Quality enhancement of canned sardine (Sardina pilchardus) by a preliminary slurry ice chilling treatment

The slurry ice technology has shown wide advantages when employed as a chilling method for marine species instead of the traditional flake ice storage. In the present work, the use of slurry ice was evaluated for the first time as a technological treatment prior to the canning processing of fish. Thus, sardine (Sardina pilchardus) specimens were stored in slurry ice for 2 and 5 days and then taken and subjected to canning. Quality assessment of the canned product was performed on the fish muscle and on the coating oil, in comparison with that of a parallel control batch previously stored in flake ice. Analyses included composition (water, lipid and NaCl contents), physical properties (firmness, cohesivity), volatile amine formation (total and trimethylamine), lipid oxidation development (anisidine value, polyene index, α‐tocopherol content and Rancimat oxidative stability) and interaction compounds formation (fluorescence assessment). An inhibition of lipid oxidation development (p <0.05) was obtained in canned sardine when applying slurry ice as a preliminary chilling storage system. The present work opens the way to the use of slurry ice instead of flake ice as a preliminary treatment of fish material prior to the canning process.     

Assessment of quality changes in frozen sardine (Sardina pilchardus) by fluorescence detection

The formation of fluorescent compounds was tested as a quality assessment during the frozen storage of sardine at −18°C (up to 24 mon) and at −10°C (up to 120 d). The fluorescence ratio between two excitation/emission maxima (393/463 and 327/415 nm) was studied in the aqueous (δF _aq) and organic (δF _or) extracts after Bligh and Dyer extraction of the white muscle. Fluorescence results were compared to common quality indices [total volatile base-nitrogen (TVB-N); conjugated dienes; thiobarbituric acid index (TBA-i); and free fatty acids (FFA)]. δF _aq showed good correlations with storage time (r=0.80 and r=0.72 at −18 and −10°C, respectively) and TBA-i (r=0.92 and r=0.81). Principal-component analysis grouped δF _aq with quality indices that are sensitive for the assessment of fish damage during frozen storage at both temperatures (TBA-i and FFA at −18°C; BVT-N, TBA-i, and FFA at −10°C). According to these results, fluorescence detection of interaction compounds in the aqueous phase can provide an accurate method to assess quality differences during frozen storage of fish.     

Influence of blanching treatment and drying methods on the drying characteristics and quality changes of dried sardine (Sardinella gibbosa) during storage

The aim of this study is to examine the drying characteristics of blanched and unblanched sardine during indoor and open sun drying processes. Changes in temperature and relative humidity of the air during drying were recorded. The color, peroxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA) content, fatty acid composition, and sensory attributes of dried samples were also evaluated once a month for 5 months of storage. High drying rates were obtained in all samples at the start of drying and then decreased with increasing drying time. The highest drying rate and effective water diffusivity (D_eff) were observed in blanched sardine during open sun drying. Blanching treatment slowed down the FFA progression during product storage but adversely affected the color, PV, and TBARS content as well as sensory properties. Although sardine dried for a longer time under indoor drying conditions, it attained a stable moisture ratio that was lower than in open sun-dried samples. Indoor drying produced a quality stable product with less lipid oxidation and the desired moisture content, higher polyunsaturated fatty acids and sensory properties. Blanching treatment negatively affected the fish quality and is therefore not recommended for commercial sardine drying.     

Rancidity development during frozen storage of mackerel (Scomber scombrus): effect of catching season and commercial presentation

Hydrolytic and oxidative rancidity development and its effect on quality loss were studied in frozen mackerel (Scomber scombrus) by biochemical and sensory indices. The effect of the lipid content on fish damage at a commercial freezer temperature (?20 °C) was studied for up to 12 months; thus, mackerel caught at two different times of the year (May and November) was checked, May being the period of minimum lipid content, while November is known to be the time of maximum lipid content. The study was also focused on two different kinds of fish products (whole fish and fillets). Increasing lipid hydrolysis was observed for all kinds of samples during the frozen storage; no differences (p >0.05) between whole fish and fillets were found for free fatty acid formation; however, mackerel from May showed a higher (p <0.05) hydrolysis development than its counterpart from November. Increasing lipid oxidation (peroxide value and thiobarbituric acid index) was observed for all kinds of samples during the frozen storage. Fillet lipid oxidation was found to be higher (p <0.05) than in whole fish. Fattier mackerel (November fish) showed a higher (p <0.05) oxidation development than its counterpart from May in the case of fillet products. Results of fluorescence assessment, related to interaction compound formation, proved to be higher (p <0.05) in fillets than in whole fish, although they were higher (p <0.05) in May samples. Sensory analysis corroborated the biochemical analyses, so that fillets showed a shorter shelf life (1 and 3 months for November and May fish, respectively) than their whole fish counterparts (5 months for November and May mackerel).     

