鱼肉蛋白质挤压过程中操作参数对挤出物水分含量及堆积密度的影响

研究了鱼肉蛋白质在双轴挤压蒸煮处理过程中,主要操作参数末段腔体温度,螺杆转速和供料水分含量对挤出物的水分含量和堆积密度两个物理性质的影响。研究的3个操作参数每一个变量设5个水平,测量相应挤出产物的水分含量和堆积密度,分别建立挤出物水分含量与操作参数,挤出物堆积密度与操作参数的回归拟合方程。结果表明,供料湿度明显影响挤出物的水分含量。供料水分含量、腔体温度和螺杆转速对挤出物的堆积密度都有影响;水分含量与操作参数,堆积密度与操作参数的回归拟合方程的相关系数R²分别是1.000和0.926,拟合的统计模型可信度高。     

鱼肉蛋白质热塑挤压组织化中过程参数的优化模型

挤压蒸煮处理可以改变鱼肉蛋白质的功能特性，这些改变与挤压机的操作参数是密不可分的。利用响应面分析方法讲究Clextral BC-45型双轴挤出蒸煮机的操作参数对鱼肉蛋白质进行热塑挤压组织化的影响。研究的3个操作参数分别是末段腔体温度，螺杆转速和喂料湿度，每一个变量设5个水平。测量作为组织化产物功能特性的持水性指数及质构特性，分别建立持水性与操作参数，质构特性与操作参数的回归拟合方程。研究结果表明喂料湿度、螺杆转速和腔体温度对挤出物质构的影响是不同的；持水性与操作参数，质构特性与操作参数的回归拟合力方程的相关系数R^2分别是1.000和0.933，拟合的统计模型可信度高。     

鱼肉蛋白质在双轴湿挤压过程中系统运行稳定性的拟合模型

利用Clexutral BC-45型双轴挤出蒸煮机对鱼肉蛋白质进行湿挤压蒸煮处理，研究挤压蒸煮操作的过程参数对挤压机系统运行稳定性的影响。主要研究的3个操作参数分别是末段腔体温度，螺杆转速以及喂料湿度。采用可旋转中心复合设计，每一个变量设5个水平。运行电流为目标函数，记录每个运行过程中相应的电流读数。研究结果用响应面分析方法进行分析，得到响应曲面和等高线。建立回归拟合方程。结果表明，螺杆转速和喂料湿度对挤压机系统运行均有影响，提高螺杆转速和喂料湿度都会降低系统运行电流。在本实验范围内的腔体温度对系统运行的影响不明显。系统运行电流对所研究的3个操作参数的回归拟合方程的相关系数R^2=0．992，拟合的统计模型具有很高的可信度。     

饲料挤压加工工艺

膨化挤压是在一定压力、水分和高温下的一种熟化工艺过程。在膨化挤压工艺中主要的设备是挤压机 (膨化机 ) ,挤压机能起到粉碎、混合、剪切、熟化、成形、膨化及灭菌等多种作用 ,可促使蛋白质变性。因为这个过程改变物质结构 ,所以膨化加工是一种复杂的物理和化学变化过程。挤压加工工艺适合水产饲料、宠物饲料以及其它特种养殖饲料的加工。用于水产饲料加工的优点有 :挤压加工工艺合并了加热和加压的作用 ,能够控制颗粒饲料密度、提高饲料转化率、增强饲料在水中的稳定性、提高养殖产量和效率。在水产饲料、宠物饲料加工方面 ,挤压加工工艺…     

挤压蒸煮操作参数对鱼蛋白高水分模拟产物组织化效果的影响

对高水分鱼蛋白的挤压组织化进行研究, 以双轴挤压设备操作参数中的进料水分、腔体温度、螺杆转速、进料速率和电机转速为影响参数, 挤压模拟产物的纤维化程度、硬度、弹性、咀嚼性和色泽为响应因素, 通过中心组合设计及响应面分析法, 探讨了高水分挤压重组技术对鱼蛋白模拟肉类产物特性的影响。结果表明: 首先, 高水分组织化模拟产物具有明显的天然肉类的纤维结构、方向性、弹性和口感。其次, 进料水分对产物的纤维化度、硬度和咀嚼性影响相当显著(P<0.01), 对模拟物色泽中的L^*和a^*影响显著(P<0.05), 进料水分的增加使产物的纤维化度、硬度、咀嚼性和a^*降低, 但提升产物 L^*; 腔体温度对产物的咀嚼性和a^*影响特别显著(P<0.01), 对硬度影响显著(P<0.05), 升高腔体温度会增加的产物咀嚼性和a^*, 硬度则先上升后下降; 进料速率对产物的纤维化度影响极其显著(P<0.01)。     

