Preservation of iced refrigerated sea bream (Sparus aurata) by irradiation: microbiological, chemical and sensory attributes

Quality and shelf life of non-irradiated and irradiated (2.5 and 5 kGy) sea bream in ice conditions and stored at +4 °C were investigated by measurement of microbiological, chemical and sensory analysis. Microbial counts for non-irradiated sea bream samples were higher than respective irradiated fish. Total volatile base nitrogen (TVB-N) values increased value of 38.64 mg/100 g for non-irradiated, sea bream during iced storage whereas for irradiated fish lower values of 13.48 and 12.06 mg/100 g were recorded at 2.5 and 5 kGy, respectively (day 19). Trimethylamine (TMA-N) values and thiobarbituric acid (TBA) values for irradiated samples were lower than non-irradiated samples. Acceptability scores for odour, taste and texture of cooked decreased with storage time. The sensory scores of sea bream stored in control and 2.5–5 kGy at +4 °C were 13 and 15 days, respectively. The results obtained from this study showed that the shelf life of sea bream stored in ice, as determined by overall acceptability all data, is 13 days for non-irradiated sea bream and 15 days for 2.5 kGy irradiated and 17 days for 5 kGy irradiated sea bream.     

Comparison of selected methods of assessing freshness quality and remaining storage life of iced gilthead sea bream (Sparus aurata)

Quality changes of whole, iced gilthead sea bream were monitored by sensory evaluation, k₁ value, GR Torrymeter, and bacterial counts. The methods were tested for their suitability to determine freshness quality and remaining storage life in ice. Depending on the measured parameter, post-mortem age of the iced fish could be predicted with an accuracy of ±1.5–3.6 days. Although assessment of cooked fish flavour is the underlying basis for establishing the state of the fish, the quality index method can be more effective for routine freshness evaluations. The k₁ value provides a useful means of monitoring early storage change, resulting primarily from autolytic reactions. Counts of sulphide-producing bacteria can be used to determine the time to rejection, while total counts at 20 °C are only poor measures of freshness quality. The GR Torrymeter offers a unique practical tool for assessing freshness quality and remaining storage life of iced gilthead sea bream.     

Effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of ungutted sea bream and sea bass. Mesophilic counts of ungutted sea bream and sea bass reached 7.39 log cfu/g and 7.26 log cfu/g after 9 days. At the end of the storage period of 14 days; TVB-N, TBA, TMA-N values of ungutted sea bream were determined as 37.5±0.51 mg/100 g, 3.82±0.03 mg MA/kg, 7.73±0.25 mg/100 g, respectively. TVB-N, TBA, TMA-N values of ungutted sea bass were reached 35.4±0.9 mg/100 g, 3.75±0.81 mg MA/kg, 6.94±0.08 mg/100 g on day 14th, respectively. Result of this study indicates that the shelf life of whole ungutted sea bream stored in ice as determined by the overall acceptability sensory scores, chemical quality and microbiological data is 12, 9 and 9 days, respectively. Each chemical, sensory and microbiological results for sea bream showed us that there was a correlation and similarity, and day 9 was the beginning of spoilage. Whole ungutted sea bass stored in ice as chemical results for sea bass showed us that day 7 was the beginning of spoilage and for sea bream day 9 was the beginning of spoilage.     

