at month 5. The use of a low temperature (−80°C) inhibited rancidity development, leading to good-quality (whole fish) and fairquality (fillets) fish products at the end of the experiment. The application of protective treatments especially designed to prevent lipid oxidation is encouraged when commercializing this species in the frozen state.     

Damage detection in horse mackerel (Trachurus trachurus) during chilled storage

Sensory and chemical analyses were performed during the chilled storage of whole and filleted horse mackerel (Trachurus trachurus), an underutilized medium-fat fish species. For both kinds of fish products, satisfactory correlations with the storage time were obtained for amine formation (total volatile basenitrogen and trimethylamine-nitrogen), lipid damage (free fatty acid formation), and formation of interaction compounds (fluorescence detection in the aqueous phase). Sensory analyses showed a gradual lower grading with time, with a shelf life of 14 d for whole-fish samples and 12 d for fillet samples. Correlation and multivariate analyses between the sensory attributes and the chemical indices showed that trimethylamine-nitrogen detection was the most accurate chemical method for damage assessment during the chilled storage of whole and filleted horse mackerel.     

Electron spin resonance study of serum lipoproteins of salmon (Oncorhynchus kisutch): Structural alterations produced in high density lipoproteins by mercury and cadmium

High denisty lipoproteins from the serum of salmon (Oncorhynchus kisutch), containing a maleimide spin label (4-male-imido-2,2,6,6-tetramethylpiperidinooxyl), were exposed to HgCl₂, CdCl₂, and CH₃HgCl under physiological conditions. Electron spin resonance spectrometry revealed that HgCl₂ and CdCl₂ produce significant alterations at sites representing weakly and strongly immobilized label. The observed changes appear to be taking place primarily in the surface architecture. No alterations were found in the normal spectra of high density lipoproteins exposed to CH₃HgCl under similar conditions. Each metal species binds strongly with the apo-high density lipoproteins; however, marked differences exist in the effects produced upon high density lipoprotein structure by the inorganic ions and CH₃HgCl.     

Fatty acid alterations during migration and early sea water growth of chum salmon (Oncorhynchus keta)

Lipid and fatty acid characteristics were examined in chum salmon fry (Oncorhynchus keta) in freshwater, at various stages in their early growth in sea water, and 7 days after their artificial introduction from freshwater into sea water. The average lipid content of salmon fry in freshwater decreased from 2.5% in newly emerged fry (30–40 mm fork length) to 1.7% in older fry (40–50 mm). Lipid content did not appear to change during migration, but steadily declined during the first 4–6 weeks of sea water growth to 1.7%. Within 7 days after artificial introduction into sea water, lipid content of the salmon had declined to 1.4%. Extended residence in freshwater, e.g., 2–3 weeks, resulted in a fatty acid pattern more characteristic of freshwater fish, whereas residence in sea water resulted in patterns more characteristic of marine fish. Salmon artificially introduced into sea water incurred substantial diminutions in polyunsaturated fatty acids. This response did not occur in wild fry in the marine environment and may therefore be due to the stresses of capture, handling, anesthesia, partial starvation and confinement to which the artificially reared fish were exposed. Presented at the ISF-AOCS World Congress, Chicago, September 1970. Contribution No. 357, College of Fisheries, University of Washington.     

Analysis of lipids extracted from salmon (Salmo salar) heads by commercial proteolytic enzymes

Fresh salmon heads were submitted to controlled proteolysis using food‐grade commercial enzymes (Alcalase®, Neutrase® and Protamex?). The release of oil under mild conditions (60°, 2 h) compared favourably with organic solvent extraction (19.8% vs. 21.5%). Lipids extracted by solvent and lipids resulting from enzymatic processes displayed a similar content of PUFA (about 35%), mainly eicosapentaenoic acid (EPA; 8.4% vs. 7.7%) and docosahexaenoic acid (DHA; 12.1% vs. 11.9%). Thin‐layer chromatography (TLC‐FID Iatroscan) showed that the polar lipid fraction accounted for 55% of total lipids (phosphatidylethanolamine, 20.7%; phosphatidylcholine, 14.8%). Salmon head phospholipids may be more effective carriers of highly unsaturated fatty acids to specific tissues than triacylglycerols, as shown by their content in EPA (10.3 and 6.9%, respectively) and DHA (33.1 and 9.1%, respectively).     

Changes of lipids in insect (Rhynchophorus phoenicis) during cooking and storage

Lipid stability of Rhynchophorus phoenicis (RP) larvae extract (edible oil) was evaluated, including the usual analytical indices and analysis by Fourier transform infrared (FTIR) spectroscopy at different periods of freezing, refrigeration storage conditions and cooking methods. A study of the quality of oil obtained showed that boiling before smoking reduced the acidity of the oil. Boiling, refrigeration for 3 days or more, freezing, sun drying, and electrical drying increased the acidity of the oil. Culinary and dehydration methods significantly increased the peroxide value, especially when boiling preceded dehydration. Cool storage had protective effects on lipid oxidation of RP larvae. Smoking methods produced good quality products.     

