鱼油脱胶、脱色脱臭工艺的研究

粗鳀鱼油不仅腥味重、颜色深、凝固点高,而且还含有少许蛋白、胶质、粘液质、游离脂肪酸、水分、脂溶色素等杂质,尤其是鱼油中多烯不饱和脂肪酸的氧化和非脂肪成分的腐败产生的臭味物质,更是有毒害作用。为此,本研究对鳀鱼油精炼工艺进行了以下两方面的试验工作:对经典的油脂加工中的脱胶、脱酸、白土脱色工艺进行了改进研究;研究超临界和亚临界状态下的几种有机和无机溶剂对粗鳀鱼油中非理想成分棗游离脂肪酸、脂溶性色素、挥发性和非挥发性的醛类、酮类、醇类臭味物质的选择性溶解,来达到脱酸、脱色、脱臭目的,以代替经典的填料塔脱酸、脱…     

鱼油的提取与精制技术探讨

利用水产加工下脚料提取鱼油并进行精制.探讨了湿法工艺提取鱼油和精炼的工艺,比较了不同脱酸工艺对产品质量的影响,介绍了白土脱色和活性碳脱色工艺条件,并对冬化和脱臭工艺进行了研究.     

精制鳀鱼油的试验

本文报告了实验室内精制鳀鱼油的试验,认为鳀鱼油脱酸时宜用中等浓度的碱液,加碱量为油重2%,温度控制在55℃,脱色采用3%活性炭和3%高岭土的混合脱色法,在脱色同时减低器内压力并通入氮气达到脱臭的目的。     

罗非鱼油的制备及其脂肪酸组成分析

本文以罗非鱼下脚料为实验材料，对其鱼油的提取与精炼工艺参数、理化特性及脂肪酸组成进行了系统研究。结果显示：罗非鱼油精炼工艺条件为80％的磷酸脱胶，添加量为油量的1％、30％的氢氧化钠脱酸，添加量为油量的2％、活性白土脱色，添加量为油量的20％、真空脱臭，时间为30min。精炼后的罗非鱼油为清亮、淡黄色液体，各项理化指标符合鱼油标准。脂肪酸分析表明，罗非鱼油含有C12-C22笠脂肪酸29种，其中饱和脂肪酸10种，单不饱和脂肪酸7种，多不饱和脂肪多烯酸12种，不饱和脂肪酸和饱和脂肪酸分别占脂肪酸总量57．58％和42．42％。单不饱和脂肪酸主要是18：1(油酸)和16：1，分别占脂肪酸总量27．66％和7．62％，多不饱和脂肪酸主要是18：2(亚油酸)和18：3(n-3)(亚麻酸)，分别占脂肪酸总量10．18％和3．04％，EPA(20：5)和DHA(22：6)含量很低，分别占脂肪酸总量0．68％和1．03％：饷和脂肪酸丰要为16：0．18：0和14：0．分别占脂肪酸总量的26．75％，5．23％和3．00％。     

罗非鱼油的制备及其脂肪酸组成分析

以罗非鱼下脚料为实验材料,对其鱼油的提取与精炼工艺参数、理化特性及脂肪酸组成进行了系统研究。结果显示：罗非鱼油精炼工艺条件为80％的磷酸脱胶,添加量为油量的1％、30％的氢氧化钠脱酸．添加量为油量的2％、活性白土脱色,添加量为油量的20％、真空脱臭,时间为30分钟。精炼后罗非鱼油为清亮、淡黄色液体,各项理化指标符合鱼油标准。脂肪酸分析表明,罗非鱼油含有C12-C22脂肪酸29种,其中饱和脂肪酸10种．单不饱和脂肪酸7种,多不饱和脂肪多烯酸12种,不饱和脂肪酸和饱和脂肪酸分别占脂肪酸总量57．58％和42．42％。单不饱和脂肪酸主要是18：1(油酸)和16：1．分别占脂肪酸总量27．66％和7．62％,多不饱和脂肪酸主要是18：2(亚油酸)和18：3(n-3)(亚麻酸),分别占脂肪酸总量10．18％和3．04％,EPA(20：5)和DHA(22：6)含量很低,分别占脂肪酸总量0．68％和1．03％;饱和脂肪酸主要为16：0．18：0和14：0,分别占脂肪酸总量的26．75％,5．23％和3．00％。     

日本鲐鱼油在不同条件下的脂质氧化

粗制与精制日本鲐鱼油贮藏于以钨丝灯泡为光源或避光条件下，分析了光氧化对鲐鱼油精制前后的氧化稳定性以及丁基羟基茴香醚(BHA)和叔丁基对苯二酚(TBHQ)的抗氧化性，并观察其过氧化值(POV)和硫代巴比妥酸(TBA)值在5℃和40℃下18天内的变化。结果表明，可见光是加速鲐鱼油氧化的重要促进因素，抗氧化剂能明显延缓其氧化，其中TBHQ比BHA效果更好，其氧化速率的顺序光照＞光照+BHA＞避光＞光照+TBHQ＞避光+BHA＞避光+TBHQ；精制鲐鱼油的POV和TBA值较粗制鲐鱼油高；高温贮藏的精制鲐鱼油只在光照条件下氧化速度加快。     

