Eel Fillets Research Articles

Application of hurdle technology for the shelf life extension of European eel (Anguilla anguilla) fillets

Fresh fish, and especially fatty species, are highly perishable due to oxidative deterioration of fish flesh and the elevated microbial load on fish surface. The implementation of a variety of “mild hurdles” may significantly decrease the rates of fish chemical degradation and microbiological spoilage, by better retaining the initial quality, compared to more intense preservation techniques. The aim of this work is the comparative study of different, single or combined, treatments at 15 °C on the quality and shelf life of chilled eel fillets. Fish fillets were treated using osmotic solutions consisting of glycerol (30%–40%–45%) and 5% NaCl with and without former antioxidant impregnation by using Rosemary Serum. In all cases, water activity decreased to approximately 0.90 after 420 min of osmotic treatment. Untreated and osmotically treated fish fillets were subsequently stored at 4 °C and their stability under chill conditions was assessed based on microbial growth and oxidative deterioration. Microbial growth of treated samples was significantly delayed, especially due to the osmotic step (OS) and the derived water activity decrease. Lipid oxidation, a major cause of rejection for fatty fish such as eel, was greatly inhibited in treated fillets, owing to both ‘hurdles’, aw lowering (OS) and antioxidant impregnation with rosemary serum (RS/OS), showing the synergistic effect of these successive procedures. Shelf life of treated eel fillets exhibited a more than 10-fold increase, as compared to the untreated samples, based on chemical composition and a 2 to 3-fold shelf life improvement, in terms of microbial growth.

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The aim of the study was the selection of appropriate enzymatic TTIs for quality and shelf life monitoring of ready-to-eat smoked fish products during refrigerated storage. The response of different types of enzymatic TTIs was kinetically modelled and correlated with the quality decay and shelf life of vacuum packed hot smoked eel and trout and cold smoked salmon fillets in the cold chain. The kinetics of shelf life determining quality indices for the tested smoked fish products were established via isothermal experiments. Mathematical models which describe the effect of the enzyme concentration, storage time and temperature on the response of the TTI were developed and validated at variable conditions. The effect of the temperature on the response change of the TTIs was expressed through activation energy and the values were calculated in the range of 80-150 kJ·mol−1. Applying the developed models, the required TTI design to reliably monitor the shelf life of the respective smoked products was determined. Shelf life of vacuum packed smoked eel, trout and salmon at 5 °C was 7.5, 11 and 2 weeks, respectively. LP-17U, M-17U and M-5U enzymatic TTI adequately monitored shelf life of vacuum packed smoked trout fillets, smoked salmon slices and smoked eel fillets, respectively.

Method for catalyst heating control

The aim of the study was the selection of appropriate enzymatic TTIs for quality and shelf life monitoring of ready-to-eat smoked fish products during refrigerated storage. The response of different types of enzymatic TTIs was kinetically modelled and correlated with the quality decay and shelf life of vacuum packed hot smoked eel and trout and cold smoked salmon fillets in the cold chain. The kinetics of shelf life determining quality indices for the tested smoked fish products were established via isothermal experiments. Mathematical models which describe the effect of the enzyme concentration, storage time and temperature on the response of the TTI were developed and validated at variable conditions. The effect of the temperature on the response change of the TTIs was expressed through activation energy and the values were calculated in the range of 80-150 kJ·mol−1. Applying the developed models, the required TTI design to reliably monitor the shelf life of the respective smoked products was determined. Shelf life of vacuum packed smoked eel, trout and salmon at 5 °C was 7.5, 11 and 2 weeks, respectively. LP-17U, M-17U and M-5U enzymatic TTI adequately monitored shelf life of vacuum packed smoked trout fillets, smoked salmon slices and smoked eel fillets, respectively.

Time temperature integrators for monitoring the shelf life of ready-to-eat chilled smoked fish products

Abstract The aim of the study was the selection of appropriate enzymatic TTIs for quality and shelf life monitoring of ready-to-eat smoked fish products during refrigerated storage. The response of different types of enzymatic TTIs was kinetically modelled and correlated with the quality decay and shelf life of vacuum packed hot smoked eel and trout and cold smoked salmon fillets in the cold chain. The kinetics of shelf life determining quality indices for the tested smoked fish products were established via isothermal experiments. Mathematical models which describe the effect of the enzyme concentration, storage time and temperature on the response of the TTI were developed and validated at variable conditions. The effect of the temperature on the response change of the TTIs was expressed through activation energy and the values were calculated in the range of 80-150 kJ·mol−1. Applying the developed models, the required TTI design to reliably monitor the shelf life of the respective smoked products was determined. Shelf life of vacuum packed smoked eel, trout and salmon at 5 °C was 7.5, 11 and 2 weeks, respectively. LP-17U, M-17U and M-5U enzymatic TTI adequately monitored shelf life of vacuum packed smoked trout fillets, smoked salmon slices and smoked eel fillets, respectively.

