Effect of delayed icing on quality changes of iced rainbow trout (Onchorynchus mykiss)

The effect of delayed icing on quality deterioration of rainbow trout (Onchorynchus mykiss) iced 0, 4 and 8 h after catch was assessed by chemical, microbiological and sensory methods. Total volatile basic nitrogen (TVB-N), free fatty acids (FFA), peroxide value (PV) and thiobarbituric acid (TBA) values increased during the pre-icing duration. Delayed icing led to significant increased (p < 0.05) in total viable counts (TVC) throughout the period of storage. This study showed that sensory analysis of rainbow trout correlated well with microbiological analysis. Results of this study according microbiological and sensory data indicated that the shelf-life of rainbow trout stored in ice immediately after catch was approximately 9–11 days, while delay in icing for 4 and 8 h shortened the shelf-life was around 5–7 and 1–3 days, respectively.     

Effect of dietary vitamin E supplementation and refrigerated storage on quality of rainbow trout fillets

Rainbow trout were fed a low vitamin E (200 mg/kg; LVE) or a high vitamin E (5000 mg/kg; HVE) diet for 9 wk to characterize the effect of vitamin E supplementation at 5000 mg/kg on fillet quality. Fish were sampled at 2, 3, 4, 5, 7, and 9 wk of the trial. Fillets were stored at 2 °C for 0, 7, and 14 d, and analyzed for pH, psychrotrophic counts, color, cook yield, shear force, crude fat and moisture content, α-tocopherol, fatty acid composition, and lipid oxidation. There was a significant feeding duration by fillet storage time interaction for psychrotrophic counts, crude fat content, cook yield, and shear force. Fillet L* value was not affected by diet, feeding duration or storage time. Fillet a* was lowest at 14-d storage, and b* values increased with fillet storage time. High vitamin E diet increased fillet α-tocopherol from 33 to 155 mg/kg. High vitamin E decreased palmitic acid and increased linoleic acid and omega-6 fatty acids. Feeding through 9 wk increased the relative proportions of unsaturated, polyunsaturated, and omega-3 fatty acids, and decreased saturated and omega-6 fatty acids. At 0-d storage, HVE diet did not affect thiobarbituric acid-reactive substances (TBARS) at any sampling week, and fasted fish generated fewer TBARS compared to non-fasted fish.     

不同保鲜剂结合微冻技术对虹鳟鱼块在贮藏期间品质的影响

为延长虹鳟鱼块货架期,本实验将新鲜虹鳟鱼块分别用蒸馏水、乳酸链球菌素(0.5 g/kg)、虾仁宝(2.5 g/kg)、海淡水鱼虾蟹贝通用保鲜剂(3.0 g/kg)处理30 min后,结合微冻技术(-3℃贮藏30 d),探究3种保鲜剂对虹鳟鱼块微生物指标、理化指标及质构特性的影响。研究结果表明:在30 d微冻货架期内,乳酸链球菌素在贮藏前23 d抑菌效果明显,23 d后三种保鲜剂抑菌效果基本相同,在相同条件下通用保鲜剂在前20 d贮藏过程中相比于其它两种保鲜剂在降低2-硫代巴比妥酸反应物(TBARS)、挥发性盐基氮(TVB-N)、pH、汁液损失方面有显著效果,保证了较好的质构特性,保鲜鱼肉品质效果最佳。本研究结果为虹鳟鱼肉在贮藏期的品质保持技术的发展提供了参考依据。     

Effect of gelatin coating incorporated with cinnamon oil on the quality of fresh rainbow trout in cold storage

Cinnamon essential oil was used in gelatin coatings to maintain the quality of refrigerated rainbow trout fillets over a period of 20 days. Fish fillets were coated with a solution of 4% gelatin incorporated with cinnamon essential oil and then stored in refrigerator (4 ± 1 °C). Coating’s preservative effect was assessed periodically (every 5 days) by microbial analyses (aerobic plate count and psychrotrophic count), chemical determinations (total volatile basic nitrogen, thiobarbituric acid, free fatty acid) and sensory characteristics. When gelatin coating with cinnamon applied to the preservation of trout fillets, a reduction in the growth of total bacteria was observe after 15 days of storage. Fish fillets with gelatin coating containing 1%, 1.5% and 2% v/v cinnamon oil produced significantly lower (P < 0.05) total volatile basic nitrogen then gelatin‐coated fillets and control until 15 days of storage period (35, 22.86, 30.33, 57.76 and 53.26 mg per 100 g of fillet, respectively). The obtained results indicate that gelatin in the form of coating enriched with cinnamon oil is suitable for the preservation of rainbow trout fresh fillets and to efficiently maintain the quality attributes to an acceptable level during storage.     

