Identification of odour‐active compounds in muscle of brown trout (Salmo trutta) as affected by dietary lipid sources

The effect of fatty acid composition on odour‐active compounds in brown trout (Salmo trutta) muscle was evaluated. The fillets were obtained from three groups of fish fed experimental diets containing either fish oil (FO), soybean oil (SO) or linseed oil (LO). Muscle fatty acid composition was shown to be influenced by diet. Thirty‐one odorous compounds were detected by gas chromatography/olfactometry (frequency‐of‐detection method). Most of these compounds were formed by the oxidation of unsaturated fatty acids. Independently of diet, (E)‐2‐pentenal, (E)‐2‐pentenol and (E)‐2‐hexenol contribute strongly to the odour of brown trout. (E,Z)‐2,4‐Heptadienal was detected with high frequency in fish fed diets containing high levels of n‐3 PUFAs (FO and LO groups). Hexanal, (E)‐2‐hexenal and 2‐nonanol seem to contribute most to the odour of fish fed diets containing vegetable oils. Many odorous compounds were derived from the oxidation of mono‐ and di‐unsaturated fatty acids, which could be promoted by high levels of PUFAs. © 2002 Society of Chemical Industry     

Bacterial microflora of wild brown trout (Salmo trutta), wild pike (Esox lucius), and aquacultured rainbow trout (Oncorhynchus mykiss)

Initial numbers of bacteria associated with wild (brown trout and pike) and cultured (rainbow trout) freshwater fish as well as with the water in which they were caught were determined. Subsequently, a total of 979 randomly selected isolates were characterized and identified to the genus level. For all counts performed (aerobes, psychrotrophs, anaerobes, Enterobacteriaceae, and enterococci), no significant differences were observed in water samples, the highest level corresponding to psychrotrophs in pike environments (4.23 X 10(3) CFU/ml). Overall, the skin and intestinal content of brown trout were the most contaminated, while rainbow trout specimens (gills and gut) yielded the lowest numbers. For all bacterial groups, pike gills had the highest numbers. Counts for all of the sampling sites compare well with findings in other temperate geographical environments. Biological characteristics (feeding and skin properties) and the use of antimicrobials in aquaculture might have influenced these results. Motile and nonmotile aerobic gram-negative bacteria together with Enterobacteriaceae accounted for 50 to 70% of the psychrotrophs isolated from water. Micrococcaceae, lactic acid bacteria, Bacillus, and coryneforms were also found. The groups represented in psychrotrophic isolates from the outer surfaces do not reflected those detected in water, so it was common that those organisms recovered in significant numbers from fish were not detected in surrounding habitat of the fish. Motile aeromonads and Carnobacterium were the dominant psychrotrophs in the guts of pike and brown trout, respectively. The intestinal content of reared fish gave a high incidence of Bacillus and coryneforms, while Enterobacteriaceae was absent. Again, rearing practices could have influenced this finding. Listeria monocytogenes was not detected in any of the examined samples. Two strains of Salmonella, which belonged to the same serovar and lysotype, were recovered from pond-water samples taken from one facility on different sampling days. From the gut of a pike specimen and from the pike's environment, two Plesiomonas shigelloides strains of different serovars were recovered. These latter four strains were resistant to a considerable number of antimicrobial compounds (multiple antibiotic resistance indices > 0.2).     

Plasma and tissue disposition of danofloxacin in brown trout (Salmo trutta fario) after intravenous and intramuscular administrations

ABSTRACT

Plasma and muscle pharmacokinetics of danofloxacin were investigated after 10 mg/kg intravenous (IV, caudal vein) and intramuscular (IM, right epaxial muscles) administrations in 168 healthy brown trout (Salmo trutta fario) at 10°C–13°C. High-performance liquid chromatography was used to determine its plasma and muscle concentrations. Pharmacokinetic parameters were analysed with a non-compartmental model. After IV administration, elimination half-life (t_1/2?z), area under the concentration–time curve (AUC_0–∞), mean residence time (MRT_0–∞), volume of distribution at steady state, total body clearance in plasma and AUC_Muscle/AUC_Plasma ratio were 22.22 h, 140.66 h*µg/mL, 23.15 h, 2.28 L/kg, 0.07 L/h/kg and 3.79, respectively. After IM administration, t_1/2?z, AUC_0–∞, MRT_0–∞, peak concentration (C_max), time to reach C_max, bioavailability in plasma and AUC_Muscle/AUC_Plasma ratio were 28.28 h, 84.39 h*µg/mL, 37.31 h, 4.79 µg/mL, 1 h, 59.99% and 8.46, respectively. Danofloxacin exhibited long t_1/2?z and good bioavailability after IM administration. Therefore, 10 mg/kg IM administration of danofloxacin in brown trout can provide AUC_0–24/MIC of > 125 and C_max/MIC of > 10 to treat diseases caused by susceptible bacteria with ≤ 0.336 µg/mL MIC.     