北太鱿鱼挤压组织化工艺初步研究

以北太平洋鱿鱼加工废弃的边角料为原料,对低值水产蛋白资源组织化的挤压工艺进行初步研究。通过研究双螺杆挤压物料湿度、机筒温度和螺杆转速对挤出物组织化度和咀嚼度的影响,得出挤压工艺条件。结果表明:随着物料湿度的增加,挤出物咀嚼度呈逐渐降低趋势,当物料湿度达到40%时,组织化度达1.41,组织化效果较好;随着机筒温度的增加,挤出物组织化度呈先增加后降低的趋势,咀嚼度则呈现相反变化趋势,当机筒温度达到140℃时,组织化效果和咀嚼度均较好;随着螺杆转速的增加,挤出物的组织化度和咀嚼度有增大的趋势,但当螺杆转速继续升高,其组织化度略有下降,而咀嚼度下降明显。单因素试验优选的北太鱿鱼蛋白组织化挤压工艺参数为:物料湿度40%~45%、机筒温度130~140℃、螺杆转速20~30 Hz。     

挤压膨化机的选用和操作

挤压膨化加工技术在特种饲料、水产饲料及饲料资源开发等方面具有与传统加工方法无可比拟的优点。近年来由于挤压膨化加工技术的发展和加工工艺的完善，加上挤压膨化机价格有所下降以及挤压膨化技术对饲料理化性质和营养价值的深入研究，进一步推动了挤压膨化机在饲料工     

膨化参数对饲料淀粉糊化度和蛋白质体外消化率的影响

试验采用胃蛋白酶-胰蛋白酶两步法和β-淀粉酶法分别测定饲料蛋白质体外消化率和淀粉糊化度,探讨了膨化工艺参数对二者的影响。结果表明：物料水分含量、喂料速度、螺杆转速和机筒温度的适度增加都使淀粉糊化度、蛋白质体外消化率增大;机筒温度过高反而使蛋白质体外消化率减小。适宜的膨化条件为：调质后水分26%-30%,喂料速度30-60 r/min,螺杆转速150-250 r/min,机筒温度120-135℃。在此条件下,饲料的淀粉糊化度为90%-92%,蛋白质体外消化率为90%-92%。     

水产饲料的加工与水中稳定性

水产养殖用颗粒饲料除了应满足鱼类营养需要量和适口性之外,还必须在水中具有良好的物理稳定性。这是与陆上动物饲料的一大区别。 水产饲料的加工一般可分为挤压法和膨化法两种。膨化又可分干法膨化和湿法膨化,采用哪一种加工方法,主要取决于鱼类的摄食习性。当然,有些鱼的摄食习性可以驯化,但需要时间和耐心。作为饲料的形态有干燥颗粒饲料、软性颗粒饲料和面团饲料等。饲料的性能有沉性饲料、慢沉饲料和漂浮饲料。如果在技     

膨化与非膨化鲤鱼育成料的养殖效果比较

近20年来,膨化技术在饲料加工中有长足的发展,被认为是一种先进的水产饲料加工技术,尽管有资金投入高、加工开支大、维生素损失等缺点,但优点仍是主要的,如膨化料在水中保形的时间长、营养成分的可消化率高、饲料系数低、养殖成本低、对水域的污染小等。由于上述认识多半是根据国外对叉尾鱼回,欧洲鳗、鲑鳟鱼类的研究作出的,对我国主养的鲤鱼及其它鲤科鱼类的了解还不充分,为此,我公司于1999年10月至2000年3月进行了非膨化的挤压硬颗粒料与膨化料的养殖效果试验。1　试验料11试验料及其制作试验料四种,其中挤压硬颗粒料一种,膨化料三种,使用…     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.