Quality and Shelf Life of Cold and Frozen Rainbow Trout (Oncorhynchus mykiss) Fillets: Effects of Fish Protein-Based Biodegradable Coatings

The Klunzinger’s ponyfish (Equulites klunzingeri) protein powder extracted with acid or alkali aided process as a biodegradable coating material for rainbow trout (Oncorhynchus mykiss) fillets during cold (+2°C) and frozen storage (–18°C) were investigated. The coating with alkaline treated protein (AlPC) and acid treated protein (AcPC) extended the shelf life of fillets from 11 to 14 days in cold storage and improved the quality parameters in three months frozen storage period. According to total viable count and total psychrophile count results, bacteria grew more quickly in uncoated fillets than coated fillets. The protein-based coating did prevent spoilage of the rainbow trout fillets as reflected by a decrease in pH, total volatile base-nitrogen and free fatty acids during cold and frozen storage period. Therefore, this study demonstrated that fish protein-based coating had a positive effect on maintaining the rainbow trout fillets quality, and edible coatings from discard fish can offer a promising alternative for preserving fish fillets.     

Superchilled,chilled and frozen storage of Atlantic mackerel (Scomber scombrus) fillets – changes in texture,drip loss,protein solubility and oxidation

Changes in quality characteristics in relation to protease activity and protein oxidation in chilled, superchilled and frozen mackerel fillets during storage were studied. The solubility of sarcoplasmic proteins was quite stable in mackerel samples for all storage experiments, whereas the solubility of myofibrillar proteins decreased in both superchilled and frozen samples. A significant correlation (r = 0.983, P < 0.05) between the increased activity of cathepsin B+L in chilled fillets and softening of the fish flesh during storage was revealed. Contrary with chilled samples, the texture of superchilled mackerel fillets became tougher along the storage period, which can be explained by a higher rate of myofibrillar oxidation (r = 0.940, P < 0.05). The hardness and drip loss decreased slightly at the end of frozen storage. Superchilling preserved the quality of mackerel fillets with the least side effects in relation to protein solubility, drip loss and softening of the fish tissue as compared to chilled and frozen storage.     

STABILITY OF WHOLE, FILLETED, AND MINCED TROUT (SALMO IRIDEUS GIBB) DURING FROZEN STORAGE

In order to determine the behavior of trout (Salmo irideus Gibb) muscle in frozen storage, five lots (whole, fillets, and minces obtained by extrusion, “mincer” and “cutter”) were made and stored at -20⁰C for one year. During this period the mince, mainly the one made with “cutter”, was more denaturated than the whole trout and fillets. The highest rate of insolubilization was reached by 255 days of storage (45% of soluble protein in minces and 60% in fillets and whole fish). Also a similar difference was noticed in the cooking drip. The variations of protein solubility do not thoroughly explain the changes in objective texture observed up to 30–75 days of storage. So, other parameters may be connected with these changes. On the other hand, after 165 days, the rancidity increase measured by the TBA value is high, especially in the mince although rancid flavor was detected at 120 days of storage.     

EFFECT OF DIETARY COMPONENTS AND SURFACE APPLICATION OF OLEORESIN ROSEMARY ON LIPID STABILITY OF RAINBOW TROUT (Oncorhynchus mykiss) MUSCLE DURING REFRIGERATED AND FROZEN STORAGE

The effect of dietary supplementation with α-tocopherol and surface application of oleoresin rosemary on the lipid stability of rainbow trout ( Oncorhynchus mykiss ) muscle during refrigerated storage (4C) and frozen storage (−20C) for 8 days and 6 months, respectively, was investigated. A significant (p < 0.05) reduction in α-tocopherol concentrations in muscle tissue during frozen storage was observed. The 2-thiobarbituric acid-reactive substances (TBARS) values of muscle samples, with or without surface application of oleoresin rosemary, increased during storage for all dietary groups. A significant (P < 0.05) interaction between dietary treatments and the time of storage was observed. Muscle tissue from fish receiving a dietary supplement of 500 mg/kg diet had the lowest TBARS values. The oxidative stability of the lipids was further improved by applying oleoresin rosemary to the surface of the fish fillets.     

