Quality assessment of gutted wild sea bass (Dicentrarchus Labrax) stored in ice, cling film and aluminium foil

The effects of aluminium foil and cling film on microbiological, chemical and sensory changes in wild sea bass (Dicentrarchus labrax) stored at chill temperature (4 °C) were studied. A quality assessment of wild sea bass stored in ice, in boxes without ice, wrapped in aluminium foil (WAF) and wrapped in cling film (WCF) at 4 °C was performed by monitoring sensory quality, nucleotide breakdown products, total volatile base nitrogen (TVB-N), and total viable counts (TVCs). The observed organoleptic shelf-life of sea bass was found to be 16 days in ice, 4 days in boxes without ice, 8 days in aluminium foil and 8 days in cling film. Demerit points did not differ significantly (P>0.05) between WCF fish and WAF fish. The nucleotide degradation pattern was found to be similar for all storage conditions except for inosine and hypoxanthine contents, which decreased after 12 days of storage for WAF and WCF. The content of TVB-N for all storage conditions showed similar tendencies until 12 days storage but reached the highest level (41.6 mg TVB-N 100 g^–1 flesh) for fish stored in WAF and WCF. No significant differences (P>0.05) were found in TVB-N concentrations within the treatments during the early stages of the storage period. Bacteria grew most quickly in the sea bass kept in boxes without ice, followed by those kept WAF, WCF and in ice. Significant differences (P<0.05) in TVC were observed amongst the treatments, especially between fish stored in boxes without ice and fish stored in ice     

The effects of gamma-irradiation on the nucleotide degradation compounds in sea bass (Dicentrarchus labrax) stored in ice

The effects of two irradiation doses (2.5 and 5 kGy) on nucleotide breakdown compounds in sea bass stored in ice were investigated. Nucleotide degradation was slower in sea bass irradiated at 2.5 and 5 kGy than untreated samples. Irradiated samples had lower hypoxanthine and inosine content than the control group. Significant differences (p < 0.05) in K and related values were found between control groups and irradiated samples (2.5 and 5 kGy). H and G values showed a good correlation with storage time (r² ? 0.98) while linear regressions of K and Ki ranged from 0.95 and 0.93 to 0.98 and 0.97, respectively. A dose of 5 kGy seemed to be more effective than that of 2.5 kGy to reduce nucleotide breakdown in sea bass. The best linear correlation was obtained from G and H values; thus, they might be used as freshness indicators for non-irradiated and irradiated sea bass.     

Comparison of effects of slurry ice and flake ice pretreatments on the quality of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored at 4 °C

Slurry ice, a biphasic system consisting of small particles of spherical ice immersed in seawater at subzero temperature, was evaluated as a new chilled method for whole sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). Two types of different chilling methods were used for two species in this study; slurry ice-treated sea bream (Group A), slurry ice-treated sea bass (Group B), flake-ice treated sea bream (Group C) and flake ice-treated sea bass (Group D). The effects of this system on the quality and shelf life of these two species were evaluated. Mesophilic counts for sea bass exceeded 7 log cfu/g, which is considered the maximum level for acceptability for freshwater and marine fish after 13 days for Groups C, D and 15 days for Groups A, B. At day 13, TVB-N values of Groups C, D reached the legal limits (35 mg/100 g set for TVB-N) for consumption. According to the results of sensory analyses, up to day 13, all the Groups were determined as ‘acceptable’ but, on day 15, the Groups A, B, C, D were no longer acceptable. Using slurry ice pretreatment for 2 h before the storage period presumably caused the deleterious effect on appearance as well as salt and water uptake. According to the results of chemical and microbiological analyses, use of slurry ice pretreatment for 2 h extended the shelf life of sea bream and sea bass stored at 4 °C for only two days longer than did use of flake ice.     

Comparison of wild and cultured sea bass (Dicentrarchus labrax) quality

Chemical composition, nutritional value and other physico-chemical parameters of sea bass from two different geographical areas (Greece and Spain) and from aquaculture and wild origin were studied. Farmed and wild fish differ in proximate composition, colour, and especially in texture, fatty acids and free amino acids (FAAs) profiles. Flesh of wild fish was firmer, which could be attributed to their lower fat content and higher level of activity. Cultured fish showed a higher content of monounsaturated fatty acids and lower of saturated and polyunsaturated fatty acids (PUFAs). Within the PUFA group, n−3 fatty acids were predominant in wild sea bass, while n−6 were more abundant in farmed fish. Some FAAs related to the characteristic flavour of fish, such as glutamic acid, aspartic acid, alanine, and glycine were more abundant in cultured sea bass. No differences between fish from both farms were found, due to the similar composition of the feed used.     