Effect of Lactobacillus cultures on microbiological,chemical and odour changes during storage of rainbow trout fillets

The purpose of this study was to investigate the effect of applying two Lactobacillus protective cultures on microbiological, chemical and odour changes during storage of refrigerated vacuum‐packed rainbow trout (Oncorrynchus mykiss) fillets. Lactobacillus sakei CECT 4808 and Lb. curvatus CECT 904^T were inoculated individually or in combination into rainbow trout fillets. The samples were vacuum‐packed and stored at 4 ± 0.5 °C and were assessed during a 20‐day storage period for microbiological (Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria (LAB), H₂S‐producing bacteria, yeasts and moulds) and chemical (pH, total volatile basic nitrogen, lipid oxidation) parameters and off‐odour. Samples inoculated with Lb. sakei and with both strains had significantly (P≤0.05) lower counts of all microbiological spoilage indicator organisms (Enterobacteriaceae, Pseudomonas spp., H₂S‐producing bacteria, yeasts and moulds) than those inoculated with Lb. curvatus or the controls. All chemical parameters examined and off‐odour scores were also significantly (P≤0.05) improved in the samples inoculated with Lb. sakei or with both strains compared with those inoculated with Lb. curvatus or the controls. Lb. sakei generally showed a better preservative effect (P≤0.05) than the combination of strains. Inoculation with Lb. sakei CECT 4808 could provide an additional hurdle to improve shelf‐life of refrigerated vacuum‐packaged trout fillets, as inoculation with this strain resulted in extension of shelf‐life by 5 days. Furthermore, this strain showed some antioxidative ability, which could retard lipid oxidation in fish. Copyright © 2006 Society of Chemical Industry     

Effect of gamma irradiation and frozen storage on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet

The present study was conducted to evaluate the combined effect of low‐dose gamma irradiation (1, 3 and 5 kGy) and frozen storage (5 months at ?20 °C) on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet. Our statistical analysis showed that irradiation process and frozen storage time had a significant effect (P < 0.05) on total volatile nitrogen (TVN), peroxide value (PV), thiobarbituric acid (TBA) and pH. The level of all of these factors increased with increasing frozen storage time. At the end of the fifth month of frozen storage, the lowest and the highest level of TVN, PV and TBA were corresponding to the irradiated samples at 3 and 5 kGy, respectively. In terms of the overall acceptability of their texture, odour, colour and taste, irradiated samples at 3 kGy had the best quality and remained acceptable after 5 months frozen storage. The optimum dose of gamma radiation of rainbow trout fillets according to chemical and sensory analysis was obtained at 3 kGy.     

Effect of Salvia officinalis L. extract on chemical,microbial, sensory and shelf life of rainbow trout fillet

Food Science and Biotechnology - The present study aimed at extending shelf life of rainbow trout fillet. Fish and seafoods are the most valuable nutrients, however, high levels of moisture, free...     

Effect of dietary levels of fat, α-tocopherol and astaxanthin on colour and lipid oxidation during storage of frozen rainbow trout (Oncorhynchus mykiss) and during chill storage of smoked trout