GEL-FORMING ABILITY OF COMMON CARP FISH (CYPRINUS CARPIO) MEAT: EFFECT OF FREEZING AND FROZEN STORAGE

Effect of freezing and frozen storage on gel‐forming ability of muscle from fresh water fish, common carp (Cyprinus carpio), was investigated. Fresh carp meat had good gel‐forming ability as revealed by large strain test (gel strength of 1027 g·cm) and dynamic viscoelastic behavior. Freezing and frozen storage at ?18C for 180 days significantly (P < 0.01) reduced the gel‐forming ability of common carp meat. Reduction in protein solubility and calcium‐activated adenosinetriphosphatase enzyme activity of common carp meat during frozen storage was also significant (P < 0.05). Structural change of proteins during frozen storage was evident from reduced viscosity and gel filtration profile. Higher drip loss and reduction in gel‐forming ability of carp meat is attributed to denaturation of proteins during frozen storage.     

Effects of cooking and reheating methods on the fatty acid profile of sea bream treated with rosemary extract

BACKGROUND: The effects of rosemary extract on the fatty acid profile of sea bream fillets cooked by different methods (oven baking, grilling and pan frying) as well as the effects of different reheating methods (microwave and conventional oven) on the fatty acid composition of fish after frozen storage for 4 months were investigated. RESULTS: The proportion of saturated fatty acids increased only slightly in fried samples but significantly in oven‐baked and grilled samples, while the proportion of polyunsaturated fatty acids (PUFAs) increased significantly in fried samples but only slightly in oven‐baked and grilled samples. The proportion of monounsaturated fatty acids remained relatively constant after cooking. Of the fatty acids analysed, the most significant increases (P < 0.05) were observed in C18:1n‐9 and C18:2n‐6 and the most significant decreases (P < 0.05) in C14:0, C16:1, C20:5n‐3 and C22:6n‐3. Although sea bream fillets fried in sunflower oil showed an increase in PUFAs, the lowest eicosapentaenoic and docosahexaenoic acid contents were found in fried samples. CONCLUSION: Sea bream fillets treated with rosemary extract showed slower oxidation than untreated fish. Neither conventional nor microwave reheating after frozen storage for 4 months had a detrimental effect on the fatty acid profile and its stability. Copyright © 2009 Society of Chemical Industry     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.     

EFFECT OF PROCESSING ON BACTERIAL POPULATION OF CUTTLE FISH AND CRAB AND DETERMINATION OF BACTERIAL SPOILAGE AND RANCIDITY DEVELOPING ON FROZEN STORAGE

Processing techniques like cooking and freezing exhibited significant (P < 0.001) reduction in the bacterial load of cuttlefish, Sepia pharaonis, and marine crab, Portunus pelagicus. Raw cuttle fish had 2.4 × 10⁷ cfu/g which on cooking reduced to 9.7 × 10⁶ cfu/g. Freezing reduced the bacterial load further as cooked frozen product had only 9.9 × 10⁴ cfu/g. Similarly, raw crab had 2.6 × 10⁷ cfu/g which on cooking reduced to 6.5 × 10⁶ cfu/g. A further reduction in bacterial load was seen after freezing as cooked frozen crab exhibited only 7.3 × 10⁴ cfu/g. Escherichia coli and Staphylococcus aureus were present in the limit of acceptability for fish and fish products. Salmonella typhimurium and Vibrio cholerae were absent even in raw stage. Biochemical analysis performed on stored frozen products of cuttle fish and crab exhibited a significant (P ≤ 0.05) increase in bacterial spoilage and rancidity with increasing days of storage. Total volatile base nitrogen, trimethylamine, thiobarbituric acid and free fatty acid contents in frozen products of cuttle fish and crab increased significantly with 120 days of frozen storage.     

Effect of frozen storage on the quality of whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus)

 Whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus) were assessed for quality (physical, chemical and sensory attributes) changes throughout 12 months of frozen storage at −18 °C. The pH, expressible water (EXW), quantities of trimethylamine (TMA), dimethylamine (DMA), formaldehyde (FA), the total volatile base nitrogen (TVB-N) the thiobarbituric acid number (TBA), peroxide value (PV) and amount of free fatty acids (FFA) increased, while sensory attributes (odour, taste, texture) decreased during the frozen storage period. A comparison of quality scores between whole fish and fillets of horse mackerel and mediterranean hake showed that there were no significant differences (P>0.05) in attribute scores. There were, however, significant differences (P<0.05) in pH, EXW, TMA, DMA, FA, TVB-N, TBA, FFA and PV. Received: 19 April 1996/Revised version: 7 September 1996     

Role of the rpoS gene in the survival of Vibrio parahaemolyticus in artificial seawater and fish homogenate