Heavy metal contamination of European eel (Anguilla anguilla) and brown trout (Salmo trutta) caught in wild ecosystems in Spain

In this study we analyzed the pattern of copper (Cu), cadmium (Cd), lead (Pb), and mercury (Hg) accumulation in liver (as a detoxifying organ) and muscle (as the most important tissue for human consumption) of brown trout (Salmo trutta) and European eel (Anguilla anguilla) caught in two wild Spanish rivers where both species are usually angled for human consumption. Cd, Pb, and Cu accumulated preferentially in the liver of both species. Hg accumulated both in the liver and muscle in brown trout, whereas it accumulated preferentially in muscle in European eel. Both high metal content and preferential accumulation of Hg in muscle suggest that European eel is more harmful than brown trout for human consumption.     

Correlated changes in skeletal muscle connective tissue and flesh texture during starvation and re‐feeding in brown trout (Salmo trutta) reared in seawater

Quantitative and qualitative changes to muscle and collagen were analysed following starvation and re‐feeding of brown trout (Salmo trutta) reared in seawater. Fish were submitted to starvation for 2 months followed by re‐feeding for 1 month and compared with a control group continuously fed. Classical effects of starvation on growth and morphometrics traits were observed with only a partial recovery of these parameters after 1 month of re‐feeding. Muscle composition of starved fish was significantly affected (lower dry matter content and higher post‐mortem pH) compared with control fish and was partially recovered in re‐fed fish compared with continuously fed fish. Muscle structure and composition were affected with thinner muscle fibre and higher connective tissue content for the starved fish but similar thickness of myosepta compared with the control group. No difference was observed after 1 month of re‐feeding. Characteristics of the connective tissue were significantly affected by starvation (more high weight molecular collagen form, higher thermal stability of skin collagen). These differences remained significant after the re‐feeding period. Starved fish showed also higher mechanical resistance of the raw flesh compared with the control group, but no difference in rheological measurements was observed after 1 month of re‐feeding. The changes in texture and their relationships with muscle composition, muscle structure and collagen characteristics are discussed. Copyright © 2004 Society of Chemical Industry     

Diffusive gradients in thin films sampler predicts stress in brown trout (Salmo trutta L.) exposed to aluminum in acid fresh waters

Increased levels of aluminum ions released from nutrient-poor soils affected by acid rain have been the primary cause of fish deaths in the acidified watersheds of southern Norway. The complex aluminum chemistry in water requires speciation methods to measure the gill-reactive species imposing toxic effects toward fish. Previously, aluminum speciation has mainly followed the fractionation principles outlined by Barnes/Driscoll, and several analogues of these fractionation principles have been used both in situ and in the laboratory. Due to rapid transformation processes, aluminum speciation in water samples may change even during short storage times. Thus, results obtained by laboratory fractionation methods might be misleading for the assessment of potentially toxic aluminum species in the water. Until now, all in situ field fractionation methods have been time and labor consuming. The DGT technique (diffusive gradients in thin films) is a new in situ sampler collecting a fraction of dissolved metal weighted according to the rate of diffusion and dissociation kinetics. In a field experiment with acid surface water we studied the DGT sampler as a new prediction tool for the gill accumulation of aluminum in trout (Salmo trutta L.) and the induced physiological stress responses measured as changes in blood glucose and plasma chloride. Aluminum determined with DGT (DGT-AI) was higher than labile monomeric aluminum (Ali) determined with a laboratory aluminum fractionation procedure (PCV--a pyrocatechol violet analogue of Barnes/Driscoll), a difference due to collection of a fraction of organically complexed aluminum by DGT and a reduction of the Ali fraction during sample storage. DGT-AI predicted the gill uptake and the aluminum-induced physiological stress responses (increased blood glucose and decreased plasma chloride, r2 from 0.6 to 0.9). The results indicate that DGT-AI is a better predictor for the stress response than laboratory-determined Ali, because the DGT sampler collects a more correct fraction of the gill-reactive aluminum species that induces the stress.     

