The Effect of Whey Protein Isolate Coating Enriched with Thyme Essential Oils on Trout Quality at Refrigerated Storage (4 ± 2°C)

ABSTRACT

The present study evaluated the effect of whey protein isolate (WPI) coating enriched with thyme essential oil (EO; 3, 5, and 7%, v/v) on whole trout chemical and microbial quality during refrigerated storage at 4 ± 2°C. As a result of this study, the addition of thyme essential oil to WPI coatings enhanced quality significantly better than that of the control and WPI coating without thyme essential oil during refrigerated storage, and this effect increased with an increase in the thyme EO concentration in WPI coating.     

Effects of Oil-in-Water Nanoemulsion Based on Sunflower Oil on the Quality of Farmed Sea Bass and Gilthead Sea Bream Stored at Chilled Temperature (2 ± 2°C)

The influence of oil-in-water nanoemulsion on the sensory, chemical, and microbiological qualities of sea bream and sea bass fillets stored at 2 ± 2°C was investigated. The results showed that the use of nanoemulsion extended the shelf life of fish one or two days when compared with the control. Treatment with nanoemulsion significantly (p < 0.05) decreased the values of chemical parameters throughout the storage period. Bacterial growth was inhibited by the use of nanoemulsion. Nanoemulsion had an inhibitory effect on protein denaturation during refrigerated storage and microwave cooking. Based on the results, it can be concluded that sunflower oil-based nanoemulsion extended the shelf life and improved the quality of both sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) fillets during storage.     

Effects of Black Cumin Oil (Nigella sativa) on Sensory,Chemical and Microbiological Properties of Rainbow Trout During 23 Days of Storage at 2 ± 1°C

In the present study, black cumin oil in the rates of 0.00 % (the control), 0.10 %, 0.40 %, 0.70 %, 1.00 % and 1.30% was added to rainbow trout feed for 144 days. After the feeding process, trout were harvested and stored at 2 ± 1°C in ice, and changes in chemical, microbiological, and sensory parameters were examined periodically. According to sensory analyses, black cumin oil used in fish meat did not cause a perceptible sensory change for all groups. Chemical analyses showed that the addition of black cumin oil to fish feed led to higher total volatile basic nitrogen content in the fish flesh. During the storage period, the highest peroxide values were observed in the groups with 1.0% and 1.3% black cumin oil added, and the lowest were in the groups with 0.0% and 0.1% added oil. The highest microbial count value was observed in the control group.     

Effect of High Pressure Processing on the Quality and Endogenous Enzyme Activities of Grass Carp (Ctenopharyngodon idellus) Fillets Stored at 4ºC

ABSTRACT

This study assessed effects of high pressure processing on physicochemical quality and endogenous enzyme activities of grass carp fillets stored at 4 ºC for 21-day storage. Fresh fillets were vacuum-packed and subjected to high pressure processing (0.1, 200, 300, 400, 500, and 600 MPa at room temperature for 15 min). Results showed that high pressure processing significantly delayed microbial growth, and reduced total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS) levels of grass carp fillets, especially for the 600 MPa group. On the 21st day, the corresponding increases of 6%, 35%, 45%, 43%, and 53% in hardness were observed for 200 MPa, 300 MPa, 400 MPa, 500 MPa, and 600 MPa samples compared with control samples, respectively. In addition, enzyme activities in different groups decreased during storage. Among them, calpain, and myofibril-bound serine proteinases (MBSP) activities were immediately reduced after high pressure treatments, while the activities of collagenase, cathepsin B, and cathepsin D were significantly (P < 0.05) inhibited when the pressure exceeded 400 MPa. However, the pressure treatments activated cathepsin L initially, and then the activity gradually decreased in treated samples. Generally, high pressure processing reduced activities of most of the endogenous enzymes and improved the quality and extended the shelf life by at least 4 ~ 6 days of refrigerated grass carp fillets.     

The Relationship Between Electric Impedance and Quality Parameters of Ungutted and Gutted Common Carp (Cyprinus carpio) Stored at 4°C

In order to understand the relationship between electric conductivity and quality parameters of common carp during storage, the electric impedances in the frequencies ranging from 1 to 20 kHz, total viable count (TVC), total volatile basic nitrogen (TVB-N), and K values of gutted and ungutted common carp were determined during 4°C storage. The result showed that the change ratio of electric impedance (Q value) of both gutted and ungutted common carp decreased with increasing storage time, while TVC, TVB-N, and K values increased gradually. There was a good correlation between Q values and TVC, TVB-N, and K values of gutted and ungutted common carp, and their correlation coefficients were 0.952, 0.965, 0.928, and 0.956, 0.975, and 0.938, respectively. This result demonstrated that Q value is valid to predict some quality parameters of common carp during 4°C storage.     