 Female rainbow trout (Oncorhynchus mykiss) with an initial weight of 0.8–0.9 kg were raised in two experiments including a total of 2550 fish divided into 17 groups. The fish were raised for 6 months on 13 different feeds (four fish groups were replicates) varying in dietary levels of fat (27% or 32%), astaxanthin (40, 70 or 100 mg astaxanthin/kg feed) and vitamin E (α-tocopherol; 100, 300 or 600 mg all-rac-α-tocopheryl acetate/kg feed). The levels of fat, astaxanthin and α-tocopherol in the fillets all increased with increasing dietary levels of each feed component. Furthermore, astaxanthin deposition was found to be significantly improved by increasing the dietary fat level from 27% to 32%, but was not affected by dietary levels of α-tocopherol. The highest deposition of α-tocopherol was found in fish fed the lowest level of astaxanthin (40 mg/kg), whereas α-tocopherol deposition was unaffected by the dietary fat level. Frozen storage (–28  °C) of gutted, cleaned and glazed raw fish for 18 months significantly reduced astaxanthin and α-tocopherol levels, while lipid oxidation, measured as thiobarbituric acid reactive substances (TBARS) was limited. In the first experiment, the highest TBARS levels were found during frozen storage in fish fed the lowest level of astaxanthin (40 mg/kg versus 70 mg/kg or 100 mg/kg); unaffected by dietary levels of α-tocopherol (100 mg/kg versus 600 mg/kg), whereas the dietary astaxanthin level (70 mg/kg versus 100 mg/kg) did not influence lipid oxidation in frozen fish in the second experiment. After brine injection, fillets of fish were smoked and a vacuum-packed (95%), sliced product in a transparent laminate was produced. The quality (pigmentation and lipid oxidation) during 3 weeks of illuminated, chill storage (3  °C) was compared for smoked products produced from fresh fish and from fish stored at –28  °C for 12 months and 18 months. Smoked fillets from fish fed 32% fat were found to be less red than those from fish fed 27% fat, and the astaxanthin content and surface redness of the smoked product decreased during chill storage. Lipid oxidation was pronounced in smoked trout, but a high level of α-tocopherol in the fillet significantly reduced lipid oxidation during chill storage of the smoked product. Lipid oxidation in smoked fillets from fish fed 32% fat was more pronounced than in fish fed 27% fat, but increasing the dietary α-tocopherol level from 300 mg/kg feed to 600 mg/kg feed effectively counteracted the negative effect of the high-fat diet on lipid oxidation in the smoked product. Astaxanthin did not affect lipid oxidation in the chill-stored smoked product, in contrast to the frozen, raw fish. Astaxanthin seems to protect against the very early stages of lipid oxidation, while α-tocopherol is more important as an antioxidant at more advanced stages of lipid oxidation. Received: 8 January 1998 / Revised version: 23 March 1998     

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.     

Nitrogen stunning of rainbow trout

This study examined the use of nitrogen gas for stunning of Rainbow Trout. It was found that nitrogen could be used as an effective stunning method and that the strong aversive reaction reported for carbon dioxide stunning was not observed. Measurement of ATP, its metabolites and pH were carried out to evaluate the effects of nitrogen stunning on post mortem muscle biochemistry. This treatment was compared to percussive stunning and air asphyxiation. Post mortem ATP levels in nitrogen stunned fish (1.96 ± 0.36 μmol g^?1) were significantly higher than for asphyxiated fish (0.2 ± 0.11 μmol g^?1) but lower than values for percussively stunned fish (5.9 ± 0.89 μmol g^?1). This work indicates that the use of gasses other than carbon dioxide for stunning of fish deserves further study.     

Effect of cadmium on the interaction of 17beta-estradiol with the rainbow trout estrogen receptor

The widely reported negative effects of xenoestrogens on the endocrine system of aquatic organisms gave raise to public concern and led to a number of screening and testing initiatives on the international level. Recent studies indicated that not only organic chemicals but also certain heavy metals, including cadmium, can mimic the effects of the endogenous estrogen receptor agonist 17beta-estradiol (E2) and lead to estrogen receptor activation. While the effects of cadmium on the endocrine system and its potential to harm living organisms are no longer in doubt, the exact mode of action is still essentially unknown. In the present study we utilized the rainbow trout ER alpha ligand binding domain (rtER-LBD) fused to glutathione-S-transferase, to study noncovalent interactions between cadmium and the rtER-LBD. ICP-MS data showed that the Cd uptake by the rtER-LBD was strongly pH-dependent. Previous results showing that Cd shields Cys residues of the rtER-LBD against chemical modification, and competitive binding experiments reported here provide insights into the specificity of the interaction of cadmium with the ER hormone binding cavity. It could, for instance, be shown that most of the cadmium adsorbed to the protein could be released into solution either under denaturing conditions, or by stripping from the protein surface using EDTA at physiological conditions. Competitive binding experiments using radio-labeled estradiol showed that, in contrast to previously published data, E2 has an affinity an order of magnitude higher for the ER than for Cd. ICP-MS experiments showed that, despite its higher affinity, increasing E2 concentrations were unable to replace Cd from the rtER-LBD that had been preequilibrated with Cd. These findings were independently confirmed by the [3H]-E2 binding assay. At the same time both ICP-MS and the [3H]-E2 binding assay showed that increasing Cd concentrations not only lead to a decrease in the specific estradiol binding, but also to the release of E2 from the preequilibrated rtER-LBD. The gradual release of [3H]-E2 from the rtER-LBD following incubation with increasing Cd concentrations indicates either direct competition for the same binding site or Cd-induced conformational changes resulting in the release of estradiol.     