Effect of gutting on microbiological,chemical, and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting on microbiological, chemical, and sensory properties of aqua-cultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads and H₂S-producing bacteria (including Shewanella putrefaciens) were the dominant bacteria at the end of the 16-day storage period in ice for both whole ungutted and gutted sea bass. Brochothrix thermosphacta and Enterobacteriaceae were also found in the spoilage microflora of ungutted and gutted sea bass but their counts were always less than those of Pseudomonads and H₂S-producing bacteria. Bacterial counts of whole ungutted sea bass were always higher than those obtained for gutted sea bass samples. Mesophilic counts for gutted and ungutted fish exceeded 7 log cfu g⁻¹ after 9 and 15 days of ice storage, respectively. Of the chemical indicators of spoilage, TMA values of ungutted sea bass increased very slowly whereas for gutted samples higher values were obtained reaching a final value of 0.73 and 4.39 mg N 100 g⁻¹, respectively (day 16). TVB-N values showed no significant increase for whole ungutted sea bass during storage reaching a value of 27.7 mg N 100 g⁻¹ (day 16) whereas for gutted fish 36.9 mg N 100 g⁻¹ was recorded. TBA values remained low for ungutted sea bass samples until day 16 of storage, whereas for gutted fish were variable. Of the chemical indices used, none proved useful means of monitoring early ungutted and gutted sea bass freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 5 days for the ungutted sea bass, a grade A for a further 2 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Gutted sea bass was given a grade E for up to 3 days, a grade A for the 4–7th days, and a grade B for the 8–10th days of storage, whereas on day 11 it was graded as unfit. Acceptability scores for odor, taste and texture of cooked ungutted and gutted sea bass decreased with time of storage. Results of this study indicate that the shelf-life of whole ungutted and gutted sea bass stored in ice as determined by the overall acceptability sensory scores and microbiological data is 13 and 8 days, respectively.     

Nucleotide degradation products of gamma‐irradiated sea bream (Sparus aurata) stored in ice

Nucleotide degradation products of irradiated sea bream stored up to 19 days in ice were investigated. Irradiation had significant effect on the nucleotide concentrations in sea bream muscle (P < 0.05). The results showed that the highest value of inosine monophosphate (IMP) was observed in irradiated sea bream at 5 kGy, followed by at 2.5 kGy. Initial inosine (INO) concentration in irradiated sea bream at 5 kGy was 4.26 μmoles g^?1, which reached maximum value of 8.83 μmoles g^?1 when fish completely spoiled (19 days). When the fish reached the limit of acceptability, the mean values of K, Ki, H and G were 86.8%, 90.3%, 59.8% and 213.9% for unirradiated sea bream, 85.2%, 87.8%, 56.8% and 197.8% for irradiated sea bream at 2.5 kGy and 88.4%, 90.9%, 57.8%, 211.5% for irradiated sea bream at 5 kGy, respectively. The results of this study indicated that nucleotide degradation was more rapid in unirradiated sea bream than those irradiated. K, Ki, H and G value in irradiated fish can be used as a freshness index because there is a good linear relationship between values and storage time of fish.     

Assessment of shelf-life of maricultured gilthead sea bream (Sparus aurata) stored in ice

Gilthead sea bream ( Sparus aurata ) were stored in melting ice (0 °C) for a period of 24 days from the time of harvest with sensory assessments of the whole raw fish and of the cooked fish flesh conducted at regular intervals. The ungutted fish was given an EC freshness grade E for up to 3 days, grade A for a further 7 days, and grade B for 4 more days after which it was graded as C (unfit). The sensory score for flavour of the cooked fillets decreased linearly with period of storage: fresh characteristic flavours were present for 2–4 days, decreasing to a relatively bland flavour after 10–12 days. Off flavours were evident by 13–15 days storage and by 18–19 days the flesh was unpalatable. With the possible exception of hypoxanthine, none of the chemicals investigated was particularly useful as an indicator of change. Changes in pH, trimethylamine and total volatile bases during the first half of the edible storage life were insignificant. Deterioration of flesh lipids, assessed by free fatty acid content and thiobarbituric acid value, appeared to present no serious problem during shelf-life. Proximate composition and sensory attributes, appropriate for routine inspection of gilthead sea bream were also determined.     