Biochemical and Microbiological Assessment of Crucifix Crab (Charybdis feriatus) Stored at 4°C

Charybdis feriatus is a highly prized crab in the local and international markets of East Asian countries. In local markets, crabs are sold live, iced, or refrigerated at 2°C – 4°C. The present study was carried out to determine the shelf life of whole crab stored at 4°C for 192 h using a set of biochemical, microbiological, and sensorial parameters. Biochemical indicators such as the total volatile base nitrogen (TVB-N) and trimethylamine nitrogen (TMA-N) increased significantly during storage and within an acceptable limit up to 144 h. Regarding the biogenic amines, cadaverine and spermidine increased significantly (p < 0.05) during the storage period. Among them, cadaverine could be proposed as a useful spoilage indicator for this crab species. The mesophilic and psychotropic bacterial count exceeded the limit of acceptance after 144 h of storage. Sensory attributes were gradually diminished with the storage time. Sensory scores were found to correlate well with both mesophiles and psychrotrophs. Based on the results of this study, the meat quality of Charybdis feriatus can be maintained up to 144 h when properly stored at a temperature of 4°C ± 1°C.     

Effects of Natural and Artificial Colorants on Hot Smoked Garfish—Belone belone (Linnaeus, 1761)—Stored at 4 ± 1ºC

In this study, the effects of natural and artificial colorants on the shelf life of hot smoked garfish were investigated in terms of its chemical, microbiological, and sensory quality. Turmeric and Sunset Yellow FCF were used as the natural and artificial colorants, respectively. The amount of total volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA), counts of total mesophilic aerobic bacteria, total psychrophilic aerobic bacteria, total yeast and molds increased during the storage (p < 0.05). The results showed that turmeric and Sunset Yellow FCF had a significant effect on pH value and salt content of hot smoked garfish samples during storage (p < 0.05). According to the sensory analysis results, the shelf life of hot smoked garfish stored at 4 ± 1ºC was determined as 17 days.     

Relationship between Lipid Oxidation,Protein Function Properties,and Freshness Changes of Salt-Treated Blunt-Snout Bream (Megalobrama amblycephala) Fillets Stored at 4°C

The aim of this study was to investigate the relationship between lipid oxidation, protein function properties, and freshness changes of blunt-snout bream (Megalobrama amblycephala) fillets treated with 2% and 4% salt during storage at 4°C. Salting with 2% and 4% salt could delay quality deterioration and protein denaturation, thus improving sensory attributes to some extent. But, 4% salt promoted lipid oxidation of blunt-snout bream fillets. There is a significant correlation (p < 0.05) between freshness indexes and lipid oxidation or protein function properties (total SH content, Ca²⁺-ATPase activity). Salting with 2% salt is an ideal treatment to control the quality of blunt-snout bream fillets stored at 4°C.     

Effect of Chitosan and Garlic Essential Oil on Microbiological and Biochemical Changes that Affect Quality in Grass Carp (Ctenopharyngodon idellus) Fillets During Storage at 4°C

Solutions of chitosan (2%, w/v), garlic essential oil (5%, v/v), and their combination (2%, w/v chitosan +5%, v/v garlic essential oil) were applied to the surface of grass carp fillets. Subsequently, sensory, microbiological analyses (total viable count (TVC), Pseudomonas spp., Aeromonas spp., and H₂S-producing bacteria), and physicochemical changes (total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and centrifugation loss) of grass carp fillets were evaluated over a 16-day storage at 4 ± 1°C. The treated samples resulted in significantly (p < 0.05) higher overall acceptance scores than the control from day 8. The TVC of grass carp fillets was reduced from the initial level (4.0 log CFU/g) to 2–3 log CFU/g when the fillets were treated with either garlic essential oil or chitosan solution. After 4 days of storage, the Pseudomonas spp. counts in the chitosan-treated samples were significantly lower (p < 0.05) than the counts in control and samples treated with garlic essential oil. A lag phase of 6 days for the counts of H₂S-producing bacteria of fish fillets that were treated with chitosan or the combination solution was observed. The combination of chitosan with garlic essential oil did not show synergistic effects, although it displayed a higher degree of antimicrobial efficacy with respect to the spoiled bacteria. However, the combination of chitosan with garlic essential oil was the most effective at inhibiting the formation of TVB-N. Samples that were treated with garlic essential oil displayed the highest TBARS levels on days 4 and 6 (p < 0.05).     