Vibrio parahaemolyticus is a foodborne pathogen isolated from coastal waters of the United States and from a variety of seafood, including fish. Seawater represents a nutrient-limiting environment for V. parahaemolyticus. During its persistence in seawater, V. parahaemolyticus is exposed to a variety of environmental stresses, including hyperosmolarity, fluctuations in temperature, and cold stress. The alternate sigma factor of RNA polymerase, designated as (RpoS), encoded by the gene rpoS has been shown to play a major role in bacterial adaptive responses to adverse environmental conditions. The present study was undertaken to investigate the role of rpoS in the survival of V. parahaemolyticus in seawater and fish. A V. parahaemolyticus rpoS mutant was constructed by the insertion of a chloramphenicol acetyltransferase gene cassette within the rpoS gene, and the wild and mutant strains were assayed for their ability to survive in artificial seawater (ASW) at 6 and 1 degrees C and in fish homogenate at 4 and 8 degrees C. The survival of the rpoS mutant of V. parahaemolyticus both in ASW and fish homogenate at either storage temperature was significantly (P < 0.05) lower than that of the wild strain. Further, the viability of V. parahaemolyticus, especially the mutant, was significantly reduced at lower storage temperatures of ASW and fish homogenate. Results of this study indicate that rpoS potentially plays an important role in the survival of V. parahaemolyticus under conditions of cold stress and hyperosmolarity.     

Lipid stability during the frozen storage of fillets from silver catfish exposed in vivo to the essential oil of Lippia alba (Mill.) NE Brown

BACKGROUND: Lippia alba is effective in sedating and reducing stress to fish during transportation. Because some in vitro studies have demonstrated the antioxidant activity of L. alba, we hypothesized that its use in vivo could result in antioxidant effects post mortem. Therefore, in this study we evaluated whether the essential oil of L. alba (EO) used as sedative for fish transport would increase the lipid stability of fillets from silver catfish during frozen storage. RESULTS: The exposure to the EO in vivo did not affect conjugated diene values. However, EO (30 and 40 µL L^?1) delayed the peak formation of peroxides (from the third to the sixth month of storage) and thiobarbituric reactive substances (from the ninth to the twelfth month of storage) when compared to control fillets. After exposure to 40 µL L^?1 EO the free fatty acid content was higher than for control at the start of fillet storage, with no differences among groups thereafter. CONCLUSION: The essential oil of L. alba used as sedative in the water to transport silver catfish can delay lipid oxidation of fillets during frozen storage. Thus L. alba may be a promising source of natural active compounds for use in aquaculture and the food industry. © 2012 Society of Chemical Industry     

INVESTIGATION OF PROTEIN DENATURATION AND PIGMENT FADING IN FARMED STEELHEAD (ONCHORHYCHUS MYKISS) FILLETS DURING FROZEN STORAGE

The present experiment was conducted to measure the extent and nature of quality loss in farmed steelhead fillets during frozen storage, to determine the possible causes of steelhead pigment fading as a result of frozen storage and to suggest some methods for improving storage conditions in order to obtain good‐quality frozen steelhead. This two‐part study confirms the importance of frozen temperature and appropriate storage conditions on the extension of product shelf life. The fading phenomenon of steelhead fillets during 10 months of frozen storage at ?20C was subsequently studied in detail over a 6‐week period for fillets stored at both ?5 and ?30C. Associated protein denaturation, tough/dry texture and rancidity were also examined. Temperature had a stronger effect on the development of rancidity in steelhead fillets than the duration of the storage period for fillets stored for up to 6 weeks. Highest levels of oxidation products were observed in the fillets stored at ?5C even in the short‐term storage experiment while extensive lipid oxidation, toughening, expressible fluid loss on thawed fillets and apparent pigment fading took place during long‐term storage at ?20C. The results from sensory evaluation of texture, color and flavor agreed well with the chemical assessment of rancidity. Flavor scores from the fillets stored at ?5C revealed a slightly oily/rancid taste as compared to the samples at ?30C after 6 weeks of storage. The expressible fluid results indicated that the binding of water to protein decreased significantly in fillets stored at ?5C as compared to the matching fillets at ?30C and during long‐term storage at ?20C. The increases in expressible fluid correlated positively with fading (L*) and negatively with redness (a*). The quantity of extractable protein nitrogen (EPN) decreased drastically over the 6‐week period in both temperature groups (?5 and ?30C), but during this relatively short experiment, the EPN levels between temperature treatments were not significantly different. In both experiments, fillet redness faded dramatically as a result of frozen storage. Abusive cold storage at ?5C resulted in far more fading than at ?30C even after 6 weeks. Fading was measured both subjectively and objectively using reflectance colorimetry, and an increase in whiteness value was concomitant with a decrease in redness. It is suggested that whiteness may be used as an accurate subjective parameter for color fading in frozen storage. Redness values were significantly higher in the fillets at ?30C. The study showed that pigment fading was not a result of a decrease in carotenoid concentration but may be related to protein denaturation, which causes muscle tissue appearance to change from translucent to opaque, thereby giving the illusion of pigment fading.     

