Postmortem changes in cazon fish muscle stored on ice

The biochemical, chemical and physical postmortem changes and their relation to the cazon muscle eating quality were studied during an 18 day storage period at 0 °C (ice). Content of ATP and breakdown products, K value, pH, trimethylamine (TMA-N), total volatile bases (TVB-N), water-holding capacity (WHC), colour and texture changes were examined. At the beginning of the study, the cazon muscle showed a low concentration of ATP and a high value of IMP. Regarding to the signs of freshness and deterioration, K value presented a linear increase (r² = 0.97) with an initial value of 1.05% and a final value of 58.9%. The TBV-N and TMA-N significantly increased (P < 0.05). As for the physical analysis whereas the pH and the WHC changed (P < 0.05); texture was not affected (P < 0.05). The overall results of this study indicated that the edible quality of cazon fish muscle was maintained during at least 18 days of ice storage.     

Postmortem changes in the adductor muscle of Pacific lions-paw scallop (Nodipecten subnodosus) during ice storage

Postmortem biochemical, chemical, and physical changes of the adductor muscle of Pacific lions-paw scallop were studied during a 15-day storage period at 0 °C (ice). Content of ATP and breakdown products, K value, pH, trimethylamine, total volatile bases, water-holding capacity, colour, and texture changes were examined. K value increased logarithmically (r² = 0.95) from an initial value of 40.3–79.7% on day 15. The spoilage indicators trimethylamine and total volatile bases increased from 15.6 to 30.7 and 1.3 to 6.8 mg N/100 g of sample, respectively, which indicated spoilage at the end of the storage period. Texture, colour, and pH were not affected; however, water-holding capacity decreased significantly, from 96.0% on day 1 to 86.0% on day 15. Overall results indicated that quality of Pacific lions-paw scallop adductor muscle was maintained during at least 12 days of ice storage.     

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.     

Effects of slaughtering methods on sensory,chemical and microbiological quality of rainbow trout (<Emphasis Type="Italic">Onchorynchus mykiss</Emphasis>) stored in ice and MAP

The effects of slaughtering methods (percussive stunning and death in ice slurry) on the quality of rainbow trout stored in ice and modified atmosphere packing (MAP) (40% CO₂, 30% N₂ and 30% O₂) were investigated in terms of sensory, chemical and microbiological analysis. Sensory analysis showed that the demerit points of fish slaughtered by percussive stunning were higher than those slaughtered by the ice slurry method, but there were no significant differences in demerit points (P>0.05). In addition, the rate of increase in demerit points in fish in MAP was significantly (P>0.05) higher at 6 and 10 days of storage than that in fish in ice for each slaughter method, which was due to increased drip, the appearance of slime and the odour of the fish in MAP packing. The mean K values of rainbow trout slaughtered by percussive stunning in this study were significantly lower (P<0.05) than those of trout slaughtered according to the ice slurry method. The level of biogenic amines, regardless of the slaughter method, showed a similar trend (P>0.05), but higher concentrations of biogenic amines were found for the ice slurry slaughter method and for fish stored in ice. There were no significant differences (P>0.05) in total viable count of fish stored in ice and MAP, regardless of the different slaughter methods used. However, fish packed in MAP showed reduction in bacterial counts compared to fish held in ice throughout study. The results of this study showed that slaughter by percussive stunning improved the quality of trout compared to the ice slurry method.     

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.     

Physical, chemical and microbiological changes in stored green asparagus spears as affected by coating of silver nanoparticles-PVP

Silver nanoparticles have recently gained increasing interests due to their antimicrobial activities in food processing applications. The aim of this study was to evaluate the effect of silver nanoparticles-PVP coating on weight loss, ascorbic acid, total chlorophyll, crude fiber, color, firmness and microbial qualities of asparagus spears stored at 2 and 10 °C. Asparagus samples were first sanitized with 100 mg l⁻¹ sodium hypochloride solution for 15 min. They were then immersed in coating solution containing silver nanoparticles for 3 min at room temperature. During 25-day storage at 2 or 10 °C, the coated asparagus demonstrated lower weight loss, greener color and tender texture compared with the control samples. The growth of microorganism was significantly hindered by the coating. Based on comprehensive comparison and evaluation, asparagus spears coated by silver nanoparticles could be kept in good quality for 25 days at 2 °C and for 20 days at 10 °C.     