Biogenic amine changes in barramundi (Lates calcarifer) slices stored at 0 °C and 4 °C

The biogenic amines formation in barramundi (Lates calcarifer) slices kept for 15 days at 0 °C and 4 °C were investigated using nine biogenic amines, total plate counts and biogenic amines formers. Significant differences in biogenic amines concentrations of barramundi slices stored at 4 °C and at 0 °C after 3 days of storage were observed. All amines, except tryptamine, 2-phenylethylamine, tyramine and agmatine in the slices increased with time during storage at both temperatures. At the end of the storage period, histamine concentrations were 82 mg/kg and 275 mg/kg for samples kept at 0 °C and 4 °C, respectively. At day 15, the total plate count was approximately 8.6 log CFU/g for sample kept at 0 °C and 9.7 log CFU/g for samples kept at 4 °C. Histamine-forming bacteria (HFB) in all samples ranged from 5.4 to 6.1 log CFU/g at 0 °C and 4 °C, respectively. The observed shelf-life of barramundi slices were 6–9 days.     

Comparison of antiatherogenic properties of lipids obtained from wild and cultured sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata)

The aggregatory properties of lipid fractions, obtained from wild and cultured specimens of sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) were studied. The total lipids were extracted and separated into polar and neutral lipids. The polar lipids and neutral lipids were further separated by thin layer chromatography and the fractions obtained were tested for their ability to aggregate platelets or inhibit the platelet-activating factor (PAF)-induced aggregation. The aggregatory properties of the lipid fractions were dependent on the fish species and whether the fish samples were wild or cultured. The lipid fractions extracted from wild gilthead sea bream showed strong aggregatory properties, while the lipid fractions extracted from farmed fish showed strong inhibitory activities. The aggregatory properties of total lipids were mainly attributed to polar lipids while the PAF antagonistic activity was attributed to neutral lipids. The biological activities of such fractions with respect to their aggregatory properties may explain, in part, the protective role of fish consumption against cardiovascular diseases.     

Nucleotide degradation and biogenic amine formation of wild white grouper (Epinephelus aeneus) stored in ice and at chill temperature (4 °C)

Sensory (cooked and uncooked), chemical (proximate composition, TVB-N, nucleotide degradation products and biogenic amines) and microbiological quality (TVC and total coliform) changes were investigated during storage of ungutted white grouper kept in ice and at chill temperature (4 °C). According to the sensory assessment, the shelf life of white grouper was 16 days in ice and 4 days for fish stored at chill temperature. TVB-N values increased with storage time. Amines found in white grouper stored in ice were TMA, putrescine, cadaverine, 2-phenylethylamine, dopamine, agmatine, tryptamine and serotonin. Histamine, spermine, spermidine were never detected with either storage condition. The acceptability limit in terms of microbial count was exceeded at 8 days in ice and at 4 days for fish stored at chill temperature. Total coliform count was 2.8 log₁₀ cfu/ml at 1 day and reached 10⁵ cfu/ml for both storage conditions.     

Proximate composition and mineral contents in aqua cultured sea bass (Dicentrarchus labrax), sea bream (Sparus aurata) analyzed by ICP-MS

The proximate composition and mineral contents of aqua cultured sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) of Aegean Sea were investigated. There were significant differences between moisture, fat and ash contents of the two species. Sodium, potassium, calcium, magnesium, manganese, iron, zinc and iodine values for sea bass and sea bream were significantly different (p < 0.05).     