The modulating effect of vitellogenin on the synthesis of 17β-estradiol by rainbow trout (Oncorhynchus mykiss) ovary

In vivo induction of vitellogenin (VTG) in response to the administration of 17-estradiol (E₂) was achieved and the protein was isolated by gel filtration column chromatography of plasma samples. Adult female trout were injected with the vitellogenic fraction every ten days from July to November and levels were measured by RIA from September to December. The results showed a significant decrease (p<0.01) in plasma E₂ levels in injected females compared with the controls. In December, after finishing the treatment, the plasma E₂ concentration increased, in injected females to reach a level similar to that of control females at vitellogenesis. The in vitro study showed that in early vitellogenic oocyte (from September) the presence of the vitellogenic fraction in the incubation medium causes a significant decrease (p<0.01) in the synthesis of E₂ by the oocytes. These data suggest that the concentration of the VTG into the oocyte can alter VTG production by the liver, moderating the production of E₂ by the ovary.     

Quality Changes and Shelf Life of Cultured and Wild Hot-Smoked Mediterranean Horse Mackerel (Trachurus mediterraneus) at Refrigerated (4 ± 1°C) Conditions

ABSTRACT

Mariculturing of horse mackerel is not known in the world. Additionally, limited studies exist on quality changes of smoked horse mackerel at refrigerated temperatures. Therefore, in this study, between 1+ and 2-year-old wild and cultured horse mackerels were hot smoked and stored at refrigerated conditions. Chemical, microbiological, and sensory analyses were performed weekly to investigate quality changes and to determine the shelf stability of the products. The results of thiobarbituric acid, trimethylamine, and total bacteria counts were obtained within the acceptable levels. Although the counts of histamine-forming bacteria increased significantly (p < 0.05) during storage, histamine values were well below the permitted limits set by Food and Drug Administration and European Union (EU). Sensory results showed that both storage groups had 3 weeks of shelf life. Total volatile basic nitrogen values supported sensory results. Therefore, the results indicate that culturing of horse mackerel did not alter the quality during storage at 4 ± 1°C.     

The Effect of Prior Frozen Storage (−20°C) on the Quality of Oven-Baked Sardines (Sardina pilchardus)

ABSTRACT

The effect of frozen storage for 3, 30, 60, 90, and 120 days on the quality of sardines baked for 15, 30, and 45 min was studied. The combination of frozen storage with the baking time in linear reduction of yield and moisture led to less juicy products, as well as significant changes in proteins and lipids. A linear increase of C16:0 followed by a linear reduction of C22:6ω-3 was detected due to frozen storage, indicating lipid oxidation. This was also confirmed by the C22:6ω-3/C16:0 and C20:5ω-3/ C16:0 ratios, which were reduced by 36.8 and 32.7%, respectively. The fatty acid profiles of sardine samples were not significantly altered due to oven-baking. A gradual reduction of eicosapentaenoic acid + docosahexaenoic acid (EPA + DHA) of the baked products was observed mainly due to frozen storage. Cholesterol and squalene content increased with increasing the time of baking. A gradual decrease of cholesterol and squalene was observed due to frozen storage.     

Relationship Between Water Migration and Quality Changes of Yellowfin Tuna (Thunnus albacares) During Storage at 0°C and 4°C by LF-NMR

This study investigated postmortem changes of yellowfin tuna (Thunnus albacares) and water migration upon storage at 0°C and 4°C as determined by low-field nuclear magnetic resonance (LF-NMR ¹H). It clearly showed that with increasing storage time, sensory scores and physical evaluations (hardness, chewiness), proton density of the water, and moisture content decreased, while total volatile basic nitrogen (TVB-N), K value, aerobic plate counts (APCs), and psychrotrophic bacterial counts increased. The results of LF-NMR showed that T₂₁ (trapped water) had extremely significant correlations with sensory evaluation, texture profile analysis, TVB-N, K value, APC, and psychrotrophic bacteria (p < 0.01) and established multiple linear regression. It was concluded that the LF-NMR was an important technique to evaluate storage time and temperature of yellowfin tuna’s quality in terms of water migration during low-temperature storage.     

