提高冻藏鮰鱼片解冻品质的研究

研究抗冻剂浸渍对-18℃,-30℃和-50℃ 3种冻藏温度的鮰鱼片解冻后的品质和蛋白质变性的影响。结果表明：添加抗冻剂降低了解冻鮰鱼片的pH值,减少解冻后水分流失,维持较低的K值和挥发性盐基氮含量,保持解冻鱼片较好的品质;降低TBARS值,缓解脂肪氧化;保持较高的盐溶蛋白含量和Ca²⁺-ATP 酶活性,减轻解冻鮰鱼片蛋白质冷冻变性的程度。     

基于LF-NMR研究包装方式和温度对鲶鱼片保水性的影响

为了考察贮藏过程中包装方式和温度对鲶鱼片保水性的影响,该试验将新鲜鲶鱼片分别经空气包装(air-package,AP)、真空包装(vacuum package,VP)和气调包装(modified atmosphere package,MAP,60%CO_2+40%N_2)后贮藏于4℃和-0.7℃的冷库中,于贮藏第0、1、4、7、10、15、20、30天测定鲶鱼片的pH值、蒸煮损失率、离心失水率等指标变化,利用低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)技术测定鲶鱼片的水分弛豫时间(T22)、弛豫面积(P22)和质子密度成像(magnetic resonance imaging,MRI),并利用扫描电镜(scanning electron microscopy,SEM)观察鲶鱼片肌纤维结构的变化,对鲶鱼片贮藏过程中保水性变化及原因进行综合判断。结果显示,随着贮藏时间的延长,各组鲶鱼片保水性均呈下降趋势,表现为蒸煮损失率和离心失水率比新鲜鲶鱼片增加,弛豫时间T22和弛豫面积P22降低。相比较而言,冰温气调(-0.7°C-MAP)样品的保水性下降最为缓慢,是鲶鱼片品质保持的较佳贮藏方法。皮尔逊相关系数分析表明弛豫面积P22与贮藏时间、蒸煮损失率及离心失水率显著相关(P0.05);MRI结果显示,鲶鱼片的水分在贮藏过程中逐渐从肌纤维内部渗出,集聚在肌束膜上;SEM表明肌纤维细胞结构发生改变,这可能是引起保水性下降的根本原因。综上所述,该研究证明利用LF-NMR技术可快速表征鲶鱼肉保水性的变化,研究结果为选择鲶鱼片的较佳贮藏条件提供了理论依据。     

Performance of intensively farmed Murray cod Maccullochella peelii peelii (Mitchell) fed newly formulated vs. currently used commercial diets, and a comparison of fillet composition of farmed and wild fish

Murray cod is a top‐order carnivore with high culture potential. Currently, there are no commercial diets formulated specifically for Murray cod. In this study, results of two growth trials on Murray cod (80–83.5‐g mean initial weight), conducted in commercial settings, using two laboratory‐formulated diets (DU1 and DU2; 48.9% and 49.1% protein, and 16.9% and 16.1% lipid, respectively, on a dry matter basis), and two commercial diets, formulated for other species (salmon – CD/S and barramundi – CD/B) but used in Murray cod farming are presented. The two commercial diets had less protein (46.6% and 44.4%) but higher lipid (21.7% and 19.5%). The energy content of the feeds tested was similar (about 20–22 kJ g^?1). The growth performance and feed utilization of Murray cod did not differ significantly amongst the diets, but the food conversion ratio and % protein efficiency ratio in fish fed the DU1 and DU2 diets were consistently better. There was significantly less carcass and muscle lipid deposition in fish fed with the latter diets. Of the fatty acids in muscle, the lowest amounts (in μg mg lipid^?1) of n‐3 (262.5±2.9), n‐6 (39.8±0.9) and polyunsaturated fatty acid (PUFA) (302.3±3.8) were observed in fish fed CD/S, and the highest in fish fed DU2 and CD/B. Fatty acids 16:0 and 18:0, 18:1n‐9 and 16:1n‐7, and 22:6n‐3, 20:5n‐3, 22:5n‐3 and 18:2n‐6 were the dominant fatty acids amongst the saturates, monoenes and PUFA, respectively, and accounted for 80.8–88.7% of all identified fatty acids (23) in muscle of Murray cod. The study showed that Murray cod could be cultured successfully on a diet (DU2) containing 20% soybean meal without compromising growth and/or carcass quality. Differences in the proximate composition and fatty acid composition of muscle of wild and farmed Murray cod were observed, the most obvious being in the latter. Wild Murray cod had significantly less (P<0.05) saturates (192.6±1.84 vs. 266.3±3.51), monoenes (156.5±8.7 vs. 207.6±6.19), n‐3 (145.2±5.24 vs. 261.8±3.2) but higher n‐6 (144.3±2.73 vs. 48.3±1.38) in muscle (all values are in μg mg lipid^?1) than in farmed fish. Wild fish also had a much lower n‐3 to n‐6 ratio (1.0±0.03 vs. 5.4±0.09).     