Determination of volatile compounds of precooked prawn (Penaeus vannamei) and cultured gilthead sea bream (Sparus aurata) stored in ice as possible spoilage markers using solid phase microextraction and gas chromatography/mass spectrometry

BACKGROUND: Solid phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) have been reported as useful techniques for analysing volatile compounds to monitor fish freshness. In this study, SPME/GC/MS was applied to cultured gilthead sea bream and precooked prawn stored in ice for 6 days in order to find possible markers of spoilage. Total volatile basic nitrogen (TVB‐N) was also determined as a common index of spoilage. RESULTS: The TVB‐N value at the end of the storage period for cultured gilthead sea bream (302.40 ± 8.50 mg kg^?1) was within the range of acceptability for edible fish (300–400 mg kg^?1) but could be considered at the beginning of spoilage. For precooked prawn the TVB‐N value at day 6 (863.04 ± 7.84 mg kg^?1) was not acceptable for human consumption. SPME/GC/MS identified 30 compounds in cultured gilthead sea bream and 49 compounds in precooked prawn. In particular, 3‐methyl‐1‐butanol, 2‐methylbutanal, 3‐methylbutanal and 3‐hydroxy‐2‐butanone increased during refrigerated storage both in the two species investigated here and in other species reported elsewhere and could be considered as markers of spoilage. CONCLUSION: This study confirmed that SPME/GC/MS can be considered an efficient method suitable for analysing the volatile compounds of both raw fish and fishery products in order to monitor loss of freshness. Copyright © 2008 Society of Chemical Industry     

Microbiological,chemical and sensory changes of whole and filleted Mediterranean aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of filleting on the microbiological, chemical and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads, H₂S‐producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria at the end of the 16 day storage period in ice for both whole ungutted and filleted sea bass. Enterobacteriaceae were also found in the spoilage microflora of whole ungutted and filleted sea bass, but their counts were always lower than those of pseudomonads, H₂S‐producing bacteria (including S putrefaciens) and B thermosphacta. Total viable counts for whole ungutted sea bass were always lower than those for filleted sea bass samples. Of the chemical indicators of spoilage, TMA (trimethylamine) values of whole ungutted sea bass increased very slowly, whereas significantly higher values were obtained for filleted samples, with respective values of 0.253 and 1.515 mg N per 100 g muscle being reached at the end of their shelf‐life (days 13 and 9 respectively). TVB‐N (total volatile basic nitrogen) values showed a slight increase for whole ungutted sea bass during storage, reaching a value of 26.77 mg N per 100 g muscle (day 13), whereas for filleted fish a corresponding value of 26.88 mg N per 100 g muscle was recorded (day 9). TBA (thiobarbituric acid) values increased slowly for whole ungutted and filleted sea bass samples throughout the entire storage period, reaching final values of 4.48 (day 13) and 13.84 (day 9) mg malonaldehyde kg^?1 respectively. Sensory assessment of raw fish using the EC freshness scale gave a grade E for up to 5 days for whole ungutted sea bass, a grade A for a further 4 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Overall acceptability scores for odour, taste and texture of cooked whole ungutted and filleted sea bass decreased with increasing time of storage. The results of this study indicate that the shelf‐life of sea bass stored in ice, as determined by overall acceptability sensory scores and microbiological data, is 8–9 days for filleted and 12–13 days for whole ungutted fish. Copyright © 2003 Society of Chemical Industry     

Effects of gutting and ungutting on microbiological, chemical, and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting and ungutting on microbiological, chemical, and sensory properties of aqua-cultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of gutted and ungutted sea bream and sea bass. The mesophilic counts reached 8.19 log cfu/g for ungutted sea bream and 7.93 log cfu/g for ungutted sea bass after 14 days of storage. The mesophilic counts reached 8.89 log cfu/g for gutted sea bream and 8.16 log cfu/g for gutted sea bass after 14 days of storage. On day 14 of storage the psychrophilic counts of ungutted sea bream and sea bass were 8.24 log cfu/g and 8.03 log cfu/g, respectively, and for gutted sea bream and sea bass were 8.93 and 8.22, respectively. At the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of ungutted sea bass were determined as 50.13 +/- 0.25 mg/100 g, 2.66 +/- 0.06 mg malonaldehit/kg, 9.86 +/- 0.01 mg/100 g respectively. TVB-N, TBA, and TMA-N values of ungutted sea bream reached 55.90 +/- 0.36 mg/100g, 2.51 +/- 0.21 mg malonaldehit/kg, 9.79 +/- 0.01 mg/100 g on day 14 respectively. And also at the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of gutted sea bass were determined as 48.00 +/- 0.26 mg/100 g, 2.48 +/- 0.03 mg malonaldehit/kg, 8.71 +/- 0.06 mg/100 g respectively. TVB-N, TBA, and TMA-N values of gutted sea bream reached 49.66 +/- 0.77 mg/100g, 2.64 +/- 0.07 mg malonaldehit/kg, 8.97 +/- 0.01 mg/100 g on day 14 respectively. The result of this study indicates that the shelf-life of whole ungutted sea bass and sea bream stored in ice as determined by the overal acceptibility sensory scores, chemical quality, and microbiological results show us that the fish were spoilt on day 14. Each chemical, sensory, and microbiological result for sea bream showed us that there was a correlation and similarity and on day 14 it was spoilt.     