Development of rancidity in salmonoid steaks during retail display. A comparison of practical storage life of wild salmon and farmed rainbow trout

The quality of wild salmon and farmed rainbow trout from aquaculture, both packed in transparent vacuum-skin packaging, was followed during storage for 6 months in an illuminated freezer cabinet (product temperature -17 degrees C, half of the packs protected against light, and half of the packs fully exposed to light), combining (a) colour determination of the carotenoid-pigment flesh by tristimulus colorimetry, (b) determination of thiobarbituric-acid-reactive substances (TBA value), (c) carotenoid analysis and, at the end of the storage experiment, (d) sensory evaluation. Rancidity developed faster in steaks of wild salmon (TBA increased during 6 months of storage from 2.8 mumols malonaldehyde/kg flesh to 12.5 mumols/kg for light-protected packages, and to 17.6 mumols/kg for packages exposed to fluorescent light) as compared to steaks of farmed rainbow trout (TBA increased from 1.2 to 5.8 mumols/kg, independent of light exposure), a finding also confirmed by sensory evaluation. In both products, the carotenoid pigment was identified as astaxanthin; salmon steaks, the product more susceptible to developing rancidity, had the lower astaxanthin content (rainbow trout 9.1 mg/kg flesh, salmon 4.9 mg/kg, prior to storage). While the astaxanthin content remained virtually constant in salmon steaks during storage, the content decreased significantly in steaks of rainbow trout, an observation which suggests the role of astaxanthin as a sacrificial protector against radical processes.     

Effect of chitosan coatings enriched with cinnamon oil on the quality of refrigerated rainbow trout

The effects of a chitosan (Ch) coating enriched with cinnamon oil (Ch + C) on quality of rainbow trout (Oncorhynchus mykiss) during refrigerated storage (4 ± 1 °C) were examined over a period of 16 days. A solution of Ch (2%, w/v) and Ch + C (2%, w/v Ch + 1.5%, v/v C) was used for the coating. The control and the coated fish samples were analysed periodically for microbiological (total viable count, psychrotrophic count), chemical (TVB-N, PV, TBA), and sensory (raw and cooked fish) characteristics. The results indicated that the effect of the Ch + C coating on the fish samples was to enable the good quality characteristics to be retained longer and to extend the shelf life during the refrigerated storage.     

Effect of chitosan edible coating enriched with lemon verbena extract and essential oil on the shelf life of vacuum rainbow trout (Oncorhynchus mykiss)

In this research, the antioxidant and antibacterial characteristics of the chitosan (CH) coating incorporated with lemon verbena essential oil (LVEO) and extract (LVE) on the quality of the rainbow trout packed by vacuum packaging at 4°C were investigated. Samples evaluated include the following: Control, VP, CH, CH-LVE 2%, CH-LVEO 1%, and CH-LVE 1%-LVEO 0.5% for 16 days at 3 days intervals. All of the samples significantly reduced Psychrotrophic bacteria, total viable counts, Enterobacteriaceae, and H₂S producing bacteria as compared with control during keeping time. Thiobarbituric acid reactive substance, peroxide value, total volatile basic nitrogen, and pH value were detected lower in all of the samples than control. CH incorporated with LVE and LVEO gave an agreeable effect on sensory characteristics. Samples containing CH-LVE 1%-LVEO 0.5% was often in priority by sensory assessors. Generally, LV can be applied as a substitution for chemical preservatives in fish meat.     