Studies on rancidity inhibition in frozen horse mackerel (Trachurus trachurus) by citric and ascorbic acids

This study is aimed to investigate the effect of aqueous solutions of citric acid (CA) and ascorbic acid (AA) on the lipid stability of horse mackerel (Trachurus trachurus) fillets and whole fish during frozen storage (up to 6 and 9 months, respectively) by means of a soaking pretreatment. Best oxidation inhibition results on fish fillets were obtained when employing a 0.5% CA solution. Lower (p <0.05) peroxide (month 3), thiobarbituric acid‐reactive substance (months 1 and 3) and fluorescent compound formation (month 6) values were obtained from CA‐treated fish fillets than from the untreated (blank control) and water‐treated (water control) fish fillets. In the case of whole fish, soaking pretreatment with a mixture consisting of 0.5% CA and 0.5% AA showed the best results in inhibiting oxidation, as lower (p <0.05) peroxide formation was observed at 6 and 9 months of frozen storage compared to the untreated or water‐soaked counterparts. Advantages of both acids (CA and AA) are discussed, and further studies based on the positive role of a CA‐AA mixture will be carried out to extend the shelf life of medium‐ and high‐fat content fish species during frozen storage.     

Quality loss related to rancidity development during frozen storage of horse mackerel (<Emphasis Type="Italic">Trachurus trachurus</Emphasis>)

The development of rancidity and its effect on quality loss were studied in frozen horse mackerel (Trachurus trachurus). Two different kinds of fish products (whole fish and fillets) were stored at a commercial freezer temperature (−20°C) for up to 12 mon and were compared to samples stored at a much lower temperature (−80°C). Analyses included: lipid hydrolysis (FFA formation) and oxidation (PV, thiobarbituric acid index, fluorescent compound formation), loss of endogenous antioxidant (α-tocopherol), protein changes (electrophoretic analysis of sarcoplasmic and SDS-soluble fractions), and sensory analysis (skin, eyes, gills, flesh odor, consistency, flesh appearance). According to biochemical indices, fillets stored at −20°C showed susceptibility to rancidity development, leading to a shelf life of 1 mon, whereas whole fish at the same temperature were still edible at month 5. The use of a low temperature (−80°C) inhibited rancidity development, leading to good-quality (whole fish) and fairquality (fillets) fish products at the end of the experiment. The application of protective treatments especially designed to prevent lipid oxidation is encouraged when commercializing this species in the frozen state.     

Effect of different cell disruption methods on lipid yield of Schizochytrium sp.

In this study, it was investigated to increase the lipid yield of the microalgae Schizochytrium sp., by applying different cell disruption methods; acid treatment with HCl, osmotic shock, enzyme applications and ultrasonic homogenizer were combined with the Bligh and Dyer or Soxhlet methods. In the Soxhlet method, the lipid and fatty acid yields decreased due to the inability of the method to break down the lipid cells sufficiently and the high temperature application. Enzyme application (hemicellulase treatment at 55°C for 2 days) prior to Bligh and Dyer method (BDE) was found more efficient in terms of lipid and DHA yield compared to other methods. BDE process increased the lipid yield to 21.72 ± 0.74% and DHA content to 19.25 ± 0.09% from lipid yield of 18.87 ± 0.4% and DHA content of 18.41 ± 0.20% by the Bligh and Dyer control (BDC). Major saturated fatty acids were 14:0, 16:0, 18:0, 24:0 and the highest saturated fatty acid was 16:0 (palmitic acid). Lipid health indices such as n-6/n-3, PUFA/SFA, atherogenicity index, thrombogenicity index and hypocholesterolemic/hypercholesterolemic ratios were almost favorable. With this study, appropriate lipid extraction methods were studied to provide an economical and environmental friendly suggestion for future studies to be used in areas such as food, feed and cosmetics grade. It was concluded that the most convenient method among the cell disruption methods was BDE owing to lipid and fatty acid yield.     