Evaluation of the EEC four-plate test and Premi test for screening antibiotic residues in trout (Salmo trutta)

The four‐plate test (FPT) method was used for the determination of sulfadiazine/trimethoprim residues in trout in the European Community (EC). This microbiological inhibition test used three media seeded with Bacillus subtilis at different pH values (6, 7.2 or 8.0) and a fourth medium seeded with Micrococcus luteus. The Premi test was also used for the determination of sulfadiazine/trimethoprim residues in trout. The effects of a trout muscle supernatant on detection limits of antibiotics with microbiological inhibition tests were measured. The supernatant was applied directly on top of the paper disks impregnated with aqueous antibiotic solutions. Inhibition zones were compared with those obtained by the same standard solution of sulfadiazine/trimethoprim without the trout supernatant. The detection limit of penicillin, sulfadimidine, streptomycin groups of antibiotics were determined for checking the test plates. For supernatant from fish fed with pellets containing antibiotics (sulfadiazine/trimethoprim), the inhibition zones increased according to the duration of the feed application. In the control group, no inhibition zones were detected. The concentration of the residues accumulated and reached a plateau after 5 days. The antibiotics were detectable in the same concentration as on day 7, but three days later (on day 10) they were no longer detectable in the fish samples. In contrast to the ‘FPT’, 3 days after discontinuing the medicated diet, there were still residues detectable by ‘Premi test’ on day 10. Data is presented that shows that the FPT and the Premi test methods are very useful for the determination of sulfadiazine/trimethoprim residues in trout.     

Consumer Acceptance of Brown Trout (Salmo trutta) as an Alternative Species to Rainbow Trout (Salmo gairdneri)

Rainbow trout and brown trout were prepared and distributed to consumers for comparative taste tests to determine consumer reaction to brown trout. In-home tests were standardized with paired samples of fish. Color of flesh, odor, flavor, texture and overall acceptability were recorded on a 9-point Hedonic scale. Sensory results indicated that brown trout raised in farm stock ponds were more acceptable than rainbow trout from similar environments, and rainbow trout from natural winter-kill lakes were more acceptable than brown trout from the same or similar lakes. Overall, we conclude that brown trout would be acceptable to consumers. Variations in acceptability related to water body of origin rather than to species of fish. Significant differences occurred in some characteristics but were inconsistent as to species.     

Determination of nutrients and volatile constituents of Agaricus bisporus (brown) at different stages

BACKGROUND: The physical properties, proximate composition, mineral and vitamin contents, and estimated volatile components of Portobello mushroom, Agaricus bisporus (brown), were analyzed in three flushes and at two different harvest times. The results showed different trends in the flushes and harvest terms studied. RESULTS: The mean values of texture, diameter, and protein of the harvested produce were 1.78–1.97 kg mm^?2, 4.67–5.02 cm, and 4.18–3.31% wet weight basis (wb), respectively. The mean Zn, Fe, P, Mg, K, Na, and Ca contents of both harvests (mg kg^?1 wb) were 8.15–7.07, 7.40–7.96, 1180.93–1038.69, 88.05–76.29, 213.29–238.82, 2652.0–2500.89, and 534.2–554.80, respectively. In terms of vitamin C, folic acid, thiamin, riboflavin, and niacin, the mean contents (mg kg^?1 wb) were 6.75–3.97, 0.09–0.08, 0.085–0.09, 0.27–0.29, and 3.62–2.94, respectively. The estimated volatile components comprised 18‐ or 16‐carbon compounds such as octadecanoic acid, hexadecanoic acid derivatives, and other important volatiles like dl‐limonene, n‐nonane, benzendicarboxylic acid, and cis‐linoleic acid esters. CONCLUSION: Nutritive contents and estimated volatiles of Portobello mushroom were evaluated in detail at different stages. Copyright © 2009 Society of Chemical Industry     

The effect of slaughter method on the quality of rainbow trout (Salmo gairdneri) during storage on ice

Rainbow trout ( Salmo gairdneri ) were stunned by electrocution, exposure to elevated concentrations of carbon dioxide and by a blow to the head, and subsequently bled. The fish were stored ungutted in ice for up to 15 days, and the changes in the textural properties of the flesh of the fish were measured by a sensory panel and with a texturometer. Parallel changes in the concentrations of spoilage-related biochemical constituents, in water-holding capacity and in bacterial counts were also determined. Slaughter by electrocution and by carbon dioxide narcotization led to a greater initial production of lactic acid and a slightly reduced pH, compared with slaughter by a blow to the head. No significant differences were found in the values of the other indices of quality, either immediately after death or during post-mortem storage.     

