A Study of Lipid Bioaccessibility in Canned Sardine (Sardina pilchardus) and Chub Mackerel (Scomber japonicus)

The lipid composition and bioaccessibility in canned sardine (Sardina pilchardus) and chub mackerel (Scomber japonicus) were studied. Triacylglycerols were absent from the bioaccessible fraction in both products and each FA had a different bioaccessibility level. While total fat bioaccessibility was in the 60–64% range, the bioaccessibility of ω6 PUFA and DHA was <55%. Bioaccessibility depended on canned fish product species: fat, EPA, DHA, and ω3 PUFA bioaccessibility levels seemed to be higher in canned sardine than in canned mackerel. Daily consumption of 278 g of canned mackerel or 47 g of canned sardine would ensure the recommended daily intake of EPA+ DHA.     

Dual effects of reversed winter–spring temperatures on year‐to‐year variation in the recruitment of chub mackerel (Scomber japonicus)

To clarify the effects of temperature on the recruitment of chub mackerel (Scomber japonicus) in the North Pacific, we investigated the influence of winter surface temperature (WST) on spawners at the time of maturity around the spawning grounds and the influence of ambient spring temperature on larvae using estimated temperature (ET) obtained from particle tracking experiments. We found a significant positive correlation between ET approximately 10 days following hatching and the recruitment per spawning stock biomass (RPS) after 2000. The closer (more meandering) the Kuroshio Current (KC) axis was in relation to the spawning ground, the higher (lower) the spring surface temperature and the higher (lower) RPS was in the spawning ground. In contrast, WST inside KC near the maturity/spawning ground was significantly negatively correlated with RPS. A significant negative correlation between the temperatures in winter and spring was detected in the area after 2000, when the conditions of the Pacific decadal oscillation index and the stability of the Kuroshio Extension were synchronous, indicating that KC shifted northward during this time. The reversed temperature pattern was consistent with the winter–spring movement of KC axis in the offshore direction and was correlated with the winter–spring difference in the intensity of the Aleutian low. These results suggest that the annual variation in chub mackerel recruitment after 2000 was strongly affected by the combined effects of ambient temperature because of the reversal of conditions that occurred between winter and spring around the maturity/spawning ground, which was related to the KC path.     

东海中部鲐鱼相对体质量指数的计算

为描述东海中部鲐鱼资源的健康状况,反映鱼类所遭受的外界压力情况,基于2009-2010年在东海中部捕获的鲐鱼的叉长和体质量数据,通过建立鲐鱼的标准体质量,计算得到东海中部鲐鱼的相对体质量指数值。根据叉长和体质量对数中值建立的标准体质量方程为:lgms=0.104574L2+2.945479L-2.014981。相对体质量与叉长的分布情况显示,当叉长小于10cm时,相对体质量指数为45~166,而当叉长为15cm时,相对体质量指数变化范围较小,为82~109。虽然在叉长小于10cm或叉长在20cm时,相对体质量指数的变动性较大,但其频率趋于正态分布。东海中部鲐鱼相对体质量指数的计算为不同海域间鲐鱼资源的相互比较研究提供了便利,也为今后更全面、准确地了解该研究海域鲐鱼群体的资源状况提供了研究基准。该指数不受体长大小所引起的误差的影响,能够较准确地在具有不同时空特征以及来自不同种群的鱼类个体之间进行相互比较,从而能够更好地为鲐鱼资源的开发与管理提出科学建议。     

Lipid Oxidation and Omega-3 Fatty Acid Retention in Salmon and Mackerel Nuggets During Frozen Storage

The extent of lipid oxidation and retention of omega (ω)-3 fatty acids in milk protein concentrate (MPC)-added mackerel and salmon mince and nuggets during 4-months frozen storage were investigated in order to develop high ω-3 seafood products. Mechanically deboned fish mince formulated with MPC and other ingredients was formed into batter-breaded nuggets with or without par-frying. The addition of MPC at 4% resulted in significantly lower thiobarbituric acid reactive substances (TBARS) values and helped retain significantly (p < 0.05) higher amounts of docosahexaenoic acid (DHA) in both salmon and mackerel mince and eicosapentaenoic acid (EPA) in the mackerel mince. There were no significant differences in peroxide values (PV) and TBARS values between nugget products with and without par-frying. EPA and DHA were retained less in par-fried than raw nuggets probably due to oil leaching and thermal degradation during frying. The reductions of EPA and DHA in salmon were 67% and 53% for raw and 57% and 39% for par-fried nuggets, while in mackerel they were 63% and 73% for raw and 57% and 56% for par-fried nuggets, respectively. Results suggest that although MPC provided some protection against lipid oxidation, additional measures are needed to improve retention of ω-3 fatty acids in mince-based seafood products during frozen storage.     