Color stability of frozen whole tilapia exposed to pre‐mortem treatment with carbon monoxide

BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre‐mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO‐treated whole, gutted tilapia, frozen for 2 and 4 months at ? 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration. RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO‐treated and untreated tilapia. However, even after 4 months of frozen storage, a*‐value of CO‐treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO‐euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO‐treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle. CONCLUSION: Color stability of tilapia fillets was significantly improved by pre‐mortem CO treatment. The color of CO‐treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre‐mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry     

Gilthead seabream (Sparus aurata): suitability for freezing and commercial alternatives

The quality of portion‐size farmed gilthead seabream (Sparus aurata) during frozen storage and the influence of post‐mortem treatments were studied in order to find new ways of marketing this species. Portion‐sized gilthead seabream, fasted for 48 h prior to slaughter, were frozen and stored at ?20 °C for up to one year. Whole fish were frozen immediately after rigor mortis; gutted fish were frozen immediately after rigor and after 5 days of storage in ice. All lots were stored at ?20 °C for up to one year. The myofibrillar protein of this species was very stable and a slight decrease of solubility in salt solutions was found only after one year of frozen storage. A slight decrease in water‐holding capacity and a slight increase in shear strength were observed, but these were lower than in other species. These changes were reflected as increased toughness and reduced juiciness in sensory analysis of the cooked fillets after one year. The main changes in the cooked fillets were observed in odour and flavour. No significant detrimental effect due to the guts was detected during frozen storage. Storage in ice prior to freezing was reflected in sensory assessment of the raw fish, mainly in terms of initial higher demerit points for fishy odour, gills and eyes; however, no effect was observed in the cooked fillets. Copyright © 2004 Society of Chemical Industry     

Deterioration of European hake (Merluccius merluccius) during frozen storage

European hake (Merluccius merluccius (L)) was frozen as whole fish and as fillets and stored at ?18°C, ?24°C and ?30°C for up to 39 weeks. Sensory properties, peroxide value and thiobarbituric acid value, lipid fatty acid composition, adenosine nucleotide degradation products, dimethylamine and formaldehyde were measured at intervals during storage. Changes at ?30°C were negligible, otherwise fillets deteriorated faster than whole fish. Hedonic rating gave a storage life of around 9 months for whole fish stored at ?18°C.     

PHYSICOCHEMICAL AND BIOCHEMICAL CHANGES IN WHOLE LIZARDFISH (SAURIDA MICROPECTORALIS) MUSCLES AND FILLETS DURING FROZEN STORAGE

The physicochemical and biochemical changes in whole lizardfish (Saurida micropectoralis) muscles and its fillets kept in air and under vacuum during frozen storage at ?20C for 24 weeks were investigated. The formaldehyde (FA) and dimethylamine contents increased with a concomitant decrease in trimethylamine‐ N‐oxide (TMAO) content as the storage time increased (P < 0.05). The Ca²⁺–adenosine 5′‐triphosphatase activity continuously decreased with a coincidental decrease in salt‐soluble fraction. The disulfide bonds were increasingly formed throughout the storage (P < 0.05). The surface hydrophobicity increased and reached the maximum at week 12 with a subsequent decrease up to the end of storage. In general, the higher changes were observed in samples kept under vacuum than those kept in air. With the same atmosphere used, the whole fish showed slightly higher changes than the fillets. A marked increase in TMAO demethylase (TMAOase) activities was observed up to 12 weeks, followed by the continuous decrease up to 24 weeks of storage. The produced FA might play an important role in inducing protein denaturation and/or aggregation in lizardfish. The TMAOase activity as well as the FA formation could be reduced to some extent with the removal of internal organs and storage in the presence of oxygen. However, a detrimental effect of oxygen, especially on the promotion of lipid oxidation, would be an obstacle.     