Effect of Thermal Microbial Inactivation and Washing on Quality Properties of Fish Sausage During Cold Storage (4°C)

The effect of microbial inactivation and washing process on physicochemical and sensory quality of pasteurized fish sausage during cold storage (4°C) was evaluated. Mince was obtained after the grinding; washed mince (WM) was obtained by single washing of mince; and surimi was obtained after three washing and dewatering cycles. Texture profile analysis results demonstrated that textural characteristics of pasteurized fish sausages remain stable during storage period (p > 0.05). Color analysis showed that Hunter L* had an increasing trend, and a* and b* had a decreasing trend over time (p < 0.05). Thus, it is possible to inactivate all microorganisms in pasteurized fish sausage without any undesirable effect on physicochemical and sensory quality.     

The role of cAMP in regulating the β-adrenergic response of rainbow trout (Oncorhynchus mykiss) red blood cells

The -adrenergic response of teleost red blood cells (RBCs) enables the fish to maintain or even enhance the oxygen affinity of haemoglobin during various stress situations. The role of CAMP in the pronounced -adrenergic response of hypoxic rainbow trout RBCs was studied. Rainbow trout RBCs were incubated with three different -agonists (noradrenaline, adrenaline and isoproterenol, 10^–9 - 10^–4 M) at two oxygen tensions (P_{O 2}, 155 and 8 mmHg), and thereafter cAMP accumulation and cellular water content were measured.The cAMP concentration of non-stimulated trout RBCs was ca. 1200 nmol/kg dw. Of the three -agonists used, isoproterenol was the most effective in formation of cAMP, followed by noradrenaline and adrenaline. Oxygen tension affected the accumulation of cAMP in two ways. At physiological catecholamine levels (1–100 nM) there was either no difference between normoxic and hypoxic cells or a slight increase in the normoxic ones. At high catecholamine concentrations the accumulation of cAMP was greater in the hypoxic than in the normoxic cells. Oxygen tension also affected the magnitude of cell swelling but had no effect on the catecholamine concentrations causing half-maximal swelling (EC₅₀-values). The results indicate that, at physiological catecholamine levels, the -adrenergic response of rainbow trout RBCs is mainly regulated on the level of the Na⁺/H⁺ exchange.     

The dynamics of in vitro 17 β-estradiol secretion by isolated ovarian follicles of the rainbow trout (Oncorhynchus mykiss)

This study investigated the effects of human chorionic gonadotropin (hCG), 17-hydroxyprogesterone (17P) and testosterone (T) on the in vitro production of 17-estradiol (E₂) by isolated ovarian follicles of the rainbow trout (Oncorhynchus mykiss). 17P at 100 ng ml^-1, and hCG at 100 IU ml^-1 stimulated E₂ production relative to controls, whereas lower doses were ineffective. T was the most effective in stimulating E₂ production, followed by 17P and hCG respectively. The timecourse of E₂ production was investigated for both static culture, and incubations with media replacement, with follicles being exposed to hormone treatment for 30 min, 1 or 3 h, or constantly. E₂ production was observed after 30 min, 3 and 3-6 h in response to T, 17P and hCG respectively. Under static culture, E₂ levels reached maximal levels in 6 h. Longer incubations resulted in further metabolism of E₂ to E₂-glucuronide, which resulted in the blurring of treatment effects after 18 h. Incubations with media replacement resulted in higher E₂ production than in static culture. The results indicate that a 6 h incubation period is sufficient to produce significant increases in E₂ production in response to hCG, 17P and T, and that incubations longer than 12 h result in losses E₂ from the incubation media. These findings have implications for the validity of using static cultures to examine the effects of hormone treatment on the activity of steroid converting enzymes in vitro.     

Effects of chronic exposure to γ-HCH (Lindane) on brain serotonergic and gabaergic systems,and serum cortisol and thyroxine levels of rainbow trout,Oncorhynchus mykiss

Rainbow trout (Oncorhynchus mykiss) were implanted intraperitoneally with 0.5 ml.100 g^–1 body weight of coconut oil alone (controls) or coconut oil contaning 0.05 mg of -HCH (Lindane). After 18 days, changes in brain serotonin and GABA metabolism, as well as in serum cortisol and thyroxine levels, were measured. A lower final body weight was observed in -HCH treated fish when compared with control fish. No significant differences were found for serum thyroxine levels between control and treated fish, but a significantly higher cortisol level was found in the -HCH-implanted trout. Although GABA levels did not differ significantly in any brain region in the two treatment groups, the activity of the serotonergic system was significantly altered by the pesticide in both the hypothalamus and the telencephalon.     