二氧化硅纳米颗粒对冰浆中冰晶粒径分布及存储演化特性的影响

分别以乙二醇水溶液和氯化钠水溶液为基液配制不同浓度的二氧化硅纳米流体并以此制备冰浆,通过显微装置获得冰晶图像,将实验得到的粒径分布与正态分布、对数正态分布、Gamma分布和Weibull分布进行对比,探讨纳米二氧化硅对冰晶平均粒径与分布特性的影响,同时观测储存过程中冰晶粒径演化规律。结果表明：加入纳米二氧化硅前后冰晶粒径分布均可用Gamma分布描述;纳米二氧化硅可起到细化晶粒的作用,而且添加浓度越高冰晶颗粒越小;当基液为乙二醇水溶液时,加入纳米二氧化硅可较好地抑制储存过程中的冰晶粒径增长,但基液为氯化钠水溶液时,纳米二氧化硅浓度需达到0.75%,才可抑制冰晶增大。研究结果证明,一定浓度的纳米二氧化硅流体可作为制冰溶液,起到减小冰晶粒径并控制冰晶生长的作用,这对冰浆流动和传热性能的改善具有重要的应用价值。     

Effect of heat inactivation of lipoxygenase on lipid oxidation in lake herring (coregonus artedii)

The role of lipoxygenase in causing lipid oxidation in lake herring was studied. Lipid oxidation was measured by assaying for 2-thiobarbituric acid-reactive substances (TBARS), and lipoxygenase activity was measured by a spectrophotometric (470 nm) method. Lipoxygenase activity was highest in light muscle, lowest in skin and intermediate in dark muscle. Light muscle contained the highest percentage of phospholipids (PL) and the least total lipid. The percentage of PL was lowest and total lipids were highest in the skin. Eicosapentaenoic acid and docosahexaenoic acid were found in larger amounts in PL than in triglycerides. Heat treatment rapidly inactivated lipoxygenase. After a 5-min heating period, lipoxygenase was totally inactivated in most cases. TBARS data indicated that samples heated at 80°C for 1.5–2.0 min were more stable than samples heated at 80°C for 2.5–5.0 min, suggesting that heat accelerated nonenzymatic oxidation.     

Effect of Eucalypt Pulp Pretreatment with Hot Acid Hydrolysis on (aZe)DP and (aZe)(EP)P Bleaching Performance

The effect of pulp pretreatment with hot acid hydrolysis on high consistency ozone bleaching was evaluated. An experimental plan was set up involving the full optimization of the A-stage and its application in Elemental Chlorine Free–ECF–[A/(aZe)DP and A(aZe)DP] and Total Chlorine Free–TCF–[A/(aZe)(EP)P and A(aZe)(EP)P] sequences for eucalypt kraft pulp bleaching. The A-stage removed a significant amount of lignin and HexA from the pulp, and the subsequent Z-stage remained efficient after completion of the A-stage. The chemical savings caused by the A-stage were significant (～7 kg ClO₂/adt). The optimum conditions for the A-stage were pH 3.0, 90°C for 120 min, and 10% consistency. The strength properties of pulps bleached with the (aZe)DP (reference) and A/(aZe)DP ECF sequences were similar, but the TCF sequence A/(aZe)(EP)P delivered slightly lower strength properties than the ECF sequences. Fiber peeling studies indicated that the HexA present in the kraft pulp is not concentrated on the fiber surface, as previously thought.     

Effect of temperature on fatty acid composition in the Nile tilapia (Oreochromis niloticus): A temperature dependent nutritive lipid profile