Freshness assessment of cultured sea bream (Sparus aurata) by chemical,physical and sensory methods

The quality changes of cultured sea bream (Sparus aurata) stored in ice for a period of up to 23 days were determined by K and related values, sensory assessment and texture by texturometer. Sensory schemes, based on the Tasmanian Food Research Unit (TFRU) scheme for raw fish and on the Torry scheme for cooked fish were modified to be appropriate for whole cultured sea bream, according to the trained panellists’ perceptions, during the storage period in ice. The TFRU sensory score of fish showed good agreement with K value and texture results throughout the storage period. The limit for acceptability of cultured sea bream stored in ice was about 17–18 days. Generally, K, K_i and G values had good correlation with the degree of freshness and can be used as freshness indicators.     

Sensory, chemical and microbiological assessment of farm-raised European sea bass (Dicentrarchus labrax) stored in melting ice

Farm raised European sea bass ( Dicentrarchus labrax ) were stored in melting ice for a period up to 22 days from the time of harvest, and sensory, chemical, and microbiological assessments were made at intervals. The storage life of the ungutted fish, determined by sensory evaluation of the cooked flesh, was 19 days. Of the chemical tests, only k ₁ value provided a useful means of monitoring early storage change. Trimethylamine, total volatile bases and pH showed practically no change during the first half of the edible storage life of the fish. Changes in free fatty acid (FFA) content and thiobarbituric acid (TBA) value could not be used to determine loss of acceptability or end of storage life. Sulphide producing bacteria constituted a very low proportion of the total aerobic flora, suggesting that the common sulphide producer Shewanella putrefaciens was not a major spoiler of sea bass in this trial.     

Assessment of European cuttlefish (Sepia officinalis, L.) nutritional value and freshness under ice storage using a developed Quality Index Method (QIM) and biochemical methods

The aim of this study was to determine the nutritional value of adult commercial cuttlefish, to develop a Quality Index Method (QIM) scheme, and to evaluate the application of some biochemical methods commonly used for freshness assessment of fish under ice storage. Additionally, shelf-life was to be determined based on both QIM and suitable biochemical methods. The nutritional value of the cuttlefish mantle in the first 24 h and after 13 days was determined. Captured cuttlefish was composed (g/100 g) by 16.60 ± 0.10 g protein, 0.09 ± 0.01 g fat, 79.55 ± 0.14 g moisture and 1.39 ± 0.03 g of ash. After 13 days of ice storage, cuttlefish was composed (g/100 g) of 11.90 ± 0.28 g protein, 0.17 ± 0.09 g fat, 87.04 ± 0.13 g moisture and 0.52 ± 0.01 g of ash. Differences (p < 0.001) were found in protein, ash and moisture but not in fat (p > 0.05). These results seem to indicate that there is impregnation of the iced water into the mantle tissue promoting protein leaching with the melting ice. TVB-N and TMA-N displayed a similar increasing tendency, peaking beyond EEC regulations proposed maximum between the 9th and 10th days. The developed QIM scheme for cuttlefish was composed of 29 demerit points, divided into 4 attributes and 13 parameters. The calculated quality index (QI) evolved linearly with storage time in ice (QI = 2.68 × days in ice − 0.61, R² = 0.9866). Storage time could be estimated with an accuracy of ± 1 day, if five cuttlefish from each sample were included in the QIM assessment. The shelf-life was determined as 8 ± 1 days by both type of methods (QIM and biochemical). However, the suitability of some biochemical methods to assess freshness need to be more thoroughly researched.     

Effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality changes of seer fish (Scomberomorus commerson) steaks stored in ice

The effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality of seer fish (Scomberomorus commerson) steaks was determined during chilled storage (1–2 °C). The O₂ absorber reduced the oxygen content in the pack to less than 0.01% corresponding to 99.96% reduction within 24 h. The use of O₂ absorber with sodium acetate dip treatment (2% w/v) extended the sensory shelf life up to 25 days compared to only 12 days for control air packs and 20 days for untreated samples with O₂ absorber. A prominent lag phase was observed for many bacterium studied, particularly for the sodium acetate treated samples with O₂ absorber. On the day of sensory rejection, both the total mesophilic and psychrotrophic counts reached 7.7–8.1 and 7.1–7.9 log cfu/g, respectively. The sodium acetate treatment and reduced O₂ atmosphere affected the type of major spoilers. In air packed samples, H₂S-producers predominated followed by Brochothrix thermosphacta, Pseudomonas spp., where as in the untreated samples with O₂ absorber, H₂S-producers predominated the microbial flora followed by Lactobacillus spp. For treated samples with O₂ absorber, B. thermosphacta formed the major micro-flora followed by Lactobacillus spp. The use of O₂ absorber inhibited the growth of Pseudomonas spp., and total Enterobacteriaceae.     

Evaluation of a slurry ice system for the commercialization of ray (Raja clavata): Effects on spoilage mechanisms directly affecting quality loss and shelf-life

The application of slurry ice, a biphasic system formed by small spherical ice crystals surrounded by seawater at sub-zero temperature, was evaluated as a new storage method for ray (Raja clavata), the elasmobranch fish species that exhibits highest commercial value in the European food markets. This advanced technique was used to compare with a control batch stored 10 days in flake ice. The results obtained in the sensory analysis indicated a significant extension of the overall quality (A class fish) from 3 days (flake ice) to 6 days (slurry ice). The development of ammonia external odour was the limiting parameter in both batches and was correlated with the activity of the endogenous mechanisms involved in the degradation of proteins and non-protein-nitrogen (NPN) rather than with the activity of proteolytic microorganisms. Storage of ray in slurry ice significantly (P<0.05) slowed down both biochemical (as estimated by the follow-up of the pH, TVB-N and K-value evolution) and microbial degradation mechanisms (estimated by the development of psychrotrophes and mesophiles counts) in chilled ray muscle. According to the parameters evaluated, storage of ray in slurry ice extends the shelf-life of this elasmobranch fish species due to a better maintenance of sensory, biochemical and microbiological quality, thus facilitating its commercialization.     

Sensory, physical, chemical and microbiological changes in European sea bass (Dicentrarchus labrax) fillets packed under modified atmosphere/air or prepared from whole fish stored in ice

Quality changes and shelf‐life in European sea bass fillets packed under 40% CO₂: 60% N₂ (MAP) and air (AIR) or prepared from the whole ungutted fish stored in ice (ROUND) were compared. Raw and cooked sensory scores, pH, colour, expressible water, malonaldehyde, total viable count, Pseudomonas spp., H₂S‐producing bacteria, Lactobacillus spp., Streptococcus spp., Staphylococcus spp., coliforms and proteolytic counts, were determined until AIR and MAP raw fillet spoilage. Raw ROUND fillets had the best quality and shelf‐life (10 vs. 8 vs. 7 days after slaughtering in ROUND, MAP and AIR, respectively), while the MAP fillets had better sensorial scores, lower pH values and better microbiological counts, but greater lightness values than the corresponding AIR fillets. MAP fillets also had the highest malonaldehyde levels. The higher correlation between Streptococcus spp. and odour scores (r = ?0.971, P < 0.01) compared to the other species could suggest that it is a specific spoilage organism in the MAP condition used.     