Combined effect of light salting,modified atmosphere packaging and oregano essential oil on the shelf-life of sea bream (Sparus aurata): Biochemical and sensory attributes

The combined effect of modified atmosphere packaging (MAP: 40% CO₂/30% O₂/30% N₂) and oregano essential oil, on the shelf-life of lightly salted cultured sea bream (Sparus aurata) fillets stored under refrigeration was studied. Quality assessment was based on sensory analysis and biochemical indices determination. Total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) values were higher in sea bream fillets stored in air followed by salted fillets stored in air. For salted sea bream fillets stored under MAP the inhibition in the TVBN and TMAN values was evident in the order MAP < MAP/0.4% (v/w) oregano oil < MAP/0.8% (v/w) oregano oil indicating the preservative effect of oregano oil. Salting had a noticeable preservative effect but produced an increase in the 2-thiobarbituric acid (TBA) values while oregano oil had a strong antioxidant activity giving the lowest TBA values. All raw sea bream fillet samples received acceptable sensory scores during the first 15–16 days of storage. The salted samples remained acceptable up to ca. 20–21 days while the MAP salted samples up to ca. 27–28 days of storage. The oregano oil addition in MAP salted samples yielded a distinct but pleasant flavor and contributed to a considerable slower process of fish spoilage given that the fillets treated with 0.8% (v/w) oregano oil were still sensory acceptable after 33 days of storage. The preservative effect was greater as the oregano oil concentration was greater.     

Influence of salting and gamma irradiation on the shelf-life extension of threadfin bream in ice

Fresh, eviscerated threadfin bream (Nemipterus japonicus) packaged in polyethylene pouches were dipped in 10% (w/w) sodium chloride for 1 h and subjected to gamma irradiation at 0, 1 or 2 kGy at ice temperature. The treated fish were stored under ice. At periodic intervals, quality of the fish was determined by sensory, chemical and microbiological parameters. The unsalted and unirradiated fish was acceptable up to 8 days in comparison to a storage life of 12 and 22 days for the unsalted fish irradiated at 1 and 2 kGy, respectively. Salting prior to irradiation at 0, 1 or 2 kGy gave a shelf life of 9, 14 and 28 days, respectively. Salting gave a firmer texture to the fish and prevented drip formation in the pouches during storage. The results suggested that while irradiation could significantly (P< 0.05) extend the refrigerated shelf life of threadfin bream, salting prior to irradiation could enhance the acceptability of the irradiated fish.     

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.     