Effects of using slurry ice on the microbiological, chemical and sensory assessments of aquacultured sea bass (Dicentrarchus labrax) stored at 4 °C

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole sea bass (Dicentrarchus labrax) a sparidae fish species of remarkable commercial interests. Four different group of chilling methods were used in this study; in slurry ice packaged on board (group A), in slurry ice packaged on company after 2 h (group B), slurry + flake ice packaged on board (group C) and only flake ice packaged on board (group D). The effect of this advanced system at the beginning of storage on quality losses and the shelf-life of aquacultured sea bass was evaluated. Mesophilic counts for sea bass exceeded 7 log cfu/g, which is considered the maximum level for acceptability for freshwater and marine fish after 13 days for groups C and D, and 15 days for groups A and B. At day 15; total volatile basic nitrogen (TVB-N) values of groups A–D reached the legal limits (35 mg/100 g set for TVB-N) for consumption. According to the results of sensory analyses, up to day 11, all the groups were determined as ‘acceptable’ but on day 13, the groups A–D were no longer acceptable. The main negative aspect related to quality loss in slurry ice group corresponded to the appearance of eyes and gills. Using slurry ice at the beginning of packaging did not affect the shelf-life of sea bass stored at 4 °C.     

Effects of using slurry ice during transportation on the microbiological, chemical, and sensory assessments of aquacultured sea bass (Dicentrarchus labrax) stored at 4 degrees C

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole sea bass (Dicentrarchus labrax) a sparidae fish species of remarkable commercial interests. In this study two different group of chilling methods were used during transportation; in slurry ice packaged (Group A), and flake ice packaged (Group B). The effect of this advanced system during transportation on quality losses and the shelf life of aquacultured sea bass was evaluated. Mesophilic counts for sea bass exceeded 7 log cfu/g, which is considered the maximum level for acceptability for freshwater and marine fish after 13 days for groups A and B. On day 13 TVB-N values of groups A and B, reached the legal limits (35 mg/100 g set for TVB-N) for consumption. According to the results of sensory analyses, up to day 9 all the groups were determined as "acceptable" but on day 13 the groups A and B were no longer acceptable. The main negative aspect related to quality loss in slurry ice group corresponded to the appearance of eyes and gills. Using slurry ice during transportation did not extend the shelf life of sea bass stored at 4 degrees C.     

The effect of holding live sea urchins (Evechinus chloroticus) in air prior to gonad removal on gonad adenine nucleotide profiles during storage at 4 °C

Sea urchin gonads are usually sold as a fresh chilled product. Thus, to evaluate the effect of live urchin’s post-harvest conditions on gonad shelf-life, gonads were extracted either immediately after harvesting or after holding urchins in air at either 4 or 15 °C for 144 and 72 h, respectively. Gonads were subsequently washed in brine and stored at 4 °C for 10 days prior to adenine nucleotide (nmol/g w/w) profile determination. A decline in ATP (control: 376.16; urchins held in air: 231.58 and 245.16) and build-up of its degradation products, mainly inosine (control: 13.25; urchins held in air: 82.87 and 52.95), was observed in gonads recovered from urchins held in air. A faster increase in ATP degradation products was detected during storage of gonads recovered from urchins held in air, with final K-values (%) of 59.34 and 48.18 being significantly higher than K-values obtained from the controls (29.69, p < 0.05), suggesting that post-harvest handling can negatively impact on gonad shelf-life.     

Effects of low concentration of salt and sucrose on the quality of bighead carp (Aristichthys nobilis) fillets stored at 4 °C

The effect of low concentration of salt and sucrose on the quality of bighead carp (Aristichthys nobilis) fillets was evaluated over a 16-day storage at refrigerated temperature (4 °C). Fish samples were brined with 1.1% salt (T1) and 1.1% salt + 0.9% sucrose (T2). The control and the treated fish samples were analysed periodically for physicochemical (pH, total volatile base nitrogen (TVB-N), water loss, electrical conductivity (EC), color), microbial (total viable counts) and sensory characteristics. No significant differences were observed between T1 and T2 for sensory score and EC (p > 0.05). Brining treatments predominantly decreased chemical changes, reflected in TVB-N and pH, retarded water loss and discoloration, inhibited bacterial growth and increased the overall sensory quality of fish, compared to untreated fillets. The results indicated that brining treatments improved the quality and safety of bighead carp fillet, which can be exploited by fish processors.     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

Quantitative changes in bacteria, amino acids and biogenic amines in sardine (Sardina pilchardus) stored at ambient temperature (25–28°C) and in ice