Biogenic amines assessment during different stages of the canning process of skipjack tuna (Katsuwonus pelamis)

The present research focused on the biogenic amines (BAs) formation in skipjack tuna (Katsuwonus pelamis) throughout the whole canning process. In agreement with its wide employment on this species, on‐board brine immersion freezing (BIF) was tested as post‐mortem processing. The study included fish samples corresponding to different stages of the canning process such as frozen, thawed, cooked and canned; after cooking, two kinds of tuna muscles were considered, that is, whole fillets (main product) and grated muscle (off‐product arising from small pieces). For the BAs (tryptamine, putrescine, cadaverine, histamine, spermidine and spermine) assessment, an HPLC‐DAD method was developed and validated in skipjack tuna samples, in agreement with different parameters such as suitability, linearity, limits of detection and quantification, precision, accuracy and robustness. Tuna submitted on‐board to BIF procedure provided low levels of spermine and spermidine (up to 27.6 mg kg^?1), while contents on the remaining BAs maintained below the limit of detection. Throughout the different stages of the canning process, skipjack tuna showed a low formation of most BAs; interestingly, histamine content was found below 10.6 mg kg^?1 level. The highest values were obtained for spermidine, these related to cooked grated tuna (from 22.6 to 66.7 mg kg^?1) and canned grated tuna (from 70.6 to 104.4 mg kg^?1). Values for pH assessment in all kinds of tuna samples corroborated the results obtained for BAs determination. BIF procedure proved to be an amenable post‐mortem processing to guarantee the quality of canned skipjack tuna.     

Kinetics of the thermal destruction of thiamine in the white flesh of rainbow trout (Salmo gairdneri)

Thin slices of white flesh from rainbow trout (Salmo gairdneri Richardson) were given different time—temperature treatments and the D and z values for total thiamine were determined. The z value (26°C) was in good agreement with previously reported data but the D values were considerably lower than published results. Thiamine appears to be less thermally stable in the fish muscle than was previously thought. This has serious repercussions when optimising thermal processing with respect to nutrient retention.     

Implications of nitrogen compounds during alcoholic fermentation from some grape varieties at different maturation stages and cultivation systems

The aim of this work was to study the influence of grape variety, cultivation system and stage of grape maturation on nitrogen compounds evolution during alcoholic fermentation. To do this, four grape varieties, Monastrell, Merlot, Syrah and Petit Verdot, traditionally cultivated and Monastrell cultivated using organic agriculture, which were collected in two different stages of maturation, were used. The results showed that, regardless of grape variety, cultivation system and stage of grape maturation, the consumption of nitrogen compounds was directly proportional (R² > 0.7) to their concentration in natural musts. This is very important as it is the first time that these results were obtained with natural musts without external addition of nitrogen compounds.     

Influence of chloride and metals on silver bioavailability to Atlantic salmon (Salmo salar) and Rainbow trout (Oncorhynchus mykiss) yolk-sac fry

The effects of differing water chloride concentrations (0-10 mM) or competing metals [Cu(II), Cd(II), Zn(II), Pb(II), Co(II) (1-10,000 nM)] on Ag(I) uptake in yolk-sac fry of two salmonid species, the Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss), were studied. None of the metals tested were strong competitors of Atlantic salmon yolk-sac fry whole body Ag(I) influx. Inhibition of Ag(I) influx was only seen with a 100-fold excess of Cu(II) or Cd(II) or a 1000-fold excess of Pb(II) or Co(II). At these concentrations, the degree of competition appears to be directly proportional to the conditional stability constant of the competing metal to the gill (metal-gill log K). The range of [Cl-] allowed an assessment of Ag+, AgCl(aq), and AgCl2- bioavailability. The pattern of Ag(I) uptake was similar for each fish species. At <1 mM Cl-, where the [Ag+] dominates, the Ag(I) accumulation rate was constant. Above 1 mM Cl-, where the [AgCl(aq)] is dominant and the [AgCl2-] increases, there was a decline in Ag(I) uptake rate. However, even when very little Ag+ was present (i.e., at 10 mM Cl-) Ag(I) accumulated, albeit at a lower rate. This was suggestive of passive influx by AgCl(aq) and indicated little or no entry of negatively charged silver chloride complexes. The decline in Ag(I) uptake above 1 mM Cl- demonstrated that, if Ag(I) was present as both Ag+ and AgCl(aq), salmonid Ag(I) accumulation was dominated by Ag+ uptake. Therefore, the order of bioavailability of the Ag(I) species was determined as Ag+ > AgCl(aq) > AgCl2-.     