Chitosan and Oregano Oil Treatments, Individually or in Combination, Used To Increase the Shelf Life of Vacuum-Packaged, Refrigerated European Eel (Anguilla anguilla) Fillets

We investigated the impact of chitosan and oregano essential oil (EO) individually or in combination on the quality of eel fillets in vacuum packaging (VP) and stored under refrigeration (4°C). Treatments studied were (i) control eel fillets stored in VP (E), (ii) eel fillets treated with 0.3% (v/w) oregano EO and stored in VP (E-OR), (iii) eel fillets treated with 2.0% (w/v) chitosan and stored in VP (E-CH), and (iv) eel fillets treated with 2.0% (w/v) chitosan and 0.3% (v/w) oregano EO and stored in VP (E-CH-OR). Treatments E-CH-OR and E-CH significantly reduced counts of mesophilic bacteria, Pseudomonas, Shewanella, and yeasts and molds during storage. Use of chitosan alone or in combination with oregano EO led to a significant reduction in concentrations of trimethylamine nitrogen and total volatile basic nitrogen in fillets, which led to lower concentrations of thiobarbituric acid reactive substances compared with the control samples. The eel samples in the E-CH and E-CH-OR groups were sensorially acceptable during the entire refrigerated storage period of 18 days. Presence of chitosan in the E-CH and E-CH-OR fillets did not negatively affect the taste of the fillets. E-CH fillets received a higher taste score than did E-CH-OR fillets probably because of the distinct and "spicy" lemon taste of chitosan, which was well received by the sensory panel. Based on overall sensory data (based on mean sensory scores of odor and taste), the shelf life was 6 days for the control fillets, 10 days for the E-OR fillets, and >18 days for the E-CH and E-CH-OR fillets stored in VP at 4°C. Overall, chitosan-treated eel fillets had lower microbial loads and a longer shelf life compared with the controls. Chitosan-treated eel fillets were preferred over oregano-treated fillets. Chitosan alone or in combination with oregano could be used as a preservative treatment and shelf-life extender for other seafoods.

Shelf-life of smoked eel fillets treated with chitosan or thyme oil

The present study examined the effect of natural antimicrobials: Chitosan, thyme oil and their combination, on the shelf-life of smoked eel fillets stored under vacuum packaging (VP) at 4°C. Based on sensory odor data smoked eel fillets had a shelf-life of 35 (control), 42 (thyme treated and>49 (thyme, chitosan-thyme treated) days. The thiobarbituric acid value (TBA) value of the control eel sample was significantly higher than the chitosan-thyme-treated eel samples. The use of chitosan singly, or in combination with thyme oil reduced lipid oxidation (TBA) of the smoked eel samples. A trimethylamine nitrogen (TMA-N) value of 10mgN/100g, could be suggested as an indication of smoked eel spoilage initiation. Control and treated eel reached total volatile basic nitrogen (TVB-N) values of 13.1–31.5mgN/100g below the maximum permissible level of TVB-N in fish and fishery products. Eel samples reached the value of 7.0logcfu/g (Total Plate Count, TPC) on days 35 (smoked) and 42 (thyme treated), whereas both chitosan and chitosan-thyme treated eel samples never reached this limit value. Results of our study show thyme or chitosan (singly, or in combination) inhibit the growth of mesophilic bacteria and extend the shelf-life of smoked eel.

Edible coating enriched with rosemary extracts to enhance oxidative and microbial stability of smoked eel fillets

Abstract The antioxidant and antimicrobial properties of rosemary essential oil (EO) and extracts, entrapped in carboxyl methyl cellulose (CMC) edible coating for smoked eel were investigated. Analysis of the EO indicated 1,8-cineole, L-camphor, a-pinene, and 1-borneol, as the main components. The solid residue generated by the EO distillation was extracted in an ultrasound bath with ethanol to give an extract rich in rosmarinic acid, diterpenes and flavonoids. The addition of the extract at 200–800 ppm (total phenol basis) in CMC coating provided antioxidant protection to smoked eel, which increased with concentration. Additionally, the combination of the extract (200 ppm) with EO (2000 ppm) retarded significantly the formation of both primary and secondary oxidation products, indicating possible synergistic effects. The antimicrobial activity of EO and extracts was moderate, with the extract at 800 ppm concentration showing the best results in decreasing the rate of total viable count, Pseudomonas spp., and lactic acid bacteria growth.