豆油代替鱼油对哲罗鱼稚鱼生长和体成分的影响

研究不同比例豆油取代粗制鱼油对哲罗鱼（Hucho taimen）稚鱼生长和体成分的影响。实验分4个组，每组设3个重复，每个重复100尾稚鱼（体质量7～8g）。第1组（G1）为对照组，添加15％鱼油，第2组（G2）、第3组（G3）和第4组（G4）分别用5％、10％和15％豆油取代鱼油。实验进行8周。结果表明，不同处理成活率和平均日增重差异不显著（P〉0．05），但随着豆油比例的增加，特定生长率和肥满度都得到提高，G3和G4组特定生长率显著高于G1组（P〉0．05）；G4组肥满度显著高于G1组（P〉0．05）。G3、G4组饵料系数显著降低（P〈0．05）。不同处理体成分中水分、粗蛋白质和粗脂肪含量均差异不显著（P〉0．05）。实验表明，豆油作为脂肪源可以完全代替鱼油用于哲罗鱼稚鱼饵料生产。     

鱼油研究的进展

<正> 从本世纪初开始,英国、加拿大、美国和日本等国先后开展了鱼油的研究。上半个世纪,鱼油研究主要集中在化学性质方面,首先是关于碳链长度及其不饱和程度,然后是关于分析技术以及改进对鱼油中特有的脂肪酸研究。1946年前后更为关心的是鱼肉的氧化问题,以后主要研究如何防止鱼油的氧化变质。由于尚未研究出真正满意的解决办法,这方面的研究工作仍在继续进行,同时鱼油的研究已转向鲜活鱼中鱼油的生化变化。鱼油特性方面的研究也在进行,不过注意力已转向化台物及异构物方面。鱼油营养研究在60年代达到高峰,以后逐步     

饲料中添加氧化鱼油对黑鲷幼鱼生长的影响

研究了饲料中添加氧化鱼油对黑鲷（Acanthopagrus schlegeli）生长性能、脂质过氧化及肝组织结构的影响。分别以新鲜鱼油（过氧化物值POV，1．27meq O2·kg^-1油）与氧化酸败鱼油（POV，45meq O2·kg^-油）为脂肪源配制等蛋等能的两种配合饲料，投喂平均体重18．9g的黑鲷幼鱼9周。结果显示，氧化鱼油显著降低了黑鲷幼鱼的增重率（WG）、饲料效率（FE）及蛋白质效率（PER）（P〈0．05）。饲料中添加氧化鱼油导致鱼体蛋白质含量极显著降低（P〈0．01）、肝脏与肌肉中脂肪含量显著升高（P〈0．05），而对鱼体、肝脏及肌肉中的水分及灰分含量无显著影响（P〉0．05）。氧化鱼油组肝脏中脂质过氧化产物丙二醛（MDA）含量显著高于对照组，而维生素E含量则显著低于对照组（P〈0．05）。饲料中添加氧化鱼油显著影响黑鲷肝脏内主要抗氧化酶活性，氧化鱼油组肝脏中超氧化物歧化酶（SOD）与过氧化氢酶（CAT）活性显著高于对照组（P〈0．05）；组织学结果显示氧化鱼油组肝脏出现明显病变，细胞核多集中在肝细胞边缘，肝细胞变大。统计分析表明，氧化酸败油脂显著降低了黑鲷的生长性能，加重了组织中脂质过氧化的程度，并导致肝脏组织发生病变。     

一种来源于米根霉的低温脂肪酶催化鱼油酯交换反应及其氧化性质的研究

以一种来源于米根霉的低温脂肪酶为研究对象,研究其水解、酯化、酯交换特性并应用于制备高含量ω-3脂肪酸甘油三酯型(TG)鱼油。以酯交换产物TG中EPA和DHA的总含量为指标,分析温度、时间、加酶量、底物质量比对鱼油酯交换的影响,并通过核磁共振分析鱼油产物的氧化性质。结果显示:当低温脂肪酶的添加量为0.9%,底物质量比为1∶1,于30℃反应18 h,EPA和DHA总含量从鱼油原料的29.39%提高到44.83%。核磁共振分析表明,当酶法酯交换温度为30℃时,TG型鱼油产物氧化程度低;而使用酯交换温度为50℃的Novozyme 435反应时,TG型鱼油产物发生明显的氧化作用,氧化程度较高。因此,该低温脂肪酶的温度条件能够对鱼油品质有较好的保障。     

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.     

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.     

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.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

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.