Effects of 3,5,3′-triiodo-L-thyronine (T3) and 6-n-propyl-2-thiouracil (PTU) on growth of GH-transgenic coho salmon, Oncorhynchus kitsutch

GH-transgeniccoho salmon (Oncorhynchus kitsutch) juveniles were fed diets containing 3,5,3-triiodo-L-thyronine (T₃; 30 ng/g fish) or 6-n-propyl-2-thiouracil (PTU; 20 ug/g fish), to assess the effect of these drugs on the physiology, growthand survival in comparison with untreated transgenicand non-transgenic salmon. After 84 days, food intake, feed efficiency, survival, growth, hepato-somatic index (HSI), viscera-somatic index (VSI), plasma L-thyroxine (T₄), T₃and growth hormone (GH) levels,and cranial morphological abnormalities were determined. Growth of transgenic salmon was significantly faster than the nontransgenic salmon,and was increased by exogenous T₃and reduced by PTU. Food intake of transgenic salmon was higher than that of the nontransgenic group, but was reduced by exogenous PTU administration. Food conversion efficiency of transgenic salmon was lower than that of nontransgenic salmon,and also was increased by T₃ but reduced by PTU in the transgenic fish. The survival rate in all transgenic groups was significantly higher than that of nontransgenic,and transgenic T₃and PTU treatment groups showed higher survivals than the transgenic-control group. The HSIand VSI of the transgenic fish were higher than the nontransgenic fish;and both parameters in the transgenic salmon were increased by PTU, but reduced by T₃. The plasma T₄ level in transgenic salmon was approximately 1.5-fold higher relative to the nontransgenic fish, whereas no difference was observed among the transgenic groups. Plasma T₃ levels in transgenic salmon were also approximately 2-fold higher relative to the nontransgenic fish. However, the plasma T₃ level in transgenic animals was increased by exogenous T₃ administration, but was reduced by exogenous PTU to that observed in nontransgenic salmon. The plasma GH level of transgenic fish was higher than that of the nontransgenic salmon,and the level was increased by the exogenous T₃, whereas exogenous PTU did not reduce significantly GH levels in transgenic salmon. Transgenic fish also displayed cranium, jawand opercular abnormalities typical of the effects of this gene construct incoho salmon, indicating that some imbalance in growth processes has been induced. However, these abnormalities (especially cranial disruptions) were diminished by administration of exogenous PTU. In conclusion, exogenous T₃and PTU treatments can induce hyperthyroidismand hypothyroidism, respectively,and have inverse effects on growthand skeletal abnormalities of transgenic salmon constitutively expressing GH.     

Pomegranate (Punica granatum L.) Peel Extracts Inhibit Microbial Growth and Lipid Oxidation in Minced Shrimps Stored at 4°C

Pomegranate peel is inherited with diverse functional properties that improve storage stability and nutritional quality of edible goods. This research was aimed at evaluating antioxidant and antimicrobial properties of pomegranate peel hydro-alcoholic extracts and to determine in situ efficacy of extracts in controlling microbial growth and lipid oxidation of shrimp meat. The results suggest that pomegranate peel ethanolic extracts (PoPetx) have significantly higher (p < 0.05) phenolic contents, 169 mg GAE/100 g accompanied with 90% free radical scavenging activities. Contrary to the normal control, incorporation of PoPetx @ 2.0% (w/w) in minced shrimp meat increased thiobarbituric acid reactive species generation by 10% during 28 days of storage at 4°C. Supplementing PoPetx @ 0.5–2.0% (w/w) to shrimp meat has shown a comparable microbial inhibitory action against total plate counts and Staphylococcus spp. The study concludes that application of pomegranate peel extracts in minced shrimp is a viable strategy to preserve chemical and microbiological quality of shrimp and products of sea origin.     

Inhibition of Melanosis,Microbial and Quality Changes of White Shrimp (Penaues vannameii) via Effect of Key Lime Juice and Vacuum Packaging at 2 ± 1ºC

This study aimed to investigate the effects of key lime juice (KL) in combination with vacuum packaging (VP) or air storage (SB) on the quality changes of white shrimp stored at 2 ± 1ºC. The quality was assessed using microbiological analysis, color measurement, pH, and total volatile base nitrogen (TVBN). Treatment with KL exhibited inhibitory activity on the growth of spoilage microflora. KL in combination with VP revealed a lower bacterial count in the range of 4.37–4.91 log CFU gˉ¹ on day 12 of storage as compared to other treatments. VP + KL and VP samples could inhibit melanosis. In addition, lower TVBN content was obtained in VP + KL (5.33 mg N/100 g), followed by VP (6.03 mg N/100 g) samples on day 12 of storage (p < 0.05). VP in combination with KL had the lowest loss of quality changes for the white shrimp. Therefore, VP + KL could be used as an alternative preservative method to extend the shelf life for white shrimp.