Antioxidant effects of chitosan in European eel (Anguilla anguilla L.) fillets during refrigerated storage

In this study, the effects of chitosan extracted from Metapenaeus stebbingi shells and commercial chitosan on lipid oxidation of European eel (Anguilla anguilla L.) during refrigerated storage (+4°C) were examined. The control and treated fillet samples were analyzed periodically for pH value, free fatty acid (FFA), thiobarbituric acid (TBA) number, and peroxide value (PV). The results indicated that both chitosans significantly reduced FFA content, TBA number, and PV (P < 0.05). It was concluded that 10 g/L of extracted chitosan solution was the optimal concentration for extending the shelf life of eel fillets.

Effects of laurel and myrtle extracts on the sensory, chemical and microbiological properties of vacuum‐packed and refrigerated European eel (Anguilla anguilla) fillets

SummaryThe effects of extracted natural antioxidant (laurel and myrtle) on the sensory, chemical (TVB‐N, TBARS, PV, FFA and pH) and microbiological (total viable count, psychrotrophic bacteria and Enterbacteriaceae counts) properties of vacuum‐packaged European eel (Anguilla anguilla) stored at 4 ± 1 °C were investigated. The TBARS values of myrtle were significantly lower than that of other groups. The peroxide value was low for European eel treated with myrtle and laurel extract. The FFA‐free fatty acid concentration increased from 0.44 (% oleic acid) (2.03) in the eel during 24 days of storage. The values of pH showed statistically significant (P &lt; 0.05) changes for all groups. The myrtle significantly reduced bacterial growth in fillets (P &lt; 0.05). The microbiological limit of 7 log cfu per gram did not exceed in the treated groups. Data showed that the extracts of myrtle and laurel contain substances that inhibit oxidation of lipids and growth of bacteria in European eel, indicating the potential value of these extracts to extend the shelf life of fish.

Origin identification method by multiple trace elemental analysis of intermuscular bones in grilled eel products produced in Japan, China, and Taiwan

Trace elemental composition in intermuscular bones of grilled eel fillets was analyzed to discriminate the geographic origin of eel products derived from Japan, China, and Taiwan. The intermuscular bones were decomposed with nitric acid-hydrogen peroxide, and twelve elements (Li, Ti, V, Mn, Ni, Co, Zn, Rb, Sr, Ba, Pb, and U) were analyzed by inductively coupled plasma mass spectrometry. Trace elemental composition including six elements: V, Co, Sr, Ba, Pb, and U, in intermusucular bones were significantly different between Japanese domestic eels and imported eels from China and Taiwan. The average content of lead in Japanese eels was 1/4 to 1/6 that in eels imported from China and Taiwan. The data of elemental content in intermuscular bones were used for linear discriminant analysis, and two discriminant models were constructed. In the Japan–China discriminant model, the discriminant probabilities between Japanese origin and Chinese origin were 82.5 and 93.3 %, respectively. In the Japan–Taiwan discriminant model, the discriminant probabilities between Japanese origin and Taiwanese origin were 87.5 and 87.0 %, respectively. Therefore, trace elemental analysis is effective for country-of-origin identification of eels processed as grilled eel fillets.

EFFECTS OF CHITOSAN ON COLOR, SENSORY AND MICROBIOLOGICAL PROPERTIES OF EUROPEAN EEL (ANGUILLA ANGUILLA ) FILLETS DURING REFRIGERATED STORAGE

ABSTRACT In this study, the effects of chitosan extracted from Metapenaeus stebbingi shells and commercial chitosan (CC) on color, sensory and microbiological properties of European eel (Anguilla anguilla) during refrigerated storage (4 ± 1C) were examined. The control and treated fillet samples were analyzed periodically for color (L*, a* and b*), sensory and microbiological (total viable count) characteristics. Both chitosans had no significant effect on L*, b*, chroma, hue and whiteness values of the European eel fillets during storage (P > 0.05). However, a* value was determined higher in control group in the last days of storage (P < 0.05), and the development of total bacteria was slower in fillets containing chitosan compared with control group. The results indicated that both chitosans improved the quality characteristics of eel fillets and extended the shelf life during the refrigerated storage, which was supported by the results of sensory and microbial analyses. PRACTICAL APPLICATIONS There is an increasing interest in food additives nowadays. Chitosan draws attention as a preservative substance in food industry because of its antioxidant and antimicrobial properties. This study investigated the effects of chitosan extracted from shrimp shells discarded in Turkey and also the commercial chitosan on color, sensory and microbiological properties of European eel, a highly perishable food, during refrigerated storage. These findings can be well utilized by researchers as well as manufacturers in the long-term storage of fish and fish products.