Shelf-Life of Spanish Mackerel (Scomberomorus commerson) from Northern Australian Waters

Abstract

The shelf-life of Spanish mackerel caught by line fishing in Northern Australian waters was evaluated. Spiked fish were stored in ice either headed and gutted or left uncut and subjected to sensory, nucleotide, pH, histamine and microbial analysts and the rigor pattern recorded. There was little difference between the two product forms. Rigor in uncut fish lasted for 14 ± 9.8 hours and in headed and gutted fish for 19.6 ± 16.3 hours. Spanish mackerel retained good sensory quality for up to 14 days. The bacterial load reached 105 cfu/g by 18 days. K values were low for most of the storage time, < 40%. Histamine levels did not develop more than 10 mg/kg during storage. The pH of Spanish mackerel did not change much even though bacterial levels become high.     

Biochemical Properties of Pelagic Fish Proteins as Affected by Isolation Methods and Gel Properties by Heating Methods

The biochemical and gel properties of Pacific sardine and Pacific mackerel were characterized as affected by preparation and cooking methods. Four to eight times more salt soluble proteins were extracted from water-washed paste than fish protein isolate (FPI) paste. Higher total sulfhydryl content was measured in FPI, indicating the exposure of sulfhydryl groups during alkaline extraction. Comparing gel properties based on two cooking methods (slow and fast), the two pelagic fish proteins performed quite differently. Heating rate did not differentiate between surimi and FPI gels from sardine. However, mackerel exhibited higher texture values when using the fast cooking method, indicating the presence of high levels of proteolytic enzymes. Water-washed surimi gels were whiter than FPI for both species. Water retention ability appeared to be higher with mackerel than sardine, regardless of isolation and cooking method. Sodium dodecyl sulfate polyacrylamide gel eletrophoresis (SDS-PAGE) also supported a difference in processing chemistry and thermal behavior between two methods for protein isolation and cooking, respectively.     

Gonadal morphogenesis and sex differentiation in cultured chub mackerel,Scomber japonicus

The timing of primordial germ‐cell (PGC) migration with regard to the gonadal anlagen, gonad formation and sex differentiation was examined histologically in the chub mackerel (Scomber japonicus) at 5–190 days post hatching (dph). At 5 dph, PGCs appeared on the peritoneal epithelium surface or in the mesentery, on the dorsal side of the abdominal cavity. By 10 dph, stromal cells around the PGCs proliferated. The gonadal primordium was formed by 15 dph. The gonadosomatic index was 0.01% at 30 dph and increased thereafter (0.32% in females and 0.04% in males at 160 dph). Ovarian differentiation occurred at 30–40 dph, indicated by ovarian cavity formation (elongation and fusion of the upper and lower ovarian edges). Meiosis was subsequently initiated. A few meiotic oocytes surrounded the cavity at 50 dph; most were in the perinucleolus stage at 60 dph and attained a diameter of 60–70 μm at 190 dph. Testicular differentiation occurred at 30 dph, indicated by the formation of the sperm duct primordium. Spermatogonia gradually proliferated, developing into spermatocytes at the chromatin–nucleolus stage (after 90 dph) and subsequently into spermatids and spermatozoa (160 dph). These data could aid the development of seeding and cell‐engineering technologies for scombrid fish.     

热泵干燥过程中竹荚鱼水分迁移特性

以竹荚鱼为试验材料,对热泵干燥过程中鱼片的内部温度分布和水分迁移特性进行了研究.结果表明:热泵干燥过程的大部分时段中(干燥中、后期),竹荚鱼片内部温度分布比较均匀,基本未呈现出整体性的温度梯度.干燥过程中,竹荚鱼片沿厚度方向存在含水率梯度,并且随着干燥温度、风速的变化而变化.热泵干燥前期,鱼体干燥速度取决于鱼体表面水分蒸发的速度;干燥后期,干燥速度取决于鱼体内部水分移动的速度.热泵干燥过程中,竹荚鱼片的水分迁移主要是含水率梯度的作用.     

鲭鱼鱼肉中组胺菌的分离及其理化性质分析

利用组氨酸肉汤培养液，对鲭鱼鱼肉中的组胺生成菌进行筛选，然后通过生物化学和形态学实验，进而对组胺生成菌进行分析。结果表明：分离得到2株组胺菌，菌种I在5～25℃的培养温度范围内，随温度升高，组胺生成量逐渐增加，在25℃组胺生成量最高，约2700mg／kg。菌种Ⅱ在20℃组胺生成量最高，约为2000mg／kg。依据2种组胺菌的特征和生理生化特征，分离菌可能分别属于摩尔摩根氏菌、嗜水性气单胞菌属。