Effect of light on colour stability of sliced smoked rainbow trout Oncorhynchus mykiss fed astaxanthin

Colour stability of sliced smoked fillets of trout fed astaxanthin exposed to light during chilled storage was monitored by instrumental colour measurements and analyses of flesh astaxanthin content. When exposed to light changes in colour parameters at the surface of sliced smoked rainbow trout fillets occurred. The slices became paler. The level of astaxanthin was not affected by either light or storage conditions. Slices exposed to light had higher TBARS values than those stored in the dark. In our experimental conditions the use of a high initial vacuum level and packaging film with a low oxygen transmission rate maintained the astaxanthin content. However these optimal packaging conditions were not able to prevent significant oxidation of lipids after the initial 2–3 days of display.     

Impact of dietary carotenoid and packaging during frozen storage on the quality of rainbow trout (Oncorhynchus mykiss) fed carotenoids

BACKGROUND: The storage life of frozen salmonids is often limited primarily by oxidation and flesh discolouration due to carotenoid degradation. The objective of this research was to determine the carotenoid changes and therefore the muscle colour modifications during 6 months of frozen storage (?18 °C) of whole rainbow trout fed astaxanthin (100 ppm) or canthaxanthin (80 ppm), kept under two different packagings: plastic film and cardboard box. RESULTS: After 6 months of frozen storage, the carotenoid type effect was seen for dry matter while there was no packaging material effect on carotenoid, total lipids, and TBARS contents of trout fillets. The time under frozen storage had an effect on carotenoid and TBARS fillet concentration. The carotenoid‐type effect was noted for the four colour parameters (lightness difference, chroma difference, hue angle difference, and total colour difference) of rainbow trout fillet, while the packaging material effect was observed only for chroma. Frozen storage time had an effect on the four colour parameters of rainbow trout fillet. CONCLUSION: Carotenoid and packaging material effects were more marked for colour parameters than for biochemical parameters. In this study, as fish were frozen and stored as whole fish, fish skin provided good protection against oxidation. Copyright © 2011 Society of Chemical Industry     

Modified atmosphere packaging of filleted rainbow trout

Shelf‐lives of filleted rainbow trout (Oncorhynchus mykiss) packaged in over‐wrap, vacuum and gas mixture conditions and stored at 1 ± 1 °C were compared by measurement of pH, total volatile bases (TVB), hypoxanthine content, lipid oxidation (TBARS value), superficial counts of aerobic psychrotrophic flora and sensory analysis (colour, odour and flavour). The gas mixtures evaluated were 10% O₂ + 50% CO₂ + 40% N₂, 10% O₂ + 50% CO₂ + 40% Ar, 20% O₂ + 50% CO₂ + 30% N₂, 20% O₂ + 50% CO₂ + 30% Ar, 30% O₂ + 50% CO₂ + 20% N₂ and 30% O₂ + 50% CO₂ + 20% Ar. Sensory quality deterioration was delayed and bacterial growth as well as increases in pH, TVB and hypoxanthine levels were reduced by modified atmosphere packaging (MAP). Lipid oxidation was higher in gas packages with 20 and 30% O₂ than in those with 10% O₂. Vacuum‐packed fillets presented the lowest TBARS values. In summary, MAP gave rise to a significant extension of shelf‐life when compared with vacuum and over‐wrap packaging. No significant differences were found between the packages containing either N₂ or Ar. The best evaluated atmosphere consisted of 10% O₂ + 50%CO₂ + 40% N₂/Ar. © 2002 Society of Chemical Industry     

Effect of permeable coatings on the storage life of fruits.

A permeable membrane coating can be produced on fruit surfaces by dipping in an aqueous dispersion of Pro-long, a mixture of sucrose esters of fatty acids and the sodium salt of carboxymethylcellulose. Mangoes (Mangifera indica L. cv. Julie) were treated with 0.75 and 1.0% w/v aqueous suspensions of Pro-long and stored at 252°C/85–95% RH. Treatment with 0.75% Pro-long significantly increased the storage life of mangoes, retarding ripening and reducing weight loss, without adversely affecting the sensory quality of the fruit. Treatment at 1% resulted in increased ethanol formation in the pulp of some mangoes.