Sensory,physical, chemical and microbiological changes in aquacultured meagre (Argyrosomus regius) fillets during ice storage

Commercial-sized meagre fillets were stored on ice at 4 °C for 18 days, in order to evaluate the loss of quality and freshness that occurs over this period of time. Physicochemical (pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVBN), trimethylamine (TMA), water activity, water-holding capacity, colour, texture and fatty acid profile), sensory and microbiological analyses were carried out at 0, 4, 7, 11, 14 and 18 days of storage. As part of the sensory analysis, attributes associated with fillet appearance, odour and texture were examined. Variations in pH, TBA, TVBN and TMA were observed throughout the storage period, although only TBA displayed a significant correlation with time (r = 0.96). L^∗ and b^∗ values increased, and the chroma and hue values decreased, reflecting the colour changes experienced by the fillets over time. With regards to the texture profile, hardness was significantly correlated with time (−0.68). All the sensory analysis attributes exhibited significant variations and correlations close to 1.00 with storage time, which is a reflection of the fillets’ loss of freshness. The correlation coefficients between aerobic mesophilic and psychrophilic bacteria, enterobacteria and coliform counts on the one hand and storage time on the other were also very high (0.99–1.00). A regression analysis using the acceptability limit set by the ICMSF standard (1986) for total aerobic mesophilic counts (7 log cfu/g) yielded a shelf-life for meagre fillets of 9 days. The TBA, sensory and microbiological analyses displayed very strong correlations with storage time, and they may be considered suitable indicators for evaluating meagre fillet spoilage during refrigerated storage.     

Effects of a humidity-stabilizing sheet on the color and K value of beef stored at cold temperatures

The effects of a humidity-stabilizing sheet containing glycerol, on the color and K value of beef stored at cold temperatures were investigated in this study. A drip-absorbing sheet seems to be effective for the preservation of meat quality, while a humidity-stabilizing sheet containing glycerol prevents the increase of metmyoglobin in cold stored beef. Maintaining samples wrapped in humidity-stabilizing sheets containing glycerol at low temperature for 7days was a functional method for conserving the concentration of inosine monophosphate. Beef samples wrapped in sheets containing glycerol had lower K values than samples wrapped in sheets not containing glycerol. When the surface of the meat starts to desiccate, the humidity-stabilizing sheet releases moisture that has been absorbed from the beef in the early stages of storage. Thus, glycerol could potentially play a role as a humidity-stabilizing controller and color preservative. This research suggests that a humidity-stabilizing sheet containing glycerol is a useful moisture controller and prevents deterioration of meat quality, discoloration, and desiccation.     

Sensory,microbiological and chemical assessment of the freshness of red mullet (Mullus barbatus) and goldband goatfish (Upeneus moluccensis) during storage in ice

The shelf life of red mullet and goldband goatfish during ice storage were studied in terms of sensory, microbiological and chemical changes. The sensory acceptability limit was 8 days for goldband goatfish (Upeneus moluccensis) and 11 days for red mullet (Mullus barbatus) stored in ice. The TVC level was correlated with sensory assessment. The TVC exceeded 7 log cfu g⁻¹ after 8 days for goldband goatfish, and 11 days for red mullet. At the end of storage period, pH, TVB-N, TBA, FFA and PV for red mullet were 7.84, 47.19 mg/100 g, 0.69 mg MA kg⁻¹, 1.17% oleic acid and 1.58 meq O₂/kg and for goldband goatfish they were 7.53, 43.97 mg/100 g, 0.74 mg MA kg⁻¹, 1.62% oleic acid and 1.68 meq O₂/kg, respectively. In red mullet, agmatine, serotonin, histamine and dopamine became the dominant amines, reaching 7.30, 5.97, 2.52 and 2.31 mg/100 g, respectively. Also the dominant amines for goldband goatfish were 4.37, 3.88, 3.38 and 2.00 mg/100 g for histamine, agmatine, dopamine and putrescine, respectively.     