Oxidative changes during ice storage of rainbow trout (Oncorhynchus mykiss) fed different ratios of marine and vegetable feed ingredients

Recently fish meal and oil have increasingly been replaced with proteins and oils from vegetable sources in the diets of farmed salmonids, but the consequences for the oxidative stability of the resulting fish products have not been investigated. The aim of the present study was to evaluate the influence of feeding regime on composition of rainbow trout fillets, as well as on lipid and protein oxidation during storage on ice. Rainbow trout were fed six different diets, which differed in their levels of marine oil and proteins vs. vegetable oil and protein. Fish fillets were characterised by measurement of fatty acid and amino acid composition, primary and secondary lipid oxidation products, astaxanthin and tocopherol content. Protein oxidation was assessed by measuring protein carbonyl content, oxidised amino acids, sulfhydryl groups and immuno-blotting against carbonyl groups. Feeding regimes significantly influenced fatty acid composition. Replacement of fish oil with vegetable oil reduced formation of primary oxidation products, but the effect on secondary oxidation products differed between different types of volatiles. The differences in protein and amino acid composition were not significant, and there were no clear effects of diets on protein oxidation, but data indicated that compounds present in the marine ingredients might have had an effect on protein oxidation.     

Thermal resistance of different life stages of codling moth (Lepidoptera: Tortricidae)

Phytosanitation regulations in several international markets require postharvest treatments to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in various commodities. Thermal treatments are gaining acceptance to replace chemical fumigation. Determining the most thermal-tolerant life stage is essential in the development of effective postharvest insect control protocols based on thermal energy. A heating block system was used to evaluate relative heat resistance of five different life stages of codling moth: white-ring eggs, black-head eggs, third-instar, fifth-instar, and diapausing larvae, at a heating rate of 15°C/min. The fifth-instar was the most heat-resistant life stage in the tested temperature range of 50–52°C except for diapausing larvae. Thermal death kinetic data of diapausing fifth-instar larvae were determined and also compared with the published TDT curve of non-diapausing larvae using the same heating block system. Both diapausing and non-diapausing larvae were dead after treatments at 50°C for 5 min and 52°C for 2 min. However, at the lower temperatures or shorter times, diapausing larvae had lower mortality than non-diapausing larvae.     

Nutritional and chemical composition of different life stages of Tribolium castaneum (Herbst)

Tribolium castaneum can survive in extremely dry environments and be one of the major insect pests of broken and processed grains or other stored dried foods. Additionally, this species has demonstrated resistance to some classes of insecticides. The objective of this work was to evaluate the nutritional and chemical composition of T. castaneum, reared on maize flour, and compare protein, lipids and fatty acids profile, amino acids and mineral contents, of different developmental stages: larvae, pupae and adults. In general all stages were rich in protein (15.3% for larvae and 17.0% for adults, wet body weight).Disparities among developmental stages regarding amino acids and fatty acids content were found. Essential amino acids were most abundant in T. castaneum; a different essential amino acid was prevalent on each developmental stage: larvae - valine; pupae - lysine; adults - histidine. Tribolium castaneum is rich in phosphorus, potassium and sulphur; larvae had a significantly higher content of phosphorus, potassium, sulphur and zinc, while adults showed significantly lower content of potassium and zinc. Larvae and pupae showed higher values of SFA (heptadecanoic and stearic acid) and PUFA (α-linolenic and linolenic acids), while MUFA showed the reverse tendency, with adults having the highest contents of hypogeic, palmitoleic and oleic acids. The nutritional differences among different developmental stages identified are due to specificities of each stage (level of chitinization, motility, energy requirements and food intake habits), as the diet offered to the insects was the same. This study can thus be considered a first step towards future directions of investigation, to a better understanding of this pest nutritional preferences and alternatives to achieve a more sustainable management of infested stored products.     

PCR-RFLP of the mitochondrial cytochrome oxidase gene: a simple method for discrimination between Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)

A DNA-based method (PCR-RFLP) has been developed for discrimination between Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). The polymerase chain reaction (PCR) was used for amplification of a 464 bp fragment of the mitochondrial cytochrome oxidase subunit II (COII) gene. Digestion of the products with endonucleases Nci I and Sau 3AI, followed by agarose gel electrophoresis of the digested products, yielded specific restriction profiles that enabled direct visual identification of the species analysed. This PCR-RFLP methodology allowed clear discrimination of Atlantic salmon and rainbow trout samples both in raw and smoked products. © 1999 Society of Chemical Industry