Effect of Combined Chitosan Coating and Modified Atmosphere Packaging on the Storability of Cold-Stored Rice Field Eel (&lt;i&gt;Monopterus albus&lt;/i&gt;) Fillets

After being caught and filleted, fresh rice field eel fillets were impregnate with chitosan coating solutions, and then stored in modified atmosphere package (MAP) (60%CO2 + 40%N2) at 2 °C for up to 25 days to determine the chemical, biochemical and physical changes. Fillets were left untreated (CN), or were treated with chitosan coating (CC), or combined chitosan coating with MAP (CCM). Total plate count (TPC), trimethylamine (TMA-N), total volatile bases (TVB-N), pH, colour, water loss, colour changes and hardness were monitored periodically. The results indicated that coating and MAP treatments retard the decay of fish compared to untreated samples. CCM more efficiently inhibited the growth of TPC (2-2.6 Log reductions during Astorage) than did CN and CC. CCM treatments predominantly reduced chemical spoilage, reflected in TVB-N, pH, and TMA-N, retarded water loss and maintained colour and hardness.

Use of immunological techniques for detecting species substitution in raw and smoked fish

Immunological techniques based on double immunodiffusion and immunodotting have been designed to detect the substitution of halibut (Hippoglossus hippoglossus) for sole (Solea solea) fillets. An immunodotting technique has been also developed to differentiate between smoked cod (Gadus morhua) and smoked eel (Anguilla anguilla) fillets. Antisera raised against water-soluble extracts of raw halibut and smoked cod were employed. Antiserum to cod proteins did not show cross-reaction with eel proteins, whereas antiserum to halibut proteins cross-reacted with sole proteins. Species-specific antiserum to halibut proteins was achieved by adsorption on a polymer of sole proteins. These methods are very easy to perform and provide the basis for the development of rapid tests for detecting species substitution in fish products.

Survey of Listeria monocytogenes in New Zealand Seafood

A Survey was carried out on oysters and mussels collected from three different areas of New Zealand for the presence of Listeria monocytogenes and fecal coliforms. Three samples of oysters contained L. monocytogenes. Fifty-two samples of processed seafood purchased from retail outlets were tested for L. monocytogenes before their designated use-by dates. Eighteen samples (35%) contained L. monocytogenes. These were cold-smoked salmon, hot-smokes squid strips, cold smoked blue cod fillet, smoked eel fillets and hot-smoked mussel samples. It was concluded that contamination of the processed seafood occurred during processing rather than form the aquaculture sites.

The Presence of 6-Methyladenine Residue at GATC Sequence in Marine Pathogenic Vibrios Genome

To investigate the development of aerobic plate count and coliform duringprocessing of roasted eel,sampling was aseptically performed at each processstage.All aquatic eels were found to be contaminated by coliform.Thiscontaminated coliform was very difficult to kill using various bactericides andwas considered to be the main cause of recontamination during processing.Data obtained in this study suggested that both the aerobic plate count andcoliform on the surface of roasted eels met the requirement for frozen preparedfoods,when the central temperature of eel fillets was higher than68.1℃ during roasting process using a gas IR machine.

Effect of microwave and open flame heating on the microbial counts and weight loss of eel.

The decimal reduction time and the thermal death time of E. coli Type I in eel bouillion were studied. And the effects of microwave and open flame heating on microbial inactivation and weight loss of eel fillet were compared. The thermal death time regression curve of E. coli in eel bouillion was found to have a Z value =5.1°C. The values read from this curve were accurate over 90% confidence. The lethal effect of microorganisms in eel fillets treated by open flame was higher than that of microwaves at 2450 MHZ if the results were evaluated under equal weight losses. The weight loss of flame-heated fillet was 0.43% for every degree (°C) increase in temperature within the range from 50°C to 80°C. And for microwave-heated fillet was 0.44% between 42°C and 87°C. The combination of heating for 2 min over flame and followed by 15 seconds in microwaves had almost the same effect in weight loss and microbial counts as that heated for 5 min by flame alone.