INHIBITION OF LISTERIA MONOCYTOGENES BY NATIVE MICROFLORA OF WHOLE CANTALOUPE1

Fresh‐cut cantalcupe has been recalled due to the possible presence of Listeria monocytogenes. Several studies have reported that naturally occurring microflora of vegetable surfaces may be antagonistic to pathogen attachment, growth or survival. To test this possibility for L. monocytogenes and cantaloupes, whole melon were treated with water, ethanol (70%) or chlorine (200 ppm) to reduce the native microflora on the melon surfaces. Treated or untreated melons were immersed in a six strain cocktail of L. monocytogenes (10⁷ CFU/mL) for 10 min and then allowed to dry for 1 h inside a biosafety cabinet followed by storage at 5, 10 and 20C for 15 days. Fresh‐cut pieces prepared from the treated or untreated melons and directly inoculated with L. monocytogenes (3.48 log CFU/g) were stored under the same conditions listed above. Populations of L. monocytogenes and five classes of native microflora were investigated. Growth of L. monocytogenes in sterile or nonsterile rind and fresh‐cut homogenates was also studied. The population of L. monocytogenes recovered from inoculated (10³ to 10⁸ CFU/mL) whole melons given no disinfection treatment or washed with water was significantly less (P < 0.05) than that recovered from melons treated with chlorine or EtOH. In general, populations of L. monocytogenes declined on the surface of treated and untreated whole melons and on fresh‐cut pieces over the 15 days storage period at the temperatures tested. However, the decline in pathogen populations was less rapid in the presence of reduced populations of native microflora. Higher populations of L. monocytogenes were attained in sterile tissue homogenates than in nonsterile homogenates. Addition of yeast and mold to sterile rind homogenates was highly inhibitory to growth and survival of the pathogen. The results of this study indicate that native microflora of whole cantaloupe inhibited attachment to rind surfaces as well as survival and growth of L. monocytogenes on cantaloupe surfaces and homogenized fresh‐cut pieces. Thus, L. monocytogenes recontamination of melons having a reduced level of native microflora following application of a disinfection treatment may be a food safety concern.     

Prediction of Quality in Frozen Cod (Gadus morhua) Fillets

Physical and chemical indices were determined on frozen cod (Gadus morhua) fillets stored for ca. 90 days at either - 12°C, - 15°C, - 22°C, - 30°C or under a set of simulated industrial fluctuating temperature conditions (SIFTC). Univariate and multivariate statistics on the quality indices gave a relationship between frozen storage textural deterioration and the chemical parameters as influenced by storage temperature. Results on the SIFTC resembled the - 12°C and - 15°C storage treatments. Chemical indices had lower activation energy values than those for the physical parameters. Ammonia, determined enzymatically, can be used as an index of frozen fish quality. The quadratic equations developed using the dependent variable of Instron raw peak force, independent of time and temperature, can predict the textural quality of frozen cod fillets.     

Effects of Rested Harvesting on Muscle Metabolite Concentrations and K-Values in Chinook Salmon (Oncorhynchus tshawytscha) Fillets during Storage at 15 °C

Abstract: Improvement of harvesting procedures in aquaculture may also improve the quality and storage properties of the fish. The use of an anesthetic allows fish to be harvested with reduced stress and exhaustion, which affect fillet properties. We report here on the effects of rested harvesting on the postharvest metabolic profiles and K-values in Chinook salmon (Oncorhynchus tshawytscha) fillets stored near to the fish's acclimation temperature at 15 °C for 36 h. Fresh rested fillets were obtained by anesthesia with AQUI-S™. They had high cut surface pHs (7.63) and high concentrations of adenosine triphosphate (ATP) and creatine phosphate (3.75 and 8.73 μmol g⁻¹ respectively), which depleted over 12 h. In contrast, fresh exhausted fillets had low cut surface pHs (6.66) and ATP and creatine phosphate were depleted. Adenosine diphosphate (ADP) and β-nicotinamide adenine dinucleotide (NAD⁺) concentrations also remained significantly higher during the first 12 h of storage in rested fillets. In fresh rested fillets inosine monophosphate (IMP) concentrations reached maximum after 12 h storage (4.78 μmol g⁻¹), whereas maximum IMP concentrations occurred immediately postharvest in the exhausted fillets (6.42 μmol g⁻¹). After 36 h storage, K-values in exhausted fillets reached 52.11% compared to 19.27% in rested fillets. Rested harvesting of Chinook salmon improved the fillets’ metabolic potential postharvest, extending metabolite depletion times, changing IMP concentrations and reducing K-values. Practical Application: This study shows that an improved metabolic potential is maintained in salmon fillets from fish harvested in a rested state (that is, with no stress and exhaustion) using an isoeugenol based anesthetic (AQUI-S™). Improved understanding of postharvest metabolic function may help to improve quality and storage properties of high value fish tissues.