Quality assessment of wild European eel (Anguilla anguilla) stored in ice

The quality assessment of wild European eel (Anguilla anguilla) stored in ice and in boxes without ice (3 ± 1 °C) was investigated by the sensory analysis, levels of nucleotide breakdown products and biogenic amines for up to 19 days. Sensory analysis was assessed using the Tasmanian Food Research Unit Scheme. K and related values (K_i, G, P, H and F_r) were used as freshness indicators. Linear regressions (r²) obtained from K, K_i, G, P, H and F_r were 0.95, 0.96, 0.83, 0.96, 0.99 and 0.96, respectively, for eel stored in ice whereas, for eel kept in boxes without ice, the values were 0.86, 0.86, 0.96, 0.91, 0.98 and 0.86, respectively. When eel stored in ice and in boxes without ice were considered at the limit of acceptability by assessors at ∼12–14 days and ∼5–7 days, respectively, the average K, K_i and P values were ∼70–85%, H values were ∼60% and F_r values were ∼10% for both storage conditions. The level of histamine exceeded the legal limit (5 mg/100 g fish) in eel stored without ice after 6–7 days and, in ice, after 13–14 days of storage, at which time eels were rejected by the sensory panel. The concentrations of biogenic amines were higher in eel stored in boxes without ice than in eel kept in ice. The levels of histamine in the muscle of eel kept in boxes without ice and in ice increased to the maximum levels of 17.9 mg/100 g on day 12 and 12.6 mg/100 g on day 19, respectively.     

Rapid Assessment of Fish Freshness and Quality by <Superscript>1</Superscript>H HR-MAS NMR Spectroscopy

A new analytical method that allows the rapid assessment of fish freshness and quality is presented. The method is based on ¹H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy and allows the rapid determination of two well-established indicators of fish freshness and quality: the K value and the trimethylamine nitrogen (TMA-N) content. The method is demonstrated on four different species of fish (sea bream, sea bass, trout, and red mullet) stored on ice at 0 °C. The results obtained are in agreement with more cumbersome methods classically used to determine the K value and the TMA-N concentration. The main advantage of the ¹H HR-MAS NMR approach is to allow a direct measurement of these two parameters directly on unprocessed fish sample without using any preliminary extraction. The total analysis time, including sample preparation, is of the order of 40 min per sample.     

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     

Microbiological,chemical and sensory assessment of iced whole and filleted aquacultured rainbow trout

The effect of filleting on microbiological, chemical, and sensory properties of aquacultured freshwater trout (Onchorynchus mykiss) stored in ice was studied. Pseudomonads, H₂S-producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria while, Enterobacteriaceae in lower counts were also found in the spoilage microflora of whole ungutted and filleted trout over an 18-day storage period in ice. Bacterial counts of whole ungutted trout were always lower than those obtained for filleted trout samples. Mesophilic counts for filleted and ungutted fish exceeded 7 log cfu/cm² after 10 and 18 days of ice storage, respectively. Of the chemical indicators of spoilage, trimethylamine (TMA) values of ungutted trout increased very slowly whereas for filleted samples higher values were obtained reaching a final value of 4.29 and 6.38 mg N/100 g, respectively (day 18). Total volatile basic nitrogen (TVB-N) values showed no significant increase for whole ungutted trout during storage reaching a value of 20.16 mg N/100 g (day 18) whereas for filleted fish a respective value of 26.06 mg N/100 g was recorded. Thiobarbituric acid (TBA) values of ungutted trout increased very slowly whereas for filleted samples higher values were obtained reaching a final value of 16.21 and 19.41 μg MA/g, respectively (day 18). Of the chemical indices used, none proved useful means of monitoring early freshness for ungutted and filleted trout freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 6 days for the ungutted trout, a grade A for a further 3 days and a grade B for an additional 6 days, after which trout was graded as C (unfit). Acceptability scores for odor, taste and texture of cooked ungutted and filleted trout decreased with time of storage. Results of this study indicated that the shelf-life of whole ungutted and filleted trout stored in ice as determined by sensorial and microbiological data is 15–16 and 10–12 days, respectively.     