Transduction of Brain Neurons in Juvenile Chum Salmon (Oncorhynchus keta) with Recombinant Adeno-Associated Hippocampal Virus Injected into the Cerebellum during Long-Term Monitoring

Corpus cerebelli in juvenile chum salmon is a multiprojective region of the brain connected via afferent and efferent projections with the higher regions of the brainstem and synencephalon, as well as with multiprojection regions of the medulla oblongata and spinal cord. During the postembryonic development of the cerebellum in chum salmon, Oncorhynchus keta, the lateral part of the juvenile cerebellum gives rise to the caudomedial part of the definitive cerebellum, which is consistent with the data reported for zebrafish and mouse cerebellum. Thus, the topographic organization of the cerebellum and its efferents are similar between fish (chum salmon and zebrafish) and mammals, including mice and humans. The distributions of recombinant adeno-associated viral vectors (rAAVs) after an injection of the base vector into the cerebellum have shown highly specific patterns of transgene expression in bipolar neurons in the latero-caudal lobe of the juvenile chum tectum opticum. The distribution of rAAVs in the dorsal thalamus, epithalamus, nucleus rotundus, and pretectal complex indicates the targeted distribution of the transgene via the thalamo-cerebellar projections. The detection of GFP expression in the cells of the epiphysis and posterior tubercle of juvenile chum salmon is associated with the transgene’s distribution and with the cerebrospinal fluid flow, the brain ventricles and its outer surface. The direct delivery of the rAAV into the central nervous system by intracerebroventricular administration allows it to spread widely in the brain. Thus, the presence of special projection areas in the juvenile chum salmon cerebellum, as well as outside it, and the identification of the transgene’s expression in them confirm the potential ability of rAAVs to distribute in both intracerebellar and afferent and efferent extracerebellar projections of the cerebellum.     

Effect of advanced chilling methods on lipid damage during sardine (Sardina pilchardus) storage

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its effect on lipid damage (hydrolysis and oxidation) was evaluated during the chilled storage of a fatty fish species, sardine (Sardina pilchardus). Slurry ice treatment was checked alone and in combination with ozone and compared to traditional flake icing during a 22‐day storage. Different lipid damage indices (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compounds, FR) were checked and compared to sensory assessment and nucleotide degradation (K value). According to lipid hydrolysis (FFA) and oxidation (PV and FR) developments, slurry ice showed an inhibitory effect (p <0.05) on lipid damage during storage, as well as an inhibition of nucleotide autolytic degradation. Ozonised slurry ice did not provide differences (p >0.05) from slurry ice alone when considering lipid hydrolysis, nucleotide degradation and some lipid oxidation indices (PV and FR), although a higher (p <0.05) TBA‐i was observed at day 22 of storage when compared to flake ice and slurry ice treatments. However, a lower (p <0.05) fluorescence development was observed for fish treated under ozonised slurry ice when compared to traditionally iced fish. Sensory assessment showed a higher shelf life for fish samples treated under ozonised slurry ice than for their counterparts under slurry ice (15 d versus 12 d), while flake icing led to a far shorter shelf life (5 d). According to sensory and biochemical (lipid matter and nucleotide) analysis, slurry ice has proved to be a promising technology for damage inhibition and quality retention in a fatty fish species such as sardine. Ozonised slurry ice was also shown to be useful, since a longer shelf life was obtained in the present experiment and a pro‐oxidant effect of ozone on sardine lipids was not proved.     

Quality enhancement of canned sardine (Sardina pilchardus) by a preliminary slurry ice chilling treatment

The slurry ice technology has shown wide advantages when employed as a chilling method for marine species instead of the traditional flake ice storage. In the present work, the use of slurry ice was evaluated for the first time as a technological treatment prior to the canning processing of fish. Thus, sardine (Sardina pilchardus) specimens were stored in slurry ice for 2 and 5 days and then taken and subjected to canning. Quality assessment of the canned product was performed on the fish muscle and on the coating oil, in comparison with that of a parallel control batch previously stored in flake ice. Analyses included composition (water, lipid and NaCl contents), physical properties (firmness, cohesivity), volatile amine formation (total and trimethylamine), lipid oxidation development (anisidine value, polyene index, α‐tocopherol content and Rancimat oxidative stability) and interaction compounds formation (fluorescence assessment). An inhibition of lipid oxidation development (p <0.05) was obtained in canned sardine when applying slurry ice as a preliminary chilling storage system. The present work opens the way to the use of slurry ice instead of flake ice as a preliminary treatment of fish material prior to the canning process.