In this study, the effects of temperature on the fatty acids profile and the effects of temperature on the degree of unsaturation of fatty acids of Oreochromis niloticus were investigated. The analysis was performed by gas chromatography. The study showed that there were large temperature variations (10.0–32.0°C) during the study period (January–December). The highest crude fat content was found in January (3380 mg/100 g) and the lowest in June (2050 mg/100 g). The fatty acids profile showed significantly different diversity (p < 0.05). Total saturated fatty acid (∑SFA) content ranged from 409.54 to 1297.61 mg/100 g, monounsaturated fatty acid (∑MUFA) from 207.68 to 665.81 mg/100 g, and polyunsaturated fatty acid (∑PUFA) from 175.12 to 972.23 mg/100 g. The ∑MUFA and ∑PUFA concentrations were highest in January and lowest in June, and the ∑SFA concentration was lowest in January and highest in June. EPA and DHA contents were highest in January (198.96 mg/100 g) and lowest in June (48.76 mg/100 g). The contents of omega-3 (653.17 mg/100 g) and omega-6 fatty acids (252.54 mg/100 g) were highest in January and lowest in June (ω-3; 106.43 and ω-6; 60.91 mg/100 g). It concluded that the degree of unsaturation of fatty acids increases with decreasing temperature. In this study, the nutritional quality of the FAs profile was assessed using lipid quality indices. The indices indicating dietary quality of lipids by their values: Atherogenic index (0.47), thrombogenic index (0.38), hypocholesterolemic to hypercholesterolemic (3.00), meat fat quality (6.78), ω6/ω3 ratio (0.39), PUFA/SFA (2.37), MUFA/SFA (1.62), PUFA/MUFA (1.46), and PUFA + MUFA/SFA (3.99). These values are within the recommended range, indicating that the lipid profile of O. niloticus has high nutritional quality, which can be further improved by harvesting the fish during the winter season. Due to the nutritional importance of O. niloticus, the culture of this species could have significant interest to the people of Karachi, especially the coastal communities. To promote the nutritional diet in local population, the government should support the aquaculture of Nile tilapia.     

Influence of Temperature Stress on Lipid Stability of Atlantic Herring (<Emphasis Type="Italic">Clupea harengus</Emphasis>) Muscle During Frozen Storage

Unstable conditions are commonly encountered during industrial storage and transportation of frozen fish. Temperature stress and fluctuations may increase the amount of unfrozen water in the muscle and enzymatic activity and lipid oxidation can thus still take place during frozen storage. The aim of this study was to investigate the changes of characteristics of different muscle types of herring at unstable modelled conditions during storage and transportation. Compositional changes, lipid oxidation and lipid hydrolysis were monitored in light and dark muscle of Atlantic herring (Clupea harengus), during frozen storage, as affected by temperature stress (samples were stored at ? 25 °C for 2 months, then stressed at ? 12 °C for 1 month, followed by storage at a stable ? 25 °C for the remaining storage duration), and compared to samples stored at a stable ? 25 °C for 14 months. The dark muscle was more sensitive to lipid oxidation than the light muscle, leading to faster degradation. Increased lipid oxidation and lipid hydrolysis were observed in temperature‐stressed samples of both muscle types. The study demonstrated the importance of avoiding temperature stress during industrial frozen storage and transportation to improve the quality and shelf life of frozen herring products. Removal of dark muscle by deep skinning could benefit both processors and customers regarding the shelf life and nutritional value of the light herring muscle.     

化学镀铜对LaMgNi3.7Co0.3储氢合金电化学性能的影响

在LaMgNi<,3.7>Co<,0.3>储氢合金粉末表面进行化学镀铜处理.覆铜后的合金粉末与镍粉混合后涂于泡沫镍上制成电极.当镀液中Cu<'2+>为1.2g/L,温度为30°C,pH为3.0,反应时间为2min时,合金电极在6 mol/L KOH电解液中的最大放电容量和循环稳定性能都有显著提高,合金电极的交换电流密度...     

Effect of vacuum‐packaging on the changes of Russian sturgeon muscle lipids during frozen storage

The changes in fatty acid composition, non‐polar (triglycerols) and polar lipids (phospholipids), total free fatty acids and total cholesterol of Russian sturgeon (Acipenser gueldenstaedtii) were studied during 360 days of storage at ?18°C. It was established that total neutral lipids and phospholipids content decreased and total free fatty acids concentration increased significantly during the frozen storage. Lower non‐polar and polar lipids content and higher free fatty acids concentration of vacuum‐packaged samples in comparison with air‐packaged samples were found. The changes in total cholesterol concentration and phospholipid classes of frozen stored sturgeon were not influenced by the frozen storage period and the type of packaging. It was established that the sturgeon polar lipids consisted mainly of phosphatidylcholine – 54.98 ± 0.85%, phosphatidylethanolamine – 28.42 ± 0.61%, and phosphatidylserine – 8.64 ± 0.45%. The increase of the total free fatty acids concentration was associated with the free n ? 3 PUFA accumulation as a result of hydrolysis of non‐polar and polar lipids. During the frozen storage DHA percentage of non‐polar lipids and phospholipids decreased approximately 3 and 1.75%, respectively. After 360 days of storage at ?18°C the n ? 3/n ? 6 PUFA ratio of total lipids decreased 4.9%.     

Effects of three conventional drying methods on the lipid oxidation,fatty acids composition,and antioxidant activities of walnut (Juglans regia L.)