Effects of dietary levels of 20:5n-3 and 22:6n-3 on tissue lipid composition in juvenile Atlantic salmon, Salmo salar, with emphasis on brain and eye

Four dietary groups of juvenile Atlantic salmon, Salmo salar L., each with three replicates, were fed diets with increasing levels of docosahexaenoic acid (22:6n-3; DHA) and eicosapentaenoic acid (20:5n-3; EPA). Fatty acid composition of brain and eye was determined at the start and approximately every 3 weeks during the experimental period, and fatty acid composition of liver and fillet was determined in fish from the final sampling. Lipid class composition of brain and eye, and fatty acid composition of these lipid classes was determined at the end of the experiment. There was no effect of increasing dietary DHA content on fatty acid composition, lipid class composition or DHA levels in the lipid classes in the juvenile Atlantic salmon brain. The increasing dietary EPA content, however, was reflected in both the total fatty acid composition and in the EPA content in neutral lipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI). A minor effect of the increasing dietary DHA content was found in the lipid composition of the juvenile salmon eye. Both EPA and 18:2n-6 levels in eye, however, clearly reflected the increasing and decreasing, respectively, dietary levels of these two fatty acids. The dietary EPA levels also affected the EPA levels in neutral lipids, PC, PE, PI and PS (phosphatidylserine) in the juvenile salmon eye. The results demonstrate that these dietary levels of DHA had no effect on brain lipid composition and only a minor effect on eye lipid composition. Furthermore, the dietary EPA levels significantly affected the lipid composition of both brain and eye. The fillet fatty acid composition reflected the dietary fatty acid composition, except for the DHA/EPA ratio, which was reversed in fillet compared with that in the diets. The liver fatty acid composition was also affected by the increasing dietary EPA and DHA levels.     

冻马哈鱼片/段加工工艺的研究

冷冻马哈鱼片/段,原料从国外进口,加工成品后再销往美国、欧盟、俄罗斯等地区.原料一般有去头去脏,或者带头去脏2种.对于一直从事淡水鱼片(鮰鱼片)加工的企业来说,其积累了丰富的经验,来料加工的这种模式在生产设备的需求和工艺上和其他鱼片加工区别不大,除了在原料的供应和产品质量控制的关注点不同外,利用公司运行的体系,可以将产品的质量控制在最佳范围之内.但在加工过程中,从原料验收到成品形成全过程都可能受到不同程度的污染,因此在加工过程中应严格按照相关操作规范进行生产加工,确保产品质量.     

Depuration and starvation improves flesh quality of grass carp (Ctenopharyngodon idella)

Farmed grass carp (Ctenopharyngodon idella) at commercial size were transported to a natural lake for long‐term depuration while being food deprived. The effect of depuration time on the quality of fish fillets was investigated based on proximate compositions, textural parameters and flavour characteristics. The results showed that protein and lipids, but not carbohydrates, were the major source of energy for grass carp during depuration and starvation. Textural parameters that included hardness, springiness, gumminess and cohesiveness increased significantly after depuration, as well as water‐holding capacity of fish muscle. Taste and odour characteristics of grass carp muscle were obviously changed by depuration based on tests by an electronic tongue and nose. Off‐flavour volatile compounds, such as nonanal and hexanal, were reduced after depuration. In conclusion, the quality of grass carp fillets was improved effectively by long‐term depuration and food deprivation. More than 20 days of depuration was appropriate for the enhancement of grass carp quality before marketing.     