Freshly caught sardines contained high levels of bacteria located mainly on the skin and the gills. These bacteria invaded and grew rapidly in sardine muscle, reaching 5x10⁸ c.f.u. g^-1 and 6x10⁸ c.f.u. g^-1 respectively after 24h at ambient temperature and 8 days in ice.
Histidine, arginine, lysine, tyrosine and methionine levels decreased during storage. The other amino acids, except proline and taurine, accumulated in the fish muscle, indicating an extensive proteolysis.
Histamine, cadaverine and putrescine accumulated to levels of 2350ppm, 1050ppm and 300ppm respectively, after 24h storage at ambient temperature. Histamine and cadaverine reached similar levels after 8 days storage in ice, whereas putrescine formation was insignificant. Spermidine and spermine levels increased slightly under ambient conditions.
Salting the fish at 8% delayed bacterial and chemical changes but only in iced sardines.
The high content of free histidine found in sardines and the susceptibility of its muscle to histamine and cadaverine formation could explain its increasing implication in incidents of histamine poisoning.     

Combined effect of vacuum-packaging and oregano essential oil on the shelf-life of Mediterranean octopus (Octopus vulgaris) from the Aegean Sea stored at 4 °C

The present study evaluated the use of vacuum packaging (alone) or with addition of oregano essential oil (EO), as an antimicrobial treatment for shelf-life extension of fresh Mediterranean octopus stored under refrigeration for a period of 23 days. Four different treatments were tested: A, control sample; under aerobic storage in the absence of oregano essential oil; VP, under vacuum packaging in the absence of oregano essential oil; and VO1, VO2, treated samples with oregano essential oil 0.2 and 0.4% (v/w), respectively, under VP. Of all the microorganisms enumerated, Pseudomonas spp., H₂S-producing bacteria and lactic acid bacteria (LAB) were the groups that prevailed in octopus samples, irrespective of antimicrobial treatment. With regard to the chemical freshness indices determined, thiobarbituric acid (TBA) values were low in all octopus samples, as could have been expected from the low fat content of the product. Both trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values of oregano treated under VP octopus samples were significantly lower compared to control samples during the entire refrigerated storage period. Based primarily on sensory evaluation (odor), the use of VP, VO1 and VO2 extended the shelf-life of fresh Mediterranean octopus by ca. 3, 11 and 20 days, respectively.     

Inhibitory effect of spices on in vitro histamine production and histidine decarboxylase activity ofMorganella morganii and on the biogenic amine formation in mackerel stored at 30°C

The inhibitory effects of clove, cinnamon, cardamom, turmeric and pepper on the histamine production and histidine decarboxylase activity ofMorganella morganii (a potent histamine-producing bacteria in fish) was examined at 30°C using HPLC. Cinnamon and clove exhibited a significant (P<0.01) inhibitory effect, whereas turmeric and cardamom had a moderate effect. These spices were applied to whole mackerel at a level of 3% and their inhibitory effect on biogenic amine formation at 30°C was also examined. As in the in vitro study, clove and cinnamon showed a significant (P< 0.05) inhibitory effect on histamine, putrescine and tyramine formation but not on that of cadaverine. Cardamom and turmeric exhibited a moderate effect and pepper was ineffective. Therefore, clove and cinnamon are more helpful than cardamom and turmeric in the minimization of the formation of toxic histamine in mackerel.     

Chemical composition and antibacterial activity of Laurus nobilis essential oil towards foodborne pathogens and its application in fresh Tuscan sausage stored at 7 °C

The presence of foodborne pathogens in fresh Tuscan sausage has been reported and these contaminations pose a potential risk to consumers. The objective of the present study was to evaluate the antimicrobial activity of bay leaf essential oil (EO) in vitro and in fresh Tuscan sausage stored at 7 °C for 14 d. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against foodborne pathogens were determined in vitro. The lowest MIC and MBC were found for Escherichia coli (MIC = MBC = 2.5 g/L) and Yersinia enterocolitica (MIC = 1.25 g/L, MBC = 2.5 g/L). Fresh Tuscan sausages were treated with bay leaf EO at 0.05 g/100 g or 0.1 g/100 g and their shelf life was compared to a non-treated control. All groups presented low levels of rancidity (TBARS < 0.5 mg MDA/kg). The EO was able to reduce the population of total coliforms (2.8 log CFU/g) and to extend the product shelf life for two days. Although the presence of the EO affected the sensory characteristics of the sausage, it was considered acceptable by consumers at both concentrations tested. Overall, the results of this study indicate that bay leaf essential oil can be applied in fresh Tuscan sausage to improve its safety and shelf life.