Effects of natural antimicrobials on inhibition of Listeria monocytogenes and on chemical, physical and sensory attributes of naturally-cured frankfurters

Due to regulations for natural and organic processed meats, sodium nitrite and many antimicrobials cannot be used. Therefore, natural and organic processed meats are more susceptible to pathogenic bacterial growth, and natural alternatives to chemical preservatives are needed. Inhibition of Listeria monocytogenes, and quality characteristics of frankfurters manufactured with 3% cranberry powder, or with 1% or 2% cranberry powder each with either cherry powder (0.6%), lime powder (60 mg/kg), or a blend of cherry, lime and vinegar (1.4%) were investigated. Cranberry powder at 3% significantly reduced L. monocytogenes growth by 5.3 log CFU/g compared to the uncured co006Etrol (P < 0.05). However, cranberry addition over 1% also resulted in significant product pH decline and negatively impacted the color, texture and sensory attributes of the frankfurters.     

Blue-back fish: Fatty acid profile in selected seasons and retention upon baking

The effects of the catching season (either Autumn/Winter or Spring) on lipid content, fatty acid profile and true retention values after oven baking were determined in anchovy (Engraulis encrasicholus), sardine (Sardina pilchardus), sprat (Sprattus sprattus) and horse mackerel (Trachurus trachurus) from the North Adriatic sea. In the raw state, the catching season induced significant changes in the flesh lipid contents of sardine and sprat. Anchovy was the species whose fatty acid composition of flesh lipids was most clearly affected by the season of catch. Oven baking had a significant, though rather modest, effect on some fatty acids and indices of sardine and anchovy lipids. When compared to the other species within the same season, spring sardine and winter sprat gave significantly higher true retention values for several individual fatty acids and some sums. Between 1 and 2.5 servings/week (depending on season) of either cooked anchovy, sardine, sprat, or 3 servings of cooked spring horse mackerel would suffice to satisfy human weekly requirements of EPA + DHA.     

Influence of starters on chemical, biochemical, and sensory changes in Turkish White-brined cheese during ripening

Turkish White-brined cheese was manufactured using Lactococcus strains (Lactococcus lactis ssp. lactis NCDO763 plus L. lactis ssp. cremoris SK11 and L. lactis ssp. lactis UC317 plus L. lactis ssp. cremoris HP) or without a starter culture, and ripened for 90 d. It was found that the use of starters significantly influenced the physical, chemical, biochemical, and sensory properties of the cheeses. Chemical composition, pH, and sensory properties of cheeses made with starter were not affected by the different starter bacteria. The levels of soluble nitrogen fractions and urea-PAGE of the pH 4.6-insoluble fractions were found to be significantly different at various stages of ripening. Urea-PAGE patterns of the pH 4.6-insoluble fractions of the cheeses showed that considerable degradation of α_s1-casein occurred and that β-casein was more resistant to hydrolysis. The use of a starter culture significantly influenced the levels of 12% trichloroacetic acid-soluble nitrogen, 5% phosphotungstic acid-soluble nitrogen, free amino acids, total free fatty acids, and the peptide profiles (reverse phase-HPLC) of 70% (vol/vol) ethanol-soluble and insoluble fractions of the pH 4.6-soluble fraction of the cheeses. The levels of peptides in the cheeses increased during the ripening period. Principal component and hierarchical cluster analyses of electrophoretic and chromatographic results indicated that the cheeses were significantly different in terms of their peptide profiles and they were grouped based on the use and type of starter and stage of ripening. Levels of free amino acid in the cheeses differed; Leu, Glu, Phe, Lys, and Val were the most abundant amino acids. Nitrogen fractions, total free amino acids, total free fatty acids, and the levels of peptides resolved by reverse phase-HPLC increased during ripening. No significant differences were found between the sensory properties of cheeses made using a starter, but the cheese made without starter received lower scores than the cheeses made using a starter. It was found that the cheese made with strains NCDO763 plus SK11 had the best quality during ripening. It was concluded that the use of different starter bacteria caused significant differences in the quality of the cheese, and that each starter culture contributed to proteolysis to a different degree.     

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.