Three walnut (Juglans regia L.) drying methods (sun drying, direct oven drying, and intermittent oven drying) were employed, and the consequent changes in lipid oxidation attributes, such as acid value (AV), peroxide value (POV), saponification value (SV), fatty acid composition, and antioxidant activity [including reducing power, superoxide anion scavenging activity, 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity (DPPH), lipoxygenase (LOX) activity, total phenols content (TPC), and total flavonoids content (TFC)] were investigated in this study. Sun drying resulted in the highest AV, POV, and SV, followed by direct oven drying and intermittent oven drying. Antioxidant activities and related compounds, TPC and TFC, were initially increased and then declined during drying, and a significant correlation was found between antioxidant activity and TPC and TFC. The LOX activities of all samples showed an increasing trend, although those of the sun-dried samples were the lowest. The walnuts dried with the intermittent oven drying method contained more linoleic acid than those dried by direct oven drying. Overall, intermittent oven drying appears to be a promising strategy for fresh walnut drying.     

Effect of Sr(Zn1/3Nb2/3)O3 modification on the energy storage performance of BaTiO3 ceramics

Lead-free (1-x)BaTiO₃-xSr(Zn_1/3Nb_2/3)O₃ (abbreviated as BT-xSZN, x = 0–0.08) relaxor ferroelectric ceramics were prepared using the traditional solid phase technology, and the effects of SZN modification on their phase structures, microstructures, dielectric performance, ferroelectricity and energy storage performance were studied in detail. A pure perovskite phase was observed in the BT-xSZN ceramics. The BT-based ceramics modified by SZN exhibited refined grain size. As the SZN content was increased, the breakdown strength initially increased and then decreased, and the ferroelectric loops gradually became ‘slim’. The BT-xSZN (x = 0.07) ceramics demonstrated a favourable energy storage performance with high recoverable energy density (W_rec = ~1.45 J/cm³) and energy storage efficiency (η = ~83.12%) at 260 kV/cm. Results indicate that the energy storage performance of BaTiO₃ ceramics modified by SZN can be remarkably improved, widening their applications in energy storage at low temperatures.     

Effect of argon-oxygen ratio on dielectric and energy storage properties of Ba(Zr0.35Ti0.65)O3 thin films

Lead-free Ba(Zr_0.35Ti_0.65)O₃(short as BZT35) ferroelectric thin films are prepared by RF magnetron sputtering on Pt/Ti/SiO₂/Si substrates. Effects of argon-to-oxygen (short as Ar/O₂) ratios on phase transition, dielectric and energy storage properties are studied. The research found that all thin films are perovskite structures. With the decrease of Ar/O₂, the oxygen vacancies (OVs) in the film are effectively suppressed, which promotes the film to obtain a larger dielectric constant, smaller dielectric loss, and lower leakage current density. The BZT35 film prepared under Ar/O₂ = 40:10 has excellent energy storage density (48.03 J/cm³) and efficiency (87.7%) because of its elongated hysteresis loop, the largest polarization difference (ΔP = 22.91 μC/cm²), higher breakdown field strength (E_b = 4.50 MV/cm) and lower leakage current density (J = 2.3 × 10^?5 A/cm²) and high power density of 7.94 MW/cm³. In addition, the BZT35 film also has excellent frequency stability (500 Hz-20 kHz). These excellent properties show that BZT35 has very broad application prospects in energy storage.     

Effect of grain size on the energy storage properties of (Ba0.4Sr0.6)TiO3 paraelectric ceramics

(Ba_0.4Sr_0.6)TiO₃ (BST) ceramics with various grain sizes (0.5–5.6 μm) were prepared by conventional solid state reaction methods. The effect of grain size on the energy storage properties of BST ceramics (T_c ≈ −65 °C) was investigated. With decreasing grain sizes, a clear tendency toward the diffuse phase transition was observed and the dielectric nonlinearity was reduced gradually, which can be explained by the Devonshire's phenomenological theory (from the viewpoint of intrinsic polarization). Based on the multi-polarization mechanism model, the relationship between the polarization behavior of polar nano-regions (the extrinsic nonlinear polarization mechanisms) and grain size was studied. The variation of the grain boundary density was thought to play an important role on the improvement of dielectric breakdown strength, account for the enhanced energy density, which was confirmed by the complex impedance spectroscopy analysis based on a double-layered dielectric model.