不同天然保鲜液对气调包装冰温贮藏鲶鱼片品质的影响

为延长鲶鱼片货架期,提高其食用安全性,该试验将新鲜鲶鱼片分别用3种天然保鲜液以及无菌蒸馏水(对照组)处理后,气调包装(60%CO2+40%N2),贮藏于–0.7℃的冰温库中,考察3种天然保鲜液对鲶鱼片感官品质、微生物指标、常规理化指标以及鱼肉蛋白氧化程度的影响。结果表明:1#保鲜液(由壳聚糖、蜂胶、溶菌酶和茶多酚等复配而成)与3#保鲜液(纯乳酸菌发酵液)降低了鲶鱼片中的菌落总数、p H值、总挥发性盐基氮(total volatile base-nitrogen,TVB-N)值和K值的上升;2#保鲜液(桂皮、丁香、生姜和大蒜)具有极好的抗氧化功能,使硫代巴比妥酸(thiobarbituric acid resctive subastances,TBARS)值在整个贮藏期间维持在较低(0.09~0.14 mg/kg)水平;3种天然保鲜液均不同程度延缓了鲶鱼肉肌原纤维蛋白的氧化,抑制了羰基含量的增加和总巯基含量的减少。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)结果显示,经3种保鲜液处理,鲶鱼片肌原纤维蛋白发生交联聚合和小片化的程度降低。由此可见3种保鲜液在不同程度上均可抑制鲶鱼片微生物生长、蛋白降解、脂肪和蛋白氧化,较好地保持鲶鱼肉的新鲜度,延缓腐败变质的发生,3组保鲜效果排序为3#1#2#,1#,2#,3#保鲜液组货架期分别达到40、30和40 d,而无菌蒸馏水处理组为20 d。研究结果为天然保鲜液在鲶鱼肉贮藏中的应用提供参考。     

Fasting combined with long catch duration modifies the physio‐metabolic response and flesh quality of rainbow trout

Pre‐slaughter handling involves fasting fish and catching them, which can affect fish welfare and flesh quality, but few studies have considered their combined effects. In this study, adult rainbow trout (320 ± 10 g average weight) were fasted for 7 days (135.6 degree days) and subjected to a long catch duration (20 min), compared with controls (no fasting or short catch duration). Condition factor, organ weight indexes and carcass yield decreased with fasting but not catch duration. Plasma concentrations of cortisol, glucose and lactate increased after a long catch, while plasma triglycerides decreased with fasting. Liver glycogen concentration was lower in fasted fish, and liver luminosity and chroma were higher after fasting with a long catch. Regarding flesh quality, rigor mortis resolved more slowly and final muscle pH at 48 hr post‐mortem was higher for fasted fish with a long catch time. Muscle glycogen concentration was higher in fasted fish, where chroma was also lower. Fasted fish had lower lipid oxidation, but there were no differences in fat content in muscle. Fasted fish with a long catch duration also had less monounsaturated and more saturated fatty acids. In conclusion, a long catch triggered a stress response that had negative effects on flesh quality, independently of fasting.     

轻盐醋渍黄鲷鱼片工业化生产技术参数的初步研究

本文研究了轻盐醋渍黄鲷鱼片工业化生产的工艺技术。通过盐渍、醋渍、加少量生姜等协同抗菌防腐处理和贯穿整个过程的温度、时间、卫生控制 ,保证了产品的质量和安全。结果表明 ,鱼片占整条鱼的重量比为 2 7～ 33% ;解冻鱼鱼片用 18～ 19%盐水浸渍 ,新鲜鱼鱼片用 2 4～ 2 5 .5 %盐水浸渍 ,2～ 3min ,制品盐份含量为 3%左右 ;米醋大约浸渍 10s ,产品pH <5 ,鱼片质地柔软适口 ;装杉木樽聚乙烯薄膜贴体热收缩包装 ,0～ 5℃冷藏 ,保藏期限为 7d。     

罗非鱼片贮藏过程中品质变化动力学模型

研究不同温度贮藏条件下罗非鱼片挥发性盐基氮（TVB—N）和菌落总数随时问的变化规律及其动力学特性,建立了TVB-N和菌落总数与贮藏温度和贮藏时间的动力学模型,以预测和控制罗非鱼片在贮藏过程中的品质和货架期。贮藏过程中罗非鱼片的TVB-N和菌落总数增加,随着贮藏温度的升高,鱼片品质劣化速度加快。TVB-N和菌落总数均符合一级化学反应动力学模型,并且与Arrhenius方程有很高的拟合度。罗非鱼片的贮藏期可通过模型进行预测。