Effect of Slaughter Method on Postmortem Changes of Grass Carp (Ctenopharyngodon idella) Stored in Icesti

ABSTRACT: The effect of 2 slaughter methods (immersion in ice-water slurry and electrical stunning followed by ice slurry asphyxiation) on the quality of grass carp ( Ctenopharyngodon idella ) stored in ice for 20 d was evaluated using sensory and chemical analysis. Electricity immediately stunned the fish and did not induce blood spots in the flesh. Fish killed by electricity showed a faster initial rate of ATP degradation and entered into rigor mortis earlier, but did not show significant differences in the sensory score when compared with fish killed by immersion in ice-water slurry. Thus, no differences were observed in the shelf life of carps between the 2 slaughter methods evaluated. The limit for acceptability of grass carp stored in ice was around 13 to 16 d. Grass carp accumulated more inosine than hypoxanthine. K, Ki, P , Fr, and H values were highly correlated with storage time and with the TFRU sensory scores in both groups; these could be used to assess the freshness quality of grass carp.     

Biochemical, sensory and microbiological attributes of bream (Megalobrama amblycephala) during partial freezing and chilled storage

BACKGROUND: Bream is one of the main farmed freshwater fish species in China. This study aimed to examine the nucleotide degradation of bream during partial freezing and chilled storage and to assess the possible usefulness of nucleotide ratios (K, Ki, H, P, Fr and G values) as freshness indices in comparison with sensory assessment and total viable counts. RESULTS: Total viable counts were 5.74 and 4.66 log(colony‐forming units g^?1) on the day of sensory rejection under chilled storage and partial freezing storage respectively. The inosine 5‐monophosphate decrease and inosine increase were faster in chilled storage than in partial freezing storage. Hypoxanthine levels increased continuously with time under both storage regimes. Among the nucleotide ratios, the K, Ki, P, G and Fr values were superior to the H value and provided useful freshness indicators for both storage conditions. CONCLUSION: Bream in chilled storage were sensorially acceptable only up to 10 days, compared with 33 days for bream in partial freezing storage. Partial freezing delayed the nucleotide degradation of bream. Copyright © 2011 Society of Chemical Industry     

Effects of tea polyphenol coating combined with ozone water washing on the storage quality of black sea bream (Sparus macrocephalus)

The present research evaluated the effects of tea polyphenol (TP) combined with ozone water (O₃) on the quality of black sea bream (Sparus macrocephalus) over a period of 15 days storage at 4 °C. A solution of TP (0.2%, w/v) was used to coat the fish after washing with ozone water (1 mg/L). Fish physicochemical (pH, K value, peroxide value, thiobarbituric acid, total volatile basic nitrogen, trimethylamine, texture, and colour), sensory, and bacteriological characteristics were all analysed. TP + O₃ treatment effectively reduced nucleotide breakdown, lipid oxidation, protein decomposition, and microbial growth, and maintained better characteristics of texture, colour, and sensory compared with the control. The efficiency of TP + O₃ treatment was also better than that of TP treatment or O₃ treatment alone. Therefore, tea polyphenol coating combined with ozone water prewashing may be a promising method of maintaining the storage quality of black sea bream and of extending fish post-mortem shelf-life during 4 °C storage.     

Effects of aluminium foil and cling film on biogenic amines and nucleotide degradation products in gutted sea bream stored at 2±1 °C

Biogenic amines and nucleotide degradation products of sea bream stored in ice, wrapped in aluminium foil (WAF) and in cling film (WCF) at 2±1 °C were investigated by using a rapid HPLC method. Results obtained from this study showed that for household purposes packing fish in different materials has a little effect on the biogenic amines formation and nucleotide degradation products. The highest decrease of IMP content was observed for sea bream in WAF, followed by WCF. INO values showed a fluctuation and remained below the levels of 5.5 μmol/g for all storage conditions. Hx value constantly increased with the storage time during chilled storage. For all of the storage condition, K and Ki value increased linearly with storage time. At the end of the storage period, K, Ki, H and G value reached 60–76%, 65–81%, 30–54% and 89–173%, respectively. Among biogenic amines, (trimetylamine) TMA, putrescine, cadaverine, spermidine, spermine, tryptamine, tyramine, β-phenylalanine and histamine were detected during storage period. TMA and putrescine were observed to increase linearly during storage period. Histamine production was only found at the end of storage period. The highest histamine values for fish wrapped in aluminium foil were 6.4 mg/100 g and fish wrapped in cling film was 4.6 mg/100 g.